JP3737329B2 - Magneto-optical recording medium - Google Patents

Description

【００９７】
表１において、比較用ディスクＮｏ．１０とは、面内磁化層２が形成されていない（膜厚＝０）、比較用の光磁気ディスクである。表１に示すように、比較用ディスクＮｏ．１０は面内磁化層２を有しないため、再生層１の遷移温度Ｔｐ１以下での面内磁化マスクが弱く、遷移温度Ｔｐ１に満たない低温の領域においても記録層４からの漏洩磁界の影響を受け、再生層１が垂直磁化状態に遷移しようとする。このため、再生分解能が低くクロストークが大きい。
【００９８】
これに対し、ディスクＮｏ．１１からディスクＮｏ．１６で表される６つの光磁気ディスク（本発明にかかる光磁気記録媒体を含んでなる光磁気ディスク）、すなわち、面内磁化層２の膜厚が順に２、４、１０、２０、４０、並びに６０ｎｍの光磁気ディスクにおいては、比較用ディスクＮｏ．１０に比べてクロストークが小さく抑えられており、面内磁化マスクが強化されていることがわかる。
【００９９】
また、面内磁化層２の膜厚が６０ｎｍを超えると、該面内磁化層２が厚くなりすぎることにより記録層４と再生層１との静磁結合が弱くなり、記録磁区６が再生層１に正確に転写されなくなる虞がある。この結果、場合によってはキャリアレベルＣ１１が低下する。このため、面内磁化層２の膜厚は６０ｎｍ以下であることがより好ましい。
【０１００】
以上のことから、面内磁化層２の膜厚を２ｎｍ以上６０ｎｍ以下の範囲内とすることにより、再生層１が垂直磁化状態に遷移（移行）する遷移温度Ｔｐ１近傍の温度において、面内磁化層２の面内磁化状態をより確実に安定化可能となることが判る。
【０１０１】
なお、本実施の形態においては、面内磁化層２と記録層４との間に非磁性中間層３が形成された構成の光磁気記録媒体について示したが、非磁性中間層３を有しない構成の光磁気記録媒体においても、面内磁化層２としてＨｏ、Ｅｒ、Ｔｍから選択される少なくとも１つの希土類金属元素と少なくとも１種類の３ｄ遷移金属元素とを含む面内磁化膜を用いることにより、再生分解能の向上およびクロストークの改善が可能である。この場合、再生層１と記録層４との間には面内磁化層２の層厚に相当する間隔（所定の間隔）が介在することとなる。
【０１０２】
（４）面内磁化層の組成とクロストーク特性との関係
次に、本実施例で用いた光磁気ディスク（上記サンプル＃１）の構成において面内磁化層２の材料であるＨｏ・Ｆｅ・Ｃｏの組成を種々変更し、上記説明の方法および測定条件に従ってクロストークの測定を行った。
【０１０３】
より具体的には、以下の表２に示すように、３ｄ遷移金属成分であるＦｅとＣｏとの重量比を一定（０．８８：０．１２）とし、ＦｅＣｏとＨｏとの重量比を種々変更してなる光磁気ディスクにおいて、クロストークの測定を行った。なお、トラックピッチは０．６μｍとし、マーク長は０．３μｍ、記録磁区間の距離は０．６μｍとした。また、記録および再生時の記録再生用レーザ照射強度は、各ディスク毎にキャリアレベルＣ１１が最大となるように設定した。尚、表２中、上記サンプル＃１と同一のディスクは、ディスクＮｏ．２４である。
【０１０４】
【表２】

【０１０５】
表２に示すように、比較用ディスクＮｏ．２１では、面内磁化層２としてのＨｏ・Ｆｅ・Ｃｏ中に占めるＨｏの割合が５重量（質量）％と低いため、そのキュリー温度が２５０℃と極めて高くなる。このため、再生層１が遷移温度Ｔｐ１に達する１６０℃の温度においても面内磁化層２の面内磁気異方性が極めて大きく、記録層４の漏洩磁束をマスクした状態を維持する。すなわち、比較用ディスクＮｏ．２１に含まれる光磁気記録媒体は、面内磁化層２の磁化が、上記遷移温度Ｔｐ１近傍の温度で減少しないという点で、本発明にかかる光磁気記録媒体とは異なる。その結果、再生層１の垂直磁化状態への遷移を妨げてしまう。これによって、十分な再生信号強度が得られず、キャリアレベルＣ１１が低下するのでクロストークの値が大きくなる。
【０１０６】
なお、比較用ディスクＮｏ．２１は、上記説明のように、面内磁化層２による上記漏洩磁束のマスク効果には優れている。したがって、例えば、再生層１として、Ｇｄ_0.31（Ｆｅ_0.78Ｃｏ_0.22）_0.69の組成からなるものに代え、その遷移温度Ｔｐ１が２５０℃近傍となるものを使用することで、好適な特性を有する光磁気ディスクとして使用することも可能である。
【０１０７】
一方、ディスクＮｏ．２２からディスクＮｏ．２６で表された光磁気ディスク、すなわち、Ｈｏ・Ｆｅ・Ｃｏ中に占めるＨｏの割合が、順に７、１０、１３、１７、２０重量（質量）％の光磁気ディスクにおいては、上記比較用ディスクＮｏ．２１と比較してクロストークが小さく抑えられていることがわかる。これは、面内磁化層２のキュリー温度Ｔｃ２（９５℃〜２００℃）が再生層１の遷移温度Ｔｐ１（１６０℃）の近傍にあるため、磁区選択的な面内磁化マスク効果が強化され、再生分解能が向上したことによる。
【０１０８】
また、比較用ディスクＮｏ．２７で表された光磁気ディスクにおいては、ディスクＮｏ．２２からディスクＮｏ．２６と比較してクロストークが増大している。これは、Ｈｏの割合が２３重量％と高いために、１）面内磁化層２のキュリー温度Ｔｃ２（７０℃）が低くなり、上記遷移温度Ｔｐ１（１６０℃）近傍で十分な面内マスク効果が得られないこと、および、２）面内磁化層２が補償組成に近いためトータル磁化が小さく、面内磁化状態を安定に保てないこと、による。
【０１０９】
なお、比較用ディスクＮｏ．２７において、例えば、再生層１としてその遷移温度Ｔｐ１が７０℃近傍となる組成のものを使用し、かつ、面内磁化層２においてＦｅＣｏよりＴＭモーメントの大きな遷移金属材料を使用すること等で、好適な特性を有する光磁気ディスクとして使用することも可能である。
【０１１０】
また、表３は、上記表２に示した測定結果で最も小さなクロストークを示したディスクＮｏ．２４（サンプル＃１）の構成において、面内磁化層２におけるＨｏとＦｅＣｏ（３ｄ遷移金属成分）との重量比を１３．０：８７．０で固定したまま、ＦｅとＣｏとの比率を種々変化させて作成した光磁気ディスク（Ｎｏ．３１〜Ｎｏ．３７）の測定結果を示す表である。尚、表３中、上記サンプル＃１と同一のディスクは、ディスクＮｏ．３４である。
【０１１１】
【表３】

【０１１２】
表３に示すように、ディスクＮｏ．３１からディスクＮｏ．３６で表された６種の光磁気ディスク、すなわち、３ｄ遷移金属成分であるＦｅとＣｏとの総重量に占めるＣｏの割合が、順に、０、５、８、１２、１６、並びに１９重量％である光磁気ディスクでは、クロストークが−２５ｄＢ以下に抑えられていることがわかる。これは、１）Ｈｏを添加したことにより、面内磁化層２の面内磁化状態が安定化し、再生分解能が向上したこと、並びに、２）キュリー温度を上昇させる調節材料としても機能するＣｏの含有量が好適な範囲内にあること、によるものである。
【０１１３】
これに対し、３ｄ遷移金属成分の総重量に占めるＣｏの割合が２３重量％である比較用ディスクＮｏ．３７においてはクロストークが増大している。これは、遷移金属成分に占めるＣｏの重量割合が高すぎることにより、面内磁化層２のキュリー温度Ｔｃ２が高くなり（２２０℃）、再生層１の面内磁化状態から垂直磁化状態への遷移が妨げられたことによる。これにより、キャリアレベルＣ１１が低下しクロストークの値が大きくなっている。なお、比較用ディスクＮｏ．３７の構成において、例えば、再生層１としてその遷移温度Ｔｐ１が２２０℃近傍となる組成のものを使用すること等で、好適な特性を有する光磁気ディスクとして使用することも可能である。
【０１１４】
上記表２および表３に示した結果から、面内磁化層２の材料としてＨｏ・Ｆｅ・Ｃｏを使用する場合、Ｈｏの占める割合が７重量（質量）％以上２０％重量以下の範囲内であり、かつ、遷移金属成分の総重量に占めるＣｏの割合が０重量％以上１９重量％以下の範囲内になるように設計することで、クロストークが小さく再生信号品質が良好な光磁気ディスクを提供可能であることがわかる。
【０１１５】
〔実施の形態２〕
本発明の他の実施の形態について、図面に基づいて説明すれば以下のとおりである。なお、これによって、本発明が限定されるものではない。また、説明の便宜上、上記の実施の形態１において示した部材と同一の機能・構造を有する部材には、同一の符号を付し、その説明を省略するものとする。
【０１１６】
本実施の形態では、光磁気記録媒体を適用してなる光磁気ディスクを例に挙げて説明を行う。
【０１１７】
図１２に示すのは、光磁気記録媒体１１ａを含んでなる光磁気ディスクの概略構成を示す断面図である。該図に示すように、本実施の形態にかかる光磁気ディスクは、基板８上に、透明誘電体保護層９、面内磁化層２、再生層１、非磁性中間層３、記録層４、並びに保護層１０がこの順に積層されて構成されている。尚、面内磁化層２、再生層１、非磁性中間層３、並びに記録層４、よりなる積層構造が光磁気記録媒体１１ａに相当する。
【０１１８】
すなわち、上記光磁気記録媒体１１ａは、上記面内磁化層２が、上記再生層１を挟んで記録層４と反対側に設けられた構成、換言すれば、該光磁気記録媒体１１ａの再生を行う光ビームの入射側を基準として、上記面内磁化層２と上記再生層１とがこの順に形成されている構成である。
【０１１９】
上記非磁性中間層３の膜厚は特に限定されるものではないが、０．５ｎｍ以上６０ｎｍ以下の範囲内に設定されていることがより好ましい。０．５ｎｍより薄い膜厚では、該非磁性中間層３を均一に形成することが困難となり、再生層１と記録層４との不所望な交換結合を遮断できなくなる虞が生じる場合がある。また、６０ｎｍを超える膜厚では、記録層４と非磁性中間層３との間隔が大きくなり過ぎ、両者の静磁結合力が弱くなる。その結果、記録層４から再生層１への記録磁区６の安定した転写が困難となり、再生信号品質が劣化する虞が生じる場合がある。
【０１２０】
次に、この光磁気ディスクの形成方法、クロストーク測定方法について説明を行う。
【０１２１】
（１）光磁気ディスクの形成方法
本実施の形態にかかる光磁気ディスクは、例えば、上記実施の形態１に記載の光磁気ディスクの形成方法において、再生層１と面内磁化層２との形成順序を逆にすることにより形成可能である。本実施の形態では、上記実施の形態１と同様の方法で、基板８、透明誘電体保護層９、面内磁化層２、再生層１、非磁性中間層３、記録層４、並びに保護層１０からなる光磁気ディスクを形成した。
【０１２２】
（２）クロストーク特性
図１２に示す光磁気ディスクの構成において面内磁化層２の膜厚を種々変更し、上記実施の形態１の測定と同一の方法および測定条件に従ってクロストークを測定した結果を表４に示す。ここで、トラックピッチは０．６μｍとし、マーク長は０．３μｍ、記録磁区間の距離は０．６μｍとした。記録および再生時の記録再生用レーザ照射強度は、各ディスク毎にキャリアレベルＣ１１が最大となるように設定した。
【０１２３】
【表４】

【０１２４】
表４において、比較用ディスクＮｏ．４０とは、面内磁化層２が形成されていない（膜厚＝０）、比較用の光磁気ディスクであり、実施の形態１に示した比較用ディスクＮｏ．１０（表１参照）と同一の光磁気ディスクである。該比較用ディスクＮｏ．４０は面内磁化層２を有しないため、再生層１の遷移温度Ｔｐ１未満の温度における面内磁化マスクが弱くなり、遷移温度Ｔｐ１に満たない低温の領域においても記録層４からの漏洩磁界の影響を受け、再生層１が垂直磁化状態に遷移しようとする。このため、表４に示すように、再生分解能が低くクロストークが大きくなる。
【０１２５】
これに対し、ディスクＮｏ．４１〜Ｎｏ．４５で表される５つの光磁気ディスク、すなわち面内磁化層２の膜厚が順に、２、４、６、８、並びに１０ｎｍの光磁気ディスクにおいては、比較用ディスクＮｏ．４０と比較してクロストークが小さく抑えられており、面内磁化マスクが強化されていることがわかる。
【０１２６】
以上のことから、上記面内磁化層２が、再生層１を挟んで記録層４と反対側に設けられた構成の場合には、該面内磁化層２の膜厚を２ｎｍ以上１０ｎｍ以下の範囲内とすることにより、１）遷移温度Ｔｐ１未満の温度において、面内磁化によるマスクが強調されて、再生層１の面内磁化状態がより確実に維持されるとともに、２）上記遷移温度Ｔｐ１以上の温度においては、再生層１をより確実に垂直磁化状態に移行させることが可能となる。
【０１２７】
なお、本実施の形態においては、再生層１と記録層４との間に非磁性中間層３が形成された構成の光磁気記録媒体１１ａについて示したが、上記遷移温度Ｔｐ１近傍の温度で磁化が減少する面内磁化膜を上記非磁性中間層３に代えて形成する、または、上記面内磁化膜を再生層１と非磁性中間層３との間に形成することによっても、再生分解能の向上、並びにクロストークの改善が可能である。また上記いずれの場合であっても、再生層１と記録層４との間には所定の間隔が介在することとなる。
【０１２８】
〔実施の形態３〕
本発明のさらに他の実施の形態について、図面に基づいて説明すれば以下のとおりである。なお、これによって、本発明が限定されるものではない。また、説明の便宜上、上記の実施の形態１において示した部材と同一の機能・構造を有する部材には、同一の符号を付し、その説明を省略するものとする。
【０１２９】
図６に示すように、本実施の形態に係る光磁気記録媒体１１’と、上記の実施の形態１に係る光磁気記録媒体１１（図１参照）との相違は、第１の面内磁化層２’と非磁性中間層３との間に、第１の面内磁化層２’よりも高いキュリー温度を有する第２の面内磁化層１３を形成し、第１の面内磁化層２’と第２の面内磁化層１３との積層構造により面内磁化部２２を構成している点にある。なお、上記「第１の面内磁化層２’」とは第２の面内磁化層１３と区別するための名称であり、上記実施の形態１における面内磁化層２と実質同一の構成を有するものである。
【０１３０】
まず、図６を用いて、本実施の形態に係る光磁気記録媒体１１’の再生原理について説明する。図６は、上記光磁気記録媒体１１’の再生時の磁化状態を説明する断面模式図である。該図に示すように、本実施の形態に係る光磁気記録媒体１１’は、再生層１、第１の面内磁化層２’、第２の面内磁化層１３、非磁性中間層３、並びに記録層４が、順次積層されて構成されている。なお、図６中の各矢印は、黒い矢印が３ｄ遷移金属元素の磁気モーメント（ＴＭモーメント）の向きを、白抜き矢印が漏洩磁束の向きをそれぞれ表している。また、以下、単に遷移金属（元素）といえば、「３ｄ遷移金属（元素）」、すなわち、ｄ（電子）殻が満たされていく主遷移元素の内、３ｄ電子殻が満たされる²¹Ｓｃ〜²⁹Ｃｕのみを指し希土類金属（場合によっては、単に希土類と称する）と区別するものとする。
【０１３１】
再生層１に隣接する上記第１の面内磁化層２’は、室温において希土類金属元素の磁気モーメント（ＲＥモーメント）の大きさとＴＭモーメントの大きさとが釣り合う補償組成と比較して、ＴＭモーメントをより多く含むＴＭ rich 組成の面内磁化膜からなり、そのキュリー温度Ｔｃ２は、再生層１が垂直磁化状態となる遷移温度Ｔｐ１近傍に設定されている。また、上記第２の面内磁化層１３は、室温においてＲＥモーメントの大きさとＴＭモーメントの大きさとが釣り合う補償組成と比較して、ＴＭモーメントをより多く含むＴＭ rich 組成の面内磁化膜からなるとともに、そのキュリー温度Ｔｃ１３が第１の面内磁化層２’のキュリー温度Ｔｃ２よりも高く設定されている。
【０１３２】
換言すればすなわち、面内磁化部２２をなす複数の面内磁化層のキュリー温度が、再生層に近づくに従って順に低くなるとともに、上記再生層に隣接する面内磁化層のキュリー温度Ｔｃ２が上記遷移温度Ｔｐ１近傍の温度となるように設計されている。
【０１３３】
また、上記第１の面内磁化層２’または上記第２の面内磁化層１３の少なくとも一方は、Ｈｏ、Ｅｒ、Ｔｍから選択される少なくとも１種類の希土類金属元素と、少なくとも１種類の３ｄ遷移金属元素とを含んで構成されている。すなわち、本実施の形態では、上記第１の面内磁化層２’と面内磁化層２（図１参照）とは同一の構成である故、該第１の面内磁化層２’にはＨｏ、Ｅｒ、Ｔｍから選択される少なくとも１つの元素および３ｄ遷移金属元素が必然的に含まれることとなるが、場合によっては、これらの元素が上記第２の面内磁化層１３にのみ含まれていてもよい。
【０１３４】
図６に示すように、上記の光磁気記録媒体は、記録層４に形成された記録磁区６が、光ビーム５により加熱されて垂直磁化状態となった再生層１の領域へと転写され、磁区７が形成され再生される。この再生の原理は、基本的に上記の実施の形態１と同じである。
【０１３５】
ただし、本実施の形態では、第１の面内磁化層２’と非磁性中間層３との間に、第１の面内磁化層２’よりもキュリー温度が高くトータル磁化の大きい第２の面内磁化層１３が形成されている。そのため、再生層１が垂直磁化状態に遷移する遷移温度Ｔｐ１未満の温度において第１の面内磁化層２’と第２の面内磁化層１３とが交換結合し、面内磁化部２２の面内磁化状態の安定性が高まる。この結果、面内磁化部２２の膜厚が比較的薄い場合でも、遷移温度Ｔｐ１未満の温度において再生層１の面内磁化状態を安定化させることができ、かつ、遷移温度Ｔｐ１以上の温度において記録層４と再生層１とを強く静磁結合させることができるので、再生マージンを拡大可能となる。
【０１３６】
つづいて、上記の光磁気記録媒体１１’を適用した光磁気ディスクについて説明する。上記光磁気ディスクは、図７に示すように、基板８上に、透明誘電体保護層９、再生層１、第１の面内磁化層２’、第２の面内磁化層１３、非磁性中間層３、記録層４、並びに保護層１０がこの順に積層されて構成されている。なお、再生層１、第１の面内磁化層２’、第２の面内磁化層１３、非磁性中間層３、並びに記録層４、よりなる積層構造が光磁気記録媒体１１’に相当する。また、上記の基板８、透明誘電体保護層９、再生層１、非磁性中間層３、記録層４、保護層１０は、上記の実施の形態１と同一の材料および方法により形成することができ、その詳細な説明を省略する。
【０１３７】
上記第２の面内磁化層１３は、第１の面内磁化層２’の面内磁気異方性をそのキュリー温度Ｔｃ２未満の温度において高めるために形成されるものである。該第２の面内磁化層１３は、希土類・遷移金属合金材料、希土類金属のみからなる材料（希土類金属同士の合金含む）、遷移金属のみからなる材料（遷移金属同士の合金含む）、または、遷移金属を主成分とする材料からなる磁性膜であり、そのキュリー温度Ｔｃ１３が第１の面内磁化層２’のキュリー温度Ｔｃ２よりも高く設定された面内磁化膜である。
【０１３８】
第２の面内磁化層１３の膜厚は特に限定されるものではないが、２ｎｍ以上に設定されていることがより望ましい。第２の面内磁化層１３の膜厚が２ｎｍより薄い場合、第２の面内磁化層１３のトータル磁化が小さくなり、第１の面内磁化層２’の面内磁化マスクを強化する効果が得られない場合がある。また、第１の面内磁化層２’および第２の面内磁化層１３の膜厚の合計、すなわち、面内磁化部２２の厚さは６０ｎｍ以下であることがより望ましい。第１の面内磁化層２’および第２の面内磁化層１３の膜厚の合計が６０ｎｍより厚い場合、記録層４と再生層１との間隔が大きくなり、記録層４と再生層１との間の静磁結合力が弱くなる場合がある。これにより、記録層４から再生層１への記録磁区６の安定した転写が困難となり、再生信号品質が劣化する虞がある。
【０１３９】
つぎに、第２の面内磁化層１３を有してなる、上記光磁気ディスクの形成方法および記録再生方法の具体例について説明を行う。
【０１４０】
（１）光磁気ディスクの形成方法
図７に示す上記光磁気ディスクの形成方法は以下のとおりである。なお、ここでは第１の面内磁化層２’および第２の面内磁化層１３の双方に、Ｈｏ・Ｆｅ・Ｃｏ合金材料を用いてなる光磁気ディスクの形成方法について示す。
【０１４１】
第一工程として、ＡｌＳｉターゲットと、Ｇｄ・Ｆｅ・Ｃｏ合金ターゲットと、第１および第２のＨｏ・Ｆｅ・Ｃｏ合金ターゲットと、Ｔｂ・Ｆｅ・Ｃｏ合金ターゲットとを備えたスパッタ装置内に、ランド部分及び案内溝部分の両方に記録を行うための案内溝を有し、かつ、ディスク状に形成されたポリカーボネート製の基板８を配置する。
【０１４２】
そして、上記実施の形態１にて説明した光磁気ディスク（図２参照）と同様の方法に従い、上記基板８上にＡｌＳｉＮからなる透明誘電体保護層９を膜厚８０ｎｍで形成する。続けて、上記透明誘電体保護層９上に、Ｇｄ_0.31（Ｆｅ_0.78Ｃｏ_0.22）_0.69の組成からなる再生層１を膜厚２５ｎｍで形成する。
【０１４３】
引き続いて第二工程として、第１のＨｏ・Ｆｅ・Ｃｏ合金ターゲットに電力を供給し、ガス圧４×１０^-3Ｔｏｒｒ（約０．５３２Ｐａ）の条件下で、上記再生層１上にＨｏ_0.13（Ｆｅ_0.88Ｃｏ_0.12）_0.87の組成からなる第１の面内磁化層２’を膜厚１０ｎｍで形成する。そして、第１のＨｏ・Ｆｅ・Ｃｏ合金ターゲットとはＦｅおよびＣｏの含有比が異なる、第２のＨｏ・Ｆｅ・Ｃｏ合金ターゲットに電力を供給し、ガス圧４×１０^-3Ｔｏｒｒ（約０．５３２Ｐａ）の条件下で、上記第１の面内磁化層２’上に第２の面内磁化層１３を膜厚１０ｎｍで形成する。
【０１４４】
なお、上記第２の面内磁化層１３は、Ｈｏを１３重量％含んでいる点では第１の面内磁化層２’と同様であるが、ＦｅおよびＣｏの含有比が異なっている。したがって、第１の面内磁化層２’とは異なるキュリー温度Ｔｃ１３を有する。また、第２の面内磁化層１３は、室温からそのキュリー温度Ｔｃ１３までの範囲内の温度条件下で、ＲＥモーメントの大きさとＴＭモーメントの大きさとが釣り合う補償組成と比較して、ＴＭモーメントをより多く含むＴＭ rich 組成の面内磁化膜であった。
【０１４５】
引き続いて第三工程として、ＡｌＳｉターゲットに電力を供給して、ガス圧４×１０^-3Ｔｏｒｒ（約０．５３２Ｐａ）の条件下で、上記第２の面内磁化層１３上に、ＡｌＳｉからなる非磁性中間層３を膜厚２ｎｍで形成する。
【０１４６】
引き続いて第四工程として、上記実施の形態１にかかる光磁気ディスク（図２参照）と同様の方法に従い、上記非磁性中間層３上に、Ｔｂ_0.25（Ｆｅ_0.84Ｃｏ_0.16）_0.75の組成からなる記録層４を膜厚６０ｎｍで形成する。そして、上記記録層４上にＡｌＳｉＮからなる保護層１０を膜厚２０ｎｍで形成することで、図７に示す光磁気ディスクが製造される。
【０１４７】
（２）クロストーク特性
図７に示す上記光磁気ディスクの記録再生特性は以下のとおりである。具体的には、波長６８０ｎｍの半導体レーザを用いた光磁気ピックアップを使用して、線速２．５ｍ／ｓの条件で上記光磁気ディスクにおけるクロストークを評価した結果について説明する。
【０１４８】
クロストークの測定には、上記実施の形態１に示したものと同様の測定方法および測定条件を用い、トラックピッチを０．６μｍ、マーク長を０．３μｍとした際のクロストークを測定した。ここで、トラックピッチとは、図４（ａ）および図４（ｂ）に示す測定トラック１１の幅方向の中心位置と、隣接トラック１２・１２’の幅方向の中心位置との距離を指す。なお、ランド部幅と案内溝部幅とは等しく、それぞれ前記トラックピッチと同一とした。また、マーク長０．３μｍとは、それぞれの記録磁区６ａを０．３μｍの長さ（直径）で形成することをいい、記録磁区６ａ・６ａ間の間隔（ピッチ）は、マーク長の２倍（すなわち０．６μｍ）に設定されている。
【０１４９】
【表５】

【０１５０】
【表６】

【０１５１】
表５に示すのは、第２の面内磁化層１３に含まれるＨｏ量を１３．０重量％に、ＦｅＣｏ（３ｄ遷移金属成分）量を８７．０重量％にそれぞれ固定した上で、ＦｅＣｏに占めるＦｅ（またはＣｏ）量を変化させて、異なるキュリー温度を示すように設計された７種類の光磁気ディスク（ディスクＮｏ．５１〜５７）における、トラックピッチ０．６μｍでの上記クロストークの測定結果である。
【０１５２】
なお、上記表６には比較のため、図７に示した光磁気ディスクの構成において、第１の面内磁化層２’として用いたＨｏ_0.13（Ｆｅ_0.88Ｃｏ_0.12）_0.87に代えて、従来技術にて示したＧｄとＦｅとからなり、Ｈｏ_0.13（Ｆｅ_0.88Ｃｏ_0.12）_0.87と等しいキュリー温度（１６０℃）を有するＧｄ_0.13Ｆｅ_0.87を用い、さらに第２の面内磁化層１３に代えて、上記表６に示す組成からなる第２の面内磁化層を用いてなる７種類の比較用光磁気ディスク（比較用ディスクＮｏ．６１〜６７）における、トラックピッチ０．６μｍでの上記トラックピッチの測定結果についても併せて示す。ここで、比較用ディスクＮｏ．６１〜６７の第２の面内磁化層のキュリー温度は、それぞれ順に、表５に示すディスクＮｏ．５１〜５７の第２の面内磁化層１３のキュリー温度と等しくなるように設計されている。
【０１５３】
表５に示すように、第１の面内磁化層２’および第２の面内磁化層１３より構成される、厚さ２０ｎｍの面内磁化部２２を備えてなる光磁気ディスク（ディスクＮｏ．５１〜ディスクＮｏ．５７）はそれぞれ、該第１の面内磁化層２’および第２の面内磁化層１３と等しいキュリー温度を示す第１・第２の面内磁化層を有してなる、対応する比較用ディスクＮｏ．６１〜６７（従来の光磁気ディスク）と比べてクロストークの値が低く、優れた特性を有することが判る。
【０１５４】
特にディスクＮｏ．５２からディスクＮｏ．５６で示した５つの光磁気ディスク、すなわち、第２の面内磁化層１３のキュリー温度が、順に、１６０℃、１７５℃、１９０℃、２２０℃、２４０℃、である光磁気ディスクにおいては、クロストークがいずれも−３２．０ｄＢ以下に抑えられていることがわかる。
【０１５５】
上記実施の形態１でも説明したように、膜厚２０ｎｍの面内磁化層２単独で面内磁化部を形成してなるディスクＮｏ．１４（サンプル＃１）において、クロストークの値は−３２．０ｄＢ（表１参照）であった。したがって、ディスクＮｏ．５２からディスクＮｏ．５６においては、層厚１０ｎｍの第２の面内磁化層１３を設けることで層厚１０ｎｍの第１の面内磁化層２’の面内磁化マスク効果が強化され、上記ディスクＮｏ．１４と同等かそれ以上の再生分解能を示すことがうかがえる。
【０１５６】
尚、ディスクＮｏ．５１では、上記ディスクＮｏ．１４のクロストークの値（−３２．０ｄＢ）と比較すれば、その値が大きくなっている。これは、第２の面内磁化層１３に用いたＨｏ・Ｆｅ・Ｃｏのキュリー温度Ｔｃ１３（１２５℃）が第１の面内磁化層２’のキュリー温度Ｔｃ２（１６０℃）より低く、上記キュリー温度Ｔｃ２近傍において第１の面内磁化層２’の面内磁気異方性を高める効果が得られないためである。この結果、再生層１の遷移温度Ｔｐ１近傍の温度（すなわち、キュリー温度Ｔｃ２近傍の温度でもある）で面内磁化マスクが弱まり、クロストークの値が大きくなる。
【０１５７】
また、ディスクＮｏ．５７では、上記ディスクＮｏ．１４のクロストークの値（−３２．０ｄＢ）と比較すれば、その値が大きくなっている。これは、第２の面内磁化層１３のキュリー温度が２８０℃と高いため、そのトータル磁化が大きくなりすぎるためである。この結果、記録層４と再生層１との静磁結合が妨げられて再生信号品質が劣化すると考えられる。
【０１５８】
以上のことから、第２の面内磁化層１３のキュリー温度Ｔｃ１３と第１の面内磁化層２’のキュリー温度Ｔｃ２とは、
Ｔｃ２≦Ｔｃ１３≦Ｔｃ２十８０℃
の関係を満たすように設定されていることがより望ましいことがわかる。第２の面内磁化層１３のキュリー温度Ｔｃ１３を上記範囲に設定することにより、クロストークが小さく再生信号品質が良好な光磁気ディスクを得ることができる。
【０１５９】
このような複数の面内磁化層のキュリー温度同士の関係は、面内磁化部が組成の異なる２種類の面内磁化層からなる場合のみにあてはまるものではない。すなわち、面内磁化部が組成の異なる少なくとも２種類以上の面内磁化層から構成される場合において、異なる面内磁化層間のキュリー温度の差が８０℃以下となるように設定すれば上記説明の効果が得られる。
【０１６０】
なお、本実施の形態では、第１の面内磁化層２’および第２の面内磁化層１３の両方にＨｏ・Ｆｅ・Ｃｏを用いた例を示したが、第１の面内磁化層２’または第２の面内磁化層１３の少なくとも一方にＨｏ、Ｅｒ、Ｔｍから選択される少なくとも１つの希土類金属元素と、少なくとも１種類の３ｄ遷移金属元素とを含む面内磁化層を用い、加えて、第２の面内磁化層１３のキュリー温度Ｔｃ１３を上記の温度範囲に設定することにより強い面内磁化マスク効果を実現することが可能となる。
【０１６１】
また、本実施の形態では、第１の面内磁化層２’上に、該第１の面内磁化層２’よりも高いキュリー温度Ｔｃ１３を有する第２の面内磁化層１３を１層のみ積層して面内磁化部２２を構成する例を示したが、特にこの構造に限定されるものではない。例えば、第１の面内磁化層２’上に第２の面内磁化層１３を複数層積層して面内磁化部を構成し、該面内磁化部において再生層１から離れた層（すなわち第２の面内磁化層１３）のキュリー温度をより高く設計することによっても、強い面内磁化マスク効果が得られる。また、上記面内磁化部に代え、再生層１から離れるにしたがってキュリー温度が高くなるように組成を変化させた面内磁化層を、再生層１に隣接して積層することによっても同様の効果が得られる。
【０１６２】
〔実施の形態４〕
本発明のさらに他の実施の形態について、図面に基づいて説明すれば以下のとおりである。なお、これによって、本発明が限定されるものではない。また、説明の便宜上、上記の実施の形態１または３において示した部材と同一の機能・構造を有する部材には、同一の符号を付し、その説明を省略するものとする。
【０１６３】
図８に示すように、本実施の形態に係る光磁気記録媒体１１”と、上記の実施の形態３に係る光磁気記録媒体１１’（図６参照）との相違は、第２の面内磁化層１３に代えて、第１の面内磁化層２’と非磁性中間層３との間に、希土類金属元素の磁気モーメントの大きさと３ｄ遷移金属元素の磁気モーメントの大きさとが釣り合う補償組成と比較してＲＥモーメントをより多く含むＲＥ rich 組成の面内磁化膜からなる第２の面内磁化層１４を形成し、第１の面内磁化層２’と第２の面内磁化層１４との積層構造により面内磁化部２３を構成している点にある。なお、説明の便宜上、希土類金属元素の磁気モーメントをＲＥモーメントと、３ｄ遷移金属元素の磁気モーメントをＴＭモーメントと称する場合がある。
【０１６４】
まず、図８を用いて、本実施の形態に係る光磁気記録媒体１１”の再生原理について説明する。図８は、上記光磁気記録媒体の再生時の磁化状態を説明する断面模式図である。該図に示すように、本実施の形態に係る光磁気記録媒体１１”は、再生層１、第１の面内磁化層２’、第２の面内磁化層１４、非磁性中間層３、並びに記録層４が、順次積層されて構成されている。なお、図８中の各矢印は、黒い矢印が３ｄ遷移金属元素の磁気モーメントの向きを、白抜き矢印が漏洩磁束の向きをそれぞれ表している。また、以下、単に遷移金属（元素）といえば、「３ｄ遷移金属（元素）」、すなわち、ｄ（電子）殻が満たされていく主遷移元素の内、３ｄ電子殻が満たされる²¹Ｓｃ〜²⁹Ｃｕのみを指し希土類金属（場合によっては、単に希土類と称する）と区別するものとする。
【０１６５】
上記第１の面内磁化層２’は、ＲＥモーメントの大きさとＴＭモーメントの大きさとが釣り合う補償組成と比較して、ＴＭモーメントをより多く含んでなるＴＭ rich 組成の面内磁化膜からなり、そのキュリー温度Ｔｃ２は、上記再生層１が垂直磁化状態となる遷移温度Ｔｐ１近傍に設定されている。また、上記第２の面内磁化層１４は、ＲＥモーメントの大きさとＴＭモーメントの大きさとが釣り合う補償組成と比較して、ＲＥモーメントをより多く含んでなるＲＥ rich 組成の面内磁化膜である。
【０１６６】
また、上記第１の面内磁化層２’または上記第２の面内磁化層１４の少なくとも一方は、Ｈｏ、Ｅｒ、Ｔｍから選択される少なくとも１種類の希土類金属元素と、少なくとも１種類の３ｄ遷移金属元素とを含んでなる材料より構成されている。
【０１６７】
図８に示すように、上記の光磁気記録媒体１１”は、記録層４に形成された記録磁区６が、光ビーム５により加熱されて垂直磁化状態となった再生層１の領域へと転写され、磁区７が形成され再生される。この再生の原理は、基本的に上記の実施の形態１ないし３と同じである。
【０１６８】
ただし、本実施の形態では、第１の面内磁化層２’と非磁性中間層３との間に、ＲＥ rich 組成の面内磁化膜からなる第２の面内磁化層１４が形成されている。そのため、再生層１が垂直磁化状態に遷移する遷移温度Ｔｐ１未満の温度において、ＲＥ rich 組成の再生層１、ＴＭ rich 組成の第１の面内磁化層２’、並びにＲＥ rich 組成の第２の面内磁化層１４は、記録層４から発生する漏洩磁界の影響を受け、それぞれのトータル磁化が同方向となるように磁化方向を揃える。
【０１６９】
この結果、上記再生層１および第１の面内磁化層２’の希土類副格子モーメントと遷移金属副格子モーメントとが反平行に揃うとともに、第１の面内磁化層２’および第２の面内磁化層１４の希土類副格子モーメントと遷移金属副格子モーメントとが反平行に揃うことになる。これにより、各層界面での磁壁エネルギーが大きくなり、面内磁化状態の安定性が高まる。よって、第１の面内磁化層２’の膜厚および第２の面内磁化層１４の膜厚の合計、すなわち、面内磁化部２３の膜厚が比較的薄い場合にも、高い面内マスク効果が得られる。
【０１７０】
すなわち、上記光磁気記録媒体１１”では、ＲＥ rich 組成の第２の面内磁化層１４を設けることにより、上記面内磁化部２３の膜厚がより薄い場合でも、遷移温度Ｔｐ１未満の温度において再生層１の面内磁化状態を安定化させることができ、かつ、遷移温度Ｔｐ１以上の温度において記録層４と再生層１とを強く静磁結合させることができるので、再生マージンを拡大可能となる。
【０１７１】
つづいて、上記の光磁気記録媒体１１”を適用した光磁気ディスクについて説明する。上記光磁気ディスクは、図９に示すように、基板８上に、透明誘電体保護層９、再生層１、第１の面内磁化層２’、第２の面内磁化層１４、非磁性中間層３、記録層４、並びに保護層１０がこの順に積層されて構成されている。なお、再生層１、第１の面内磁化層２’、第２の面内磁化層１４、非磁性中間層３、並びに記録層４、よりなる積層構造が光磁気記録媒体１１”に相当する。また、上記の基板８、透明誘電体保護層９、再生層１、非磁性中間層３、記録層４、保護層１０は、上記の実施の形態１と同一の材料および方法により形成することができ、その詳細な説明を省略する。
【０１７２】
上記第２の面内磁化層１４は、第１の面内磁化層２’のキュリー温度Ｔｃ２未満の温度において、磁壁エネルギーを利用して該第１の面内磁化層２’の面内磁気異方性を高めるべく形成されるものである。該第２の面内磁化層１４は、例えば、希土類・遷移金属合金材料、希土類金属のみからなる材料（希土類金属同士の合金含む）、又は、希土類金属を主成分とする材料からなる磁性膜である。
【０１７３】
第２の面内磁化層１４の膜厚は特に限定されるものではないが、２ｎｍ以上に設定されていることがより望ましい。第２の面内磁化層１４の膜厚が２ｎｍより薄い場合、第２の面内磁化層１４のトータル磁化が小さくなり、第１の面内磁化層２’の面内磁化マスクを強化する効果が得られない場合がある。また、第１の面内磁化層２’および第２の面内磁化層１４の膜厚の合計、すなわち、面内磁化部２３の厚さは６０ｎｍ以下であることがより望ましい。第１の面内磁化層２’および第２の面内磁化層１４の膜厚の合計が６０ｎｍより厚い場合、記録層４と再生層１との間隔が大きくなり、記録層４と再生層１との間の静磁結合力が弱くなる場合がある。これにより、記録層４から再生層１への記録磁区６の安定した転写が困難となり、再生信号品質が劣化する虞がある。
【０１７４】
つぎに、上記構成の光磁気ディスクの形成方法および記録再生方法の具体例を説明する。
【０１７５】
（１）光磁気ディスクの形成方法
図９に示す上記光磁気ディスクの形成方法は以下のとおりである。なお、ここでは第１の面内磁化層２’および第２の面内磁化層１４の双方に、Ｈｏ・Ｆｅ・Ｃｏ合金材料を用いてなる光磁気ディスクの形成方法について示す。
【０１７６】
第一工程として、ＡｌＳｉターゲットと、Ｇｄ・Ｆｅ・Ｃｏ合金ターゲットと、第１および第２のＨｏ・Ｆｅ・Ｃｏ合金ターゲットと、Ｔｂ・Ｆｅ・Ｃｏ合金ターゲットとを備えたスパッタ装置内に、ランド部分及び案内溝部分の両方に記録を行うための案内溝を有し、かつ、ディスク状に形成されたポリカーボネート製の基板８を配置する。
【０１７７】
そして、上記実施の形態１にかかる光磁気ディスク（図２参照）と同様の方法に従い、上記基板８上にＡｌＳｉＮからなる透明誘電体保護層９を膜厚８０ｎｍで形成する。続けて、上記透明誘電体保護層９上に、Ｇｄ_0.31（Ｆｅ_0.78Ｃｏ_0.22）_0.69の組成からなる再生層１を膜厚２５ｎｍで形成する。
【０１７８】
引き続いて第二工程として、第１のＨｏ・Ｆｅ・Ｃｏ合金ターゲットに電力を供給し、ガス圧４×１０^-3Ｔｏｒｒ（約０．５３２Ｐａ）の条件下で、上記再生層１上にＨｏ_0.13（Ｆｅ_0.88Ｃｏ_0.12）_0.87の組成からなる第１の面内磁化層２’を膜厚７ｎｍで形成する。そして、第１のＨｏ・Ｆｅ・Ｃｏ合金ターゲットとは各元素の含有比が異なる、第２のＨｏ・Ｆｅ・Ｃｏ合金ターゲットに電力を供給し、ガス圧４×１０^-3Ｔｏｒｒ（約０．５３２Ｐａ）の条件下で、上記第１の面内磁化層２’上に第２の面内磁化層１４を膜厚７ｎｍで形成する。すなわち、この光磁気ディスクにおいて面内磁化部２３の厚さは１４ｎｍである。
【０１７９】
上記第２の面内磁化層１４の組成は、Ｈｏ_0.36（Ｆｅ_0.72Ｃｏ_0.28）_0.64であり、そのキュリー温度Ｔｃ１４は１６０℃であった。また、第２の面内磁化層１４は、室温からそのキュリー温度Ｔｃ１４までの範囲内の温度条件下で、ＲＥモーメントの大きさとＴＭモーメントの大きさとが釣り合う補償組成と比較して、ＲＥモーメントをより多く含むＲＥ rich 組成の面内磁化膜であった。
【０１８０】
引き続いて第三工程として、ＡｌＳｉターゲットに電力を供給して、ガス圧４×１０^-3Ｔｏｒｒ（約０．５３２Ｐａ）の条件下で、上記第２の面内磁化層１４上に、ＡｌＳｉからなる非磁性中間層３を膜厚２ｎｍで形成する。
【０１８１】
引き続いて第四工程として、上記実施の形態１にかかる光磁気ディスク（図２参照）と同様の方法に従い、上記非磁性中間層３上に、Ｔｂ_0.25（Ｆｅ_0.84Ｃｏ_0.16）_0.75の組成からなる記録層４を膜厚６０ｎｍで形成する。そして、上記記録層４上にＡｌＳｉＮからなる保護層１０を膜厚２０ｎｍで形成することで、図９に示す光磁気ディスクが製造される。
【０１８２】
（２）クロストーク特性
図９に示す上記光磁気ディスク（以下、サンプル＃２と称する）の記録再生特性は以下のとおりである。具体的には、波長６８０ｎｍの半導体レーザを用いた光磁気ピックアップを使用して、線速２．５ｍ／ｓの条件で上記光磁気ディスクにおけるクロストークを評価した結果について説明する。
【０１８３】
クロストークの測定には、上記実施の形態１に示したものと同様の測定方法および測定条件を用いた。なお、記録に当たっては、記録再生用レーザを５．６ｍＷで連続照射しながら記録磁界を±１５ｋＡ／ｍで変調することにより、記録層４に記録磁界の向きに対応した上向き磁化と下向き磁化との繰り返しパターンを０．３μｍのマーク長で形成した。ここで、マーク長０．３μｍとは、それぞれの記録磁区を０．３μｍの長さ（直径）で形成することをいい、記録磁区間の間隔（ピッチ）は、マーク長の２倍（すなわち０．６μｍ）に設定される。
【０１８４】
図１０は、記録再生用レーザを１．８ｍＷで連続照射して測定したサンプル＃２のクロストークのトラックピッチ依存性を示すグラフである。ここで、トラックピッチとは、図４（ａ）および図４（ｂ）に示す測定トラック１１の幅方向の中心位置と、隣接トラック１２・１２’の幅方向の中心位置との距離を指す。なお、ランド部幅と案内溝部幅とは等しく、それぞれ前記トラックピッチと同一とした。また、比較のため、上記実施の形態１にて説明した光磁気ディスク（サンプル＃１）、すなわちサンプル＃２の構成において第２の面内磁化層１４を省略し、第１の面内磁化層２’（面内磁化層２と同一）の膜厚を２０ｎｍとした光磁気ディスク（図２参照）のクロストークのトラックピッチ依存性を示すグラフもあわせて記載している。
【０１８５】
サンプル＃２とサンプル＃１とを比較すると、図１０に示すように、いずれのトラックピッチにおいてもほぼ同等のクロストークの値が得られた。さらに、サンプル＃１の面内磁化層２の膜厚が２０ｎｍであるのに対し、サンプル＃２の面内磁化部２３の厚さが１４ｎｍであるため、面内磁化部２３を用いれば、より薄い膜厚でも十分に高い面内磁化マスク効果が得られることがわかる。さらに、サンプル＃１とサンプル＃２について、再生時に外部磁界を印加し記録層４と再生層１との静磁結合力を調べた。その結果、サンプル＃２はサンプル＃１と比較して外部磁界の印加に対し、より安定であることが確認された。
【０１８６】
このように、本発明にかかる光磁気記録媒体１１”を含んでなる光磁気ディスク（サンプル＃２）は、第２の面内磁化層１４を設けることにより、面内磁化部２３の膜厚がより薄い場合においても高い面内磁化マスク効果が得られ、良好な再生信号品質を実現することのできる光磁気ディスクである。
【０１８７】
以上説明したように、ＲＥ rich 組成の第２の面内磁化層１４をさらに設けることにより、面内磁化部２３の薄膜化が可能となり、記録パワーおよび再生パワーを低減することができるとともに、記録層４と再生層１との静磁結合力が強まり、再生マージンが拡大する、等の効果が得られる。
【０１８８】
なお、本実施の形態では、第１の面内磁化層２’および第２の面内磁化層１４の双方にＨｏ・Ｆｅ・Ｃｏ材料を用いた例を示したが、特にこの構造に限定されるものではない。例えば、第１の面内磁化層２’または第２の面内磁化層１４の少なくとも一方として、Ｈｏ、Ｅｒ、Ｔｍから選択される少なくとも１種類の希土類金属元素と、少なくとも１種類の３ｄ遷移金属元素とを含む面内磁化層を用い、さらに、第１の面内磁化層２’をＴＭ rich 組成、第２の面内磁化層１４をＲＥ rich 組成とすることで強い面内磁化マスク効果が得られる。
【０１８９】
また、本実施の形態では、ＲＥ rich 組成の面内磁化層（第２の面内磁化層１４に相当）とＴＭ rich 組成の面内磁化層（第１の面内磁化層２’に相当）とを１層づつ積層して面内磁化部２３を形成する例を示したが、特にこの構造に限定されるものではない。例えば、ＴＭ rich 組成の面内磁化層と、ＲＥ rich 組成の面内磁化層とを交互に繰り返し積層することで３層以上の面内磁化層を含んでなる面内磁化部とし、より強い面内磁化マスク効果を実現できる構成としてもよい。
【０１９０】
なお、ＴＭ rich 組成の面内磁化層と、ＲＥ rich 組成の面内磁化層とを交互に繰り返し積層して面内磁化部を構成する場合、該面内磁化部をなすＴＭ rich 組成の面内磁化層同士（または、ＲＥ rich 組成の面内磁化層同士）は完全同一の組成である必要はない。
【０１９１】
さらに、本実施の形態とは異なり再生層がＴＭ rich 組成の材料からなる場合には、該再生層に隣接する第１の面内磁化層をＲＥ rich 組成の材料から、第１の面内磁化層上に積層される第２の面内磁化層をＴＭ rich 組成の材料から、それぞれ構成すればよい。
【０１９２】
（３）面内磁化層の組成とクロストーク特性との関係
次に、本実施例で用いた光磁気ディスク（上記サンプル＃２）の構成において第２の面内磁化層１４の材料であるＨｏ・Ｆｅ・Ｃｏの組成を種々変更し、上記「（２）クロストーク特性」の測定と同一の方法および測定条件に従ってクロストークの測定を行った。換言すれば、第２の面内磁化層１４、すなわち、ＲＥ rich のＨｏ・Ｆｅ・Ｃｏ層のキュリー温度が種々変化されてなる光磁気ディスクについて、クロストークの測定を行った。
【０１９３】
より具体的には、以下の表７に示すように、希土類金属元素であるＨｏと３ｄ遷移金属成分であるＦｅＣｏとの重量比を、０．３６：０．６４で一定とし、上記ＦｅＣｏに占めるＦｅ（またはＣｏ）の含有量を種々変更してなる６つの光磁気ディスクにおいて、上記の測定が行われた。なお、トラックピッチは０．６μｍとし、マーク長は０．３μｍ、記録磁区間の距離は０．６μｍとした。ここで、トラックピッチとは、図４（ａ）および図４（ｂ）に示す測定トラック１１の幅方向の中心位置と、隣接トラック１２・１２’の幅方向の中心位置との距離を指す。なお、ランド部幅と案内溝部幅とは等しく、それぞれ前記トラックピッチと同一とした。
【０１９４】
また、以下に示す表８には比較のため、図９に示した光磁気ディスクの構成において、第１の面内磁化層２’として用いたＨｏ_0.13（Ｆｅ_0.88Ｃｏ_0.12）_0.87に代えて、従来技術にて示したＧｄとＦｅとからなり、Ｈｏ_0.13（Ｆｅ_0.88Ｃｏ_0.12）_0.87と等しいキュリー温度（１６０℃）を有するＧｄ_0.13Ｆｅ_0.87を用い、さらに第２の面内磁化層１４に代えて、該表８に示す組成からなる第２の面内磁化層を用いてなる６種類の比較用光磁気ディスク（比較用ディスクＮｏ．８１〜８６）における、トラックピッチ０．６μｍでの上記トラックピッチの測定結果についても併せて示す。
【０１９５】
なお、上記比較用ディスクＮｏ．８１〜８６に含まれる第２の面内磁化層はそれぞれ、Ｇｄ量を３６．０重量％に、ＦｅＣｏ量を６４．０重量％に固定した上で、ＦｅＣｏに占めるＦｅ（またはＣｏ）量を変化させて、異なるキュリー温度を示すように設計されている。より具体的には、比較用ディスクＮｏ．８１〜８６の第２の面内磁化層のキュリー温度は、それぞれ順に、表７に示すディスクＮｏ．７１〜７６の第２の面内磁化層１４のキュリー温度と等しくなるように設計されている。
【０１９６】
【表７】

【０１９７】
【表８】

【０１９８】
表７に示すように、第１の面内磁化層２’および第２の面内磁化層１４より構成される、厚さ１４ｎｍの面内磁化部２３を備えてなる光磁気ディスク（ディスクＮｏ．７１〜ディスクＮｏ．７６）はいずれも、該第１の面内磁化層２’および第２の面内磁化層１４と等しいキュリー温度を示す第１・第２の面内磁化層を有してなる、対応する比較用ディスクＮｏ．８１〜８６と比べてクロストークの値が低く、優れた特性を有することが判る。
【０１９９】
特にディスクＮｏ．７２からディスクＮｏ．７５で示した５つの光磁気ディスク、すなわち、第２の面内磁化層１４のキュリー温度が、順に、１６０℃、１９５℃、２２５℃、２４０℃、である光磁気ディスクにおいては、クロストークがいずれも−３２．３ｄＢ以下に抑えられていることがわかる。
【０２００】
上記実施の形態１でも説明したように、膜厚２０ｎｍの面内磁化層２単独で面内磁化部を形成してなるディスクＮｏ．１４（サンプル＃１）において、クロストークの値は−３２．０ｄＢ（表１参照）であった。したがって、ディスクＮｏ．７２からディスクＮｏ．７５においては、第２の面内磁化層１４を設けることで第１の面内磁化層２’の面内磁化マスク効果が強化され、より薄い面内磁化膜（面内磁化部２３の厚さ１４ｎｍ）で上記ディスクＮｏ．１４以上の再生分解能を示すことがうかがえる。
【０２０１】
尚、ディスクＮｏ．７１では、上記ディスクＮｏ．１４のクロストークの値（−３２．０ｄＢ）と比較すれば、その値が大きくなっている。これは、第２の面内磁化層１４に用いたＨｏ・Ｆｅ・Ｃｏのキュリー温度（１３０℃）が第１の面内磁化層２’のキュリー温度Ｔｃ２（１６０℃）より低く、上記キュリー温度Ｔｃ２近傍において第１の面内磁化層２’の面内磁気異方性を高める効果が得られないためである。この結果、再生層１の遷移温度Ｔｐ１近傍の温度（すなわち、キュリー温度Ｔｃ２近傍の温度でもある）で面内磁化マスクが弱まり、クロストークの値が大きくなる。
【０２０２】
また、ディスクＮｏ．７６では、上記ディスクＮｏ．１４のクロストークの値（−３２．０ｄＢ）と比較すれば、その値が大きくなっている。これは、第２の面内磁化層１４のキュリー温度が２７０℃と高いため、そのトータル磁化が大きくなりすぎるためである。この結果、記録層４と再生層１との静磁結合が妨げられて再生信号品質が劣化すると考えられる。
【０２０３】
以上のことから、第２の面内磁化層１４のキュリー温度Ｔｃ１４と第１の面内磁化層２’のキュリー温度Ｔｃ２とは、
Ｔｃ２≦Ｔｃ１４≦Ｔｃ２十８０℃
の関係を満たすように設定されていることがより望ましいことがわかる。第２の面内磁化層１４のキュリー温度Ｔｃ１４を上記範囲に設定することにより、クロストークが小さく再生信号品質が良好な光磁気ディスクを得ることができる。
【０２０４】
なお、本実施の形態では、第１の面内磁化層２’および第２の面内磁化層１４の両方にＨｏ・Ｆｅ・Ｃｏを用いた例を示したが、第１の面内磁化層２’または第３の面内磁化層１４の少なくとも一方に、Ｈｏ、Ｅｒ、Ｔｍから選択される少なくとも１種類の希土類金属元素と、少なくとも１種類の３ｄ遷移金属元素とを含む面内磁化膜を用い、加えて、第２の面内磁化層１４のキュリー温度Ｔｃ１４を上記の温度範囲に設定することで強い面内磁化マスク効果が得られる。
【０２０５】
また、本実施の形態では第１の面内磁化層２’上にＲＥ rich 組成の面内磁化層（第２の面内磁化層１４）を１層のみ積層する例を示したが、この構成に限定されるものではない。例えば、ＴＭ rich 組成の面内磁化層とＲＥ rich 組成の面内磁化層とを交互に繰り返し積層して３層以上の面内磁化層からなる面内磁化部を構成し、さらに、再生層１から離れた面内磁化層ほどキュリー温度を高くすることによっても、強い面内磁化マスク効果が得られる。
【０２０６】
本発明にかかる光磁気記録媒体はまた、室温において面内磁化状態であり、遷移温度Ｔｐ１以上の温度において垂直磁化状態に移行する再生層と、垂直磁化膜からなり情報が光磁気記録される記録層と、非磁性材料からなり上記再生層と記録層との間に配された中間層とを有してなる光磁気記録媒体において、上記再生層の少なくとも一方面側に隣接して設けられ、上記遷移温度Ｔｐ１近傍の温度でその磁化が減少する面内磁化層をさらに有し、上記面内磁化層が、Ｈｏ、Ｅｒ、Ｔｍから選択される少なくとも１種類の希土類金属元素と、少なくとも１種類の３ｄ遷移金属元素とを含んでなる構成であってもよい。
【０２０７】
本発明にかかる光磁気記録媒体は、例えば、光磁気ディスク、光磁気テープ、光磁気カード、等における光記録媒体として、好適に使用することができる。
【０２０８】
【発明の効果】
本発明にかかる光磁気記録媒体は、以上のように、遷移温度Ｔｐ１以上の温度において面内磁化状態から垂直磁化状態に移行する再生層と、垂直磁化膜からなる記録層と、上記再生層に隣接して設けられ、上記遷移温度Ｔｐ１近傍の温度でその磁化が減少する面内磁化層とを含んでなる光磁気記録媒体において、上記面内磁化層がＨｏ、Ｆｅ、並びにＣｏからなる希土類・３ｄ遷移金属合金材料からなる層であって、上記希土類・３ｄ遷移金属合金材料に占めるＨｏの割合が７質量％以上２０質量％以下の範囲内であり、かつ、３ｄ遷移金属に占めるＣｏの割合が０質量％以上１９質量％以下の範囲内である構成である。
【０２０９】
上記の構成によれば、上記面内磁化層が、Ｈｏ、Ｆｅ、並びにＣｏからなる希土類・３ｄ遷移金属合金材料からなり、上記希土類・３ｄ遷移金属合金材料に占めるＨｏの割合が７質量％以上２０質量％以下の範囲内であり、かつ、３ｄ遷移金属に占めるＣｏの割合が０質量％以上１９質量％以下の範囲内であるため、上記再生層の垂直磁化状態への移行を急峻に行うことが可能となる。これにより、クロストークが小さく、良好な再生信号品質で再生可能な光磁気記録媒体を提供することが可能となるという効果を奏する。
【０２１０】
本発明にかかる光磁気記録媒体は、室温において面内磁化状態であり、遷移温度Ｔｐ１以上の温度において垂直磁化状態に移行する再生層と、上記再生層と所定の間隔をおいて配され、垂直磁化膜からなり情報が光磁気記録される記録層と、上記再生層の何れか一方の面側に隣接して設けられ、上記遷移温度Ｔｐ１近傍の温度でその磁化が減少する面内磁化層とを含んでなる光磁気記録媒体において、上記面内磁化層が、ＨｏＦｅＣｏ、ＥｒＦｅＣｏ、ＴｍＦｅＣｏの何れかによって構成され、上記面内磁化層が、上記再生層を挟んで記録層と反対側に少なくとも１層設けられるとともに、上記再生層を挟んで記録層と反対側に設けられた面内磁化層の膜厚の合計が、２ｎｍ以上１０ｎｍ以下の範囲内である構成である。
【０２１１】
本発明にかかる光磁気記録媒体は、上記の構成に加えて、上記再生層が、室温以上の温度において、ＲＭ rich 組成であるとともに、上記面内磁化層が、室温以上の温度において、ＴＭ rich 組成である構成である。
【０２１２】
上記の構成によれば、上記遷移温度Ｔｐ１未満の温度において、再生層および面内磁化層は漏洩磁界の影響を受け、それぞれのトータル磁化が同じ方向となるように磁化方向を揃える。この結果、再生層の磁化は強く面内方向に引きつけられることとなり、上記遷移温度Ｔｐ１未満の温度において、その面内磁化状態をより安定化させることが可能となるという効果を併せて奏する。
【０２１３】
本発明にかかる光磁気記録媒体は、上記の構成に加えて、遷移温度Ｔｐ１以上の温度において面内磁化状態から垂直磁化状態に移行する再生層と、垂直磁化膜からなる記録層と、上記再生層に隣接して設けられ、複数の面内磁化層が積層されてなる面内磁化部とを有してなる光磁気記録媒体において、上記面内磁化部は、組成の異なる少なくとも２種類の上記面内磁化層を含んでなるとともに、上記再生層に隣接する面内磁化層は、上記遷移温度Ｔｐ１近傍の温度でその磁化が減少する性質を有しており、さらに、上記複数の面内磁化層の少なくとも１つが、ＨｏＦｅＣｏ、ＥｒＦｅＣｏ、ＴｍＦｅＣｏの何れかによって構成される構成である。
【０２１４】
上記の構成によれば、面内磁化層をＧｄ・Ｆｅを用いて形成した場合と比較して、上記遷移温度Ｔｐ１未満の温度において再生層の面内磁化状態をより安定化させることが可能となるという効果を併せて奏する。
【０２１５】
本発明にかかる光磁気記録媒体は、上記の構成に加えて、上記面内磁化部をなす複数の面内磁化層はいずれも、少なくとも１種類の希土類金属元素と、少なくとも１種類の３ｄ遷移金属元素とを含んでなり、上記面内磁化部はさらに、ＴＭ rich 組成の面内磁化層と、ＲＥ rich 組成の面内磁化層とが積層されてなる構成である。
【０２１６】
上記の構成によれば、面内磁化層間の界面での磁壁エネルギーが大きくなり、面内磁化状態の安定性がさらに高まるので、高い面内マスク効果を得ることが可能となるという効果を併せて奏する。
【０２１７】
本発明にかかる光磁気記録媒体は、上記の構成に加えて、上記複数の面内磁化層のキュリー温度が、再生層に近づくに従って順に低くなり、かつ再生層に隣接する面内磁化層のキュリー温度Ｔｃ２が上記遷移温度Ｔｐ１近傍の温度である構成である。
【０２１８】
上記の構成によれば、再生層から遠位に位置する面内磁化層ほど高いトータル磁化を有し、該再生層に対しより近位に位置する面内磁化層と交換結合するので、遷移温度Ｔｐ１未満の温度において再生層の面内磁化状態をより安定化させることができ、かつ、遷移温度Ｔｐ１以上の温度において記録層と再生層とを強く静磁結合させることができるので、再生マージンを拡大可能となるという効果を併せて奏する。
【０２１９】
本発明にかかる光磁気記録媒体は、上記の構成に加えて、上記面内磁化部をなす複数の面内磁化層において、キュリー温度の最大値と最小値との差が８０℃以下である構成である。
【０２２０】
上記の構成によれば、クロストークが小さく、良好な再生信号品質で再生可能な光磁気記録媒体を提供することが可能となるという効果を併せて奏する。
【０２２１】
本発明にかかる光磁気記録媒体は、上記の構成に加えて、上記面内磁化層が、上記再生層と記録層との間に少なくとも１層設けられるとともに、この面内磁化層の膜厚の合計が、２ｎｍ以上６０ｎｍ以下の範囲内である構成である。
【０２２２】
本発明にかかる光磁気記録媒体は、上記の構成に加えて、上記面内磁化層が、上記再生層を挟んで記録層と反対側に少なくとも１層設けられるとともに、この面内磁化層の膜厚の合計が、２ｎｍ以上１０ｎｍ以下の範囲内である構成である。
【０２２３】
上記いずれかの構成によれば、上記遷移温度Ｔｐ１未満の温度においては、再生層の面内磁化状態がより確実に維持されるとともに、上記遷移温度Ｔｐ１以上の温度においては、再生層をより確実に垂直磁化状態に移行させることが可能となるという効果を併せて奏する。
【図面の簡単な説明】
【図１】 本発明の実施の一形態にかかる光磁気記録媒体の、再生時の磁化状態を示す断面模式図である。
【図２】 図１に示す光磁気記録媒体が適用された光磁気ディスクの概略構成を示す断面図である。
【図３】 Ｇｄ・Ｆｅ材料およびＨｏ・Ｆｅ・Ｃｏ材料における、磁化容易軸方向の組成依存性を示すグラフである。
【図４】 （ａ）・（ｂ）は、光磁気ディスクにおけるクロストークの測定方法を説明する概略図である。
【図５】 図２に示す光磁気ディスク、および、図１４に示す従来の光磁気ディスクにおける、クロストークのトラックピッチ依存性を示すグラフである。
【図６】 本発明の他の実施の形態にかかる光磁気記録媒体の、再生時の磁化状態を示す断面模式図である。
【図７】 図６に示す光磁気記録媒体が適用された光磁気ディスクの概略構成を示す断面図である。
【図８】 本発明のさらに他の実施の形態にかかる光磁気記録媒体の、再生時の磁化状態を示す断面模式図である。
【図９】 図８に示す光磁気記録媒体が適用された光磁気ディスクの概略構成を示す断面図である。
【図１０】 図２および図９に示す光磁気ディスクにおける、クロストークのトラックピッチ依存性を示すグラフである。
【図１１】 面内磁化層の材料としてＥｒ・Ｆｅ・Ｃｏを用いたサンプル＃１（ａ）、Ｔｍ・Ｆｅ・Ｃｏを用いたサンプル＃１（ｂ）、および比較用サンプル＃ｒ１のクロストークのトラックピッチ依存性を示すグラフである。
【図１２】 本発明のさらに他の実施の形態にかかる光磁気記録媒体が適用された光磁気ディスクの概略構成を示す断面図である。
【図１３】 従来の光磁気記録媒体の、再生時の磁化状態を示す断面模式図である。
【図１４】 図１３に示す光磁気記録媒体が適用された光磁気ディスクの概略構成を示す断面図である。
【符号の説明】
１ 再生層
２ 面内磁化層
２’ 第１の面内磁化層（面内磁化層）
４ 記録層
６ 記録磁区（情報）
１１ 光磁気記録媒体
１１’ 光磁気記録媒体
１１” 光磁気記録媒体
１３ 第２の面内磁化層（面内磁化層）
１４ 第２の面内磁化層（面内磁化層）
２２ 面内磁化部
２３ 面内磁化部
Ｔｃ２ 面内磁化層のキュリー温度
Ｔｐ１ 再生層の遷移温度[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a magneto-optical recording medium such as a magneto-optical disk, a magneto-optical tape, a magneto-optical card, and the like applied to a magneto-optical recording / reproducing apparatus.
[0002]
[Prior art]
  Conventionally, a magneto-optical recording medium has been put to practical use as a rewritable optical recording medium. In such a magneto-optical recording medium, the recording bit diameter and recording which are recording magnetic domains (information, recording magnetic domains) with respect to the beam diameter of the light beam emitted from the semiconductor laser focused on the magneto-optical recording medium There is a drawback that the reproduction characteristics deteriorate as the bit interval decreases.
[0003]
  This is because adjacent recording bits are included within the beam diameter of the light beam focused on the target recording bit, so that individual recording bits cannot be separated and reproduced.
[0004]
  As means for solving this problem, various magnetic super-resolution reproduction techniques using a magnetic multilayer film have been developed. These magnetic super-resolution reproduction technologies form a magnetic mask area to form a magnetic aperture that is smaller than the beam spot, reducing intersymbol interference during reproduction, and below the diffraction limit of light. A signal (information) having a period of 1 can be reproduced.
[0005]
  Among these magnetic super-resolution reproduction techniques, Japanese Patent Application Laid-Open No. 9-320134 discloses information consisting of a reproduction layer that is in-plane magnetization at room temperature and becomes perpendicular magnetization above a predetermined temperature, and a perpendicular magnetization film. A magneto-optical recording layer, and an in-plane magnetization layer between the reproduction layer and the recording layer, adjacent to the reproduction layer, and having magnetization reduced in the vicinity of the predetermined temperature. A magneto-optical recording medium provided with is disclosed. This magneto-optical recording medium can emphasize a mask due to in-plane magnetization in the reproducing layer, and a high reproduction signal quality can be obtained even when the recording bit diameter and the recording bit interval are small.
[0006]
  Here, the reproduction principle of the magneto-optical recording medium disclosed in JP-A-9-320134 will be described with reference to FIG. FIG. 13 is a schematic cross-sectional view for explaining the magnetization state during reproduction of the magneto-optical recording medium. This magneto-optical recording medium is constituted by laminating a reproducing layer 201, an in-plane magnetic layer 202, a nonmagnetic intermediate layer 203, and a recording layer 204 in this order. In each of the arrows in the figure, the black arrow represents the direction of the magnetic moment of the transition metal element (hereinafter sometimes simply referred to as TM moment), and the white arrow represents the direction of the leakage magnetic flux. Further, hereinafter, simply referring to the transition metal (element), “3d transition metal (element)”, that is, the 3d electron shell among the main transition elements satisfying the d (electron) shell is satisfied.^{twenty one}Sc ~²⁹It refers only to Cu and is distinguished from rare earth metal elements (in some cases, simply called rare earth or rare earth metal).
[0007]
  The reproducing layer 201 is in an in-plane magnetization state at room temperature and has a transition temperature (predetermined temperature) Tp.₂₀₁It is made of a rare earth / transition metal alloy material that becomes perpendicularly magnetized at the above temperature. For example, compared to a compensation composition in which the magnitude of the magnetic moment of rare earth metal (hereinafter sometimes simply referred to as the RE moment) and the magnitude of the TM moment are balanced, the rare earth / transition metal having a RE rich composition containing more RE moment. If an alloy material is used, since the total magnetization is large at room temperature, the demagnetizing field makes the magnetization direction parallel to the film surface (in-plane magnetization direction). On the other hand, transition temperature Tp₂₀₁In the vicinity (or higher), the total magnetization decreases due to the cancellation of the rare earth metal sublattice moment and the transition metal sublattice moment, and the perpendicular anisotropy becomes larger than the demagnetizing field, resulting in perpendicular magnetization. The transitional characteristics can be realized.
[0008]
  The in-plane magnetization layer 202 qualitatively has magnetization in a direction parallel (horizontal) to the film surface, and in addition, a transition temperature Tp₂₀₁The temperature in the vicinity is set as the Curie temperature or the transition temperature Tp₂₀₁When the temperature exceeds the vicinity, the magnitude of magnetization decreases as the temperature rises.
[0009]
  In the magneto-optical recording medium, since the reproducing layer 201 and the in-plane magnetic layer 202 are adjacent to each other, the transition temperature Tp₂₀₁If the temperature is lower than that, the in-plane magnetization of the in-plane magnetization layer 202 and the in-plane magnetization of the reproduction layer 201 are exchange coupled. That is, the magnetization of the reproducing layer 201 remains in the in-plane direction. As the material of the in-plane magnetization layer 202, a rare earth / transition metal alloy mainly composed of Gd · Fe (representing an alloy of Gd and Fe) is used.
[0010]
  The nonmagnetic intermediate layer 203 is made of a nonmagnetic material and is formed between the in-plane magnetic layer 202 and the recording layer 204 to block exchange coupling therebetween. The recording layer 204 is a perpendicular magnetization film made of a rare earth / transition metal alloy material.
[0011]
  On the other hand, at the time of reproduction, the light beam 205 is focused and irradiated from the reproduction layer 201 side to the magneto-optical recording medium so as to center on the recording magnetic domain 206 of the recording layer 204 to be reproduced. In accordance with the temperature distribution of the magneto-optical recording medium generated by the concentrated irradiation of the light beam 205, the magnitude of magnetization is limited only in the region (indicated by hatching in the figure) facing the recording magnetic domain 206 in the in-plane magnetization layer 202. As a result, the magnetic flux leakage from the recording magnetic domain 206 is generated so as to penetrate the in-plane magnetic layer 202. The leakage magnetic flux and the total magnetization of the reproducing layer 201 are magnetostatically coupled, whereby the magnetization information of the recording magnetic domain 206 is transferred to the region of the reproducing layer 201 in the perpendicular magnetization state, and the magnetic domain 207 is formed. At this time, the total magnetization direction of the magnetic domains 207 in the reproducing layer 201 is the same as the direction of the recording magnetic domains 206 in the recording layer 204.
[0012]
  As described above, in the magneto-optical recording medium, the light beam 205 is focused and irradiated to cause the transition temperature Tp.₂₀₁Only the region heated to the above temperature becomes a perpendicular magnetization state and contributes to the reproduction, thereby realizing a super-resolution reproduction operation. Thereby, it is possible to reproduce a signal having a period equal to or less than the diffraction limit of light without reducing the reproduction signal amplitude.
[0013]
[Problems to be solved by the invention]
  However, in the above magneto-optical recording medium, if the track pitch is narrowed to achieve higher density recording, the mask strength by the in-plane magnetic layer 202 becomes insufficient, and signal leakage from adjacent tracks, that is, There is a problem that the crosstalk increases and a good reproduction signal quality cannot be obtained.
[0014]
  With reference to FIG. 13, a problem during reproduction of the magneto-optical recording medium will be described. At the time of reproduction, the region of the reproduction layer 201 that is completely perpendicularly magnetized, that is, the transition temperature Tp₂₀₁Ideally, only the information (recording magnetic domain 206) corresponding to the above region is reproduced. However, in practice, as shown in the figure, the transition temperature Tp₂₀₁The region that is less than and near the transition temperature, that is, the region corresponding to the center peripheral portion of the light beam 205 is also affected by the leakage magnetic field generated from the recording layer 204. Therefore, as shown in the figure, in the reproducing layer 201 and the in-plane magnetization layer 202, the magnetization in the region corresponding to the central peripheral portion of the light beam 205 is not a complete in-plane magnetization but a magnetization inclined with respect to the film surface. It becomes a state.
[0015]
  This is because 1) the in-plane magnetic layer 202 is in the vicinity of its Curie temperature (in other words, the transition temperature Tp).₂₀₁The magnetization of the reproducing layer 201 cannot be maintained in the in-plane direction, and 2) Gd · Fe is a material having a relatively large perpendicular magnetic anisotropy, and particularly has a large amount of Gd. The composition is caused by the fact that the magnetization of the in-plane magnetic layer 202 is close to perpendicular magnetization.
[0016]
  For this reason, in the peripheral region of the magnetic domain 207 formed in the reproducing layer 201, the magnetic mask by the in-plane magnetic layer 202 does not sufficiently function, and the reproducing resolution is lowered. In addition, when recording is performed with a narrow track pitch, there is a problem that crosstalk increases.
[0017]
  The present invention has been made in order to solve the above-described problems. The object of the present invention is to produce a good reproduction signal with little occurrence of crosstalk even when recording / reproduction is performed with a small recording bit diameter and a small recording bit interval. Is to provide a magneto-optical recording medium.
[0018]
[Means for Solving the Problems]
  In order to solve the above-described problems, a magneto-optical recording medium according to the present invention is an in-plane magnetization state at room temperature and transitions to a perpendicular magnetization state at a temperature equal to or higher than a transition temperature Tp1, and the reproduction layer And a recording layer made of a perpendicularly magnetized film on which information is magneto-optically recorded, and the reproducing layerEither oneA magneto-optical recording medium including an in-plane magnetic layer provided adjacent to the surface side and whose magnetization decreases at a temperature in the vicinity of the transition temperature Tp1;The in-plane magnetic layer is a layer made of a rare earth / 3d transition metal alloy material made of Ho, Fe, and Co, and the proportion of Ho in the rare earth / 3d transition metal alloy material is 7% by mass or more and 20% by mass or less. And the proportion of Co in the 3d transition metal is in the range of 0% by mass to 19% by mass.It is characterized by that.
[0019]
  According to the above configuration, since the reproducing layer and the in-plane magnetic layer adjacent thereto are exchange-coupled at a temperature lower than the transition temperature Tp1, the mask by in-plane magnetization is emphasized in the reproducing layer, and the in-plane magnetization state is increased. Maintained. On the other hand, at a temperature not lower than the transition temperature Tp1 and not lower than the temperature near the transition temperature Tp1, the magnetization of the in-plane magnetic layer decreases and the reproducing layer shifts to a perpendicular magnetization state, and information is transferred from the recording layer to the reproducing layer. (Playback) is performed.
[0020]
  Furthermore, the in-plane magnetic layer isA layer made of a rare earth / 3d transition metal alloy material made of Ho, Fe, and Co, and a ratio of Ho in the rare earth / 3d transition metal alloy material is in the range of 7 mass% to 20 mass%, In addition, the proportion of Co in the 3d transition metal is in the range of 0% by mass to 19% by mass.Therefore, the reproducing layer can be sharply shifted from the in-plane magnetization state to the perpendicular magnetization state. As a result, the reproduction resolution can be increased. For example, even when the track pitch is narrow, it is possible to provide a magneto-optical recording medium that has small crosstalk and can be reproduced with good reproduction signal quality.
[0021]
  In order to solve the above problems, the magneto-optical recording medium according to the present invention also has a reproducing layer that is in an in-plane magnetization state at room temperature and transitions to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1, and A recording layer made of a perpendicularly magnetized film, which is arranged at a predetermined interval, is provided adjacent to one of the surfaces of the reproducing layer and the reproducing layer, and has a temperature in the vicinity of the transition temperature Tp1. In a magneto-optical recording medium including an in-plane magnetization layer whose magnetization decreases, the in-plane magnetization layer is composed of any one of HoFeCo, ErFeCo, and TmFeCo, and the in-plane magnetization layer serves as the reproduction layer. At least one layer is provided on the opposite side of the recording layer across the recording layer, and the total thickness of the in-plane magnetic layers provided on the opposite side of the recording layer across the reproducing layer is in the range of 2 nm to 10 nm. It is characterized in that.
[0022]
  In the magneto-optical recording medium according to the present invention, in addition to the above-described configuration, the reproducing layer has a magnetic moment magnitude of the rare earth metal element and a magnetic moment of the 3d transition metal element at a temperature not lower than the room temperature and lower than the transition temperature Tp1. Compared with the compensation composition in which the magnitude is balanced, the magnetic moment of the rare earth metal element is increased, and the in-plane magnetic layer has a magnitude of the magnetic moment of the rare earth metal element and the 3d transition metal at a temperature higher than room temperature. Compared with the compensation composition in which the magnitude of the magnetic moment of the element is balanced, the magnetic moment of the 3d transition metal element is more included.
[0023]
  According to the above configuration, at the temperature lower than the transition temperature Tp1, the reproducing layer and the in-plane magnetic layer are affected by the leakage magnetic field, and the magnetization directions are aligned so that the total magnetizations thereof are in the same direction. For this reason, both rare earth metal sublattice moments and transition metal sublattice moments are aligned antiparallel, and the domain wall energy at the interface between the two increases. As a result, the magnetization of the reproducing layer is strongly attracted in the in-plane direction, and the in-plane magnetization state can be further stabilized at a temperature lower than the transition temperature Tp1.
[0024]
  In order to solve the above problems, the magneto-optical recording medium according to the present invention also has a reproducing layer that is in an in-plane magnetization state at room temperature and transitions to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1, and A recording layer made of a perpendicularly magnetized film and magneto-optically recorded with information, and a reproducing layerEither oneIn a magneto-optical recording medium having an in-plane magnetized portion that is provided adjacent to the plane side and is formed by laminating a plurality of in-plane magnetized layers, the in-plane magnetized portion includes at least two types of different compositions. The in-plane magnetization layer includes the in-plane magnetization layer, and the in-plane magnetization layer adjacent to the reproduction layer among the plurality of in-plane magnetization layers has a property that the magnetization decreases at a temperature near the transition temperature Tp1. And at least one of the plurality of in-plane magnetization layers isConsists of one of HoFeCo, ErFeCo, and TmFeCoIt is characterized by that.
[0025]
  According to the above configuration, the in-plane magnetization state of the reproducing layer is further stabilized at a temperature lower than the transition temperature Tp1 as compared with the case where the in-plane magnetization layer is formed using Gd · Fe as in the prior art. It becomes possible.
[0026]
  In the magneto-optical recording medium according to the present invention, in addition to the above configuration, each of the plurality of in-plane magnetization layers forming the in-plane magnetization portion includes at least one kind of rare earth metal element and at least one kind of 3d transition metal. The in-plane magnetized portion further includes a 3d-comparing composition in which the magnitude of the magnetic moment of the rare earth metal element and the magnitude of the magnetic moment of the 3d transition metal element are balanced at a temperature of room temperature or higher. An in-plane magnetized layer containing more of the magnetic moment of the transition metal element (that is, an in-plane magnetized layer having a TM rich composition), and the magnetic moment magnitude of the rare earth metal element and the 3d transition metal element Compared with a compensation composition that balances the magnitude of the magnetic moment, an in-plane magnetic layer (ie, RE rich) that contains more of the magnetic moment of the rare earth metal element. It is characterized by being composed by laminating the formed in-plane magnetized layer) and.
[0027]
  According to the above configuration, the in-plane magnetized portion is formed by laminating the in-plane magnetized layer having the RE rich composition and the in-plane magnetized layer having the TM rich composition. The transition metal sublattice moments are anti-parallel. As a result, the domain wall energy at the interface of each layer is increased, and the stability of the in-plane magnetization state is further increased, so that a high in-plane mask effect can be obtained.
[0028]
  In the magneto-optical recording medium according to the present invention, in addition to the above-described configuration, the Curie temperatures of the plurality of in-plane magnetization layers forming the in-plane magnetization portion are sequentially lowered as the reproduction layer is approached, and adjacent to the reproduction layer. The Curie temperature Tc2 of the in-plane magnetic layer is a temperature in the vicinity of the transition temperature Tp1.
[0029]
  According to the above configuration, the in-plane magnetic layer located farther from the reproducing layer has a higher total magnetization, and is exchange-coupled to the in-plane magnetic layer located more proximal to the reproducing layer. As a result, even if the film thickness of the in-plane magnetized portion is relatively thin, the in-plane magnetization state of the reproducing layer can be stabilized at a temperature lower than the transition temperature Tp1, and recording can be performed at a temperature equal to or higher than the transition temperature Tp1. Since the layer and the reproduction layer can be strongly magnetostatically coupled, the reproduction margin can be expanded.
[0030]
  In addition to the above configuration, the magneto-optical recording medium according to the present invention has a difference between the maximum value and the minimum value of the Curie temperature of 80 ° C. or less in the plurality of in-plane magnetization layers forming the in-plane magnetization portion. It is characterized by.
[0031]
  According to the above configuration, it is possible to provide a magneto-optical recording medium that is small in crosstalk and can be reproduced with good reproduction signal quality.
[0032]
  In the magneto-optical recording medium according to the present invention, in addition to the above configuration, at least one in-plane magnetic layer is provided between the reproducing layer and the recording layer, and between the reproducing layer and the recording layer. The total film thickness of the in-plane magnetic layers provided in is in the range of 2 nm to 60 nm.
[0033]
  In the magneto-optical recording medium according to the present invention, in addition to the above configuration, the in-plane magnetization layer is provided at least one layer on the opposite side of the recording layer with the reproducing layer interposed therebetween, and recording is performed with the reproducing layer interposed therebetween. The total thickness of the in-plane magnetic layers provided on the side opposite to the layer is in the range of 2 nm to 10 nm.
[0034]
  According to any of the above configurations, at a temperature lower than the transition temperature Tp1, the mask by in-plane magnetization is emphasized, and the in-plane magnetization state of the reproducing layer is more reliably maintained, and the transition temperature Tp1 or higher is maintained. At this temperature, the reproducing layer can be more reliably transferred to the perpendicular magnetization state.
[0035]
  When only one in-plane magnetic layer is formed, the “total film thickness of in-plane magnetic layers” refers to the film thickness of one in-plane magnetic layer itself.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
  [Embodiment 1]
  An embodiment of the present invention will be described below with reference to the drawings. First, the reproduction principle of the magneto-optical recording medium 11 according to the present embodiment will be described with reference to FIG. This figure is a schematic sectional view for explaining the magnetization state during reproduction of the magneto-optical recording medium 11.
[0037]
  As shown in FIG. 1, a magneto-optical recording medium 11 according to the present embodiment includes a reproducing layer 1, an in-plane magnetic layer 2, a nonmagnetic intermediate layer (intermediate layer) 3, and a recording layer 4 that are sequentially stacked. It is configured. In addition, as for each arrow in FIG. 1, the black arrow represents the direction of the magnetic moment (hereinafter, simply referred to as TM moment) of the transition metal element, and the white arrow represents the direction of the leakage magnetic flux. Further, hereinafter, simply referring to the transition metal (element), “3d transition metal (element)”, that is, the 3d electron shell among the main transition elements satisfying the d (electron) shell is satisfied.^{twenty one}Sc ~²⁹It refers only to Cu and is distinguished from rare earth metal elements (in some cases, simply called rare earth or rare earth metal).
[0038]
  The reproducing layer 1 is made of a rare earth / transition metal alloy material that is in an in-plane magnetization state at room temperature and transitions to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1. The “room temperature” refers to a temperature between 5 ° C. and 35 ° C. as generally defined.
[0039]
  More specifically, the in-plane magnetic layer 2 includes at least one kind of rare earth metal element selected from Ho, Er, and Tm and at least one kind of 3d transition metal. An in-plane magnetization film having magnetization in a direction parallel (horizontal) to the surface. The in-plane magnetic layer 2 is configured so that, for example, the vicinity of the transition temperature Tp1 at which the reproducing layer 1 shifts (transitions) to the perpendicular magnetization state is the Curie temperature Tc2. The nonmagnetic intermediate layer 3 is made of a nonmagnetic material and is formed between the in-plane magnetic layer 2 and the recording layer 4 to block exchange coupling between the two (in-plane magnetic layer 2 and recording layer 4). . The recording layer 4 is made of a rare earth / transition metal alloy material, and is a perpendicular magnetization film on which information is magneto-optically recorded.
[0040]
  In such a magneto-optical recording medium 11, since the reproducing layer 1 and the in-plane magnetic layer 2 are adjacent to each other, at a temperature lower than the transition temperature Tp1, the in-plane magnetization of the in-plane magnetic layer 2 and the reproducing layer 1 Exchange coupling with in-plane magnetization. That is, the magnetization of the reproducing layer 1 remains in the in-plane direction.
[0041]
  On the other hand, at the time of reproduction, the light beam 5 is focused and irradiated on the magneto-optical recording medium 11 from the reproduction layer 1 side so as to center on the recording magnetic domain (information) 6 of the recording layer 4 to be reproduced. In accordance with the temperature distribution of the magneto-optical recording medium generated by the concentrated irradiation of the light beam 5, the magnitude of magnetization only in the region facing the recording magnetic domain 6 in the in-plane magnetic layer 2 (the region indicated by the oblique lines in the figure). Decreases, and a leakage magnetic flux from the recording magnetic domain 6 is generated so as to penetrate the in-plane magnetic layer 2. Then, the leakage magnetic flux and the total magnetization of the reproducing layer 1 are magnetostatically coupled, whereby the magnetization information of the recording magnetic domain 6 is transferred to the region of the reproducing layer 1 in the perpendicular magnetization state. Is formed. At this time, the total magnetization direction of the magnetic domains 7 in the reproducing layer 1 is the same as the direction of the recording magnetic domains 6 in the recording layer 4. As described above, in the magneto-optical recording medium according to the present embodiment, only the region where the temperature is raised to the temperature equal to or higher than the transition temperature Tp1 among the regions of the reproducing layer 1 where the light beam 5 is condensed and irradiated is perpendicular. It becomes a magnetized state and contributes to reproduction, and a super-resolution reproduction operation is realized.
[0042]
  Here, the reproducing layer 1 is in the in-plane magnetization state at room temperature, and realizes a magnetic characteristic that the reproducing layer 1 shifts to a perpendicular magnetization state as the temperature rises (more specifically, at a temperature equal to or higher than the transition temperature Tp1). Therefore, for example, compared to a compensation composition in which the magnitude of the magnetic moment of the rare earth metal element (hereinafter sometimes referred to as the RE moment) and the magnitude of the TM moment are balanced, the RE rich composition contains more RE moments. Yes. Therefore, in the reproducing layer 1, the TM moment direction and the total magnetization direction are antiparallel.
[0043]
  On the other hand, it is desirable that the composition of the recording layer 4 is adjusted so that a large leakage magnetic flux is generated in a region where the temperature has risen. Therefore, the recording layer 4 has, for example, 1) a temperature near room temperature as its compensation temperature, and 2) a TM having a TM composition compared with a compensation composition in which the magnitude of the RE moment and the magnitude of the TM moment are balanced. A TM rich composition perpendicular magnetization film containing more moments is used. In this case, the TM moment direction of the recording layer 4 and the total magnetization direction are parallel to each other. When the recording layer 4 and the reproducing layer 1 are magnetostatically coupled, the magnetic domains are transferred so that the total magnetization of both layers is parallel. Therefore, the TM moment direction of the recording layer 4 and the TM moment direction of the reproducing layer 1 are antiparallel.
[0044]
  In addition, the in-plane magnetic layer 2 is more preferably a magnetic film having a TM rich composition containing more TM moment than a compensation composition in which the magnitude of the RE moment and the magnitude of the TM moment are balanced at room temperature. desirable. As a result, at a temperature lower than the transition temperature Tp1, the reproducing layer 1 having the RE rich composition and the in-plane magnetic layer 2 having the TM rich composition are affected by the leakage magnetic field generated from the recording layer 4, and the total magnetization thereof has the same direction. The magnetization direction is aligned so that For this reason, the rare earth metal sublattice moments of the reproducing layer 1 and the in-plane magnetic layer 2 and the transition metal sublattice moments of the reproducing layer 1 and the in-plane magnetic layer 2 are aligned in antiparallel. The domain wall energy at the interface with the in-plane magnetic layer 2 is increased. Therefore, the magnetization of the reproducing layer 1 is strongly attracted in the in-plane direction, and the in-plane magnetization state is stabilized. The in-plane magnetic layer 2 includes at least one rare earth metal element selected from Ho, Er, and Tm. The rare earth metal element that contributes to the formation of the RE moment is particularly the Ho, Er, It is not limited only to Tm.
[0045]
  Further, the in-plane magnetization layer 2 only needs to have a configuration in which the magnetization decreases at a temperature in the vicinity of the transition temperature Tp1 and the function of masking the leakage magnetic flux decreases, and the vicinity of the transition temperature Tp1 is set to the Curie temperature Tc2 as described above. In addition to the above, it may be one in which the magnitude of magnetization decreases as the temperature rises under a temperature condition near the transition temperature Tp1.
[0046]
  Next, a magneto-optical disk to which the magneto-optical recording medium 11 is applied will be described. As shown in FIG. 2, the magneto-optical disk has a transparent dielectric protective layer 9, a reproducing layer 1, an in-plane magnetic layer 2, a nonmagnetic intermediate layer 3, a recording layer 4, and a protective layer 10 on a substrate 8. They are stacked in this order. A laminated structure including the reproducing layer 1, the in-plane magnetic layer 2, the nonmagnetic intermediate layer 3, and the recording layer 4 corresponds to the magneto-optical recording medium 11.
[0047]
  In the magneto-optical disk, the Curie temperature recording method is used as the recording method. That is, the light beam 5 (see FIG. 1) emitted from the semiconductor laser as the light source is narrowed down to the reproducing layer 1 through the substrate 8 and the transparent dielectric protective layer 9, and the recording layer 4 is heated to the Curie temperature Tc4 or higher. . At the same time, an external magnetic field is applied to control the magnetization state of the recording layer 4 to perform magneto-optical recording of information on the magneto-optical recording medium 11.
[0048]
  The reproduction of the magneto-optical recording medium 11 uses the magneto-optical effect known as the polar Kerr effect by intensively irradiating the light beam 5 (see FIG. 1) set at a weaker power than that at the time of recording. Done. The polar Kerr effect is a phenomenon in which the direction of rotation of the polarization plane of reflected light is reversed due to the direction of magnetization perpendicular to the light incident surface.
[0049]
  The substrate 8 is made of a transparent base material such as polycarbonate and is formed in a disk shape, and a guide groove for guiding the light beam 5 is formed on the film forming surface. In this embodiment, the guide groove may be 1) only the land portion or a guide groove for recording only on the guide groove portion, and 2) the land portion and the guide groove portion. It may be a guide groove for recording on both sides.
[0050]
  The transparent dielectric protective layer 9 is, for example, AlN, SiN, AlSiN, Ta₂O_ThreeIt is desirable to use a transparent dielectric such as. The film thickness of the transparent dielectric protective layer 9 is set so as to achieve a good interference effect with respect to the incident light beam 5 and increase the polar Kerr rotation angle of the medium. That is, the thickness of the transparent dielectric protective layer 9 is set to about (λ / (4n)) based on the wavelength λ of the light beam 5 and the refractive index n of the transparent dielectric protective layer 9. Since the refractive index n of the transparent dielectric protective layer 9 is usually about 1.7 to 2.5, for example, when the wavelength λ of the light beam 5 is 680 nm, the film thickness is in the range of about 70 nm to 100 nm. What is necessary is just to set so that it may become inside.
[0051]
  The reproducing layer 1 is 1) in the in-plane magnetization state at room temperature, 2) transitions to the perpendicular magnetization state at a transition temperature Tp1 higher than room temperature, and 3) within the range of the transition temperature Tp1 to its Curie temperature Tc1. It is a magnetic film made of a rare earth / transition metal alloy material that is perpendicularly magnetized at temperature.
[0052]
  The Curie temperature Tc1 of the reproduction layer 1 is not particularly limited, but is preferably 160 ° C. or higher. When Tc1 <160 ° C., a decrease in Kerr rotation angle with a decrease in the Curie temperature Tc1 becomes significant, and the reproduction signal intensity decreases, and good reproduction characteristics cannot be obtained. Note that the higher the Curie temperature Tc1, the greater the total magnetization of the reproducing layer 1 near the transition temperature Tp1, so that stronger magnetostatic coupling between the recording layer 4 and the reproducing layer 1 can be realized. However, the upper limit of the Curie temperature Tc1 is Limited by the material used.
[0053]
  Further, the transition temperature Tp1 at which the reproducing layer 1 is in a perpendicular magnetization state is not particularly limited as long as it is lower than the Curie temperature Tc1, but it is more preferably within a range of 60 ° C. or higher and 250 ° C. or lower. When the transition temperature Tp1 is less than 60 ° C., it is difficult to stably maintain the in-plane magnetization state at room temperature. Further, it becomes susceptible to disturbances such as a leakage magnetic field from the optical pickup, and stable super-resolution reproduction cannot be performed. On the other hand, when the transition temperature Tp1 exceeds 250 ° C., the transition temperature Tp1 and the Curie temperature Tc4 of the recording layer 4 approach each other. As a result, the recording layer 4 is heated to a temperature equal to or higher than its Curie temperature Tc4 even by a slight fluctuation in reproduction power, so that recorded information is erased and a practical reproduction power margin cannot be obtained.
[0054]
  More preferably, the thickness of the reproducing layer 1 is set in the range of 10 nm to 80 nm. When the thickness of the reproducing layer 1 is less than 10 nm, the light beam is transmitted through the reproducing layer 1 and reflected by the in-plane magnetic layer 2. That is, the amount of light actually reflected from the reproduction layer 1 is reduced, the reproduction signal intensity is lowered, and the reproduction signal quality is deteriorated. Further, since the magnetostatic coupling between the leakage magnetic flux generated from the recording layer 4 and the reproducing layer 1 becomes weak, transfer of the recording magnetic domain from the recording layer 4 to the reproducing layer 1 cannot be realized stably. On the other hand, when the thickness of the reproducing layer 1 is greater than 80 nm, the recording sensitivity is significantly deteriorated due to the increase in the thickness.
[0055]
  Examples of the reproducing layer 1 that satisfies the magnetic characteristics described above include Gd · Fe (representing an alloy of Gd and Fe), Gd · Fe · Co, Gd · Dy · Fe · Co, Gd · Tb · Fe · Co. It is possible to employ a thin film of a rare earth / transition metal alloy material made of Gd, Nd, Fe, Co, or the like. Moreover, in order to improve the moisture resistance and oxidation resistance of the above materials, a metal element such as Ta, Cr, Ti, Al, Si, or the like may be added to these materials.
[0056]
  The in-plane magnetic layer 2 includes at least one kind of rare earth metal element selected from Ho, Er, Tm, and at least one kind of 3d transition metal element, and as described above, This is an in-plane magnetization film composed of a magnetic film whose magnetization decreases at a temperature near the transition temperature Tp1 (temperature at which the reproducing layer 1 shifts to the perpendicular magnetization state). The in-plane magnetic layer 2 includes other rare earth elements such as Gd, Dy, Tb, Pr, Nd, Pm, Sm, in addition to at least one rare earth metal element selected from Ho, Er, Tm. Metal elements can also be included.
[0057]
  The nonmagnetic intermediate layer 3 is a nonmagnetic film formed to block exchange coupling between the in-plane magnetic layer 2 and the recording layer 4. As the nonmagnetic intermediate layer 3, a nonmagnetic metal such as Al, Ta, Ti, Au, or Cu; Si; a nonmagnetic metal composite containing two or more of these nonmagnetic metals or Si; Is possible. It is also possible to use a nonmagnetic dielectric such as AlN, SiN, AlSiN.
[0058]
  The film thickness of the nonmagnetic intermediate layer 3 is more preferably set to 0.5 nm or more. If the thickness of the nonmagnetic intermediate layer 3 is less than 0.5 nm, it may be difficult to form the nonmagnetic intermediate layer 3 uniformly, and the exchange coupling between the in-plane magnetic layer 2 and the recording layer 4 is blocked. There is a risk that it will not be possible.
[0059]
  Furthermore, it is more desirable that the total thickness of the in-plane magnetic layer 2 and the nonmagnetic intermediate layer 3 is set to 60 nm or less. If the total thickness of these layers is larger than 60 nm, that is, if the distance between the recording layer 4 and the reproducing layer 1 becomes too large, the magnetostatic coupling force between the recording layer 4 and the reproducing layer 1 becomes weak. As a result, stable transfer of magnetic domains from the recording layer 4 to the reproducing layer 1 becomes difficult, and the quality of the reproduced signal may be deteriorated.
[0060]
  The recording layer 4 is a perpendicular magnetization film made of a rare earth / transition metal alloy (alloy containing at least a rare earth metal element and a transition metal element), and its compensation temperature Tcomp4 is set to −70 ° C. or more and 80 ° C. or less. It is more desirable. When Tcomp4 <−70 ° C., the recording layer 4 has a relatively large magnetization even before reaching the transition temperature Tp1 at which the reproducing layer 1 transitions to the perpendicular magnetization state. There is a possibility that a leakage magnetic field is applied. As a result, under the influence of this leakage magnetic field, the reproducing layer 1 attempts to transition in the perpendicular magnetization direction before reaching the transition temperature Tp1, which causes noise and degrades the reproduced signal quality. When Tcomp4> 80 ° C., the magnetization of the recording layer 4 is small even when the reproducing layer 1 reaches the transition temperature Tp1 and the magnetostatic coupling between the recording layer 4 and the reproducing layer 1 is weak. There is a fear. As a result, at a temperature in the vicinity of the transition temperature Tp1, the transfer of the recording magnetic domain from the recording layer 4 to the reproducing layer 1 becomes unstable, and the reproduction signal quality may be deteriorated.
[0061]
  The Curie temperature Tc4 of the recording layer 4 is set to be higher than at least the transition temperature Tp1 at which the reproducing layer 1 is in the perpendicular magnetization state. In addition, the Curie temperature Tc4 is more preferably in the range of 180 ° C. or higher and 300 ° C. or lower.
[0062]
  If Tc4 <180 ° C., the Curie temperature Tc4 may be too low in some cases. That is, at the time of reproducing the magneto-optical recording medium 11, more specifically, when the reproducing layer 1 is heated to the transition temperature Tp1 or more to transfer the recording magnetic domain 6 to the reproducing layer 1, the recording layer is not affected by a slight temperature rise. 4 may be raised to a temperature above the Curie temperature Tc4. As a result, there may be a problem that recorded information is erased. That is, the reproduction power margin is narrowed. Furthermore, as the Curie temperature Tc4 of the recording layer 4 decreases, the leakage magnetic flux generated from the recording layer 4 decreases, so that it becomes difficult to maintain a stable magnetostatic coupling state between the reproducing layer 1 and the recording layer 4. The reproduction signal quality deteriorates.
[0063]
  When Tc4> 300 ° C., it is necessary to heat the recording layer 4 to a temperature exceeding 300 ° C. in order to perform recording. As a result, the deterioration of recording sensitivity becomes remarkable. In addition, since the reproducing layer 1, the in-plane magnetic layer 2, and the recording layer 4 are heated to 300 ° C. or more during recording, the reproduction signal quality is deteriorated due to recording erasure as well as the magnetic characteristics of each magnetic layer. May occur.
[0064]
  The film thickness of the recording layer 4 is more preferably set within a range of 30 nm to 120 nm. When the film thickness of the recording layer 4 is less than 30 nm, the leakage magnetic flux generated from the recording layer 4 becomes small. As a result, it is difficult to maintain a stable magnetostatic coupling state between the reproduction layer 1 and the recording layer 4, and there is a possibility that the reproduction signal quality is deteriorated. Further, when the thickness of the recording layer 4 is larger than 120 nm, there is a possibility that the recording sensitivity is significantly deteriorated due to the increase in the thickness.
[0065]
  Examples of the recording layer 4 that satisfies the above magnetic characteristics include Tb / Fe, Tb / Fe / Co, Dy / Fe, Dy / Fe / Co, Tb / Dy / Fe, Tb / Dy / Fe / Co, and the like. It is possible to employ a perpendicular magnetization film made of a material. Further, in order to improve the moisture resistance and oxidation resistance of the materials, a metal element such as Ta, Cr, Ti, Al or Si may be added to these materials.
[0066]
  The protective layer 10 is made of AlN, SiN, AlSiN, Ta₂O_ThreeOr a non-magnetic metal alloy material containing at least one kind of non-magnetic metal such as Al, Ti, Ta, Ni, etc., and the reproducing layer 1, the in-plane magnetic layer 2, and the recording It is formed for the purpose of preventing oxidation of an alloy material (usually a rare earth / transition metal alloy material) used for the layer 4. The film thickness of the protective layer 10 is more preferably set in the range of 5 nm to 60 nm.
[0067]
  Further, although not shown, a heat diffusion metal layer made of Al, Al.Ta, Al.Ti, Al.Cr, Al.Ni, Al.Co, Cu, Ag, or the like can be added on the protective layer 10. As a result, the thermal characteristics of the magneto-optical recording medium 11 can be improved. In addition, an ultraviolet curable resin layer, a thermosetting resin layer, a lubrication layer, or the like can be formed on the protective layer 10 or the heat diffusion metal layer.
[0068]
  For the purpose of low magnetic field recording, a perpendicular magnetization film having a coercive force smaller than the coercive force of the recording layer 4 and having a Curie temperature higher than the Curie temperature Tc4 of the recording layer 4, such as Gd.Fe.Co. , Gd · Tb · Fe · Co, Gd · Dy · Fe · Co, etc. may be laminated so as to be adjacent to the recording layer 4.
[0069]
  Next, a specific example of a method for forming and recording / reproducing a magneto-optical disk having the above configuration will be described.
[0070]
  (1) Method for forming magneto-optical disk
  The method for forming the magneto-optical disk shown in FIG. 2 is as follows. Here, a method of forming a magneto-optical disk using Ho · Fe · Co as the in-plane magnetic layer 2 will be described.
[0071]
  As a first step, a land portion and a guide groove portion are formed in a sputtering apparatus including an AlSi target, a Gd · Fe · Co alloy target, a Ho · Fe · Co alloy target, and a Tb · Fe · Co alloy target. A polycarbonate substrate 8 having a guide groove for recording on both and formed in a disk shape is disposed. The inside of the sputtering apparatus is 1 × 10^-6Torr (approximately 1.33 × 10^-FourPa), and then a mixed gas of argon and nitrogen is introduced into the sputtering apparatus. Subsequently, a gas pressure of 4 × 10 is introduced.^-3Electric power is supplied to the AlSi target under the condition of Torr (about 0.532 Pa), and the transparent dielectric protective layer 9 made of AlSiN is formed on the substrate 8 with a film thickness of 80 nm.
[0072]
  As the second step, the inside of the sputtering apparatus is again 1 × 10^-6Torr (approximately 1.33 × 10^-FourPa) to a vacuum pump, and then argon gas is introduced into the sputtering apparatus, followed by a gas pressure of 4 × 10^-3Electric power is supplied to the Gd · Fe · Co alloy target under the condition of Torr (about 0.532 Pa), and the Gd · Fe · Co alloy target is coated with Gd_0.31(Fe_0.78Co_0.22)_0.69The reproduction layer 1 having the composition is formed with a film thickness of 25 nm. Gd_0.31(Fe_0.78Co_0.22)_0.69That is, an FeCo alloy containing Fe and Co in a weight ratio of 0.78: 0.22 and a Gd · Fe · Co alloy containing Gd in a weight ratio of 0.69: 0.31. Refers to material. Further, the formed reproduction layer 1 was in an in-plane magnetization state at room temperature and transitioned to a perpendicular magnetization state at 160 ° C. (corresponding to the transition temperature Tp1), and its Curie temperature Tc1 was 300 ° C.
[0073]
  Subsequently, as a third step, power is supplied to the Ho · Fe · Co alloy target, and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), Ho is formed on the reproduction layer 1._0.13(Fe_0.88Co_0.12)_0.87The in-plane magnetic layer 2 having the composition is formed with a film thickness of 20 nm. The formed in-plane magnetization layer 2 was an in-plane magnetization film having a Curie temperature Tc2 of 160 ° C. and having magnetization in the film plane from room temperature to the Curie temperature Tc2.
[0074]
  Subsequently, as a fourth step, power is supplied to the AlSi target, and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), the nonmagnetic intermediate layer 3 made of AlSi is formed on the in-plane magnetic layer 2 with a film thickness of 2 nm.
[0075]
  Subsequently, as a fifth step, power is supplied to the Tb / Fe / Co alloy target, and the gas pressure is 4 × 10.^-3On the nonmagnetic intermediate layer 3 under the condition of Torr (about 0.532 Pa), Tb_0.25(Fe_0.84Co_0.16)_0.75The recording layer 4 having the composition is formed with a film thickness of 60 nm. The formed recording layer 4 has a compensation temperature of 25 ° C. and a Curie temperature Tc 4 of 270 ° C., and is always magnetized in a direction perpendicular to the film surface within a temperature range from room temperature to the Curie temperature Tc 4. It was a perpendicular magnetization film having
[0076]
  As a sixth step, a mixed gas of argon and nitrogen is introduced into the sputtering apparatus, power is supplied to the AlSi target, and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), the protective layer 10 made of AlSiN is formed on the recording layer 4 with a film thickness of 20 nm.
[0077]
  Here, with reference to FIG. 3, the Ho · Fe · Co material used as the in-plane magnetic layer 2 in the present embodiment and the Gd used as the in-plane magnetic layer 202 in the prior art (see FIG. 13). -The composition dependence of the magnetization direction of Fe material is demonstrated.
[0078]
  FIG. 3 shows Gd_XFe_(1-X)And Ho_x(Fe_0.88Co_0.12)_(1-X)Value of the remanent magnetization (Mr) in the direction perpendicular to the film surface at room temperature, normalized remanent magnetization (Mr / Ms) normalized by the saturation magnetization value (Ms), and the rare earth occupying in each material It is the graph which showed the relationship with the ratio (X) of a metal element. Since the Curie temperature of Ho is lower than that of Gd, the content of Fe and Co is adjusted so that the Curie temperature of Gd · Fe and the Curie temperature of Ho · Fe · Co are equal when X = 0.13. did. Specifically, a part of Fe in the Ho · Fe material was replaced with Co, and the proportion of Co in the 3d transition metal component (that is, Fe and Co) was 12%. Gd when X = 0.13_XFe_(1-X)And Ho_x(Fe_0.88Co_0.12)_(1-X)In either case, the Curie temperature was 160 ° C.
[0079]
  First, Gd_XFe_(1-X)As for X, the value of normalized remanent magnetization is extremely small when the X is 0.15 or less, indicating that the film is an in-plane magnetization film having an easy axis of magnetization in the film surface direction. However, when the composition of X is 0.16 or more, the value of normalized remanent magnetization increases rapidly as X increases and changes to a perpendicular magnetization film having an easy axis in the direction perpendicular to the film surface. You can see that In contrast, Ho_x(Fe_0.88Co_0.12)_(1-X)Is an in-plane magnetization film having an extremely small value of normalized remanent magnetization and having an easy axis in the film surface direction when X is 0.20 or less. When the content of Ho is further increased (that is, when the value of X is increased beyond 0.20), the value of the normalized remanent magnetization increases rapidly and is perpendicular to the film surface. It turns out that it changes to the perpendicular magnetization film | membrane which has a magnetization easy axis.
[0080]
  As compared with Gd · Fe, Ho · Fe · Co is a material that can realize a more stable in-plane magnetization state. In particular, in the in-plane magnetization layer 2 that functions as a mask layer for leakage magnetic flux. It shows that it is a suitable material. Further, in the case of Gd · Fe having a TM rich composition showing in-plane magnetization as shown in FIG. 3, the Curie temperature rises as the Gd content increases, whereas in the case of Ho · Fe · Co, the Curie temperature However, the Curie temperature increases as the Ho content decreases.
[0081]
  Therefore, in the magneto-optical recording medium in which the transition temperature Tp1 of the reproducing layer 1 is set to be relatively high in order to prevent the influence of disturbance such as a leakage magnetic field from the pickup, the Curie temperature Tc2 of the in-plane magnetization layer 2 is set to the transition temperature Tp1. In order to set in the vicinity, when Gd · Fe is used as the in-plane magnetic layer as in the prior art, it is necessary to increase the Gd content and raise its Curie temperature. However, if the Gd content is increased (that is, if X is increased in FIG. 3), the stability of the in-plane magnetization state is significantly reduced, the in-plane magnetization mask becomes weak, and the crosstalk increases. Incurs quality degradation. On the other hand, when Ho · Fe · Co is used for the in-plane magnetic layer 2 as in the present embodiment, the Curie temperature Tc2 is raised if Ho is reduced (that is, if X is reduced in FIG. 3). In addition, the in-plane magnetization state can be further stabilized.
[0082]
  In this way, if Ho · Fe · Co is used as the in-plane magnetization layer 2, it is possible to easily realize an increase in the Curie temperature Tc 2 and stabilization of the in-plane magnetization state. It is possible to manufacture the magneto-optical recording medium 11 in which the influence of the leakage magnetic field is reduced. Thereby, the in-plane magnetization mask effect at a temperature lower than the transition temperature Tp1 of the reproducing layer 1 is enhanced, the reproducing resolution is improved, and the crosstalk is reduced.
[0083]
  (2) Crosstalk characteristics
  The crosstalk characteristics of the magneto-optical disk described above (referred to as sample # 1) are as follows. Specifically, the results of evaluating the crosstalk in the magneto-optical disk using a magneto-optical pickup using a semiconductor laser having a wavelength of 680 nm under the condition of a linear velocity of 2.5 m / s will be described.
[0084]
  First, a crosstalk measurement method will be described with reference to FIGS. 4 (a) and 4 (b). In measurement, the measurement track 11 (in FIG. 4A, the land portion of the recording layer 4 of the magneto-optical disk having guide grooves for recording on both the land portion and the guide groove portion indicates the guide groove portion. And the adjacent tracks 12 and 12 'on both sides of the measurement track 11 (refer to the guide groove portion in FIG. 4 (a), but may be a land portion). While continuously irradiating at 4.0 mW, an erasing magnetic field of −40 kA / m is applied to align the magnetization of the recording layer 4 in one direction.
[0085]
  Then, the recording magnetic field is modulated at ± 15 kA / m while continuously irradiating the recording / reproducing laser at 5.8 mW onto the measurement track 11, so that upward magnetization and downward magnetization corresponding to the direction of the recording magnetic field are applied to the recording layer 4. Are recorded with a mark length of 0.3 μm (FIG. 4A). Here, the mark length of 0.3 μm means that each recording magnetic domain 6a is formed with a length (diameter) of 0.3 μm. The interval (pitch) between the recording magnetic domains 6a and 6a is set to twice the mark length (that is, 0.6 μm). Then, the recording / reproducing laser is continuously irradiated onto the measurement track 11 at 2.0 mW, and the carrier level (referred to as C11) is measured.
[0086]
  Next, an erasing magnetic field of −40 kA / m was applied to the measurement track 11 while irradiating the recording laser at 4.0 mW, and the magnetization of the recording layer 4 was aligned in one direction again. Then, the recording magnetic field is modulated at ± 15 kA / m while continuously irradiating the recording / reproducing laser at 5.8 mW to the adjacent tracks 12 and 12 ', so that the upward magnetization corresponding to the direction of the recording magnetic field is applied to the recording layer 4. And a repetitive pattern of downward magnetization are recorded with a mark length of 0.3 μm (FIG. 4B). Here, the interval between the recording magnetic domains 6b and 6b is set to 0.6 μm. Then, the recording / reproducing laser is continuously irradiated onto the measurement track 11 at 2.0 mW, and the carrier level (referred to as C12) is measured. The difference between C12 and C11 (value of C12−C11) measured by the above method was defined as crosstalk.
[0087]
  FIG. 5 is a graph showing the track pitch dependence of the crosstalk of sample # 1 measured by the above method. Here, the track pitch refers to the distance between the center position in the width direction of the measurement track 11 shown in FIGS. 4A and 4B and the center position in the width direction of the adjacent tracks 12 and 12 ′. The width of the land portion and the width of the guide groove portion are the same and are the same as the track pitch.
[0088]
  For comparison, FIG. 5 also shows crosstalk fluctuation values of a conventional magneto-optical disk (comparative sample # r1) using Gd · Fe as the material of the in-plane magnetic layer. As shown in FIG. 14, the comparative sample # r1 includes a polycarbonate substrate 208; a transparent dielectric protective layer 209 made of AlSiN having a thickness of 80 nm; Gd_0.31(Fe_0.78Co_0.22)_0.69Reproduction layer 201 having the composition: Gd with a thickness of 20 nm_0.13Fe_0.87In-plane magnetic layer 202 made of; nonmagnetic intermediate layer 203 made of AlSi with a thickness of 2 nm; Tb with a thickness of 60 nm_0.25(Fe_0.84Co_0.16)_0.75And a protective layer 210 made of AlSiN having a film thickness of 20 nm. Note that also in the comparative sample # r1, the transition temperature Tp at which the reproducing layer 201 is in the perpendicular magnetization state₂₀₁And the Curie temperature Tc of the in-plane magnetic layer 202₂₀₂Both were 160 degreeC.
[0089]
  The recording layer 204 of the comparative sample # r1 was provided with the same land portion and guide groove portion as those of the sample # 1. The crosstalk measurement of the comparative sample # r1 was performed by the same measurement method as the sample # 1 with the recording laser power set to 5.8 mW and the reproduction laser power set to 2.0 mW. In FIG. 5, the land portion is a measurement track (corresponding to the measurement track 11 in FIG. 4A) and the guide groove portion is an adjacent track (corresponding to the adjacent tracks 12 and 12 ′ in FIG. 4A). Only the crosstalk measurement results are shown.
[0090]
  Comparing sample # 1 and comparative sample # r1, it can be seen that the crosstalk of sample # 1 is low at any track pitch, and the difference is particularly noticeable at a track pitch of 0.6 μm or less. . This is because, in sample # 1, by using Ho · Fe · Co as the in-plane magnetization layer 2, the in-plane magnetization state is stabilized and the in-plane magnetization mask is strengthened. This is because the transition from the state to the perpendicular magnetization state occurs more abruptly (steeply) than the comparative sample # r1, thereby improving the reproduction resolution.
[0091]
  Thus, it can be seen that sample # 1 according to the present embodiment is a magneto-optical disk having better reproduction signal quality and recording / reproduction sensitivity than conventional comparative sample # r1 at any track pitch. . Further, as shown in FIG. 5, it can be seen that the magneto-optical disk is suitable for high-density recording since the increase in crosstalk under a narrow track pitch condition is small as compared with the comparative sample # r1.
[0092]
  Further, as a material of the in-plane magnetic layer 2, Ho_0.13(Fe_0.88Co_0.12)_0.87Instead of Er_0.13(Fe_0.85Co_0.15)_0.87Or Tm_0.13(Fe_0.82Co_0.18)_0.87For the two types of samples (magneto-optical disks including the magneto-optical recording medium according to the present invention) having the same configuration as the above-described sample # 1 except that is used, the same measurement method as that of the sample # 1 is used. Crosstalk was measured. Er_0.13(Fe_0.85Co_0.15)_0.87And Tm_0.13(Fe_0.82Co_0.18)_0.87In any of these cases, the Curie temperature Tc2 was 160 ° C., and the in-plane magnetization film had magnetization in the film plane within the temperature range from room temperature to the Curie temperature Tc2.
[0093]
  FIG. 11 shows Ho as a material of the in-plane magnetic layer 2._0.13(Fe_0.88Co_0.12)_0.87Instead of Er_0.13(Fe_0.85Co_0.15)_0.87# 1 (a) using Tm, Tm_0.13(Fe_0.82Co_0.18)_0.87Is a graph showing the track pitch dependence of the crosstalk of sample # 1 (b) using the above and the comparative sample # r1. As is clear from the figure, the crosstalk was smaller in both sample # 1 (a) and sample # 1 (b) than in comparative sample # r1. That is, it was confirmed that the reproduction signal quality was improved by stabilizing the in-plane magnetization state of the in-plane magnetization layer 2.
[0094]
  As described above, by using an in-plane magnetization film containing at least one kind of rare earth metal element selected from Ho, Er, and Tm and at least one kind of 3d transition metal element as the in-plane magnetization layer 2. Even when information recorded with a smaller bit diameter and narrower track pitch than in the prior art is reproduced, 1) a good reproduction signal can be obtained, and 2) the magneto-optical recording medium 11 with less occurrence of crosstalk is provided. It becomes possible.
[0095]
  (3) Relationship between the thickness of the in-plane magnetic layer and the crosstalk characteristics
  Next, Table 1 shows the result of measuring the crosstalk by the above-described measurement method with various changes in the thickness of the in-plane magnetic layer 2 in the configuration of the magneto-optical disk (sample # 1) used in this example. Here, the track pitch was 0.6 μm, the mark length was 0.3 μm, and the distance between the recording magnetic sections was 0.6 μm. The recording / reproducing laser irradiation intensity during recording and reproduction was set so that the carrier level C11 was maximized for each disk. In Table 1, the same disk as the sample # 1 has a disk No. 1 in which the in-plane magnetic layer 2 has a thickness of 20 nm. 14.
[0096]
[Table 1]

[0097]
  In Table 1, the comparative disk No. Reference numeral 10 denotes a comparative magneto-optical disk in which the in-plane magnetic layer 2 is not formed (film thickness = 0). As shown in Table 1, the comparative disk No. 10 does not have the in-plane magnetic layer 2, the in-plane magnetization mask at the transition temperature Tp 1 or lower of the reproducing layer 1 is weak, and the influence of the leakage magnetic field from the recording layer 4 is low even in a low temperature region that does not reach the transition temperature Tp 1. In response, the reproducing layer 1 attempts to transition to a perpendicular magnetization state. For this reason, the reproduction resolution is low and the crosstalk is large.
[0098]
  On the other hand, the disk No. 11 to disk No. 16, the magneto-optical disk including the magneto-optical recording medium according to the present invention, that is, the in-plane magnetic layer 2 has a thickness of 2, 4, 10, 20, 40 in order. In the 60 nm magneto-optical disk, the comparative disk No. It can be seen that the crosstalk is suppressed to be smaller than that of 10 and the in-plane magnetization mask is strengthened.
[0099]
  On the other hand, when the thickness of the in-plane magnetic layer 2 exceeds 60 nm, the in-plane magnetic layer 2 becomes too thick, so that the magnetostatic coupling between the recording layer 4 and the reproducing layer 1 becomes weak, and the recording magnetic domain 6 becomes the reproducing layer. 1 may not be accurately transferred. As a result, the carrier level C11 is lowered in some cases. For this reason, the film thickness of the in-plane magnetic layer 2 is more preferably 60 nm or less.
[0100]
  From the above, by setting the film thickness of the in-plane magnetic layer 2 within the range of 2 nm to 60 nm, the in-plane magnetization at a temperature in the vicinity of the transition temperature Tp1 at which the reproducing layer 1 transitions (transitions) to the perpendicular magnetization state. It can be seen that the in-plane magnetization state of the layer 2 can be more reliably stabilized.
[0101]
  In the present embodiment, a magneto-optical recording medium having a configuration in which the nonmagnetic intermediate layer 3 is formed between the in-plane magnetic layer 2 and the recording layer 4 has been described. However, the nonmagnetic intermediate layer 3 is not provided. Also in the magneto-optical recording medium having the configuration, by using an in-plane magnetization film including at least one rare earth metal element selected from Ho, Er, and Tm and at least one 3d transition metal element as the in-plane magnetization layer 2. It is possible to improve reproduction resolution and crosstalk. In this case, an interval (predetermined interval) corresponding to the layer thickness of the in-plane magnetic layer 2 is interposed between the reproducing layer 1 and the recording layer 4.
[0102]
  (4) Relationship between the composition of the in-plane magnetic layer and the crosstalk characteristics
  Next, in the configuration of the magneto-optical disk (sample # 1) used in this example, the composition of Ho.Fe.Co that is the material of the in-plane magnetic layer 2 is variously changed, and according to the method and measurement conditions described above. Crosstalk was measured.
[0103]
  More specifically, as shown in Table 2 below, the weight ratio of Fe and Co, which is a 3d transition metal component, is constant (0.88: 0.12), and the weight ratio of FeCo and Ho is various. The crosstalk was measured on the modified magneto-optical disk. The track pitch was 0.6 μm, the mark length was 0.3 μm, and the distance between the recording magnetic sections was 0.6 μm. Further, the recording / reproducing laser irradiation intensity at the time of recording and reproducing was set so that the carrier level C11 was maximized for each disk. In Table 2, the same disc as the sample # 1 is disc No. 24.
[0104]
[Table 2]

[0105]
  As shown in Table 2, the comparative disk No. In No. 21, since the ratio of Ho in Ho · Fe · Co as the in-plane magnetic layer 2 is as low as 5% by weight (mass), the Curie temperature is as extremely high as 250 ° C. For this reason, the in-plane magnetic anisotropy of the in-plane magnetic layer 2 is extremely large even at a temperature of 160 ° C. at which the reproducing layer 1 reaches the transition temperature Tp1, and the leakage flux of the recording layer 4 is maintained in a masked state. That is, the comparative disk No. 21 is different from the magneto-optical recording medium according to the present invention in that the magnetization of the in-plane magnetic layer 2 does not decrease at a temperature near the transition temperature Tp1. As a result, the transition of the reproducing layer 1 to the perpendicular magnetization state is hindered. As a result, sufficient reproduction signal intensity cannot be obtained, and the carrier level C11 is lowered, so that the value of crosstalk increases.
[0106]
  The comparative disk No. 21 is excellent in the masking effect of the leakage magnetic flux by the in-plane magnetic layer 2 as described above. Therefore, for example, as the reproduction layer 1, Gd_0.31(Fe_0.78Co_0.22)_0.69It is possible to use a magneto-optical disk having suitable characteristics by using one having a transition temperature Tp1 in the vicinity of 250 ° C. instead of the one having the above composition.
[0107]
  On the other hand, the disc No. No. 22 to disc no. In the magneto-optical disk represented by No. 26, that is, the magneto-optical disk in which the proportion of Ho in Ho, Fe, Co is 7, 10, 13, 17, 20% by weight (mass) in order, the above-mentioned comparative disk No. As can be seen from FIG. This is because the Curie temperature Tc2 (95 ° C. to 200 ° C.) of the in-plane magnetic layer 2 is in the vicinity of the transition temperature Tp1 (160 ° C.) of the reproducing layer 1, and the magnetic domain selective in-plane magnetization mask effect is enhanced. This is due to improved playback resolution.
[0108]
  The comparative disk No. In the magneto-optical disk represented by No. 27, the disk No. No. 22 to disc no. Compared to 26, crosstalk is increased. This is because the ratio of Ho is as high as 23% by weight. 1) The Curie temperature Tc2 (70 ° C.) of the in-plane magnetic layer 2 is lowered, and a sufficient in-plane mask effect is obtained in the vicinity of the transition temperature Tp1 (160 ° C.). And 2) the in-plane magnetization layer 2 is close to the compensation composition, so that the total magnetization is small and the in-plane magnetization state cannot be kept stable.
[0109]
  The comparative disk No. 27, for example, by using the reproducing layer 1 having a composition having a transition temperature Tp1 of around 70 ° C. and using a transition metal material having a TM moment larger than that of FeCo in the in-plane magnetic layer 2, etc. It can also be used as a magneto-optical disk having suitable characteristics.
[0110]
  Table 3 shows the disk No. that showed the smallest crosstalk among the measurement results shown in Table 2 above. In the configuration of 24 (sample # 1), the ratio of Fe to Co was varied while the weight ratio of Ho to FeCo (3d transition metal component) in the in-plane magnetic layer 2 was fixed at 13.0: 87.0. It is a table | surface which shows the measurement result of the magneto-optical disks (No. 31-No. 37) produced by changing. In Table 3, the same disk as the sample # 1 has a disk No. 34.
[0111]
[Table 3]

[0112]
  As shown in Table 3, the disk No. 31 to disk no. The ratio of Co to the total weight of Fe and Co, which are the 3d transition metal components, is 0, 5, 8, 12, 16, and 19% by weight in order, It can be seen that the crosstalk is suppressed to -25 dB or less in the magneto-optical disk. This is because 1) the addition of Ho stabilizes the in-plane magnetization state of the in-plane magnetic layer 2 and improves the reproducibility, and 2) Co also functions as an adjustment material that raises the Curie temperature. This is because the content is within a preferable range.
[0113]
  In contrast, the comparative disk No. 1 in which the proportion of Co in the total weight of the 3d transition metal component is 23% by weight At 37, crosstalk increases. This is because the Curie temperature Tc2 of the in-plane magnetic layer 2 is increased (220 ° C.) because the weight ratio of Co in the transition metal component is too high, and the transition from the in-plane magnetization state of the reproducing layer 1 to the perpendicular magnetization state is performed. Because it was hindered. As a result, the carrier level C11 decreases and the crosstalk value increases. The comparative disk No. In the configuration of 37, for example, a reproducing layer 1 having a composition having a transition temperature Tp1 of around 220 ° C. can be used as a magneto-optical disk having suitable characteristics.
[0114]
  From the results shown in Table 2 and Table 3 above, when Ho, Fe, Co is used as the material of the in-plane magnetic layer 2, the proportion of Ho is within the range of 7 wt (mass)% to 20 wt%. In addition, by designing the ratio of Co in the total weight of the transition metal component to be in the range of 0% by weight to 19% by weight, a magneto-optical disk with low crosstalk and good reproduction signal quality can be obtained. It can be seen that it can be provided.
[0115]
  [Embodiment 2]
  Other embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited thereby. For convenience of explanation, members having the same functions and structures as those shown in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0116]
  In the present embodiment, a magneto-optical disk to which a magneto-optical recording medium is applied will be described as an example.
[0117]
  FIG. 12 is a cross-sectional view showing a schematic configuration of a magneto-optical disk including the magneto-optical recording medium 11a. As shown in the figure, the magneto-optical disk according to the present embodiment includes a transparent dielectric protective layer 9, an in-plane magnetic layer 2, a reproducing layer 1, a nonmagnetic intermediate layer 3, a recording layer 4, on a substrate 8. The protective layer 10 is laminated in this order. A laminated structure including the in-plane magnetic layer 2, the reproducing layer 1, the nonmagnetic intermediate layer 3, and the recording layer 4 corresponds to the magneto-optical recording medium 11a.
[0118]
  That is, the magneto-optical recording medium 11a has a configuration in which the in-plane magnetic layer 2 is provided on the opposite side of the recording layer 4 with the reproducing layer 1 interposed therebetween, in other words, reproduction of the magneto-optical recording medium 11a. The in-plane magnetic layer 2 and the reproducing layer 1 are formed in this order with reference to the incident side of the light beam to be performed.
[0119]
  The film thickness of the nonmagnetic intermediate layer 3 is not particularly limited, but is preferably set in the range of 0.5 nm or more and 60 nm or less. When the thickness is less than 0.5 nm, it is difficult to form the nonmagnetic intermediate layer 3 uniformly, and there is a possibility that undesired exchange coupling between the reproducing layer 1 and the recording layer 4 cannot be cut off. On the other hand, when the film thickness exceeds 60 nm, the distance between the recording layer 4 and the nonmagnetic intermediate layer 3 becomes too large, and the magnetostatic coupling force between the two becomes weak. As a result, stable transfer of the recording magnetic domain 6 from the recording layer 4 to the reproduction layer 1 becomes difficult, and there is a possibility that the reproduction signal quality may be deteriorated.
[0120]
  Next, a method for forming the magneto-optical disk and a method for measuring crosstalk will be described.
[0121]
  (1) Method for forming magneto-optical disk
  The magneto-optical disk according to the present embodiment can be formed, for example, by reversing the formation order of the reproducing layer 1 and the in-plane magnetic layer 2 in the magneto-optical disk forming method described in the first embodiment. It is. In the present embodiment, the substrate 8, the transparent dielectric protective layer 9, the in-plane magnetic layer 2, the reproducing layer 1, the nonmagnetic intermediate layer 3, the recording layer 4, and the protective layer are processed in the same manner as in the first embodiment. A magneto-optical disk consisting of 10 was formed.
[0122]
  (2) Crosstalk characteristics
  Table 4 shows the results of measuring crosstalk according to the same method and measurement conditions as those of the first embodiment with various changes in the thickness of the in-plane magnetic layer 2 in the configuration of the magneto-optical disk shown in FIG. Here, the track pitch was 0.6 μm, the mark length was 0.3 μm, and the distance between the recording magnetic sections was 0.6 μm. The recording / reproducing laser irradiation intensity during recording and reproduction was set so that the carrier level C11 was maximized for each disk.
[0123]
[Table 4]

[0124]
  In Table 4, the comparative disk No. 40 is a comparative magneto-optical disk in which the in-plane magnetic layer 2 is not formed (film thickness = 0), and the comparative disk No. 40 shown in the first embodiment. 10 (see Table 1). The comparative disk No. Since 40 does not have the in-plane magnetic layer 2, the in-plane magnetization mask at a temperature lower than the transition temperature Tp1 of the reproducing layer 1 becomes weak, and the leakage magnetic field from the recording layer 4 is reduced even in a low temperature region that does not reach the transition temperature Tp1. Under the influence, the reproducing layer 1 attempts to transition to a perpendicular magnetization state. For this reason, as shown in Table 4, the reproduction resolution is low and the crosstalk is large.
[0125]
  On the other hand, the disk No. 41-No. In the five magneto-optical disks represented by 45, that is, the magneto-optical disks in which the in-plane magnetic layer 2 has thicknesses of 2, 4, 6, 8, and 10 nm in this order, the comparative disk No. Compared to 40, crosstalk is suppressed to a small value, and it can be seen that the in-plane magnetization mask is strengthened.
[0126]
  From the above, when the in-plane magnetic layer 2 is provided on the side opposite to the recording layer 4 with the reproducing layer 1 interposed therebetween, the in-plane magnetic layer 2 has a thickness of 2 nm to 10 nm. By being within the range, 1) the mask by in-plane magnetization is emphasized at a temperature lower than the transition temperature Tp1, and the in-plane magnetization state of the reproducing layer 1 is more reliably maintained, and 2) the transition temperature Tp1 At the above temperature, the reproducing layer 1 can be more surely shifted to the perpendicular magnetization state.
[0127]
  In the present embodiment, the magneto-optical recording medium 11a having the configuration in which the nonmagnetic intermediate layer 3 is formed between the reproducing layer 1 and the recording layer 4 is shown. However, the magnetization is performed at a temperature near the transition temperature Tp1. The in-plane magnetization film in which the magnetic field is reduced is formed in place of the nonmagnetic intermediate layer 3 or the in-plane magnetization film is formed between the reproduction layer 1 and the nonmagnetic intermediate layer 3 to improve the reproduction resolution. It is possible to improve the crosstalk. In either case, a predetermined interval is interposed between the reproducing layer 1 and the recording layer 4.
[0128]
  [Embodiment 3]
  Still another embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited thereby. For convenience of explanation, members having the same functions and structures as those shown in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0129]
  As shown in FIG. 6, the difference between the magneto-optical recording medium 11 ′ according to the present embodiment and the magneto-optical recording medium 11 according to the first embodiment (see FIG. 1) is the first in-plane magnetization. A second in-plane magnetic layer 13 having a Curie temperature higher than that of the first in-plane magnetic layer 2 ′ is formed between the layer 2 ′ and the nonmagnetic intermediate layer 3. The in-plane magnetized portion 22 is constituted by a laminated structure of 'and the second in-plane magnetized layer 13. The “first in-plane magnetic layer 2 ′” is a name for distinguishing from the second in-plane magnetic layer 13, and has substantially the same configuration as the in-plane magnetic layer 2 in the first embodiment. It is what you have.
[0130]
  First, the reproduction principle of the magneto-optical recording medium 11 'according to the present embodiment will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view for explaining the magnetization state during reproduction of the magneto-optical recording medium 11 '. As shown in the figure, the magneto-optical recording medium 11 ′ according to the present embodiment includes a reproducing layer 1, a first in-plane magnetization layer 2 ′, a second in-plane magnetization layer 13, a nonmagnetic intermediate layer 3, In addition, the recording layer 4 is sequentially laminated. In addition, as for each arrow in FIG. 6, the black arrow represents the direction of the magnetic moment (TM moment) of the 3d transition metal element, and the white arrow represents the direction of the leakage magnetic flux. Further, hereinafter, simply referring to the transition metal (element), “3d transition metal (element)”, that is, the 3d electron shell among the main transition elements satisfying the d (electron) shell is satisfied.^{twenty one}Sc ~²⁹It refers only to Cu and is distinguished from rare earth metals (in some cases, simply called rare earths).
[0131]
  The first in-plane magnetization layer 2 ′ adjacent to the reproducing layer 1 has a TM moment compared to a compensation composition in which the magnitude of the magnetic moment (RE moment) of the rare earth metal element and the magnitude of the TM moment are balanced at room temperature. It consists of an in-plane magnetized film with a TM rich composition that contains more, and its Curie temperature Tc2 is set near the transition temperature Tp1 at which the reproducing layer 1 is in a perpendicular magnetization state. The second in-plane magnetized layer 13 is made of an in-plane magnetized film having a TM rich composition that contains more TM moment as compared with a compensation composition in which the magnitude of the RE moment and the magnitude of the TM moment are balanced at room temperature. At the same time, the Curie temperature Tc13 is set higher than the Curie temperature Tc2 of the first in-plane magnetic layer 2 ′.
[0132]
  In other words, the Curie temperatures of the plurality of in-plane magnetization layers forming the in-plane magnetization unit 22 decrease in order as they approach the reproduction layer, and the Curie temperature Tc2 of the in-plane magnetization layer adjacent to the reproduction layer changes as described above. The temperature is designed to be near the temperature Tp1.
[0133]
  Further, at least one of the first in-plane magnetic layer 2 ′ or the second in-plane magnetic layer 13 includes at least one kind of rare earth metal element selected from Ho, Er, and Tm and at least one kind of 3d. And a transition metal element. That is, in the present embodiment, since the first in-plane magnetic layer 2 ′ and the in-plane magnetic layer 2 (see FIG. 1) have the same configuration, the first in-plane magnetic layer 2 ′ includes At least one element selected from Ho, Er, and Tm and a 3d transition metal element are necessarily included, but in some cases, these elements are included only in the second in-plane magnetic layer 13. It may be.
[0134]
  As shown in FIG. 6, in the magneto-optical recording medium, the recording magnetic domain 6 formed in the recording layer 4 is transferred to the region of the reproducing layer 1 which is heated by the light beam 5 to be in the perpendicular magnetization state, A magnetic domain 7 is formed and regenerated. The principle of this reproduction is basically the same as in the first embodiment.
[0135]
  However, in the present embodiment, the second in-plane magnetic layer 2 ′ and the nonmagnetic intermediate layer 3 have a higher Curie temperature and a larger total magnetization than the first in-plane magnetic layer 2 ′. An in-plane magnetic layer 13 is formed. Therefore, the first in-plane magnetization layer 2 ′ and the second in-plane magnetization layer 13 are exchange-coupled at a temperature lower than the transition temperature Tp1 at which the reproducing layer 1 transitions to the perpendicular magnetization state, and the surface of the in-plane magnetization portion 22 The stability of the internal magnetization state is increased. As a result, even when the in-plane magnetized portion 22 is relatively thin, the in-plane magnetization state of the reproducing layer 1 can be stabilized at a temperature lower than the transition temperature Tp1, and at a temperature equal to or higher than the transition temperature Tp1. Since the recording layer 4 and the reproduction layer 1 can be strongly magnetostatically coupled, the reproduction margin can be expanded.
[0136]
  Next, a magneto-optical disk to which the magneto-optical recording medium 11 'is applied will be described. As shown in FIG. 7, the magneto-optical disk has a transparent dielectric protective layer 9, a reproducing layer 1, a first in-plane magnetic layer 2 ′, a second in-plane magnetic layer 13, and a nonmagnetic material on a substrate 8. The intermediate layer 3, the recording layer 4, and the protective layer 10 are laminated in this order. A laminated structure including the reproducing layer 1, the first in-plane magnetic layer 2 ′, the second in-plane magnetic layer 13, the nonmagnetic intermediate layer 3, and the recording layer 4 corresponds to the magneto-optical recording medium 11 ′. . The substrate 8, the transparent dielectric protective layer 9, the reproducing layer 1, the nonmagnetic intermediate layer 3, the recording layer 4, and the protective layer 10 can be formed by the same materials and methods as those of the first embodiment. Detailed description thereof will be omitted.
[0137]
  The second in-plane magnetization layer 13 is formed to increase the in-plane magnetic anisotropy of the first in-plane magnetization layer 2 'at a temperature lower than its Curie temperature Tc2. The second in-plane magnetic layer 13 is made of a rare earth / transition metal alloy material, a material made of only a rare earth metal (including an alloy of rare earth metals), a material made of only a transition metal (including an alloy of transition metals), or It is a magnetic film made of a material mainly composed of a transition metal, and is an in-plane magnetization film whose Curie temperature Tc13 is set higher than the Curie temperature Tc2 of the first in-plane magnetization layer 2 ′.
[0138]
  The film thickness of the second in-plane magnetic layer 13 is not particularly limited, but is more preferably set to 2 nm or more. When the thickness of the second in-plane magnetization layer 13 is less than 2 nm, the total magnetization of the second in-plane magnetization layer 13 is reduced, and the effect of strengthening the in-plane magnetization mask of the first in-plane magnetization layer 2 ′ is achieved. May not be obtained. Further, the total thickness of the first in-plane magnetization layer 2 ′ and the second in-plane magnetization layer 13, that is, the thickness of the in-plane magnetization portion 22 is more preferably 60 nm or less. When the total thickness of the first in-plane magnetic layer 2 ′ and the second in-plane magnetic layer 13 is greater than 60 nm, the distance between the recording layer 4 and the reproducing layer 1 becomes large, and the recording layer 4 and the reproducing layer 1 May be weakened. This makes it difficult to stably transfer the recording magnetic domain 6 from the recording layer 4 to the reproduction layer 1, and there is a possibility that the reproduction signal quality is deteriorated.
[0139]
  Next, specific examples of the magneto-optical disk forming method and recording / reproducing method having the second in-plane magnetic layer 13 will be described.
[0140]
  (1) Method for forming magneto-optical disk
  The method for forming the magneto-optical disk shown in FIG. 7 is as follows. Here, a method for forming a magneto-optical disk using a Ho.Fe.Co alloy material for both the first in-plane magnetic layer 2 'and the second in-plane magnetic layer 13 will be described.
[0141]
  As a first step, in a sputtering apparatus including an AlSi target, a Gd · Fe · Co alloy target, first and second Ho · Fe · Co alloy targets, and a Tb · Fe · Co alloy target, A polycarbonate substrate 8 having a guide groove for recording on both the part and the guide groove part and formed in a disk shape is disposed.
[0142]
  Then, a transparent dielectric protective layer 9 made of AlSiN is formed on the substrate 8 with a film thickness of 80 nm according to the same method as the magneto-optical disk (see FIG. 2) described in the first embodiment. Subsequently, on the transparent dielectric protective layer 9, Gd_0.31(Fe_0.78Co_0.22)_0.69The reproduction layer 1 having the composition is formed with a film thickness of 25 nm.
[0143]
  Subsequently, as the second step, power is supplied to the first Ho · Fe · Co alloy target, and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), Ho is formed on the reproduction layer 1._0.13(Fe_0.88Co_0.12)_0.87A first in-plane magnetic layer 2 ′ having the composition is formed with a thickness of 10 nm. Then, power is supplied to the second Ho · Fe · Co alloy target having a different content ratio of Fe and Co from the first Ho · Fe · Co alloy target, and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), the second in-plane magnetic layer 13 is formed with a film thickness of 10 nm on the first in-plane magnetic layer 2 ′.
[0144]
  The second in-plane magnetic layer 13 is the same as the first in-plane magnetic layer 2 ′ in that it contains 13 wt% Ho, but the content ratio of Fe and Co is different. Therefore, it has a Curie temperature Tc13 different from that of the first in-plane magnetic layer 2 '. Further, the second in-plane magnetic layer 13 has a TM moment as compared with a compensation composition in which the magnitude of the RE moment and the magnitude of the TM moment are balanced under a temperature condition within a range from room temperature to its Curie temperature Tc13. It was an in-plane magnetized film with a TM rich composition that contained more.
[0145]
  Subsequently, as a third step, power is supplied to the AlSi target and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), the nonmagnetic intermediate layer 3 made of AlSi is formed with a film thickness of 2 nm on the second in-plane magnetic layer 13.
[0146]
  Subsequently, as a fourth step, Tb is formed on the nonmagnetic intermediate layer 3 according to the same method as the magneto-optical disk according to the first embodiment (see FIG. 2)._0.25(Fe_0.84Co_0.16)_0.75The recording layer 4 having the composition is formed with a film thickness of 60 nm. Then, by forming the protective layer 10 made of AlSiN with a film thickness of 20 nm on the recording layer 4, the magneto-optical disk shown in FIG. 7 is manufactured.
[0147]
  (2) Crosstalk characteristics
  The recording / reproducing characteristics of the magneto-optical disk shown in FIG. 7 are as follows. Specifically, the results of evaluating the crosstalk in the magneto-optical disk using a magneto-optical pickup using a semiconductor laser having a wavelength of 680 nm under the condition of a linear velocity of 2.5 m / s will be described.
[0148]
  For the measurement of crosstalk, the same measurement method and measurement conditions as those shown in the first embodiment were used, and the crosstalk was measured when the track pitch was 0.6 μm and the mark length was 0.3 μm. Here, the track pitch refers to the distance between the center position in the width direction of the measurement track 11 shown in FIGS. 4A and 4B and the center position in the width direction of the adjacent tracks 12 and 12 ′. The land portion width and the guide groove portion width are equal and are the same as the track pitch. The mark length of 0.3 μm means that each recording magnetic domain 6a is formed with a length (diameter) of 0.3 μm, and the interval (pitch) between the recording magnetic domains 6a and 6a is twice the mark length. (That is, 0.6 μm).
[0149]
[Table 5]

[0150]
[Table 6]

[0151]
  Table 5 shows that the amount of Ho contained in the second in-plane magnetic layer 13 is fixed to 13.0% by weight and the amount of FeCo (3d transition metal component) is fixed to 87.0% by weight. Of the crosstalk at a track pitch of 0.6 μm in seven types of magneto-optical disks (disk Nos. 51 to 57) designed to show different Curie temperatures by changing the amount of Fe (or Co) in the disk. It is a measurement result.
[0152]
  In Table 6, for comparison, Ho used as the first in-plane magnetic layer 2 'in the configuration of the magneto-optical disk shown in FIG._0.13(Fe_0.88Co_0.12)_0.87Instead of Gd and Fe shown in the prior art, Ho_0.13(Fe_0.88Co_0.12)_0.87Gd having a Curie temperature (160 ° C.) equal to_0.13Fe_0.87In addition, in place of the second in-plane magnetic layer 13, seven types of comparative magneto-optical disks (comparative disk No. 61) using the second in-plane magnetic layer having the composition shown in Table 6 above are used. To 67), the measurement result of the track pitch at a track pitch of 0.6 μm is also shown. Here, the comparative disk No. The Curie temperatures of the second in-plane magnetization layers Nos. 61 to 67 are respectively the disk Nos. Shown in Table 5. It is designed to be equal to the Curie temperature of the second in-plane magnetization layer 13 of 51 to 57.
[0153]
  As shown in Table 5, a magneto-optical disk (disc No. 1) comprising an in-plane magnetized portion 22 having a thickness of 20 nm and composed of a first in-plane magnetized layer 2 ′ and a second in-plane magnetized layer 13. 51 to disc No. 57) have first and second in-plane magnetization layers that exhibit the same Curie temperature as the first in-plane magnetization layer 2 ′ and the second in-plane magnetization layer 13, respectively. Corresponding disc No. Compared with 61-67 (conventional magneto-optical disk), the value of crosstalk is low and it turns out that it has the outstanding characteristic.
[0154]
  In particular, disc no. No. 52 to disc no. In the five magneto-optical disks indicated by 56, that is, the Curie temperatures of the second in-plane magnetic layer 13 are 160 ° C., 175 ° C., 190 ° C., 220 ° C., 240 ° C. in this order, It can be seen that the crosstalk is suppressed to -32.0 dB or less.
[0155]
  As described in the first embodiment, the disk No. 1 in which the in-plane magnetized portion is formed by the in-plane magnetized layer 2 having a thickness of 20 nm alone. 14 (sample # 1), the crosstalk value was −32.0 dB (see Table 1). Therefore, the disc No. No. 52 to disc no. 56, the in-plane magnetization mask effect of the first in-plane magnetization layer 2 'having a layer thickness of 10 nm is enhanced by providing the second in-plane magnetization layer 13 having a layer thickness of 10 nm. It can be seen that the reproduction resolution is equal to or higher than 14.
[0156]
  The disk No. 51, the disk No. Compared to the value of 14 crosstalk (-32.0 dB), the value is larger. This is because the Curie temperature Tc13 (125 ° C.) of the Ho · Fe · Co used for the second in-plane magnetic layer 13 is lower than the Curie temperature Tc2 (160 ° C.) of the first in-plane magnetic layer 2 ′. This is because the effect of increasing the in-plane magnetic anisotropy of the first in-plane magnetization layer 2 ′ cannot be obtained in the vicinity of the temperature Tc2. As a result, the in-plane magnetization mask is weakened at a temperature in the vicinity of the transition temperature Tp1 of the reproducing layer 1 (that is, a temperature in the vicinity of the Curie temperature Tc2), and the value of crosstalk is increased.
[0157]
  Also, the disc No. 57, the disk No. Compared to the value of 14 crosstalk (-32.0 dB), the value is larger. This is because the total magnetization becomes too large because the Curie temperature of the second in-plane magnetic layer 13 is as high as 280 ° C. As a result, it is considered that the magnetostatic coupling between the recording layer 4 and the reproducing layer 1 is hindered and the reproduction signal quality is deteriorated.
[0158]
  From the above, the Curie temperature Tc13 of the second in-plane magnetic layer 13 and the Curie temperature Tc2 of the first in-plane magnetic layer 2 'are
    Tc2 ≦ Tc13 ≦ Tc2 + 80 ° C.
It can be seen that it is more desirable to set so as to satisfy the relationship. By setting the Curie temperature Tc13 of the second in-plane magnetic layer 13 in the above range, a magneto-optical disk with small crosstalk and good reproduction signal quality can be obtained.
[0159]
  Such a relationship between the Curie temperatures of the plurality of in-plane magnetization layers does not apply only to the case where the in-plane magnetization portion is composed of two types of in-plane magnetization layers having different compositions. That is, in the case where the in-plane magnetization portion is composed of at least two types of in-plane magnetization layers having different compositions, if the Curie temperature difference between the different in-plane magnetization layers is set to be 80 ° C. or less, the above description An effect is obtained.
[0160]
  In the present embodiment, an example in which Ho.Fe.Co is used for both the first in-plane magnetic layer 2 'and the second in-plane magnetic layer 13 has been described. An in-plane magnetic layer containing at least one rare earth metal element selected from Ho, Er, and Tm and at least one 3d transition metal element is used for at least one of 2 ′ or the second in-plane magnetic layer 13, In addition, a strong in-plane magnetization mask effect can be realized by setting the Curie temperature Tc13 of the second in-plane magnetization layer 13 to the above temperature range.
[0161]
  In the present embodiment, only one second in-plane magnetic layer 13 having a Curie temperature Tc13 higher than that of the first in-plane magnetic layer 2 ′ is provided on the first in-plane magnetic layer 2 ′. Although an example in which the in-plane magnetized portion 22 is configured by stacking has been shown, it is not particularly limited to this structure. For example, a plurality of second in-plane magnetization layers 13 are stacked on the first in-plane magnetization layer 2 ′ to form an in-plane magnetization section, and a layer separated from the reproducing layer 1 in the in-plane magnetization section (ie, A strong in-plane magnetization mask effect can also be obtained by designing the Curie temperature of the second in-plane magnetization layer 13) to be higher. Further, the same effect can be obtained by laminating an in-plane magnetic layer whose composition is changed so as to increase the Curie temperature as the distance from the reproduction layer 1 increases, instead of the in-plane magnetization portion. Is obtained.
[0162]
  [Embodiment 4]
  Still another embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited thereby. For convenience of explanation, members having the same functions and structures as those shown in the first or third embodiment are given the same reference numerals, and explanation thereof is omitted.
[0163]
  As shown in FIG. 8, the difference between the magneto-optical recording medium 11 ″ according to the present embodiment and the magneto-optical recording medium 11 ′ according to the third embodiment (see FIG. 6) is the second in-plane. Instead of the magnetic layer 13, the compensation composition in which the magnitude of the magnetic moment of the rare earth metal element and the magnitude of the magnetic moment of the 3d transition metal element are balanced between the first in-plane magnetized layer 2 ′ and the nonmagnetic intermediate layer 3. The second in-plane magnetization layer 14 made of an in-plane magnetization film having a RE rich composition containing more RE moment than the first in-plane magnetization layer 2 ′ and the second in-plane magnetization layer 14 is formed. The in-plane magnetized portion 23 is constituted by a laminated structure of 2. In addition, for convenience of explanation, the magnetic moment of the rare earth metal element may be referred to as the RE moment and the magnetic moment of the 3d transition metal element may be referred to as the TM moment. is there.
[0164]
  First, the reproduction principle of the magneto-optical recording medium 11 ″ according to the present embodiment will be described with reference to FIG. 8. FIG. 8 is a schematic cross-sectional view illustrating the magnetization state during reproduction of the magneto-optical recording medium. As shown in the figure, the magneto-optical recording medium 11 ″ according to the present embodiment includes a reproducing layer 1, a first in-plane magnetic layer 2 ′, a second in-plane magnetic layer 14, and a nonmagnetic intermediate layer 3. The recording layer 4 is sequentially laminated. In addition, as for each arrow in FIG. 8, the black arrow represents the direction of the magnetic moment of the 3d transition metal element, and the white arrow represents the direction of the leakage magnetic flux. Further, hereinafter, simply referring to the transition metal (element), “3d transition metal (element)”, that is, the 3d electron shell among the main transition elements satisfying the d (electron) shell is satisfied.^{twenty one}Sc ~²⁹It refers only to Cu and is distinguished from rare earth metals (in some cases, simply called rare earths).
[0165]
  The first in-plane magnetized layer 2 ′ is composed of an in-plane magnetized film having a TM rich composition containing more TM moment as compared with a compensation composition in which the magnitude of the RE moment and the magnitude of the TM moment are balanced. The Curie temperature Tc2 is set in the vicinity of the transition temperature Tp1 at which the reproducing layer 1 is in a perpendicular magnetization state. The second in-plane magnetized layer 14 is an in-plane magnetized film having an RE rich composition that includes more RE moments than a compensation composition in which the magnitude of the RE moment and the TM moment are balanced. .
[0166]
  Further, at least one of the first in-plane magnetic layer 2 ′ or the second in-plane magnetic layer 14 includes at least one kind of rare earth metal element selected from Ho, Er, and Tm and at least one kind of 3d. It is comprised from the material containing a transition metal element.
[0167]
  As shown in FIG. 8, the magneto-optical recording medium 11 ″ is transferred to the region of the reproducing layer 1 in which the recording magnetic domain 6 formed in the recording layer 4 is heated by the light beam 5 to be in the perpendicular magnetization state. Then, the magnetic domain 7 is formed and reproduced, and the principle of this reproduction is basically the same as in the first to third embodiments.
[0168]
  However, in the present embodiment, a second in-plane magnetization layer 14 made of an in-plane magnetization film having a RE rich composition is formed between the first in-plane magnetization layer 2 ′ and the nonmagnetic intermediate layer 3. Yes. Therefore, at a temperature lower than the transition temperature Tp1 at which the reproducing layer 1 transitions to the perpendicular magnetization state, the reproducing layer 1 having the RE rich composition, the first in-plane magnetic layer 2 ′ having the TM rich composition, and the second having the RE rich composition are used. The in-plane magnetization layer 14 is affected by the leakage magnetic field generated from the recording layer 4 and aligns the magnetization directions so that the total magnetizations thereof are in the same direction.
[0169]
  As a result, the rare-earth sublattice moment and the transition metal sublattice moment of the reproducing layer 1 and the first in-plane magnetization layer 2 ′ are aligned antiparallel, and the first in-plane magnetization layer 2 ′ and the second plane The rare earth sublattice moment and the transition metal sublattice moment of the inner magnetization layer 14 are aligned antiparallel. Thereby, the domain wall energy at the interface of each layer increases, and the stability of the in-plane magnetization state increases. Therefore, even if the total thickness of the first in-plane magnetization layer 2 ′ and the second in-plane magnetization layer 14, that is, the in-plane magnetization portion 23 is relatively thin, a high in-plane A mask effect is obtained.
[0170]
  That is, in the magneto-optical recording medium 11 ″, by providing the second in-plane magnetization layer 14 having the RE rich composition, even when the in-plane magnetization portion 23 is thinner, the magneto-optical recording medium 11 ″ is at a temperature lower than the transition temperature Tp1. The in-plane magnetization state of the reproducing layer 1 can be stabilized, and the recording layer 4 and the reproducing layer 1 can be strongly magnetostatically coupled at a temperature equal to or higher than the transition temperature Tp1, so that the reproduction margin can be expanded. Become.
[0171]
  Next, a magneto-optical disk to which the magneto-optical recording medium 11 ″ is applied will be described. As shown in FIG. 9, the magneto-optical disk has a transparent dielectric protective layer 9, a reproducing layer 1, The first in-plane magnetic layer 2 ′, the second in-plane magnetic layer 14, the nonmagnetic intermediate layer 3, the recording layer 4, and the protective layer 10 are laminated in this order. A laminated structure including the first in-plane magnetic layer 2 ′, the second in-plane magnetic layer 14, the nonmagnetic intermediate layer 3, and the recording layer 4 corresponds to the magneto-optical recording medium 11 ″. The substrate 8, the transparent dielectric protective layer 9, the reproducing layer 1, the nonmagnetic intermediate layer 3, the recording layer 4, and the protective layer 10 can be formed by the same materials and methods as those of the first embodiment. Detailed description thereof will be omitted.
[0172]
  The second in-plane magnetic layer 14 uses the domain wall energy at a temperature lower than the Curie temperature Tc2 of the first in-plane magnetic layer 2 ′ to change the in-plane magnetic layer 2 ′. It is formed to increase the directivity. The second in-plane magnetized layer 14 is, for example, a magnetic film made of a rare earth / transition metal alloy material, a material made of only a rare earth metal (including an alloy of rare earth metals), or a material mainly composed of a rare earth metal. is there.
[0173]
  The film thickness of the second in-plane magnetic layer 14 is not particularly limited, but is more preferably set to 2 nm or more. When the thickness of the second in-plane magnetization layer 14 is less than 2 nm, the total magnetization of the second in-plane magnetization layer 14 is reduced, and the effect of strengthening the in-plane magnetization mask of the first in-plane magnetization layer 2 ′ is achieved. May not be obtained. Further, it is more desirable that the total thickness of the first in-plane magnetization layer 2 ′ and the second in-plane magnetization layer 14, that is, the thickness of the in-plane magnetization portion 23 is 60 nm or less. When the total thickness of the first in-plane magnetic layer 2 ′ and the second in-plane magnetic layer 14 is greater than 60 nm, the distance between the recording layer 4 and the reproducing layer 1 becomes large, and the recording layer 4 and the reproducing layer 1 May be weakened. This makes it difficult to stably transfer the recording magnetic domain 6 from the recording layer 4 to the reproduction layer 1, and there is a possibility that the reproduction signal quality is deteriorated.
[0174]
  Next, a specific example of a method for forming and recording / reproducing a magneto-optical disk having the above configuration will be described.
[0175]
  (1) Method for forming magneto-optical disk
  The method for forming the magneto-optical disk shown in FIG. 9 is as follows. Here, a method for forming a magneto-optical disk using a Ho.Fe.Co alloy material for both the first in-plane magnetic layer 2 'and the second in-plane magnetic layer 14 will be described.
[0176]
  As a first step, in a sputtering apparatus including an AlSi target, a Gd · Fe · Co alloy target, first and second Ho · Fe · Co alloy targets, and a Tb · Fe · Co alloy target, A polycarbonate substrate 8 having a guide groove for recording on both the part and the guide groove part and formed in a disk shape is disposed.
[0177]
  Then, according to the same method as the magneto-optical disk according to the first embodiment (see FIG. 2), the transparent dielectric protective layer 9 made of AlSiN is formed on the substrate 8 with a film thickness of 80 nm. Subsequently, on the transparent dielectric protective layer 9, Gd_0.31(Fe_0.78Co_0.22)_0.69The reproduction layer 1 having the composition is formed with a film thickness of 25 nm.
[0178]
  Subsequently, as the second step, power is supplied to the first Ho · Fe · Co alloy target, and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), Ho is formed on the reproduction layer 1._0.13(Fe_0.88Co_0.12)_0.87A first in-plane magnetic layer 2 ′ having the composition is formed with a film thickness of 7 nm. Then, power is supplied to the second Ho · Fe · Co alloy target having a different content ratio of each element from the first Ho · Fe · Co alloy target, and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), the second in-plane magnetic layer 14 is formed to a thickness of 7 nm on the first in-plane magnetic layer 2 ′. That is, the thickness of the in-plane magnetized portion 23 in this magneto-optical disk is 14 nm.
[0179]
  The composition of the second in-plane magnetization layer 14 is Ho._0.36(Fe_0.72Co_0.28)_0.64The Curie temperature Tc14 was 160 ° C. In addition, the second in-plane magnetic layer 14 has an RE moment as compared with a compensation composition in which the magnitude of the RE moment and the magnitude of the TM moment are balanced under a temperature condition in the range from room temperature to the Curie temperature Tc14. It was an in-plane magnetized film with an RE rich composition that contained more.
[0180]
  Subsequently, as a third step, power is supplied to the AlSi target and the gas pressure is 4 × 10.^-3Under the condition of Torr (about 0.532 Pa), the nonmagnetic intermediate layer 3 made of AlSi is formed with a film thickness of 2 nm on the second in-plane magnetic layer 14.
[0181]
  Subsequently, as a fourth step, Tb is formed on the nonmagnetic intermediate layer 3 according to the same method as the magneto-optical disk according to the first embodiment (see FIG. 2)._0.25(Fe_0.84Co_0.16)_0.75The recording layer 4 having the composition is formed with a film thickness of 60 nm. Then, by forming the protective layer 10 made of AlSiN with a film thickness of 20 nm on the recording layer 4, the magneto-optical disk shown in FIG. 9 is manufactured.
[0182]
  (2) Crosstalk characteristics
  The recording / reproducing characteristics of the magneto-optical disk (hereinafter referred to as sample # 2) shown in FIG. 9 are as follows. Specifically, the results of evaluating the crosstalk in the magneto-optical disk using a magneto-optical pickup using a semiconductor laser having a wavelength of 680 nm under the condition of a linear velocity of 2.5 m / s will be described.
[0183]
  For the measurement of crosstalk, the same measurement method and measurement conditions as those shown in the first embodiment were used. In recording, the recording magnetic field is modulated at ± 15 kA / m while continuously irradiating the recording / reproducing laser at 5.6 mW, so that the recording layer 4 has an upward magnetization and a downward magnetization corresponding to the direction of the recording magnetic field. A repetitive pattern was formed with a mark length of 0.3 μm. Here, the mark length of 0.3 μm means that each recording magnetic domain is formed with a length (diameter) of 0.3 μm, and the interval (pitch) of the recording magnetic section is twice the mark length (ie, 0). .6 μm).
[0184]
  FIG. 10 is a graph showing the track pitch dependence of the crosstalk of sample # 2 measured by continuously irradiating the recording / reproducing laser at 1.8 mW. Here, the track pitch refers to the distance between the center position in the width direction of the measurement track 11 shown in FIGS. 4A and 4B and the center position in the width direction of the adjacent tracks 12 and 12 ′. The land portion width and the guide groove portion width are equal and are the same as the track pitch. For comparison, the second in-plane magnetization layer 14 is omitted in the configuration of the magneto-optical disk (sample # 1) described in the first embodiment, that is, the sample # 2, and the first in-plane magnetization layer is omitted. A graph showing the track pitch dependence of the crosstalk of a magneto-optical disk (see FIG. 2) in which the film thickness of 2 ′ (same as the in-plane magnetic layer 2) is 20 nm is also shown.
[0185]
  Comparing sample # 2 and sample # 1, as shown in FIG. 10, substantially the same crosstalk value was obtained at any track pitch. Furthermore, since the thickness of the in-plane magnetization layer 2 of the sample # 1 is 20 nm, the thickness of the in-plane magnetization portion 23 of the sample # 2 is 14 nm. It can be seen that a sufficiently high in-plane magnetization mask effect can be obtained even with a thin film thickness. Further, with respect to Sample # 1 and Sample # 2, an external magnetic field was applied during reproduction, and the magnetostatic coupling force between the recording layer 4 and the reproduction layer 1 was examined. As a result, it was confirmed that sample # 2 was more stable with respect to application of an external magnetic field than sample # 1.
[0186]
  As described above, in the magneto-optical disk (sample # 2) including the magneto-optical recording medium 11 ″ according to the present invention, the film thickness of the in-plane magnetization portion 23 is increased by providing the second in-plane magnetization layer 14. The magneto-optical disk can obtain a high in-plane magnetization mask effect even when it is thinner, and can realize good reproduction signal quality.
[0187]
  As described above, by further providing the second in-plane magnetization layer 14 having the RE rich composition, it is possible to reduce the thickness of the in-plane magnetization portion 23, and the recording power and the reproduction power can be reduced. The magnetostatic coupling force between the layer 4 and the reproduction layer 1 is increased, and the reproduction margin is increased.
[0188]
  In the present embodiment, an example is shown in which the Ho • Fe • Co material is used for both the first in-plane magnetic layer 2 ′ and the second in-plane magnetic layer 14, but the present embodiment is particularly limited to this structure. It is not something. For example, as at least one of the first in-plane magnetic layer 2 ′ or the second in-plane magnetic layer 14, at least one kind of rare earth metal element selected from Ho, Er, and Tm and at least one kind of 3d transition metal are used. A strong in-plane magnetization masking effect can be obtained by using an in-plane magnetic layer containing an element, further setting the first in-plane magnetic layer 2 ′ to a TM rich composition and the second in-plane magnetic layer 14 to an RE rich composition. can get.
[0189]
  In this embodiment, an in-plane magnetic layer having an RE rich composition (corresponding to the second in-plane magnetic layer 14) and an in-plane magnetic layer having a TM rich composition (corresponding to the first in-plane magnetic layer 2 ′). In this example, the in-plane magnetized portion 23 is formed by laminating one layer at a time. However, the present invention is not particularly limited to this structure. For example, an in-plane magnetization layer including three or more in-plane magnetization layers can be obtained by alternately and repeatedly laminating an in-plane magnetization layer having a TM rich composition and an in-plane magnetization layer having a RE rich composition. It is good also as a structure which can implement | achieve an internal magnetization mask effect.
[0190]
  When an in-plane magnetized portion is formed by alternately and repeatedly laminating an in-plane magnetized layer having a TM rich composition and an in-plane magnetized layer having an RE rich composition, the in-plane of the TM rich composition forming the in-plane magnetized portion. The magnetized layers (or the in-plane magnetized layers having the RE rich composition) do not need to have the same composition.
[0191]
  Further, unlike the present embodiment, when the reproduction layer is made of a material having a TM rich composition, the first in-plane magnetization layer adjacent to the reproduction layer is changed from the material having the RE rich composition to the first in-plane magnetization. The second in-plane magnetization layer stacked on the layer may be made of a material having a TM rich composition.
[0192]
  (3) Relationship between the composition of the in-plane magnetic layer and the crosstalk characteristics
  Next, in the configuration of the magneto-optical disk (sample # 2) used in this example, the composition of Ho.Fe.Co that is the material of the second in-plane magnetic layer 14 is variously changed, and the above "(2) Crosstalk was measured according to the same method and measurement conditions as the measurement of “crosstalk characteristics”. In other words, the crosstalk was measured for the magneto-optical disk in which the Curie temperature of the second in-plane magnetic layer 14, that is, the RE rich Ho · Fe · Co layer was variously changed.
[0193]
  More specifically, as shown in Table 7 below, the weight ratio of Ho, which is a rare earth metal element, and FeCo, which is a 3d transition metal component, is constant at 0.36: 0.64 and occupies the above FeCo. The above measurement was performed on six magneto-optical disks having various contents of Fe (or Co). The track pitch was 0.6 μm, the mark length was 0.3 μm, and the distance between the recording magnetic sections was 0.6 μm. Here, the track pitch refers to the distance between the center position in the width direction of the measurement track 11 shown in FIGS. 4A and 4B and the center position in the width direction of the adjacent tracks 12 and 12 ′. The land portion width and the guide groove portion width are equal and are the same as the track pitch.
[0194]
  For comparison, Table 8 below shows the Ho used as the first in-plane magnetic layer 2 'in the configuration of the magneto-optical disk shown in FIG._0.13(Fe_0.88Co_0.12)_0.87Instead of Gd and Fe shown in the prior art, Ho_0.13(Fe_0.88Co_0.12)_0.87Gd having a Curie temperature (160 ° C.) equal to_0.13Fe_0.87Further, in place of the second in-plane magnetic layer 14, six types of comparative magneto-optical disks (comparative disk No. 81) using the second in-plane magnetic layer having the composition shown in Table 8 are used. To 86), the measurement result of the track pitch at a track pitch of 0.6 μm is also shown.
[0195]
  The comparative disk No. In each of the second in-plane magnetization layers included in 81 to 86, the Gd amount is fixed to 36.0% by weight and the FeCo amount is fixed to 64.0% by weight. Designed to vary and show different Curie temperatures. More specifically, the comparative disk No. The Curie temperatures of the second in-plane magnetized layers 81 to 86 are respectively the disk Nos. Shown in Table 7. It is designed to be equal to the Curie temperature of the second in-plane magnetization layer 14 of 71 to 76.
[0196]
[Table 7]

[0197]
[Table 8]

[0198]
  As shown in Table 7, a magneto-optical disk (disc No. 1) comprising an in-plane magnetized portion 23 having a thickness of 14 nm and composed of a first in-plane magnetized layer 2 ′ and a second in-plane magnetized layer 14. 71 to disc No. 76) have first and second in-plane magnetization layers that exhibit the same Curie temperature as the first in-plane magnetization layer 2 ′ and the second in-plane magnetization layer 14. Corresponding disc No. It can be seen that the crosstalk value is lower than those of 81-86 and has excellent characteristics.
[0199]
  In particular, disc no. 72 to disk no. In the five magneto-optical disks indicated by 75, that is, the magneto-optical disks in which the Curie temperatures of the second in-plane magnetization layer 14 are 160 ° C., 195 ° C., 225 ° C., and 240 ° C. in this order, crosstalk occurs. It can be seen that both are suppressed to -32.3 dB or less.
[0200]
  As described in the first embodiment, the disk No. 1 in which the in-plane magnetized portion is formed by the in-plane magnetized layer 2 having a thickness of 20 nm alone. 14 (sample # 1), the crosstalk value was −32.0 dB (see Table 1). Therefore, the disc No. 72 to disk no. 75, the in-plane magnetization mask effect of the first in-plane magnetization layer 2 ′ is enhanced by providing the second in-plane magnetization layer 14, and a thinner in-plane magnetization film (thickness of the in-plane magnetization portion 23) is obtained. 14 nm) at the disc No. It can be seen that the reproduction resolution is 14 or more.
[0201]
  The disk No. 71, the disk No. Compared to the value of 14 crosstalk (-32.0 dB), the value is larger. This is because the Curie temperature (130 ° C.) of the Ho · Fe · Co used for the second in-plane magnetization layer 14 is lower than the Curie temperature Tc 2 (160 ° C.) of the first in-plane magnetization layer 2 ′. This is because the effect of increasing the in-plane magnetic anisotropy of the first in-plane magnetization layer 2 ′ cannot be obtained in the vicinity of Tc2. As a result, the in-plane magnetization mask is weakened at a temperature in the vicinity of the transition temperature Tp1 of the reproducing layer 1 (that is, a temperature in the vicinity of the Curie temperature Tc2), and the value of crosstalk is increased.
[0202]
  Also, the disc No. 76, the disk No. Compared to the value of 14 crosstalk (-32.0 dB), the value is larger. This is because the total magnetization becomes too large because the Curie temperature of the second in-plane magnetization layer 14 is as high as 270 ° C. As a result, it is considered that the magnetostatic coupling between the recording layer 4 and the reproducing layer 1 is hindered and the reproduction signal quality is deteriorated.
[0203]
  From the above, the Curie temperature Tc14 of the second in-plane magnetic layer 14 and the Curie temperature Tc2 of the first in-plane magnetic layer 2 'are
    Tc2 ≦ Tc14 ≦ Tc2 + 80 ° C.
It can be seen that it is more desirable to set so as to satisfy the relationship. By setting the Curie temperature Tc14 of the second in-plane magnetic layer 14 in the above range, a magneto-optical disk with small crosstalk and good reproduction signal quality can be obtained.
[0204]
  In the present embodiment, an example in which Ho · Fe · Co is used for both the first in-plane magnetic layer 2 ′ and the second in-plane magnetic layer 14 has been described. An in-plane magnetization film including at least one kind of rare earth metal element selected from Ho, Er, and Tm and at least one kind of 3d transition metal element is formed on at least one of 2 ′ or the third in-plane magnetization layer 14. In addition, a strong in-plane magnetization mask effect can be obtained by setting the Curie temperature Tc14 of the second in-plane magnetization layer 14 to the above temperature range.
[0205]
  In the present embodiment, an example in which only one in-plane magnetic layer (second in-plane magnetic layer 14) having a RE rich composition is stacked on the first in-plane magnetic layer 2 ′ has been described. It is not limited to. For example, an in-plane magnetization layer composed of three or more in-plane magnetization layers is formed by alternately and repeatedly laminating an in-plane magnetization layer having a TM rich composition and an in-plane magnetization layer having a RE rich composition. A stronger in-plane magnetization mask effect can also be obtained by increasing the Curie temperature in the in-plane magnetization layer that is farther from the surface.
[0206]
  The magneto-optical recording medium according to the present invention is also a recording in which information is magneto-optically recorded, consisting of a reproducing layer that is in-plane magnetization at room temperature and transitions to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1, and a perpendicular magnetization film. In a magneto-optical recording medium comprising a layer and an intermediate layer made of a nonmagnetic material and disposed between the reproducing layer and the recording layer, provided adjacent to at least one surface side of the reproducing layer, It further has an in-plane magnetization layer whose magnetization decreases at a temperature near the transition temperature Tp1, and the in-plane magnetization layer includes at least one kind of rare earth metal element selected from Ho, Er, and Tm, and at least one kind. The 3d transition metal element may be included.
[0207]
  The magneto-optical recording medium according to the present invention can be suitably used as an optical recording medium in, for example, a magneto-optical disk, a magneto-optical tape, a magneto-optical card, and the like.
[0208]
【The invention's effect】
  As described above, the magneto-optical recording medium according to the present invention includes a reproducing layer that transitions from an in-plane magnetization state to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1, a recording layer that includes a perpendicular magnetization film, and the reproducing layer. In a magneto-optical recording medium comprising an in-plane magnetization layer that is provided adjacently and whose magnetization decreases at a temperature near the transition temperature Tp1.The in-plane magnetic layer is a layer made of a rare earth / 3d transition metal alloy material made of Ho, Fe, and Co, and the proportion of Ho in the rare earth / 3d transition metal alloy material is 7% by mass or more and 20% by mass or less. And the proportion of Co in the 3d transition metal is in the range of 0% by mass to 19% by mass.It is a configuration.
[0209]
  According to the above configuration, the in-plane magnetic layer isIt is made of a rare earth / 3d transition metal alloy material comprising Ho, Fe, and Co, and the ratio of Ho in the rare earth / 3d transition metal alloy material is in the range of 7% by mass to 20% by mass, and the 3d transition The proportion of Co in the metal is in the range of 0% by mass to 19% by mass.Therefore, it is possible to make a steep transition to the perpendicular magnetization state of the reproducing layer. As a result, it is possible to provide a magneto-optical recording medium that is small in crosstalk and can be reproduced with good reproduction signal quality.
[0210]
  The magneto-optical recording medium according to the present invention is in an in-plane magnetization state at room temperature, and is arranged at a predetermined interval from the reproduction layer that transitions to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1. A recording layer made of a magnetized film on which information is magneto-optically recorded, and an in-plane magnetized layer provided adjacent to one of the surfaces of the reproducing layer and whose magnetization decreases at a temperature near the transition temperature Tp1; In the magneto-optical recording medium comprising: The total thickness of the in-plane magnetic layers provided on the side opposite to the recording layer with the reproducing layer interposed therebetween is in the range of 2 nm to 10 nm.
[0211]
  In addition to the above configuration, the magneto-optical recording medium according to the present invention has an RM rich composition in the reproducing layer at a temperature of room temperature or higher, and a TM rich composition in the in-plane magnetic layer at a temperature of room temperature or higher. The composition is a composition.
[0212]
  According to the above configuration, at the temperature lower than the transition temperature Tp1, the reproducing layer and the in-plane magnetic layer are affected by the leakage magnetic field, and the magnetization directions are aligned so that the total magnetizations thereof are in the same direction. As a result, the magnetization of the reproducing layer is strongly attracted in the in-plane direction, and the in-plane magnetization state can be further stabilized at a temperature lower than the transition temperature Tp1.
[0213]
  In addition to the above-described configuration, the magneto-optical recording medium according to the present invention includes a reproducing layer that transitions from an in-plane magnetization state to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1, a recording layer that includes a perpendicular magnetization film, and the above-described reproduction layer. In the magneto-optical recording medium provided adjacent to the layer and having an in-plane magnetization unit formed by laminating a plurality of in-plane magnetization layers, the in-plane magnetization unit includes at least two types of the above-described in-plane magnetization units. The in-plane magnetization layer that includes the in-plane magnetization layer and that is adjacent to the reproduction layer has a property that its magnetization decreases at a temperature near the transition temperature Tp1, and further, the plurality of in-plane magnetization layers At least one of the layersConsists of one of HoFeCo, ErFeCo, and TmFeCoIt is a configuration.
[0214]
  According to the above configuration, it is possible to further stabilize the in-plane magnetization state of the reproducing layer at a temperature lower than the transition temperature Tp1 as compared with the case where the in-plane magnetization layer is formed using Gd · Fe. It also has the effect of becoming.
[0215]
  In the magneto-optical recording medium according to the present invention, in addition to the above configuration, each of the plurality of in-plane magnetization layers forming the in-plane magnetization portion includes at least one kind of rare earth metal element and at least one kind of 3d transition metal. The in-plane magnetization portion further includes a TM rich composition in-plane magnetization layer and a RE rich composition in-plane magnetization layer.
[0216]
  According to the above configuration, the domain wall energy at the interface between the in-plane magnetization layers is increased, and the stability of the in-plane magnetization state is further increased, so that it is possible to obtain a high in-plane mask effect. Play.
[0217]
  In addition to the above-described configuration, the magneto-optical recording medium according to the present invention has a Curie temperature of the plurality of in-plane magnetization layers that decreases in order as it approaches the reproduction layer, and the Curie of the in-plane magnetization layer adjacent to the reproduction layer. The temperature Tc2 is a temperature in the vicinity of the transition temperature Tp1.
[0218]
  According to the above configuration, since the in-plane magnetic layer located farther from the reproducing layer has a higher total magnetization and is exchange-coupled to the in-plane magnetic layer located more proximal to the reproducing layer, the transition temperature Since the in-plane magnetization state of the reproducing layer can be further stabilized at a temperature lower than Tp1, and the recording layer and the reproducing layer can be strongly magnetostatically coupled at a temperature equal to or higher than the transition temperature Tp1, the reproduction margin can be increased. It also has the effect that it can be expanded.
[0219]
  In addition to the above configuration, the magneto-optical recording medium according to the present invention has a configuration in which the difference between the maximum value and the minimum value of the Curie temperature is 80 ° C. or less in the plurality of in-plane magnetization layers forming the in-plane magnetization portion. It is.
[0220]
  According to said structure, there exists an effect that it becomes possible to provide a magneto-optical recording medium with small crosstalk and reproducible with favorable reproduction signal quality.
[0221]
  In the magneto-optical recording medium according to the present invention, in addition to the above configuration, at least one in-plane magnetic layer is provided between the reproducing layer and the recording layer. The total is in the range of 2 nm to 60 nm.
[0222]
  In the magneto-optical recording medium according to the present invention, in addition to the above configuration, at least one in-plane magnetic layer is provided on the opposite side of the recording layer with the reproducing layer interposed therebetween, and the in-plane magnetic layer film The total thickness is in the range of 2 nm to 10 nm.
[0223]
  According to any of the above configurations, the in-plane magnetization state of the reproduction layer is more reliably maintained at a temperature lower than the transition temperature Tp1, and the reproduction layer is more reliably maintained at a temperature equal to or higher than the transition temperature Tp1. In addition, there is an effect that it is possible to shift to the perpendicular magnetization state.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a magnetization state during reproduction of a magneto-optical recording medium according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a schematic configuration of a magneto-optical disk to which the magneto-optical recording medium shown in FIG. 1 is applied.
FIG. 3 is a graph showing the composition dependency in the easy axis direction of Gd · Fe material and Ho · Fe · Co material.
FIGS. 4A and 4B are schematic diagrams for explaining a method of measuring crosstalk in a magneto-optical disk. FIGS.
5 is a graph showing the track pitch dependence of crosstalk in the magneto-optical disk shown in FIG. 2 and the conventional magneto-optical disk shown in FIG. 14;
FIG. 6 is a schematic cross-sectional view showing a magnetization state during reproduction of a magneto-optical recording medium according to another embodiment of the present invention.
7 is a cross-sectional view showing a schematic configuration of a magneto-optical disk to which the magneto-optical recording medium shown in FIG. 6 is applied.
FIG. 8 is a schematic cross-sectional view showing a magnetization state during reproduction of a magneto-optical recording medium according to still another embodiment of the present invention.
FIG. 9 is a cross-sectional view showing a schematic configuration of a magneto-optical disk to which the magneto-optical recording medium shown in FIG. 8 is applied.
10 is a graph showing the track pitch dependence of crosstalk in the magneto-optical disk shown in FIGS. 2 and 9. FIG.
FIG. 11 shows crosstalk between sample # 1 (a) using Er.Fe.Co as the material of the in-plane magnetic layer, sample # 1 (b) using Tm.Fe.Co, and comparative sample # r1. It is a graph which shows track pitch dependence.
FIG. 12 is a cross-sectional view showing a schematic configuration of a magneto-optical disk to which a magneto-optical recording medium according to still another embodiment of the present invention is applied.
FIG. 13 is a schematic cross-sectional view showing a magnetization state during reproduction of a conventional magneto-optical recording medium.
14 is a cross-sectional view showing a schematic configuration of a magneto-optical disk to which the magneto-optical recording medium shown in FIG. 13 is applied.
[Explanation of symbols]
1 Playback layer
2 In-plane magnetic layer
2 'first in-plane magnetic layer (in-plane magnetic layer)
4 Recording layer
6 recorded magnetic domains (information)
11 Magneto-optical recording medium
11 'magneto-optical recording medium
11 "magneto-optical recording medium
13 Second in-plane magnetic layer (in-plane magnetic layer)
14 Second in-plane magnetic layer (in-plane magnetic layer)
22 In-plane magnetization
23 In-plane magnetization
Tc2 Curie temperature of in-plane magnetic layer
Tp1 transition layer transition temperature

Claims (9)

A reproducing layer that is in an in-plane magnetization state at room temperature and transitions to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1;
A recording layer which is arranged at a predetermined interval from the reproducing layer and is composed of a perpendicular magnetization film on which information is magneto-optically recorded;
A magneto-optical recording medium comprising: an in-plane magnetization layer provided adjacent to any one surface side of the reproducing layer, the magnetization of which decreases at a temperature near the transition temperature Tp1;
The in-plane magnetic layer is a layer made of a rare earth / 3d transition metal alloy material made of Ho, Fe, and Co,
The ratio of Ho in the rare earth / 3d transition metal alloy material is in the range of 7 to 20% by mass, and the ratio of Co in the 3d transition metal is in the range of 0 to 19% by mass. A magneto-optical recording medium characterized by the above. A reproducing layer that is in an in-plane magnetization state at room temperature and transitions to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1;
A recording layer that is arranged at a predetermined interval from the reproducing layer and is composed of a perpendicular magnetization film on which information is magneto-optically recorded;
A magneto-optical recording medium comprising: an in-plane magnetization layer provided adjacent to one of the surfaces of the reproducing layer, the magnetization of which decreases at a temperature near the transition temperature Tp1;
The in-plane magnetic layer is composed of any one of HoFeCo, ErFeCo, TmFeCo,
The in-plane magnetic layer is provided on at least one layer opposite to the recording layer with the reproducing layer interposed therebetween,
A magneto-optical recording medium, wherein the total thickness of the in-plane magnetic layers provided on the opposite side of the recording layer with the reproducing layer interposed therebetween is in the range of 2 nm to 10 nm. Compared to the compensation composition in which the reproducing layer has a magnetic moment magnitude of the rare earth metal element and a magnetic moment magnitude of the 3d transition metal element at a temperature higher than room temperature and lower than the transition temperature Tp1, the magnetic moment of the rare earth metal element And more
Compared with the compensation composition in which the in-plane magnetization layer balances the magnitude of the magnetic moment of the rare earth metal element and the magnitude of the magnetic moment of the 3d transition metal element at a temperature of room temperature or higher, the magnetic moment of the 3d transition metal element is further increased. The magneto-optical recording medium according to claim 1, comprising a large amount. A reproducing layer that is in an in-plane magnetization state at room temperature and transitions to a perpendicular magnetization state at a temperature equal to or higher than the transition temperature Tp1;
A recording layer which is arranged at a predetermined interval from the reproducing layer and is composed of a perpendicular magnetization film on which information is magneto-optically recorded;
In a magneto-optical recording medium having an in-plane magnetization portion provided adjacent to any one surface side of the reproducing layer and having a plurality of in-plane magnetization layers laminated,
The in-plane magnetization portion includes at least two types of the in-plane magnetization layers having different compositions, and the in-plane magnetization layer adjacent to the reproduction layer among the plurality of in-plane magnetization layers has the transition temperature Tp1. It has the property that its magnetization decreases at a nearby temperature,
Furthermore, at least one of the plurality of in-plane magnetic layers is composed of any one of HoFeCo, ErFeCo, and TmFeCo . Each of the plurality of in-plane magnetized layers forming the in-plane magnetized portion includes at least one kind of rare earth metal element and at least one kind of 3d transition metal element,
The in-plane magnetized portion further includes
In-plane magnetization comprising more of the magnetic moment of the 3d transition metal element compared to a compensation composition in which the magnitude of the magnetic moment of the rare earth metal element and the magnitude of the magnetic moment of the 3d transition metal element are balanced at temperatures above room temperature Layers,
An in-plane magnetic layer comprising more rare earth metal element magnetic moment than the compensation composition in which the magnitude of the magnetic moment of the rare earth metal element and the magnitude of the magnetic moment of the 3d transition metal element are balanced at a temperature higher than room temperature The magneto-optical recording medium according to claim 4, wherein:   The Curie temperatures of the plurality of in-plane magnetization layers forming the in-plane magnetization portion are sequentially decreased as the reproduction layer is approached, and the Curie temperature Tc2 of the in-plane magnetization layer adjacent to the reproduction layer is in the vicinity of the transition temperature Tp1. 6. The magneto-optical recording medium according to claim 4, wherein the magneto-optical recording medium is a temperature.   7. The difference between the maximum value and the minimum value of the Curie temperature in the plurality of in-plane magnetization layers forming the in-plane magnetization portion is 80 ° C. or less. 7. Magneto-optical recording medium. The in-plane magnetic layer is provided at least one layer between the reproducing layer and the recording layer,
The total thickness of the provided-plane magnetized layer between the reproducing layer and the recording layer, as claimed in claim 1,4,5,6,7, characterized in that in the range of 2nm or 60nm or less The magneto-optical recording medium according to any one of the above. The in-plane magnetic layer is provided on at least one layer opposite to the recording layer with the reproducing layer interposed therebetween,
The total thickness of the in-plane magnetic layers provided on the opposite side of the recording layer with the reproducing layer interposed therebetween is in the range of 2 nm to 10 nm . 8. The magneto-optical recording medium according to any one of items 7 .

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