JP3658586B2

JP3658586B2 - Magnetic recording medium, method for manufacturing the same, and magnetic storage device

Info

Publication number: JP3658586B2
Application number: JP2002354502A
Authority: JP
Inventors: 譲稲垣; 好文松田; 四男屋久; 晃石川
Original assignee: 株式会社日立グローバルストレージテクノロジーズ
Priority date: 2002-12-06
Filing date: 2002-12-06
Publication date: 2005-06-08
Anticipated expiration: 2016-03-26
Also published as: JP2003196824A

Description

【０００１】
【発明の属する技術分野】
本発明は、磁気ディスク等の情報記録用磁気記録媒体、その製造方法及び磁気記憶装置に係り、特に面記録が高密度の磁気記録媒体、その製造方法及び磁気記憶装置に関する。
【０００２】
【従来の技術】
従来、磁化を面内方向に反転させて記録する面内磁気記録用の媒体は、Ｃｏのような強磁性金属を主成分としたＣｏ基合金系磁性薄膜を情報記録層としている。１平方インチ当たり１ギガビット以上の高密度の情報記録を可能とするためには、この記録層に対して保磁力を高め、媒体ノイズを小さくすることが要求されている。
【０００３】
一般に、保磁力（Ｈｃ）を大きくするためにＣｏＣｒＰｔ合金磁性膜中のＰｔ添加量を増し、これを体心立方構造（ｂｃｃ）のＣｒ又はＣｒを主成分とする合金系非磁性下地膜上にエピタキシャル成長させる方法が、例えば、ジャーナル・オブ・アプライド・フイジックス，７３巻（１９９３年）第５５６９〜５５７１頁（Ｊ．Ａｐｐｌ．Ｐｈｙｓ．，ｖｏｌ．７３，Ｎｏ．１０，（１９９３）ｐ．５５６９〜５５７１）に提案されている。
【０００４】
また、媒体ノイズ低減のための有効な方法として、媒体をスパッタリングで形成する際、Ａｒ圧を１０ｍＴｏｒｒ以上に増加することより記録層の結晶粒を空間的に分離することにより、磁性結晶粒を磁気的に孤立化させる方法（例えば、アイ・イー・イー・イートランザクションオンマグネチックス、２６巻（１９９０年）第１５７８〜１５８０頁（ＩＥＥＥＴｒａｎｓ．ｏｎＭａｇｎ．，Ｖｏｌ．２６，Ｎｏ．５（１９９０）ｐ．１５７８〜１５８０））が知られている。また、ＣｏＣｒＰｔ磁性膜中のＣｒの濃度を増してＣｒを結晶粒界に偏析させる方法（例えば、アイ・イー・イー・イートランザクションオンマグネチックス、２９巻（１９９３年）第３６６７〜３６６９頁（ＩＥＥＥＴｒａｎｓ．ｏｎＭａｇｎ．，Ｖｏｌ．２９，Ｎｏ．６（１９９３）ｐ．３６６７〜３６６９））が知られている。
【０００５】
さらに、媒体ノイズ低減のための手法として、Ｃｒを主成分とする非磁性下地膜を２層化し、基板側に配置された第１の下地膜として、Ｘ線回析において体心立方構造の（１１０）配向を主体とする結晶構造を有する非磁性下地膜を膜厚０．５〜８ｎｍ形成し、その上に体心立方構造の（２００）配向を主体とする第２の非磁性下地膜を膜厚２０〜３００ｎｍ形成する方法が、特開平７−５７２３８号に記載されている。また、静磁気特性や電磁変換特性を向上させる方法として、Ｃｒを主成分とする非磁性下地膜に酸素を含有させて結晶配向性を向上させる手法が特開平１−２９０１１８号に記載されている。
【０００６】
さらに、高密度記録を実現するためには、ビット境界の磁化からの反磁界に打ち勝って磁化を記録方向に保持しておくために、保磁力を高くすると同時に、上記記録層の膜厚ｔと残留磁束密度Ｂｒの積Ｂｒ・ｔを小さくして反磁界を小さくする必要がある（例えば、アイ・イー・イー・イートランザクションオンマグネチックス、２９巻（１９９３年）第３６７０〜３６７２頁（ＩＥＥＥＴｒａｎｓ．ｏｎＭａｇｎ．，Ｖｏｌ．２９，Ｎｏ．６（１９９３）ｐ．３６７０〜３６７２））。
【０００７】
【発明が解決しようとする課題】
上記従来技術、すなわち、磁性膜中Ｐｔ濃度の増加による高保磁力化は、貴金属であるＰｔが高価で、製造コストが上昇する問題があった。このため、他の方法により保磁力を向上する技術が求められていた。また、磁性膜の結晶粒を分離したり、Ｃｒ濃度を増して低ノイズ化する方法は、保磁力角形比（Ｓ^*）の値が低下し、その結果、再生出力が低下する問題があった。さらに、上記方法により媒体ノイズを低減すると、保磁力の環境温度に対する変化率を室温（２５℃）の保磁力で規格化した値（以下、規格化保磁力温度変化率という）が増加し、低温においては保磁力が増加してオーバーライトが困難となり、高温においては保磁力が低下して再生出力が低下する問題が生じた。従来、低ノイズ化と保磁力温度変化率の低減を両立して実現する手法は知られていなかった。
【０００８】
また、特開平７−５７２３８号に記載の手法では、基板側に配置された第１の下地膜を０．５〜８ｎｍ、好ましくは０．５〜１．５ｎｍという、他の膜に比べて１／１０以下の極めて薄い膜厚で形成する必要があり、ディスク面内での膜厚分布の制御や、量産プロセスで大量の磁気記録媒体を一定の品質で製造することが困難であった。また、保磁力を向上したり保磁力温度変化率を低減する効果については記述されていない。
【０００９】
また、特開平１−２９０１１８号に記載の手法では、保磁力やＳ^*を向上できるが、媒体ノイズを低減させたり、保磁力温度変化率を低減する効果は記述されていない。
【００１０】
以上述べたように、より高密度化を実現するためには、磁性膜中のＰｔ濃度を増加することなく保磁力を向上し、また、Ｓ^*の値を下げず、規格化保磁力温度変化率を増加することなく媒体ノイズを低減することが必要である。
【００１１】
さらに、磁気抵抗効果型素子を用いた記録・再生分離型ヘッドと上記磁気記録媒体を、どのように組み合わせることにより高い記録密度を持つ磁気ディスク装置を実現できるかについては、十分に検討されていなかった。前述の１平方インチ当たり１ギガビット以上の記録密度を達成するためには、２．０ｋＯｅを超えるＨｃが必要になることが分かっている。
【００１２】
本発明の第１の目的は、高密度な情報の記録再生が可能な、高保磁力、高Ｓ^*、低ノイズ、かつ信頼性の高い磁気記録媒体を提供することにある。
本発明の第２の目的は、上記のような高保磁力、高Ｓ^*、低ノイズの磁気記録媒体の製造方法を提供することである。
本発明の第３の目的は、上記のような高保磁力、高Ｓ^*、低ノイズの磁気記録媒体を用いた信頼性の高い磁気記憶装置を提供することである。
【００１３】
【課題を解決するための手段】
上記第１の目的を達成するために、本発明の磁気記録媒体は、基板上に、少なくとも二層の非磁性下地膜を介し、Ｃｏ基合金系の磁性膜からなる情報記録層を配置し、上記非磁性下地膜の内の最も基板側に配置された第１の非磁性下地膜を、Ｃｒを主成分とし、Ｚｒ、Ｓｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ及びＹからなる群から選ばれた少なくとも一種の元素並びに酸素を含有する複合膜とし、上記元素の濃度が１原子％以上、２０原子％以下、酸素の濃度が１原子％以上、３０原子％以下となるようにしたものである。
【００１４】
上記非磁性下地膜の内の最も情報記録層側に配置された第２の非磁性下地膜は、Ｃｒを主成分とし、Ｔｉ、Ｍｏ、Ｗ及びＶからなる群から選ばれた少なくとも一種の元素を、５原子％以上、５０原子％以下の濃度で含有する合金からなり、Ｘ線回析において体心立方構造の（１１０）配向を主体とする結晶構造を有することが好ましい。
【００１５】
さらに、上記第１の非磁性下地膜をＸ線回析において非晶質とし、膜厚を１０ｎｍ以上、１００ｎｍ以下とし、上記第２の非磁性下地膜の膜厚を２ｎｍ以上、１５ｎｍ以下とし、上記磁性膜をＸ線回析において六方細密充填構造の（１０．０）配向の結晶構造とすると、保磁力を向上したり温度変化率を低減する効果が現われるので好ましい。特に、上記第１の非磁性下地膜の平均粒径を２ｎｍ以上、３０ｎｍ以下とすると、媒体ノイズを低く保つことができる。また、上記非磁性下地膜の厚みが１０ｎｍ以上であれば量産プロセスの制御が容易となり、厚みが１００ｎｍ以下であれば所望の粒径の範囲に保つことができる。
【００１６】
上記Ｚｒ、Ｓｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ、Ｙからなる群の元素はＣｒに比べて酸素と結合しやすい性質を有し、複合膜中では主として酸化物の状態で存在する。このように、非磁性下地膜をＺｒ、Ｓｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ、Ｙからなる群の元素の酸化物とＣｒとの複合膜とすることにより、粒径が小さく、かつ均一化し、Ｘ線回析において非晶質膜とすることができる。これは、Ｚｒ、Ｓｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ、Ｙからなる元素群の酸化物がＣｒの結晶粒の結晶成長を抑制する効果があるためである。これらの酸化物は膜中で偏析して存在すると保磁力の向上や保磁力温度変化率の低減が可能となるので好ましい。
【００１７】
上記非磁性下地膜の、Ｚｒ、Ｓｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ、Ｙからなる群の元素の酸化物の添加濃度は、上記元素群の合計濃度を１原子％以上、２０原子％以下、酸素の濃度を１原子％以上、３０原子％以下とすると、Ｘ線回析において非晶質構造とすることができる。このような複合膜は、Ｚｒ、Ｓｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ、Ｙからなる群の元素の酸化物とＣｒからなるターゲットを用いて、スパッタリングすることにより容易に形成できる。また、上記元素の酸化物を２種類以上添加した場合も同様の特性向上が図られる。
【００１８】
さらに、非磁性下地膜が少なくともに二層以上で構成され、その内の最も基板側に配置された第１の非磁性下地膜が上記複合膜からなり、非磁性下地膜の内の最も情報記録層側に配置された第２の非磁性下地膜を、体心立方構造（ｂｃｃ）のＣｒを主成分とする合金からなり、かつ、その（１１０）結晶格子の大きさが、六方細密充填構造（ｈｃｐ）のＣｏ合金磁性膜の（１０．１）結晶格子の大きさと実質的に整合するように形成すると、Ｈｃを２ｋＯｅ以上、５ｋＯｅ以下、Ｓ^*を０．７以上、０．９５以下と高く保つことができ、１Ｇｂ／ｉｎ²以上の高い記録密度においても十分な再生出力が得られるので好ましい。ここで、第２の非磁性下地膜の結晶格子の大きさが、上記磁性膜の結晶格子の大きさと実質的に整合するとは、それらの結晶格子の大きさの差が±５％程度の範囲にあればよいことを意味する。特に、上記第２の非磁性下地膜をＣｒ−Ｔｉ或はＣｒ−Ｍｏ系合金とし、Ｔｉ或はＭｏの添加濃度を１０−２０原子％とすると、Ｃｏ−Ｃｒ−Ｐｔ系合金磁性膜との結晶格子の整合性が増すとともに、結晶粒径を小さくできるので、媒体ノイズを低減できて好ましい。
【００１９】
また、上記複合膜からなる非磁性下地膜を形成すると、磁性膜の結晶粒中の、（１０．０）面が基板と平行となるように配向成長した結晶粒の比率を増すことができる。その結果、磁性膜の磁化容易軸であるｃ軸が基板面と平行となり、保磁力や残留磁化角形比（Ｓ）の値が向上する。その結果、１Ｇｂ／ｉｎ²以上の高い記録密度においても十分な再生出力が得られる。
【００２０】
以上述べたような、結晶構造、結晶配向性、格子整合性の改良の結果、保磁力や保磁力温度変化率を改良することができる。特に、上記第２の非磁性下地膜の膜厚を５ｎｍ以上、１５ｎｍ以下とすると、上記保磁力温度変化率は顕著に低減する。その結果、５℃から５５℃の温度範囲で保磁力の変化が低減し、オーバーライトや再生出力の変動を低減できて好ましい。
【００２１】
さらに、上記磁気記録媒体において、総磁性膜厚ｔを１０ｎｍ、３０ｎｍ以下とし、保磁力Ｈｃを２．０ｋＯｅ以上とすると、磁化遷移領域の磁化の乱れが低減して磁化遷移領域の幅が減少し、高記録密度領域においても高い出力が得られるので好ましい。特にＢｒｔを３０Ｇμｍ以上、１００Ｇμｍ以下とすると媒体ノイズが低減し、高い媒体Ｓ／Ｎが得られるので好ましい。また、良好な重ね書き（オーバーライト）特性を保証するためには保磁力Ｈｃは４ｋＯｅ以下とすることが好ましい。
【００２２】
さらに、上記磁気記録媒体において、ヘッド走行方向と垂直の方向に測定した媒体保護膜表面の中心線平均粗さＲａを０．３ｎｍ以上、３ｎｍ以下とすると、ヘッド浮上量が０．０２μｍ以上、０．１μｍ以下でも安定に浮上するため好ましい。また、媒体表面のＲａを従来より小さい値とした場合に、ＣＳＳ動作時の磁気ヘッドの粘着を制御するには、磁性膜上に保護膜を形成した後にマスクを用いてプラズマエッチングすることで表面に高さ２０ｎｍ以下の微細な凹凸を形成したり、Ａｌ等の低融点金属化合物、混合物のターゲットを用いて保護膜表面に微細な突起が生じるように形成したり、或は熱処理によって表面に微細な凹凸を形成すると、ＣＳＳ動作時にヘッドと媒体の摩擦力が低減でき、ヘッドが媒体に粘着する問題が回避されるので好ましい。
【００２３】
さらに、Ｃｒ、Ｍｏ、Ｗ、Ｖ、Ｔａ、Ｎｂ、Ｚｒ、Ｔｉ、Ｂ、Ｂｅ、Ｃ、Ｎｉ−Ｐ、Ｎｉ−Ｂの少なくとも一つを主たる成分として、膜厚が０．５ｎｍ以上、５ｎｍ以下である非磁性中間層により、磁性膜を２層以上に多層化すると単層の磁性膜に比べて媒体ノイズがさらに低下するので好ましい。
【００２４】
さらに、磁性膜の保護層としてカーボン、水素添加カーボン又はカーボンを主たる成分とする非磁性材料を膜厚５〜２０ｎｍ形成し、さらに吸着性のパーフルオロアルキルポリエーテル等の潤滑層を膜厚３〜１０ｎｍ設けることにより信頼性が高く、高密度記録が可能な磁気記録媒体が得られる。保護層にはＷＣ、（Ｗ−Ｍｏ）−Ｃ等の炭化物、（Ｚｒ−Ｎｂ）−Ｎ、Ｓｉ₃Ｎ₄等の窒化物、ＳｉＯ₂、ＺｒＯ₂等の酸化物、或はＢ、Ｂ₄Ｃ、ＭｏＳ₂、Ｒｈ等を用いると耐摺動性、耐食性を向上できるので好ましい。これらの保護膜はマスクを用いて表面をエッチングし、面積比で１〜２０％の突起を設けるか、成膜条件、組成等を調節し、保護膜中に異なる相からなる突起物を析出せしめることで、保護膜が磁性膜表面に比べて大きな面粗さを有することがより好ましい。
【００２５】
また、上記第２の目的を達成するために、本発明の磁気記録媒体の製造方法は、基板上に、少なくとも二層の非磁性下地膜を形成し、ついでＣｏ基合金系の磁性膜からなる情報記録層を形成するもので、非磁性下地膜の内の最も基板側に配置された第１の非磁性下地膜の形成を、Ｃｒと、Ｚｒ、Ｓｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ及びＹからなる群から選ばれた少なくとも１種の元素の酸化物との混合物からなり、上記元素の添加濃度が、１原子％以上、２０原子％以下であるターゲットを用い、純Ａｒ中で、酸素ガスを用いずにスパッタリングにより行なうようにしたものである。
【００２６】
ここで、第１の非磁性下地膜は室温で形成し、その後に基板を１５０℃以上、４００℃以下に加熱してから第２の非磁性下地膜を形成すると、保磁力が向上し、温度変化率を低減するので好ましい。また、媒体を形成するに当たっては、磁性膜を形成する際の基板温度を２００℃以上、４００℃以下とすると、磁性膜中のＣｒの偏析が促進されてＨｃが向上するので好ましい。
【００２７】
さらに、上記第３の目的を達成するために、本発明の磁気記憶装置は、上記いずれか一の磁気記録媒体と、この磁気記録媒体に情報を記録・再生する磁気ヘッドとを備えるようにしたものである。
【００２８】
なお、上記の磁気記憶媒体と組み合わせて磁気記憶装置とするための磁気ヘッドとしては、再生素子に磁気抵抗効果型素子を用いた記録・再生分離型ヘッドであることが好ましい。上記の磁気記録媒体は、磁気抵抗効果型素子の特徴である高い再生感度との組み合わせにより、例えば、１平方インチ当たり１ギガビット以上の記録密度で記録・再生する場合にも十分なＳ／Ｎが得られる。
【００２９】
さらに、この磁気ヘッドの再生部を、互いの磁化方向が外部磁界によって相対的に変化することによって大きな抵抗変化を生じる複数の導電性磁性層とこの導電性磁性層の間に配置された導電性非磁性層を含む磁気抵抗センサによって構成し、かつ、磁性層の厚さｔと、記録時における磁気記録媒体に対する磁気ヘッドの相対的な走行方向に磁界を印加して測定したＢｒとの積Ｂｒ・ｔを３０Ｇμｍ以上、８０Ｇμｍ以下とし、上記方向に磁界を印加して測定した上記磁気記録媒体の保磁力Ｈｃを、２．２キロエルステッド以上とすることにより、１平方インチ当たり２ギガビット以上の高密度な情報の記録再生も可能となる。
【００３０】
【発明の実施の形態】
以下、本発明の実施の形態を添付図面を参照して詳細に説明する。図１は、本発明の面内磁気記録媒体の断面構造の模式図である。同図において、１１はＡｌ−Ｍｇ合金、化学強化ガラス、結晶化ガラス、チタン、シリコン、カーボン又はセラミックス等からなる基板、１２及び１２’は基板１１の両面に形成したＮｉ−Ｐ、Ｎｉ−Ｗ−Ｐ等からなる非磁性メッキ層である。Ａｌ−Ｍｇ合金を基板として用いた場合にはこのようなメッキ層を備えたものを基板として使用する。なお、基板にＳｉ単結晶、ガラス、カーボン等を用いた場合は非磁性メッキ層を形成しなくてもよい。
【００３１】
また、１３及び１３’は、Ｃｒを主成分とし、Ｚｒ、Ｓｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ、Ｙからなる群の少なくとも一種の元素と酸素とを含有する複合膜からなる第１の非磁性下地膜、１４及び１４’は、Ｃｒ、Ｍｏ、Ｗ、Ｖ、Ｎｂ、Ｔａ、Ｃｕ、Ａｇ、Ｍｎ、Ｚｒ、Ｈｆ若しくはＳｉからなる金属又はＣｒ、Ｍｏ、Ｗ、Ｖ、Ｎｂ、Ｔａ、Ｃｕ、Ａｇ、Ｍｎ、Ｚｒ、Ｈｆ若しくはＳｉのいずれかを主成分とする合金からなる第２の非磁性下地膜である。なお、非磁性下地膜を３層とするとき、中間の層にも上記と同じ材質が用いられる。
【００３２】
さらに、１５及び１５’は、非磁性下地膜の上に形成したＣｏ−Ｓｍ、Ｃｏ−Ｎｉ−Ｃｒ、Ｃｏ−Ｎｉ−Ｐｔ、Ｃｏ−Ｎｉ−Ｐ、Ｃｏ−Ｃｒ−Ｔａ、Ｃｏ−Ｃｒ−Ｐｔ、Ｃｏ−Ｃｒ−Ｗ、Ｃｏ−Ｃｒ−Ｓｉ、Ｃｏ−Ｃｒ−Ｔａ−Ｐｔ等からなる合金磁性膜からなる情報記録層、１６及び１６’は、情報記録層の上に形成したカーボン、ボロン、ＳｉＯ₂、ＺｒＯ₂等からなる非磁性保護膜である。
【００３３】
このような面内磁気記録媒体を次ぎのようにして作製した。強化ガラス基板、結晶化ガラス基板、Ｎｉ−Ｐをメッキしてその表面を鏡面研磨したＡｌ合金基板等の種々の磁気ディスク用基板を用い、上記磁気記録用媒体を構成する各膜をそれぞれ別々の成膜室で形成する枚葉式スパッタ装置で、タクト時間１０秒一定で一枚ずつ順次送り、ＤＣマグネトロンスパッタ法により各膜を形成した。ここで成膜条件は、主真空槽の背圧：５×１０^-8Ｔｏｒｒ以下、基板加熱温度：１００〜３００℃、Ａｒガス圧：５〜３０ｍＴｏｒｒ、投入電力：ターゲットサイズが６インチに対して１〜４ｋＷである。上記種々の基板上に、Ｃｒを主成分とする一層以上の非磁性下地膜を形成し、さらに、連続して膜厚１０〜３０ｎｍの種々の組成のＣｏ、Ｃｒ及びＴａ又はＣｏ、Ｃｒ及びＰｔを主成分とする合金磁性膜を形成し、その上にカーボン保護膜を形成した。そして、これらの膜の磁気特性、結晶学的特性等を評価した。
【００３４】
また、図２（ａ）、（ｂ）は、本発明の磁気記憶装置の平面模式図及びそのＡＡ’線断面模式図である。この磁気記憶装置は、一枚又は複数枚の磁気ディスク２１と、磁気ディスクの情報記録面に対応した磁気ヘッド２３と、磁気ディスクを回転駆動する駆動部２２と、磁気ヘッド駆動手段２４と、信号処理部２５とを有する。前記磁気記録媒体に、磁気ヘッドとして電磁誘導型記録磁気抵抗効果型素子再生の複合ヘッド（ＭＲヘッド）を組み合わせて用いることが好ましい。
【００３５】
【実施例】
〈実施例１〉
外径６５ｍｍ、内径２０ｍｍ、厚さ０．６ｍｍのガラスディスク基板に付着し研磨材等の汚れを洗浄して乾燥させた。
【００３６】
この基板を枚葉式直流マグネトロンスパッタ装置の基板仕込み室に装填して真空に排気した後、当該基板を加熱室、非磁性下地膜形成室、磁性膜形成室、非磁性保護膜形成室及び取り出し室の順に、真空度５×１０^-8Ｔｏｒｒ以下の主排気槽を介しながら搬送し、それぞれの室でそれぞれの膜を形成した。
【００３７】
まず、８ｍＴｏｒｒのアルゴン圧のもとで、Ｚｒ添加濃度の異なるＣｒ−ＺｒＯ₂ターゲットに１ｋＷの電力を加えて、膜厚１０〜１００ｎｍのＣｒ−Ｚｒ−Ｏ非磁性下地膜を第１の非磁性下地膜として形成した。次いで加熱室で２７０℃に加熱し、８ｍＴｏｒｒのアルゴン圧のもとでＣｒ−２０原子％Ｔｉターゲットに４ｋＷの電力を加えて、膜厚２〜１５ｎｍのＣｒ−Ｔｉ下地膜を第２の非磁性下地膜として形成した。この下地膜の上に、８ｍＴｏｒｒのアルゴン圧のもとでターゲットに１．５ｋＷの電力を加えて、Ｃｏ−２０原子％Ｃｒ−６原子％Ｐｔからなる膜厚２０ｎｍの合金磁性膜を積層した。さらに、この磁性膜の上に１０ｍＴｏｒｒのアルゴン圧のもとでターゲットに１．５ｋＷの電力を加えて、膜厚１０ｎｍのカーボン保護膜を形成した。そして、当該保護膜上に吸着性のパーフルオロアルキルポリエーテル等の潤滑層を形成して２．５インチ磁気ディスクとした。
【００３８】
こうして形成した磁気ディスクの静磁気特性（保磁力Ｈｃ、角形比Ｓ^*）や記録再生特性を以下の方法により評価した。静磁気特性は、上記磁気ディスクを、その半径２０ｍｍの位置から８ｍｍ×８ｍｍの略正方形状に切り出し、片面の磁性膜を削り落とした試料を作製し、振動試料型磁力計（ＶＳＭ）を用いて最大印加磁界を１３ｋＯｅとして面内方向の静磁気特製を求めた。また、記録再生特性の評価には、磁気ヘッドとして、記録用にギャップ長０．４μｍ、トラック幅３．５μｍ、巻線数１７回の薄膜型ヘッド、再生用にシールド間隔０．２５μｍ、トラック幅２．３μｍのＭＲヘッドを有する記録再生分離型ヘッドを用い、線記録密度１８０ｋＢＰＩのときのＳ／Ｎの値を求めた。
【００３９】
ＺｒＯ₂を添加した非磁性複合膜はＸ線回析において回析ピークは検出されなかった。オージェ電子分光分析により測定した、上記非磁複合下地膜中のＺｒの濃度と、磁性膜のＨｃとの関係を図３に示す。Ｚｒの濃度を１原子％以上、２０原子％以下とすることにより、Ｈｃを向上できた。また、同試料の媒体ノイズを、Ｚｒを添加しない試料の値で規格化した、規格化媒体ノイズと上記複合下地膜中のＺｒ濃度との関係を図４に示す。Ｚｒの濃度を１原子％以上２０原子％以下とすることにより、媒体ノイズを低減できた。また、これらの試料において、Ｂｒと磁性膜厚ｔとの積はＢｒｔは８０Ｇμｍ、Ｓ^*はＺｒ添加濃度によらず約０．８と一定であり、Ｓ^*を減少せずに媒体ノイズを低減できることが確認できた。また、このときの複合下地膜中のオージェ電子分光分析により測定した酸素の濃度は、Ｚｒ濃度が増すに従い増加して、１原子％以上、３０原子％以下であることが確認された。
【００４０】
さらに、周囲の温度を５℃から１００℃まで変化させながら測定した、規格化保磁力温度変化率（室温の保磁力で規格化）とＺｒ添加濃度との関係を図５に示す。Ｚｒの濃度を１原子％以上、２０原子％以下とすることにより、規格化保磁力温度変化率が低減できた。一方、上記第２の非磁性下地膜であるＣｒ−Ｔｉ合金下地膜の膜厚を２０ｎｍ以上にすると、上記保磁力温度変化率の低減効果は減少した。
【００４１】
さらに、同試料の、線記録密度１８０ｋＢＰＩのときのＳ／Ｎの値と、上記複合下地膜中のＺｒ濃度との関係を図６に示した。Ｚｒの濃度を１原子％以上、２０原子％以下とすることにより、Ｓ／Ｎを向上できた。上記方法により形成された磁気記録媒体をＸ線回折分析した結果、上記非磁性複合下地膜にＺｒを添加するに従い、磁性膜の配向が六方晶構造の（１０．１）配向から、（１０．０）配向に変化し、基板面内方向に磁化容易軸（ｃ軸）が配向するようになった。これに伴い、残留磁化角形比（Ｓ）の値が０．８から０．９に向上した。一方、Ｃｒ−Ｔｉ下地膜の（１１０）Ｘ線回析強度はＺｒ添加濃度が増すに従い減少した。これは、結晶粒の微細化を表している。
【００４２】
〈実施例２〉
実施例１におけるＺｒの代わりにＳｉ、Ａｌ、Ｔｉ、Ｖ、Ｔａ、Ｙをそれぞれ１０原子％添加した磁気ディスクを製造し、そのＨｃ、規格化ノイズ、線記録密度１８０ｋＢＰＩのときのＳ／Ｎ、規格化保磁力温度変化率を評価した。その値を表１に示す。比較例には上記元素群を添加しない場合の特性を示す。
【００４３】
【表１】

【００４４】
いずれの場合も、無添加の試料に比べて特性向上が図られることが確認された。また、各元素の添加濃度を変化させた場合も、実施例１と同様、添加濃度を１原子％以上、２０原子％以上、酸素濃度を１原子％以上、３０原子％以下とすることにより特性向上が図られた。さらに、上記元素を２種以上添加した場合も同様の特性向上が図られることが確認できた。
【００４５】
さらに実施例１における第２の非磁性下地膜として、Ｃｒ−Ｔｉの代わりに、Ｃｒ−２０原子％Ｍｏ、Ｃｒ−２０原子％Ｗ、Ｃｒ−２０原子％Ｖを用いた磁気ディスクを製造し、その特性を評価した。この場合も実施例１の磁気ディスクと略同様の結果が得られた。
【００４６】
〈実施例３〉
実施例１、２と同等の特性を有する磁気ディスクを使用し、ＣｏＴａＺｒ合金を記録用磁極材料とし、ＭＲヘッドを用い、図２（ａ）及び図２（ｂ）に示した磁気記録装置を試作した。このように、上記磁気記録媒体と、ＭＲヘッド及び高精度のヘッド位置決め装置とを組み合わせることにより、１平方インチ当たり１．５ギガビットの面記録密度で記録再生エラー率が１０^-8の以下の特性が得られた。
【００４７】
本実施例では、ＣｏＴａＺｒ合金を磁極材とする複合型磁気ヘッドを用いた場合について説明したが、ＮｉＦｅ、ＦｅＣ合金等を記録用磁極材とする複合型磁気ヘッドを用いた場合にも同様な効果が得られる。さらに、上記磁気ヘッドの再生部を、従来の磁気抵抗効果よりも格段に大きい巨大磁気抵抗効果を利用した磁気抵抗センサによって構成することにより、１平方インチ当たり２ギガビット以上の高い面記録密度で記録再生エラー率が１０^-8以下の特性が得られた。
【００４８】
【発明の効果】
本発明によれば、保磁力温度変化率が小さく、１平方インチ当たり１ギガビット以上と極めて高い面記録密度で記録可能な面内磁気記録媒体が得られた。さらにこの磁気記録媒体と組み合わせた磁気記憶装置は、１平方インチ当たり１ギガビット以上と極めて高い面記録密度を有し、高い信頼性を示した。
【図面の簡単な説明】
【図１】本発明の一実施例の磁気記録媒体の縦断面構造図。
【図２】本発明の一実施例の磁気記憶装置の平面模式図及びそのＡ−Ａ’線縦断面図。
【図３】本発明の一実施例の非磁性複合下地膜中のＺｒの濃度と、磁性膜Ｈｃとの関係を表す図。
【図４】本発明の一実施例の非磁性複合下地膜中のＺｒの濃度と、規格化媒体ノイズとの関係を表す図。
【図５】本発明の一実施例の非磁性複合下地膜中のＺｒの濃度と、規格化保磁力温度変化率の関係を表す図。
【図６】本発明の一実施例の非磁性複合下地膜中のＺｒの濃度と、線記録密度１８０ｋＢＰＩのときのＳ／Ｎとの関係を表す図。
【符号の説明】
１１…基板
１２、１２’…非磁性メッキ膜
１３、１３’…第１の非磁性下地膜
１４、１４’…第２の非磁性下地膜
１５、１５’…情報記録層
１６、１６’…非磁性保護膜
２１…磁気ディスク
２２…駆動部
２３…磁気ヘッド
２４…磁気ヘッド駆動手段
２５…信号処理部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an information recording magnetic recording medium such as a magnetic disk, a manufacturing method thereof, and a magnetic storage device, and more particularly to a magnetic recording medium having a high surface recording density, a manufacturing method thereof, and a magnetic storage device.
[0002]
[Prior art]
Conventionally, an in-plane magnetic recording medium for recording by reversing the magnetization in the in-plane direction uses a Co-based alloy-based magnetic thin film mainly composed of a ferromagnetic metal such as Co as an information recording layer. In order to enable high-density information recording of 1 gigabit or more per square inch, it is required to increase the coercive force and reduce the medium noise for the recording layer.
[0003]
In general, in order to increase the coercive force (Hc), the amount of Pt added in the CoCrPt alloy magnetic film is increased, and this is formed on the alloy-based nonmagnetic underlayer having a body-centered cubic structure (bcc) of Cr or Cr as a main component. For example, Journal of Applied Physics, Vol. 73 (1993) 5569-5571 (J. Appl. Phys., Vol. 73, No. 10, (1993) p. 5569-5571). ) Is proposed.
[0004]
In addition, as an effective method for reducing the medium noise, when the medium is formed by sputtering, the magnetic crystal grains are magnetically separated by spatially separating the crystal grains of the recording layer by increasing the Ar pressure to 10 mTorr or more. (E.g., IEE Transaction on Magnetics, Vol. 26 (1990), pp. 1578 to 1580 (IEEE Trans. On Magn., Vol. 26, No. 5 (1990) p. 1578 to 1580)) are known. Further, a method of increasing the concentration of Cr in the CoCrPt magnetic film to segregate Cr to the grain boundaries (for example, IEE Transactions on Magnetics, Vol. 29 (1993), pages 3667-3669 (IEEE) Trans. On Magn., Vol. 29, No. 6 (1993) p. 3667-3669)).
[0005]
Further, as a technique for reducing the medium noise, the nonmagnetic underlayer mainly composed of Cr is formed into two layers, and the first underlayer disposed on the substrate side has a body-centered cubic structure in X-ray diffraction ( 110) A nonmagnetic underlayer having a crystal structure mainly composed of an orientation is formed to a thickness of 0.5 to 8 nm, and a second nonmagnetic underlayer mainly composed of a (200) orientation having a body-centered cubic structure is formed thereon. A method for forming a film thickness of 20 to 300 nm is described in JP-A-7-57238. Japanese Patent Laid-Open No. 1-290118 discloses a method for improving crystal orientation by adding oxygen to a nonmagnetic underlayer mainly composed of Cr as a method for improving magnetostatic characteristics and electromagnetic conversion characteristics. .
[0006]
Further, in order to realize high density recording, in order to overcome the demagnetizing field from the magnetization at the bit boundary and keep the magnetization in the recording direction, the coercive force is increased and at the same time the film thickness t of the recording layer It is necessary to reduce the product Br · t of the residual magnetic flux density Br to reduce the demagnetizing field (for example, IEE Transactions on Magnetics, Vol. 29 (1993), pages 3670 to 3672 (IEEE Trans). On Magn., Vol. 29, No. 6 (1993) p. 3670-3672)).
[0007]
[Problems to be solved by the invention]
The above prior art, that is, the increase in coercive force by increasing the Pt concentration in the magnetic film has a problem that the precious metal Pt is expensive and the manufacturing cost increases. For this reason, the technique which improves a coercive force by the other method was calculated | required. In addition, the method of separating the crystal grains of the magnetic film or increasing the Cr concentration to reduce the noise can be achieved by the coercive force squareness ratio (S ^* ) Is lowered, and as a result, there is a problem that the reproduction output is lowered. Further, when the medium noise is reduced by the above method, the value obtained by normalizing the change rate of the coercive force with respect to the environmental temperature by the coercive force at room temperature (25 ° C.) (hereinafter referred to as the normalized coercive force temperature change rate) increases. In this case, the coercive force increases and overwriting becomes difficult. At high temperatures, the coercive force decreases and the reproduction output decreases. Conventionally, there has been no known method for realizing both low noise and a reduction in the coercive force temperature change rate.
[0008]
In the method described in Japanese Patent Laid-Open No. 7-57238, the first base film disposed on the substrate side is 0.5 to 8 nm, preferably 0.5 to 1.5 nm, which is 1 in comparison with other films. It is necessary to form the film with a very thin film thickness of / 10 or less, and it is difficult to manufacture a large amount of magnetic recording media with a constant quality by controlling the film thickness distribution in the disk surface or by a mass production process. Further, there is no description on the effect of improving the coercive force or reducing the coercive force temperature change rate.
[0009]
In the method described in JP-A-1-290118, the coercive force and S ^* However, the effect of reducing the medium noise or reducing the coercive force temperature change rate is not described.
[0010]
As described above, in order to achieve higher density, the coercive force is improved without increasing the Pt concentration in the magnetic film, and S ^* Therefore, it is necessary to reduce the medium noise without lowering the value of the above and without increasing the rate of change in the normalized coercive force temperature.
[0011]
Furthermore, it has not been sufficiently studied how a magnetic disk device having a high recording density can be realized by combining a recording / reproducing separated type head using a magnetoresistive element and the magnetic recording medium. It was. In order to achieve the above-mentioned recording density of 1 gigabit per square inch or more, it has been found that Hc exceeding 2.0 kOe is required.
[0012]
A first object of the present invention is a high coercive force, high S, capable of recording and reproducing high-density information. ^* Another object of the present invention is to provide a magnetic recording medium with low noise and high reliability.
The second object of the present invention is to provide a high coercive force and a high S as described above. ^* Another object of the present invention is to provide a method for manufacturing a low noise magnetic recording medium.
The third object of the present invention is to provide a high coercive force and a high S as described above. ^* Another object of the present invention is to provide a highly reliable magnetic storage device using a low noise magnetic recording medium.
[0013]
[Means for Solving the Problems]
In order to achieve the first object, in the magnetic recording medium of the present invention, an information recording layer made of a Co-based alloy-based magnetic film is disposed on a substrate with at least two nonmagnetic underlayers interposed therebetween. The first nonmagnetic underlayer disposed on the most substrate side among the nonmagnetic underlayers is selected from the group consisting mainly of Cr and consisting of Zr, Si, Al, Ti, V, Ta, and Y. A composite film containing at least one element and oxygen is used so that the concentration of the element is 1 atomic% to 20 atomic% and the oxygen concentration is 1 atomic% to 30 atomic%.
[0014]
The second nonmagnetic underlayer disposed on the most information recording layer side of the nonmagnetic underlayer is at least one element selected from the group consisting of Ti, Mo, W, and V containing Cr as a main component. Preferably in a concentration of 5 atomic% or more and 50 atomic% or less, and preferably has a crystal structure mainly composed of a (110) orientation of a body-centered cubic structure in X-ray diffraction.
[0015]
Further, the first nonmagnetic underlayer is amorphous in X-ray diffraction, the film thickness is 10 nm or more and 100 nm or less, and the second nonmagnetic underlayer film is 2 nm or more and 15 nm or less, It is preferable that the magnetic film has a (10.0) -oriented crystal structure with a hexagonal close packed structure in X-ray diffraction, since the effect of improving the coercive force and reducing the temperature change rate appears. In particular, when the average particle size of the first nonmagnetic underlayer is 2 nm or more and 30 nm or less, the medium noise can be kept low. Further, if the thickness of the nonmagnetic undercoat film is 10 nm or more, the mass production process can be easily controlled, and if the thickness is 100 nm or less, the desired particle size can be maintained.
[0016]
The element of the group consisting of Zr, Si, Al, Ti, V, Ta, and Y has a property of being more easily bonded to oxygen than Cr and exists mainly in an oxide state in the composite film. Thus, by making the nonmagnetic underlayer film a composite film of an oxide of a group consisting of Zr, Si, Al, Ti, V, Ta, Y and Cr, the particle size is small and uniform, An amorphous film can be formed by X-ray diffraction. This is because the oxide of the element group consisting of Zr, Si, Al, Ti, V, Ta, and Y has an effect of suppressing crystal growth of Cr crystal grains. It is preferable that these oxides are segregated in the film because the coercive force can be improved and the coercive force temperature change rate can be reduced.
[0017]
The additive concentration of the oxide of the group consisting of Zr, Si, Al, Ti, V, Ta, and Y in the nonmagnetic undercoat film is such that the total concentration of the group of elements is 1 atomic% or more and 20 atomic% or less. When the oxygen concentration is 1 atomic% or more and 30 atomic% or less, an amorphous structure can be obtained in X-ray diffraction. Such a composite film can be easily formed by sputtering using an oxide of an element of the group consisting of Zr, Si, Al, Ti, V, Ta, and Y and a target consisting of Cr. Further, when two or more kinds of oxides of the above elements are added, the same characteristics can be improved.
[0018]
Further, the nonmagnetic underlayer is composed of at least two layers, and the first nonmagnetic underlayer disposed on the most substrate side of the nonmagnetic underlayer is composed of the above composite film, and is the most information recording layer among the nonmagnetic underlayers. The second nonmagnetic underlayer disposed on the layer side is made of an alloy mainly composed of Cr having a body-centered cubic structure (bcc), and the size of the (110) crystal lattice is a hexagonal close packed structure When formed so as to substantially match the size of the (10.1) crystal lattice of the Co alloy magnetic film of (hcp), Hc is 2 kOe or more and 5 kOe or less, S ^* Can be kept as high as 0.7 or more and 0.95 or less, 1 Gb / in ² It is preferable because sufficient reproduction output can be obtained even at the above high recording density. Here, the fact that the size of the crystal lattice of the second nonmagnetic underlayer substantially matches the size of the crystal lattice of the magnetic film means that the difference in the size of the crystal lattice is in the range of about ± 5%. It means that if you are in. In particular, when the second non-magnetic underlayer is made of Cr—Ti or Cr—Mo alloy, and the addition concentration of Ti or Mo is 10-20 atomic%, the Co—Cr—Pt alloy magnetic film The crystal lattice matching is increased, and the crystal grain size can be reduced, which is preferable because the medium noise can be reduced.
[0019]
In addition, when the non-magnetic underlayer made of the composite film is formed, the ratio of crystal grains that are oriented and grown so that the (10.0) plane is parallel to the substrate in the crystal grains of the magnetic film can be increased. As a result, the c-axis, which is the easy axis of magnetization of the magnetic film, becomes parallel to the substrate surface, and the coercive force and the residual magnetization squareness ratio (S) are improved. As a result, 1Gb / in ² Sufficient reproduction output can be obtained even at the above high recording density.
[0020]
As described above, the coercive force and the coercive force temperature change rate can be improved as a result of the improvement of the crystal structure, crystal orientation, and lattice matching. In particular, when the thickness of the second nonmagnetic underlayer is 5 nm or more and 15 nm or less, the coercive force temperature change rate is significantly reduced. As a result, it is preferable that the change in coercive force is reduced in the temperature range of 5 ° C. to 55 ° C., and fluctuations in overwrite and reproduction output can be reduced.
[0021]
Furthermore, in the above magnetic recording medium, if the total magnetic film thickness t is 10 nm, 30 nm or less, and the coercive force Hc is 2.0 kOe or more, the magnetization disorder in the magnetization transition region is reduced and the width of the magnetization transition region is reduced. It is preferable because a high output can be obtained even in a high recording density region. In particular, Brt of 30 Gμm or more and 100 Gμm or less is preferable because medium noise is reduced and a high medium S / N can be obtained. In order to guarantee good overwriting characteristics, the coercive force Hc is preferably 4 kOe or less.
[0022]
Further, in the magnetic recording medium, when the center line average roughness Ra of the surface of the medium protective film measured in the direction perpendicular to the head running direction is 0.3 nm or more and 3 nm or less, the head flying height is 0.02 μm or more, 0 .1 μm or less is preferable because it floats stably. In order to control the adhesion of the magnetic head during CSS operation when Ra on the surface of the medium is smaller than the conventional value, the surface is formed by plasma etching using a mask after forming a protective film on the magnetic film. The surface of the protective film is formed to have fine protrusions on the surface using a low melting point metal compound such as Al or a mixture target, or finely formed on the surface by heat treatment. It is preferable to form unevenness because the frictional force between the head and the medium can be reduced during the CSS operation, and the problem of the head sticking to the medium can be avoided.
[0023]
Furthermore, the main component is at least one of Cr, Mo, W, V, Ta, Nb, Zr, Ti, B, Be, C, Ni-P, and Ni-B, and the film thickness is 0.5 nm or more and 5 nm or less. It is preferable that the nonmagnetic intermediate layer is a magnetic film having two or more layers because the medium noise is further reduced as compared with a single-layer magnetic film.
[0024]
Further, as a protective layer of the magnetic film, a nonmagnetic material mainly composed of carbon, hydrogenated carbon or carbon is formed to a thickness of 5 to 20 nm, and a lubricating layer such as an adsorptive perfluoroalkyl polyether is formed to a thickness of 3 to 3 nm. By providing 10 nm, a magnetic recording medium with high reliability and high density recording can be obtained. For the protective layer, carbides such as WC, (W-Mo) -C, (Zr-Nb) -N, Si _Three N _Four Nitride such as SiO ₂ , ZrO ₂ Oxides such as B or B _Four C, MoS ₂ , Rh or the like is preferable because it can improve sliding resistance and corrosion resistance. The surface of these protective films is etched using a mask, and protrusions with an area ratio of 1 to 20% are provided, or film formation conditions, compositions, etc. are adjusted to deposit protrusions of different phases in the protective film. Thus, it is more preferable that the protective film has a larger surface roughness than the surface of the magnetic film.
[0025]
In order to achieve the second object, the method of manufacturing a magnetic recording medium of the present invention comprises forming a non-magnetic underlayer film of at least two layers on a substrate and then comprising a Co-based alloy-based magnetic film. An information recording layer is formed, and the formation of the first nonmagnetic underlayer disposed on the most substrate side among the nonmagnetic underlayers is made by using Cr, Zr, Si, Al, Ti, V, Ta and Y An oxygen gas in pure Ar using a target consisting of a mixture with an oxide of at least one element selected from the group consisting of: an element having an additive concentration of 1 atomic% to 20 atomic% This is performed by sputtering without using.
[0026]
Here, when the first nonmagnetic underlayer is formed at room temperature and then the substrate is heated to 150 ° C. or higher and 400 ° C. or lower and then the second nonmagnetic underlayer is formed, the coercive force is improved and the temperature is increased. This is preferable because the rate of change is reduced. In forming the medium, it is preferable that the substrate temperature when forming the magnetic film is 200 ° C. or higher and 400 ° C. or lower because the segregation of Cr in the magnetic film is promoted and Hc is improved.
[0027]
Furthermore, in order to achieve the third object, a magnetic storage device of the present invention comprises any one of the above magnetic recording media and a magnetic head for recording / reproducing information on the magnetic recording medium. Is.
[0028]
The magnetic head used in combination with the above magnetic storage medium as a magnetic storage device is preferably a recording / reproducing separated type head using a magnetoresistive element as a reproducing element. The above magnetic recording medium has a sufficient S / N even when recording / reproducing at a recording density of 1 gigabit per square inch or more, for example, in combination with high reproduction sensitivity which is a characteristic of the magnetoresistive element. can get.
[0029]
Furthermore, the reproducing part of this magnetic head is made of a conductive layer disposed between the conductive magnetic layer and a plurality of conductive magnetic layers that cause a large change in resistance due to relative changes in their magnetization directions due to an external magnetic field. A product Br composed of a magnetoresistive sensor including a non-magnetic layer and the thickness t of the magnetic layer and Br measured by applying a magnetic field in the relative running direction of the magnetic head with respect to the magnetic recording medium during recording・ By setting t to 30 Gμm or more and 80 Gμm or less and the coercive force Hc of the magnetic recording medium measured by applying a magnetic field in the above direction to 2.2 kiloOersted or more, a high of 2 gigabits or more per square inch It is also possible to record / reproduce dense information.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a cross-sectional structure of an in-plane magnetic recording medium of the present invention. In the figure, 11 is a substrate made of Al—Mg alloy, chemically tempered glass, crystallized glass, titanium, silicon, carbon or ceramics, and 12 and 12 ′ are Ni—P and Ni—W formed on both surfaces of the substrate 11. A nonmagnetic plating layer made of -P or the like. When an Al—Mg alloy is used as a substrate, a substrate having such a plating layer is used as the substrate. In addition, when Si single crystal, glass, carbon, etc. are used for a board | substrate, it is not necessary to form a nonmagnetic plating layer.
[0031]
13 and 13 ′ are first non-magnetic elements composed of a composite film containing Cr as a main component and containing at least one element of the group consisting of Zr, Si, Al, Ti, V, Ta, and Y and oxygen. Underlayers 14 and 14 'are made of Cr, Mo, W, V, Nb, Ta, Cu, Ag, Mn, Zr, Hf or Si, or Cr, Mo, W, V, Nb, Ta, Cu, This is a second non-magnetic underlayer made of an alloy mainly containing any one of Ag, Mn, Zr, Hf, and Si. In addition, when the nonmagnetic underlayer has three layers, the same material as above is used for the intermediate layer.
[0032]
Further, 15 and 15 'are Co-Sm, Co-Ni-Cr, Co-Ni-Pt, Co-Ni-P, Co-Cr-Ta, Co-Cr-Pt formed on the nonmagnetic underlayer. , Co-Cr-W, Co-Cr-Si, Co-Cr-Ta-Pt, etc., an information recording layer made of an alloy magnetic film, and 16 and 16 'are carbon, boron, SiO ₂ , ZrO ₂ It is a nonmagnetic protective film made of, for example.
[0033]
Such an in-plane magnetic recording medium was manufactured as follows. Various magnetic disk substrates such as a tempered glass substrate, a crystallized glass substrate, and an Al alloy substrate whose surface is mirror-polished by plating with Ni-P are used, and each film constituting the magnetic recording medium is separately provided. Each film was formed by DC magnetron sputtering using a single-wafer sputtering apparatus formed in the film forming chamber and sequentially feeding one by one at a constant tact time of 10 seconds. Here, the film forming conditions are as follows: back pressure of main vacuum chamber: 5 × 10 ^-8 Below Torr, substrate heating temperature: 100 to 300 ° C., Ar gas pressure: 5 to 30 mTorr, input power: 1 to 4 kW for a target size of 6 inches. One or more nonmagnetic underlayers mainly composed of Cr are formed on the various substrates, and Co, Cr and Ta, or Co, Cr and Pt having various thicknesses of 10 to 30 nm are continuously formed. An alloy magnetic film containing as a main component was formed, and a carbon protective film was formed thereon. Then, the magnetic characteristics, crystallographic characteristics, etc. of these films were evaluated.
[0034]
2A and 2B are a schematic plan view and a schematic cross-sectional view taken along line AA ′ of the magnetic memory device of the present invention. This magnetic storage device includes one or a plurality of magnetic disks 21, a magnetic head 23 corresponding to the information recording surface of the magnetic disk, a drive unit 22 that rotationally drives the magnetic disk, a magnetic head drive unit 24, a signal And a processing unit 25. The magnetic recording medium is preferably used in combination with a composite head (MR head) for reproducing an electromagnetic induction recording magnetoresistive element as a magnetic head.
[0035]
【Example】
<Example 1>
Attached to a glass disk substrate having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.6 mm, dirt such as an abrasive was washed and dried.
[0036]
After this substrate is loaded into the substrate preparation chamber of a single-wafer DC magnetron sputtering apparatus and evacuated to vacuum, the substrate is removed from the heating chamber, nonmagnetic underlayer forming chamber, magnetic film forming chamber, nonmagnetic protective film forming chamber, and the like. The degree of vacuum is 5 × 10 ^-8 The film was conveyed through the main exhaust tank below Torr, and each film was formed in each chamber.
[0037]
First, Cr—ZrO having different Zr addition concentrations under an argon pressure of 8 mTorr. ₂ A power of 1 kW was applied to the target to form a 10 to 100 nm thick Cr—Zr—O nonmagnetic underlayer as the first nonmagnetic underlayer. Next, it is heated to 270 ° C. in a heating chamber, 4 kW of power is applied to the Cr-20 atomic% Ti target under an argon pressure of 8 mTorr, and a 2-15 nm thick Cr—Ti underlayer film is formed as a second nonmagnetic film. A base film was formed. On this base film, an alloy magnetic film having a thickness of 20 nm made of Co-20 atomic% Cr-6 atomic% Pt was laminated by applying a power of 1.5 kW to the target under an argon pressure of 8 mTorr. Further, a carbon protective film having a thickness of 10 nm was formed on the magnetic film by applying a power of 1.5 kW to the target under an argon pressure of 10 mTorr. Then, a lubricating layer such as adsorptive perfluoroalkyl polyether was formed on the protective film to obtain a 2.5 inch magnetic disk.
[0038]
Magnetostatic characteristics (coercivity Hc, squareness ratio S) of the magnetic disk thus formed ^* ) And recording / reproducing characteristics were evaluated by the following methods. The magnetostatic characteristics are obtained by cutting the magnetic disk into a substantially square shape of 8 mm × 8 mm from a radius of 20 mm, preparing a sample by scraping off one side of the magnetic film, and using a vibrating sample magnetometer (VSM). A static magnetic special product in the in-plane direction was determined with a maximum applied magnetic field of 13 kOe. For the evaluation of recording / reproducing characteristics, the magnetic head is a thin film type head having a gap length of 0.4 μm and a track width of 3.5 μm and a winding number of 17 for recording, and a shield interval of 0.25 μm and a track width for reproducing. Using a recording / reproducing separated type head having an MR head of 2.3 μm, the S / N value at a linear recording density of 180 kBPI was determined.
[0039]
ZrO ₂ No diffraction peak was detected in the X-ray diffraction of the nonmagnetic composite film to which was added. FIG. 3 shows the relationship between the Zr concentration in the nonmagnetic composite underlayer and the Hc of the magnetic film, measured by Auger electron spectroscopy. Hc could be improved by setting the concentration of Zr to 1 atom% or more and 20 atom% or less. FIG. 4 shows the relationship between the normalized medium noise and the Zr concentration in the composite base film obtained by normalizing the medium noise of the sample with the value of the sample not added with Zr. By setting the concentration of Zr to 1 atom% or more and 20 atom% or less, medium noise could be reduced. Moreover, in these samples, the product of Br and the magnetic film thickness t is 80 Gμm for Brt, S ^* Is constant at about 0.8 regardless of the Zr addition concentration, and S ^* It was confirmed that the media noise can be reduced without reducing the noise. Further, it was confirmed that the oxygen concentration measured by Auger electron spectroscopy in the composite underlayer at this time increased as the Zr concentration increased and was 1 atomic percent or more and 30 atomic percent or less.
[0040]
Furthermore, FIG. 5 shows the relationship between the normalized coercive force temperature change rate (normalized by the coercive force at room temperature) and the Zr addition concentration measured while changing the ambient temperature from 5 ° C. to 100 ° C. The normalized coercivity temperature change rate could be reduced by setting the concentration of Zr to 1 atom% or more and 20 atom% or less. On the other hand, when the film thickness of the Cr—Ti alloy base film as the second nonmagnetic base film was set to 20 nm or more, the effect of reducing the coercive force temperature change rate decreased.
[0041]
Further, FIG. 6 shows the relationship between the S / N value at the linear recording density of 180 kBPI and the Zr concentration in the composite base film of the sample. S / N could be improved by setting the concentration of Zr to 1 atom% or more and 20 atom% or less. As a result of X-ray diffraction analysis of the magnetic recording medium formed by the above method, as Zr is added to the nonmagnetic composite underlayer, the orientation of the magnetic film changes from the (10.1) orientation of the hexagonal structure to (10. 0) Orientation changed, and the easy axis (c-axis) was oriented in the in-plane direction of the substrate. Along with this, the value of the remanent magnetization squareness ratio (S) was improved from 0.8 to 0.9. On the other hand, the (110) X-ray diffraction intensity of the Cr—Ti underlayer decreased as the Zr addition concentration increased. This represents the refinement of crystal grains.
[0042]
<Example 2>
A magnetic disk to which 10 atomic% of Si, Al, Ti, V, Ta, and Y was added instead of Zr in Example 1 was manufactured, and its Hc, normalized noise, S / N at a linear recording density of 180 kBPI, The normalized coercivity temperature change rate was evaluated. The values are shown in Table 1. The comparative example shows characteristics when the above element group is not added.
[0043]
[Table 1]

[0044]
In either case, it was confirmed that the characteristics were improved as compared with the additive-free sample. In addition, when the addition concentration of each element is changed, as in Example 1, the characteristics are obtained by setting the addition concentration to 1 atomic% or more and 20 atomic% or more and the oxygen concentration to 1 atomic% or more and 30 atomic% or less. Improvements were made. Furthermore, it was confirmed that the same characteristics were improved when two or more of the above elements were added.
[0045]
Further, a magnetic disk using Cr-20 atomic% Mo, Cr-20 atomic% W, Cr-20 atomic% V instead of Cr-Ti as the second nonmagnetic underlayer in Example 1, Its characteristics were evaluated. In this case, the same result as that of the magnetic disk of Example 1 was obtained.
[0046]
<Example 3>
The magnetic recording device shown in FIGS. 2 (a) and 2 (b) is prototyped using a magnetic disk having the same characteristics as in Examples 1 and 2, using a CoTaZr alloy as a recording magnetic pole material, and an MR head. did. Thus, by combining the magnetic recording medium, the MR head, and the high-precision head positioning device, a recording / reproducing error rate of 10 gigabytes per square inch is obtained with a surface recording density of 1.5 gigabits. ^-8 The following characteristics were obtained.
[0047]
In this embodiment, the case of using a composite magnetic head using a CoTaZr alloy as a magnetic pole material has been described. Is obtained. Furthermore, the reproducing part of the magnetic head is constituted by a magnetoresistive sensor using a giant magnetoresistive effect that is much larger than the conventional magnetoresistive effect, thereby recording at a high surface recording density of 2 gigabits or more per square inch. Playback error rate is 10 ^-8 The following characteristics were obtained:
[0048]
【The invention's effect】
According to the present invention, an in-plane magnetic recording medium having a small coercive force temperature change rate and capable of recording at a very high surface recording density of 1 gigabit per square inch or more was obtained. Further, the magnetic storage device combined with this magnetic recording medium has a very high surface recording density of 1 gigabit per square inch or more, and exhibits high reliability.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a magnetic recording medium according to an embodiment of the present invention.
FIG. 2 is a schematic plan view of a magnetic memory device according to an embodiment of the present invention and a longitudinal sectional view taken along line AA ′.
FIG. 3 is a diagram showing the relationship between the concentration of Zr in the nonmagnetic composite underlayer and the magnetic film Hc in one embodiment of the present invention.
FIG. 4 is a graph showing the relationship between the Zr concentration in the nonmagnetic composite underlayer of one embodiment of the present invention and the normalized medium noise.
FIG. 5 is a graph showing the relationship between the Zr concentration in the nonmagnetic composite underlayer of one embodiment of the present invention and the normalized coercivity temperature change rate.
FIG. 6 is a graph showing the relationship between the Zr concentration in the nonmagnetic composite underlayer and the S / N when the linear recording density is 180 kBPI according to one embodiment of the present invention.
[Explanation of symbols]
11 ... Board
12, 12 '... non-magnetic plating film
13, 13 '... first nonmagnetic underlayer
14, 14 '... second nonmagnetic underlayer
15, 15 '... information recording layer
16, 16 '... nonmagnetic protective film
21 ... Magnetic disk
22 ... Drive unit
23 ... Magnetic head
24. Magnetic head driving means
25. Signal processor

Claims

In a magnetic recording medium in which an information recording layer made of a Co-based alloy-based magnetic film is disposed on a substrate via at least two non-magnetic underlayers.
The first nonmagnetic underlayer disposed on the most substrate side among the nonmagnetic underlayers is at least one selected from the group consisting of Zr, Si, Al, Ti, V, and Y, containing Cr as a main component. complex is an amorphous film ing from film, the first of said at least one element concentration 0 atom% greater than 20 atoms to be contained in the non-magnetic undercoat layer which is segregated to the oxide of the element contained in % Or less, and the product Br · t of the residual magnetic flux density Br and the thickness t of the magnetic film at the time of information recording is 30 Gμm to 80 Gμm.

The second nonmagnetic underlayer disposed on the most information recording layer side of the nonmagnetic underlayer is at least one element selected from the group consisting of Ti, Mo, W, and V containing Cr as a main component. 2. The magnetic material according to claim 1, comprising a crystal structure mainly composed of a (110) orientation of a body-centered cubic structure. recoding media.

2. The magnetic recording medium according to claim 1, wherein the first nonmagnetic underlayer is amorphous and has a thickness of 10 nm to 100 nm.

3. The magnetic recording medium according to claim 2, wherein the thickness of the second nonmagnetic underlayer is 2 nm or more and 15 nm or less.

A method of manufacturing a magnetic recording medium, comprising forming at least two layers of a nonmagnetic underlayer on a substrate and then forming an information recording layer comprising a Co-based alloy-based magnetic film,
The formation of the first nonmagnetic underlayer is made of a mixture of Cr and an oxide of at least one element selected from the group consisting of Zr, Si, Al, Ti, V, and Y. A method for forming a magnetic recording medium, wherein a target having a concentration of greater than 0 atomic% and not greater than 20 atomic% is used for sputtering in pure Ar without using oxygen gas.

6. The first nonmagnetic undercoat film is formed at room temperature, and then the substrate is heated to 150 ° C. or higher and 400 ° C. or lower, and then the second nonmagnetic undercoat film is formed. Of forming a magnetic recording medium.