JP2000215533A - Magneto-optical recording medium, magneto-optical recording and reproducing method using the same, and magneto-optical recording and reproducing device - Google Patents
Magneto-optical recording medium, magneto-optical recording and reproducing method using the same, and magneto-optical recording and reproducing deviceInfo
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- JP2000215533A JP2000215533A JP11018207A JP1820799A JP2000215533A JP 2000215533 A JP2000215533 A JP 2000215533A JP 11018207 A JP11018207 A JP 11018207A JP 1820799 A JP1820799 A JP 1820799A JP 2000215533 A JP2000215533 A JP 2000215533A
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- layer
- recording
- reproducing
- magneto
- magnetic field
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Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は光ビームを照射して
情報の記録再生を行う光磁気記録再生技術に関する。The present invention relates to a magneto-optical recording / reproducing technique for recording / reproducing information by irradiating a light beam.
【0002】[0002]
【従来の技術】膜面に対して垂直な方向に磁化容易軸を
有する磁性膜に光ビームを照射して加熱し、加熱部の保
磁力を低下して、保磁力が低下した部分に磁界を印加
し、磁化の向きを印加磁界の向きに揃えて、情報の記録
・消去を行い、磁化の向きに応じたカー回転を利用して
情報の再生を行う光磁気記録再生方法は、音楽用ミニデ
ィスク、パソコン用バックアップファイル等に実用化さ
れており、今後も情報量の増大に伴い大容量化、高転送
速度化が期待されている。光磁気記録の記憶容量即ち記
録密度は、光源の波長、焦点レンズのNAで主に規定さ
れ、記録マークのサイズ(最短ビット長相当のマーク長
もしくはトラックピッチに相当するマーク幅)は、焦点
位置におけるレーザスポットの全半値幅(FWHM)程
度の大きさになる。基本的にはこのFWHMが最短マー
ク長、最短スペース(マーク間)長、トラックピッチを
規定するので、波長とNAが決まれば記録密度はほぼ決
定される。この波長限界を打破する技術として、磁界変
調記録によるFWHMよりも短いマークとスペースの記
録、磁気的超解像再生(MSR)による狭ピッチマーク
列の低符号間干渉再生、磁区拡大再生(MAMMOS)
による微細マークの高C/N再生が提案されている。磁
界変調記録は外部磁界を情報変調し記録ビームはDC的
もしくは単一周波数でパルス的に照射する。記録光スポ
ットが記録トラック上のある位置に居る時に例えば下向
きに記録飽和磁界以上の大きさの磁界が印加されている
と、その瞬間にスポットのFWHM相当の範囲の記録層
の磁化は下向きに磁化する。スポットが媒体に対して例
えばFWHMの半分移動した時に、上向きに記録飽和磁
界以上の大きさの磁界が印加されていると、その瞬間に
スポットのFWHM相当の範囲の記録層の磁化は上向き
に磁化する事になるので、前に下向きに磁化したFWH
M相当の磁化の半分は上向きに磁化され、結果的にFW
HMよりも短いマーク、スペースの記録が可能となるの
が磁界変調記録の利点である。磁界変調記録によりFW
HM相当の長さよりも狭ピッチでマークを記録する事は
出来るが、これを単にe−2径がFWHMの倍程度の領
域に跨るガウス形のスポット(通常記録と同一のスポッ
トが用いられる)で再生すると符号間干渉が大きく実用
的なC/Nが得られにくい。そこで例えばJoint−
MORIS/ISOM97テクニカルダイジェストの
p.70,p.78,p.80,p.174,p.25
4等に開示されているMSR再生、もしくは例えばJo
int−MORIS/ISOM97テクニカルダイジェ
ストのp.36,p.42,p.262又はH10電気
学会全国大会予稿S.10−6に開示されているMAM
MOS再生技術が提案されている。MSR,MAMMO
Sとも細かく分類すると各種の方法に分類されるが、基
本的にはMSRは、複数の磁性層間(最も簡単には記録
層と再生層間)の交換相互作用もしくは静磁的相互作用
を利用して、記録層の磁化の一部のみを再生層に転写、
転写部以外の領域はマスクをかけて再生分解能を上げる
技術であり、MAMMOSはやはり複数の磁性層間(最
も簡単には記録層と再生層間)の交換相互作用もしくは
静磁的相互作用を利用して、記録層の磁化の一部のみを
再生層に転写、転写した磁区を磁壁移動力、もしくは核
生成力を利用して拡大し再生C/Nを向上する技術であ
る。2. Description of the Related Art A magnetic film having an axis of easy magnetization in a direction perpendicular to the film surface is irradiated with a light beam and heated to reduce the coercive force of a heating portion and to apply a magnetic field to a portion where the coercive force is reduced. The magneto-optical recording / reproducing method of recording and erasing information by applying the magnetization direction to the direction of the applied magnetic field and reproducing the information using Kerr rotation according to the direction of the magnetization is a music miniature. It has been put to practical use for disks, backup files for personal computers, etc., and is expected to have a larger capacity and a higher transfer rate as the amount of information increases. The storage capacity of magneto-optical recording, that is, the recording density, is mainly determined by the wavelength of the light source and the NA of the focusing lens, and the size of the recording mark (the mark length corresponding to the shortest bit length or the mark width corresponding to the track pitch) depends on the focal position. Is about the full width at half maximum (FWHM) of the laser spot. Basically, the FWHM defines the shortest mark length, the shortest space (between marks) length, and the track pitch. Therefore, if the wavelength and NA are determined, the recording density is almost determined. Techniques for overcoming this wavelength limit include recording of marks and spaces shorter than FWHM by magnetic field modulation recording, low inter-code interference reproduction of narrow pitch mark arrays by magnetic super-resolution reproduction (MSR), and magnetic domain expansion reproduction (MAMMOS)
Has been proposed for high C / N reproduction of fine marks. The magnetic field modulation recording modulates information of an external magnetic field and irradiates a recording beam in a DC manner or in a pulse at a single frequency. If the recording light spot is at a certain position on the recording track, for example, if a magnetic field having a magnitude equal to or larger than the recording saturation magnetic field is applied downward, the magnetization of the recording layer in the range equivalent to the FWHM of the spot is magnetized downward at that moment. I do. If a magnetic field having a magnitude equal to or larger than the recording saturation magnetic field is applied upward when the spot moves half of the FWHM with respect to the medium, for example, the magnetization of the recording layer corresponding to the FWHM of the spot is magnetized upward at that moment. FWH magnetized downward before
Half of the magnetization corresponding to M is magnetized upward, resulting in FW
The advantage of magnetic field modulation recording is that marks and spaces shorter than HM can be recorded. FW by magnetic field modulation recording
A mark can be recorded at a narrower pitch than the length corresponding to the HM, but this is simply performed with a Gaussian spot (the same spot as that used for normal recording is used) in which the e-2 diameter spans about twice the area of the FWHM. Reproduction causes large intersymbol interference and makes it difficult to obtain a practical C / N. So, for example, Joint-
MORIS / ISOM97 Technical Digest p. 70, p. 78, p. 80, p. 174, p. 25
4 or the like, or for example, Jo
int-MORIS / ISOM97 Technical Digest p. 36, p. 42, p. 262 or H10 IEEJ National Convention S.S. MAM disclosed in 10-6
MOS regeneration technology has been proposed. MSR, MAMMO
S is also classified into various methods if it is finely classified. Basically, the MSR uses an exchange interaction or a magnetostatic interaction between a plurality of magnetic layers (in the simplest case, a recording layer and a reproducing layer). Transfer only a part of the magnetization of the recording layer to the reproducing layer,
The area other than the transfer area is a technique for increasing the reproduction resolution by using a mask, and MAMMOS also utilizes an exchange interaction or a magnetostatic interaction between a plurality of magnetic layers (most simply, a recording layer and a reproduction layer). In this technique, only a part of the magnetization of the recording layer is transferred to the reproducing layer, and the transferred magnetic domain is enlarged by using the domain wall moving force or the nucleation force to improve the reproducing C / N.
【0003】上記した従来技術によればマークピッチを
スポットのFWHM長よりも短く出来るので、波長限界
以上の高密度記録再生が可能であるが、磁界変調記録は
高速データ転送の要求を満たす上では、外部磁界を記録
膜から数ミクロン程度の近接した位置に設けなければな
らないので、基本的には貼り合せディスクが使用出来ず
ディスクとしての容量はそれほど向上しない。又、磁界
源の消費電力、ディスクチルト時の磁界源とディスクと
の接触などの課題も有している。又、マーク長、スペー
ス長を短く出来るが、マーク幅はFWHM相当なのでト
ラックピッチを詰める効果は無い。According to the above-mentioned prior art, the mark pitch can be made shorter than the FWHM length of the spot, so that high-density recording / reproduction exceeding the wavelength limit is possible. Since the external magnetic field must be provided at a position close to the recording film by several microns, basically, a bonded disk cannot be used, and the capacity of the disk is not so much improved. There are also problems such as power consumption of the magnetic field source and contact between the magnetic field source and the disk during disk tilt. Although the mark length and the space length can be shortened, the mark width is equivalent to FWHM, so that there is no effect of reducing the track pitch.
【0004】又、MSR,MAMMOSは最も簡単な構
成においても、記録磁性層以外に再生磁性層を必要とす
るので、記録磁性層が一層で構わない磁界変調記録で
は、二層磁性層の比較的簡単な構成で実施出来るが、記
録磁性層の多層化が必要な(オーバライト可能な)光変
調記録に適用しようとする場合、Joint−MORI
S/ISOM97テクニカルダイジェストのp.174
に開示されている様に、磁性層数だけで六層、干渉層、
反射層を合わせると十層もの複雑な媒体構成を必要とし
て、実用的では無い。[0004] Even in the simplest configuration, the MSR and MAMMOS require a reproducing magnetic layer in addition to the recording magnetic layer. This method can be implemented with a simple configuration, but when applying to optical modulation recording that requires a multi-layered recording magnetic layer (that can be overwritten), Joint-MORI
S / ISOM97 Technical Digest p. 174
As disclosed in 6, the number of magnetic layers alone, the interference layer,
The combination of the reflective layers requires a complicated medium configuration of ten layers, which is not practical.
【0005】[0005]
【発明が解決しようとする課題】本発明は掲記した従来
技術の課題を解決する為のもので、磁界変調記録とMS
R,MAMMOS再生の組合せと同等の簡単な層構成
で、磁界変調記録同様にマークピッチを詰める事が可能
な上にトラックピッチをも詰める事が可能な、光変調記
録と高分解能再生を両立する光磁気記録媒体、それを用
いた記録再生方法及び記録再生装置を提供する事をその
目的としている。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is intended to solve the above-mentioned problems by magnetic field modulation recording and MS.
With a simple layer structure equivalent to the combination of R and MAMMOS reproduction, it is possible to narrow the mark pitch as well as the magnetic field modulation recording and also the track pitch. It is an object of the present invention to provide a magneto-optical recording medium, a recording / reproducing method and a recording / reproducing apparatus using the same.
【0006】[0006]
【課題を解決するための手段】本発明は上記した目的を
実現する手段として、光ビーム入射側から、再生磁性
層、記録磁性層、光導電層、磁石層の順に積層してなる
事を特徴とする光磁気記録媒体、前記した記録磁性層と
光導電層の間、光導電層と磁石層の間から選ばれた少な
くも一つの界面に導電層が設けられている事を特徴とす
る前記の光磁気記録媒体、磁石層はメモリ保持温度にお
いて、膜面に対して垂直な方向に一様に同じ向きに磁化
されている事を特徴とする前記の光磁気記録媒体、再生
磁性層はメモリ保持温度において、面内に磁化されてい
る事を特徴とする前記の光磁気記録媒体、及び上記した
媒体に記録パワーレベルの光ビームを照射して、照射部
の光導電層を導電性にスイッチングし、伝導電子を介し
記録磁性層と磁石層を交換結合状態にして、磁石層の磁
化の向きに記録磁性層の磁化の向きを揃えて記録を行
い、再生パワーレベルの光ビームを照射して、照射部の
記録磁性層の磁化を再生磁性層に転写して再生を行う事
を特徴とする光磁気記録再生方法、再生磁性層に転写さ
れた磁区を拡大して再生する事を特徴とする前記の光磁
気記録再生方法、消去パワーレベルの光ビームを照射し
て、記録磁性層に対し、記録時に印加される交換磁界の
向きとは逆向きの磁界を印加して、消去動作を行う事を
特徴とする前記の光磁気記録再生方法、及び前記の光磁
気記録媒体に記録パワーレベルの光ビームを照射して、
照射部の光導電層を導電性にスイッチングし、伝導電子
を介し記録磁性層と磁石層を交換結合状態にして、磁石
層の磁化の向きに記録磁性層の磁化の向きを揃えて記録
を行い、再生パワーレベルの光ビームを照射して、照射
部の記録磁性層の磁化を再生磁性層に転写して再生を行
う事を特徴とする光磁気記録再生装置を提供するもので
ある。According to the present invention, as a means for realizing the above object, a reproducing magnetic layer, a recording magnetic layer, a photoconductive layer, and a magnet layer are laminated in this order from the light beam incident side. A magneto-optical recording medium, wherein the conductive layer is provided on at least one interface selected from between the recording magnetic layer and the photoconductive layer, between the photoconductive layer and the magnet layer. Wherein the magneto-optical recording medium and the magnetic layer are uniformly magnetized in the same direction in a direction perpendicular to the film surface at the memory holding temperature. At the holding temperature, the above-mentioned magneto-optical recording medium characterized in that it is magnetized in the plane, and the above-mentioned medium is irradiated with a light beam at a recording power level, and the irradiated part of the photoconductive layer is switched to conductive. And the recording magnetic layer and the magnet layer through conduction electrons In the exchange-coupled state, recording is performed with the magnetization direction of the recording magnetic layer aligned with the magnetization direction of the magnet layer, and a light beam at the reproducing power level is irradiated to change the magnetization of the recording magnetic layer of the irradiated part to the reproducing magnetic layer. Magneto-optical recording / reproducing method, characterized in that the magnetic domain transferred to the reproducing magnetic layer is reproduced by enlarging the magnetic domain transferred to the reproducing magnetic layer. Irradiating a beam to the recording magnetic layer, by applying a magnetic field in a direction opposite to the direction of the exchange magnetic field applied at the time of recording, and performing the erasing operation, the magneto-optical recording and reproducing method, and Irradiating the magneto-optical recording medium with a light beam at a recording power level,
Switching the photoconductive layer of the irradiated part to conductive, making the recording magnetic layer and the magnet layer exchange-coupled via conduction electrons, and performing recording with the magnetization direction of the recording magnetic layer aligned with the magnetization direction of the magnet layer Another object of the present invention is to provide a magneto-optical recording / reproducing apparatus characterized in that a reproducing power level light beam is irradiated to transfer the magnetization of the recording magnetic layer of the irradiated portion to the reproducing magnetic layer to perform reproduction.
【0007】本発明の光磁気記録媒体の記録原理は従来
技術とは本質的に異なり、従来が、記録光照射による記
録磁性層の加熱→記録層の保磁力の低下→保磁力低下部
の記録層の磁化の向きを印加磁界の向きに揃える、とい
う一連のヒートモードプロセスに従っていたものを、本
発明は、記録光照射→スポット中央部の光導電膜の光励
起による導電化→伝導電子を介した記録磁性層と磁石層
の交換結合→記録層の磁化の向きが磁石層のそれに揃
う、という一連のフォトンモードプロセスに従う記録原
理を用いる。記録光照射部の記録層の保磁力の低下はヒ
ートモードで齎されるという部分はヒートモードなの
で、正確にはフオトンモード・ヒートモードのハイブリ
ッドプロセスという事が出来る。[0007] The recording principle of the magneto-optical recording medium of the present invention is essentially different from that of the prior art. Conventionally, the recording magnetic layer is heated by irradiating the recording light → the coercive force of the recording layer is reduced → the recording of the coercive force reduced portion According to a series of heat mode processes of aligning the direction of magnetization of the layer with the direction of the applied magnetic field, the present invention provides recording light irradiation → conduction by photoexcitation of the photoconductive film in the center of the spot → conduction electrons. A recording principle according to a series of photon mode processes is used in which exchange coupling between the recording magnetic layer and the magnet layer → the magnetization direction of the recording layer is aligned with that of the magnet layer. Since the part where the coercive force of the recording layer of the recording light irradiating part is brought down in the heat mode is the heat mode, it can be accurately described as a photon mode / heat mode hybrid process.
【0008】磁石層自体は記録過程で磁化反転せず、記
録層に交換磁界を供給するだけである。記録するマーク
の位置が決まっている例えばマークポジション記録方式
を採用する場合には、磁石層の磁化の向きはマークを記
録すべき位置のみで、記録層の初期磁化(初期を消去向
きに設定する場合)とは逆向きに設定されていれば良い
が、より記録密度が高いマークエッジ記録を行う場合に
は、記録マーク位置は特定出来ないので、磁石層はメモ
リ保持温度(一般的には室温付近)で膜面に垂直に一様
に同向きの磁化を有しているのが好ましい。[0008] The magnet layer itself does not undergo magnetization reversal during the recording process, but merely supplies an exchange magnetic field to the recording layer. For example, when a mark position recording method in which the position of a mark to be recorded is determined is adopted, the magnetization direction of the magnet layer is only the position where the mark is to be recorded, and the initial magnetization of the recording layer (the initial direction is set to the erasing direction). In the case of performing mark edge recording with a higher recording density, the recording mark position cannot be specified, so the magnet layer is set at the memory holding temperature (generally room temperature). (In the vicinity), it is preferable to have the same magnetization perpendicular to the film surface.
【0009】初期状態としては例えば記録磁性層の磁化
の向きと磁石層のそれを逆向きにする。この様な初期状
態は記録層と磁石層の室温保磁力を異ならせておけば、
例えば室温で保磁力の大きい方の層の保磁力以上の磁界
を印加して、両層の磁化の向きを同一に揃えた後に、保
磁力の大きい方の層の保磁力未満で保磁力の小さい方の
層の保磁力以上の磁界を最初とは逆向きに印加すれば良
い。両層の室温での保磁力が緊切している場合は記録パ
ワーレベルの光ビームをDC的に照射して、外部から記
録層と磁石層の交換力以上の磁界を交換磁界とは逆向き
に印加すれか、後述する磁石層から記録層に印加する漏
洩磁界を用いれば良い。As an initial state, for example, the direction of magnetization of the recording magnetic layer is made opposite to that of the magnet layer. In such an initial state, if the room temperature coercive force of the recording layer and the magnet layer are different,
For example, after applying a magnetic field equal to or greater than the coercive force of the layer with the larger coercive force at room temperature and aligning the magnetization directions of both layers to the same direction, the coercive force of less than the coercive force of the layer with the larger coercive force is small. A magnetic field greater than the coercive force of the other layer may be applied in a direction opposite to the first direction. When the coercive force at room temperature of both layers is tight, irradiate a light beam at the recording power level in a DC manner, and apply a magnetic field greater than the exchange force between the recording layer and the magnet layer from the outside in the opposite direction to the exchange magnetic field. Or a leakage magnetic field applied from a magnet layer described later to the recording layer may be used.
【0010】記録プロセスではスポット中央部の光導電
膜中に伝導電子が十分に生成される程度のパワーレベル
の光を照射する。伝導電子が十分に生成され交換力が記
録層の保磁力を上回った部分の記録層の磁化が磁石層の
それに揃う。交換力の大きさは、光導電膜の光導電特性
の他に、両磁性層の選び方で制御可能な界面磁壁エネル
ギー、記録層の磁化・膜厚に依存し、記録部の保磁力の
大きさはき録層の熱磁気特性に依存するので、記録パワ
ーレベルの選び方も含めて適正な設定を行うと、スポッ
トのFWHMよりも微細なマークを記録する事が出来
る。しかもマークサイズは原理的にスポット中央部の光
導電膜中に十分な数の伝導電子が生成された箇所に相当
するので、従来の磁界変調記録とは異なり、マーク長・
スペース長が狭く出来るに止まらず、マーク幅も狭く出
来るのでトラックピッチを詰める事が可能である。In the recording process, light having a power level enough to generate conduction electrons in the photoconductive film at the center of the spot is irradiated. The portion of the recording layer where the conduction electrons are sufficiently generated and the exchange force exceeds the coercive force of the recording layer has the same magnetization as that of the magnet layer. The magnitude of the exchange force depends not only on the photoconductive properties of the photoconductive film but also on the interface domain wall energy that can be controlled by the choice of the two magnetic layers and the magnetization and thickness of the recording layer. Since it depends on the thermomagnetic characteristics of the recording layer, if the setting is properly made including the selection of the recording power level, a mark finer than the FWHM of the spot can be recorded. Moreover, the mark size is in principle equivalent to the location where a sufficient number of conduction electrons are generated in the photoconductive film at the center of the spot.
Not only can the space length be reduced, but also the mark width can be reduced, so that the track pitch can be reduced.
【0011】微細マークの再生はMSRもしくはMAM
MOS技術によって再生する事が可能である。MSR再
生方式としては、再生スポットの一部に磁気的な光学開
口を有するもので有れば何でも良く、RAD(Rear
−Aperture−Detection),FAD
(Front−Aperture−Detectio
n),CAD(Central−Aperture−D
etection)のいづれも適用可能であり、又、記
録磁性層と再生磁性層間は交換結合されていても、そう
で無く静磁的に結合されているだけでも良い。MAMM
OS再生もH10電気学会全国大会予稿S.10−6中
に開示されている種々の方式が適用可能である。本発明
の実施に最低限必要な磁性層の数は三層であり、例えば
従来の光変調オーバライト可能なMSR媒体に比較する
と格段に簡単な構成である。The reproduction of a fine mark is performed by MSR or MAM.
Reproduction is possible by MOS technology. The MSR reproduction method may be any method as long as it has a magnetic optical aperture in a part of the reproduction spot.
-Aperture-Detection), FAD
(Front-Aperture-Detection
n), CAD (Central-Aperture-D)
(Election) can be applied, and the recording magnetic layer and the reproducing magnetic layer may be exchange-coupled or may be merely magnetostatically coupled. MAMM
OS regeneration was also submitted to the H10 IEEJ National Convention. Various schemes disclosed in 10-6 are applicable. The minimum number of magnetic layers required for implementing the present invention is three, which is a much simpler configuration than, for example, a conventional MSR medium capable of overwriting with light modulation.
【0012】本発明に用いる事の出来る記録磁性層材料
は、従来の光磁気記録に用いられている希土類(RE:
Gd,Tb,Dy,Nd等)−遷移金属(TM:Fe,
Co等)合金系薄膜、Co/Pt,Co/Pd等の多層
人工格子系薄膜、PtMnSbに代表されるホイッスラ
ー合金系薄膜、Baフェライトに代表さつれる酸化物磁
性体等の中から自由に選択する事が出来、代表的にはT
bFeCo薄膜等が選択される。光導電層としては、動
作レーザエネルギーよりも光学ギャップが狭い材料で有
れば何でも良く、Si,Ge,InGaP,CdSe,
ZnTe,GaN,GaAs,ZnSe,ZnO,Al
As,AlSb,Si−C等から自由に選択出来る。
又、光学ギャップ中の不純物準位への励起、もしくは不
純物準位を介したマルチフォトン励起により伝導電子を
生成する場合は光学ギャップが動作レーザエネルギーよ
りも高くても構わない。代表的には非晶質Si等が選択
される。磁石層としては、記録層よりもキューリー点が
高い磁性層ならば何でも良く、後述の光変調オーバライ
ト記録において記録層へ大きな漏洩磁界を供給する上で
は、磁化の温度変化が大きい膜材料が良い。具体的には
記録層よりもキューリー点の高いRE−TM薄膜、多層
人工格子、ホイッスラー合金、Co−Pt合金膜の他
に、磁気記録に使用されているCo−Cr系薄膜等を用
いる事が出来る。再生磁性層はMSR効果もしくはMA
MMOS効果を有するもので有れば何でも良いが、垂直
磁気異方性が記録磁性層よりも小さいRE−TM膜、例
えばGd−FeCo膜が好適である。後述する光変調オ
ーバライト動作を平易にする為には、室温で面内磁化、
再生温度で垂直磁化、記録温度付近でも垂直磁化の膜を
用いて、再生層と記録層の間に比較的キューリー点に低
いゲート層を配するのが好ましい。The recording magnetic layer material which can be used in the present invention is a rare earth element (RE: RE) used in conventional magneto-optical recording.
Gd, Tb, Dy, Nd, etc.)-Transition metal (TM: Fe,
(Co etc.) alloy thin film, multilayer artificial lattice based thin film such as Co / Pt, Co / Pd, Whistler alloy thin film represented by PtMnSb, oxide magnetic material represented by Ba ferrite, etc. And typically T
A bFeCo thin film or the like is selected. As the photoconductive layer, any material may be used as long as the material has an optical gap narrower than the operating laser energy. Si, Ge, InGaP, CdSe,
ZnTe, GaN, GaAs, ZnSe, ZnO, Al
It can be freely selected from As, AlSb, Si-C and the like.
In the case where conduction electrons are generated by excitation to an impurity level in the optical gap or multiphoton excitation through the impurity level, the optical gap may be higher than the operating laser energy. Typically, amorphous Si or the like is selected. As the magnet layer, any magnetic layer having a higher Curie point than the recording layer may be used. For supplying a large leakage magnetic field to the recording layer in light modulation overwrite recording described later, a film material having a large temperature change in magnetization is preferable. . Specifically, in addition to the RE-TM thin film having a higher Curie point than the recording layer, a multilayer artificial lattice, a Whistler alloy, a Co-Pt alloy film, a Co-Cr thin film used for magnetic recording may be used. I can do it. The reproducing magnetic layer has the MSR effect or MA
Any material may be used as long as it has an MMOS effect, but a RE-TM film having a perpendicular magnetic anisotropy smaller than that of the recording magnetic layer, for example, a Gd-FeCo film is preferable. In order to simplify the light modulation overwrite operation described later, in-plane magnetization at room temperature,
It is preferable to arrange a gate layer having a relatively low Curie point between the reproducing layer and the recording layer by using a film having perpendicular magnetization at the reproducing temperature and perpendicular magnetization even near the recording temperature.
【0013】前記した記録磁性層と光導電層、もしくは
光導電層と磁石層は直接積層されていても構わないが、
一般的に半導体膜特にSi,Ge系と磁性体膜とは反応
してシリサイド等の界面層を形成して、記録層と磁石層
の伝導電子を介する交換結合を損ねる場合が有るので、
好ましくは記録層と光導電層の界面と光導電層と磁石層
の界面には導電性のバリア層を設けるのが良い。バリア
層材料は、磁性体とも半導体とも反応し難い導電性材料
であれば何でも良いが、TiN,ITO等の化合物系導
電膜を用いるのが好ましい。導電性バリア層は、磁性層
として酸化物磁性体を用いる場合、もしくは光導電層と
して酸化物を用いる場合には特に設ける必要は無い。Although the recording magnetic layer and the photoconductive layer or the photoconductive layer and the magnet layer may be directly laminated,
In general, a semiconductor film, particularly an Si or Ge system, and a magnetic film react with each other to form an interface layer such as silicide, which may impair exchange coupling of the recording layer and the magnet layer via conduction electrons.
Preferably, a conductive barrier layer is provided at the interface between the recording layer and the photoconductive layer and at the interface between the photoconductive layer and the magnet layer. The barrier layer material may be any conductive material that does not easily react with a magnetic substance and a semiconductor, but it is preferable to use a compound conductive film such as TiN or ITO. The conductive barrier layer need not be provided particularly when an oxide magnetic material is used as the magnetic layer or when an oxide is used as the photoconductive layer.
【0014】以上に概説した光磁気記録媒体を使用して
本発明の光磁気記録再生方法は、基本的には、記録パワ
ーレベルの光ビームを照射して、照射部の光導電層を導
電性にスイッチングし、伝導電子を介し記録磁性層と磁
石層を交換結合状態にして、磁石層の磁化の向きに記録
磁性層の磁化の向きを揃えて記録を行い、再生パワーレ
ベルの光ビームを照射して、照射部の記録磁性層の磁化
を再生磁性層に転写してMSRもしくはMAMMOS再
生を行うが、再生磁性層に転写された磁区を拡大して再
生するMAMMOS再生がより微細なマークでも高いC
/Nを得る上では好ましく、さらに好ましくは、消去パ
ワーレベルの光ビームを照射して、記録磁性層に対し、
記録時に印加される交換磁界の向きとは逆向きの磁界を
印加して消去動作を行う、光変調オーバライト動作を行
うのが良い。消去パワーレベルの光を照射して記録層に
記録時の交換磁界の向きとは逆向きの磁界を印加する方
法には幾つかが挙げられる。最も簡単にはDC外部磁界
の印加であり、パワーレベルが異なると交換磁界の大き
さが異なる事を利用する。即ち消去パワーレベルとして
記録パワーレベル照射時よりも交換磁界が小さいパワー
を選び、外部磁界として交換磁界とは向きが逆で、記録
時の交換磁界よりも小さく消去時の交換磁界よりも大き
な磁界を用いれば良い。The magneto-optical recording / reproducing method of the present invention using the magneto-optical recording medium outlined above basically involves irradiating a light beam at the recording power level to make the irradiated portion of the photoconductive layer conductive. The recording magnetic layer and the magnet layer are exchange-coupled via conduction electrons, and the recording is performed with the magnetization direction of the recording magnetic layer aligned with the magnetization direction of the magnet layer. Then, the magnetization of the recording magnetic layer of the irradiated portion is transferred to the reproducing magnetic layer to perform the MSR or MAMMOS reproduction. However, the MAMMOS reproduction for enlarging and reproducing the magnetic domain transferred to the reproducing magnetic layer is high even with a finer mark. C
/ N, and more preferably, irradiating a light beam of an erasing power level to the recording magnetic layer.
It is preferable to perform an optical modulation overwrite operation in which an erasing operation is performed by applying a magnetic field opposite to the direction of the exchange magnetic field applied during recording. There are several methods for applying a magnetic field in the direction opposite to the direction of the exchange magnetic field during recording to the recording layer by irradiating light at the erasing power level. The simplest is the application of a DC external magnetic field, and utilizes the fact that the magnitude of the exchange magnetic field differs at different power levels. That is, a power having an exchange magnetic field smaller than that at the time of recording power level irradiation is selected as the erasing power level, and a magnetic field having a direction opposite to the exchange magnetic field and smaller than the exchange magnetic field at the time of recording and larger than the exchange magnetic field at the time of erasure is selected as the external magnetic field. You can use it.
【0015】外部磁界以外に媒体を構成する各磁性層か
らの漏洩磁界を利用すると光変調オーバライトがしやす
くなる。磁石層の熱磁気特性の選び方にも依存するが、
磁石層の磁化の大きさが室温から高温側に向けて低下す
る様に選べば、磁石層から記録層に印加する漏洩磁界は
磁石層の磁化の向きとは逆向き即ち消去向きになるので
オーバライトしやすくなる。磁石層としてRE−TM膜
を選べば、REとTMの副格子磁化の向きはそのままで
ネットの磁化の向きを補償点以上で逆転出来るので、よ
り大きな漏洩磁界を発生する事が出来る。漏洩磁界の大
きさは磁石層の膜厚でも調整可能である。When a leakage magnetic field from each magnetic layer constituting the medium is used in addition to the external magnetic field, light modulation overwriting is easily performed. Although it depends on how to select the thermomagnetic properties of the magnet layer,
If the magnitude of the magnetization of the magnet layer is selected so as to decrease from room temperature to the high temperature side, the leakage magnetic field applied from the magnet layer to the recording layer is opposite to the direction of the magnetization of the magnet layer, that is, the erasing direction. It becomes easier to write. If a RE-TM film is selected as the magnet layer, the direction of the magnetization of the net can be reversed above the compensation point while maintaining the direction of the sublattice magnetization of the RE and TM, so that a larger leakage magnetic field can be generated. The magnitude of the leakage magnetic field can be adjusted by the thickness of the magnet layer.
【0016】磁石層の漏洩磁界以外に、前記した様に、
再生磁性層から発生する漏洩磁界の利用も可能である。
例えば再生層に室温で面内磁化、加熱で垂直磁化になる
膜を選び、再生層と記録層の間に比較的キューリー点の
低いゲート層を挿入し、層間を交換結合させておく。再
生時はゲート層はキューリー点未満とすると、記録層の
磁化の向きに先ずゲート層の磁化が揃い、これが再生層
に転写されて、MSR再生もしくはMAMMOS再生を
実現する。消去時は再生よりも高いパワーレベルを選び
ゲート層をキューリー点以上に加熱する。ゲート層がキ
ューリー点以上に加熱されている部分では再生層と記録
層の間には交換力作用しない。外部から補助的に比較的
小さな外部磁界を消去向きに印加しておくと、再生層の
磁化の向きは消去時にはき録層の磁化の向きの如何に関
わらず消去向きを向く。この磁化の空間分布に起因して
記録層に消去向きの漏洩磁界を印加して光変調オーバラ
イト記録を実現しやすくする。記録パワーレベルとして
消去パワーレベルよりも高いパワーを選べば記録時には
再生層もキューリー点以上に加熱する事が出来るので、
消去時には消去向きの漏洩磁界を発生するが、記録時に
は消去向きの磁界を発生させずに記録も同時に行いやす
くするといった工夫も出来る。In addition to the leakage magnetic field of the magnet layer, as described above,
It is also possible to use a leakage magnetic field generated from the reproducing magnetic layer.
For example, a film having in-plane magnetization at room temperature and perpendicular magnetization upon heating is selected for the reproducing layer, a gate layer having a relatively low Curie point is inserted between the reproducing layer and the recording layer, and the layers are exchange-coupled. At the time of reproduction, assuming that the gate layer is below the Curie point, the magnetization of the gate layer is first aligned in the direction of magnetization of the recording layer, and this is transferred to the reproduction layer to realize MSR reproduction or MAMMOS reproduction. At the time of erasing, a power level higher than that of reproducing is selected, and the gate layer is heated to the Curie point or higher. No exchange force acts between the reproducing layer and the recording layer in a portion where the gate layer is heated above the Curie point. If a relatively small external magnetic field is applied from the outside in an erasing direction, the direction of magnetization of the reproducing layer is oriented in the erasing direction at the time of erasing regardless of the direction of magnetization of the recording layer. Due to the spatial distribution of the magnetization, a leakage magnetic field in the erasing direction is applied to the recording layer to facilitate light modulation overwrite recording. If the recording power level is higher than the erasing power level, the reproducing layer can be heated above the Curie point during recording.
Although a leakage magnetic field suitable for erasing is generated at the time of erasing, a device can be devised such that recording is not performed at the same time and recording is facilitated at the same time.
【0017】本発明の光磁気記録媒体は、上記した光変
調オーバライト動作を適用するのが好ましいが、磁界変
調オーバライト動作を適用する事も可能である。通常の
磁界変調記録では外部磁界は零レベルを中心にプラスマ
イナス対象に振るが、本発明に磁界変調記録を適用する
際には、記録向き磁界はあくまでも記録層と磁石層間の
交換磁界とするので、記録向きには外部磁界は印加する
必要が無い(補助的に印加しても良いが記録向き磁界の
主成分は交換磁界とする)。消去向き磁界を交換磁界と
逆向きで交換磁界よりも大きく設定するやり方を採用す
るのが良い。The magneto-optical recording medium of the present invention preferably employs the above-described optical modulation overwrite operation, but it is also possible to apply the magnetic field modulation overwrite operation. In the ordinary magnetic field modulation recording, the external magnetic field is oscillated in plus or minus around the zero level, but when applying the magnetic field modulation recording to the present invention, the recording direction magnetic field is merely an exchange magnetic field between the recording layer and the magnet layer. It is not necessary to apply an external magnetic field in the recording direction (although the external magnetic field may be applied supplementarily, the main component of the recording magnetic field is an exchange magnetic field). It is preferable to adopt a method of setting the erasing direction magnetic field to be opposite to the exchange magnetic field and larger than the exchange magnetic field.
【0018】本発明の光磁気記録再生装置は、前記した
本発明の光磁気記録媒体を搭載して、上記した光磁気記
記録再生方法を実現する装置である。光変調記録装置で
有る事が好ましく、少なくもオーバライト記録で無い場
合(記録時と消去時で外部磁界が異なる場合)には、消
去時の外部磁石は記録層と磁石層の間の交換磁界の向き
とは逆向きに印加される。オーバライト記録装置として
少なくも記録、消去、再生の三つの異なるパワーレベル
を具備している場合が装置として好ましいが、この場合
には媒体内部の漏洩磁界の大きさと向きに応じて外部磁
界の向きと大きさが決定される。外部磁界は無くても良
いが、有る場合でも媒体との間の距離は数mm程度離し
て配置され、貼り合せディスクの使用を可能とする。記
録パワーレベルと消去パワーレベルの大小関係は、記録
層と磁石層の間に作用する交換磁界の大きさと、各層の
漏洩磁界の温度特性で決定される。本発明は記録原理的
に高速のフォトンモードプロセスを主とし、再生も高速
の磁気転写、もしくは磁気的拡大を用いるので、ディス
ク回転速度は速い方が良い。A magneto-optical recording / reproducing apparatus according to the present invention is an apparatus which mounts the above-described magneto-optical recording medium according to the present invention and realizes the above-described magneto-optical recording / reproducing method. It is preferable that the device is an optical modulation recording device. At least in the case of not overwriting recording (when the external magnetic field is different between recording and erasing), the external magnet during erasing is an exchange magnetic field between the recording layer and the magnet layer. Is applied in a direction opposite to the direction of It is preferable that the overwrite recording device has at least three different power levels of recording, erasing, and reproduction, but in this case, the direction of the external magnetic field depends on the magnitude and direction of the leakage magnetic field inside the medium. And the size are determined. An external magnetic field may not be provided, but even if it is present, the distance from the medium is set at a distance of about several millimeters, thereby enabling the use of a bonded disc. The magnitude relationship between the recording power level and the erasing power level is determined by the magnitude of the exchange magnetic field acting between the recording layer and the magnet layer and the temperature characteristics of the leakage magnetic field of each layer. The present invention mainly uses a high-speed photon mode process in principle of recording, and uses high-speed magnetic transfer or magnetic expansion for reproduction. Therefore, it is better that the disk rotation speed is high.
【0019】[0019]
【発明の実施の形態】以下、図面を参照して本発明の実
施の形態を実施例を用いて説明する。 [実施例1]図1は本発明の光磁気記録媒体の一実施例
の断面構成図であり基本構成に対応する。図1におい
て、11は再生磁性層、12は記録磁性層、13は光導
電層、14は磁石層、15は基板、16は第一干渉層、
17は中間層、18は保護層である。再生層、記録層、
光導電層、磁石層に使用可能な材料は前記した通りであ
るが、この実施例1では、再生層として膜厚30nmの
GdFe膜、記録層として膜厚60nmのTbFeCo
膜、光導電層として膜厚100nmのCuO膜(光学ギ
ャップ:2eV)、磁石層として膜厚50nmのGdT
bFeCo膜を各々用いた。基板としては光ディスクと
して一般的に用いられるグルーブ(トラッキングガイド
用の溝)の設けられたポリカーボネイト基板を用いた。
クロストーク、クロスイレーズ等の特性を調べる目的で
トラックピッチは0.2μmから0.5μmの間で変え
た。この他、熱磁気特性、光導電性等を測定する為の石
英基板を適宜用いた。干渉層、中間層、保護層は本発明
自体の実施には必ずしも設ける必要は無いが、干渉層は
再生信号エンハンスメントの為、中間層は層間の磁気的
相互作用の制御と、再生層、記録層間の温度差制御の
為、保護層はその名の通りに媒体の酸化防止の為の機能
を有する。本実施例1では、干渉層として膜厚100n
mのSiN膜、中間層として膜厚15nmのSiN膜、
保護層としては膜厚100nmのSiN膜を各々使用し
た。図1の媒体の作成は例えば以下の手順で実施する事
が出来る。Embodiments of the present invention will be described below with reference to the accompanying drawings. [Embodiment 1] FIG. 1 is a sectional view showing an embodiment of a magneto-optical recording medium according to the present invention, and corresponds to a basic structure. In FIG. 1, 11 is a reproducing magnetic layer, 12 is a recording magnetic layer, 13 is a photoconductive layer, 14 is a magnet layer, 15 is a substrate, 16 is a first interference layer,
17 is an intermediate layer and 18 is a protective layer. Playback layer, recording layer,
The materials that can be used for the photoconductive layer and the magnet layer are as described above. In Example 1, a GdFe film having a thickness of 30 nm was used as the reproducing layer, and a TbFeCo film having a thickness of 60 nm was used as the recording layer.
Film, a 100 nm thick CuO film (optical gap: 2 eV) as a photoconductive layer, and a 50 nm thick GdT as a magnet layer
Each of the bFeCo films was used. As the substrate, a polycarbonate substrate provided with a groove (a groove for tracking guide) generally used as an optical disk was used.
The track pitch was changed between 0.2 μm and 0.5 μm in order to examine characteristics such as crosstalk and cross erase. In addition, a quartz substrate for measuring thermomagnetic properties, photoconductivity and the like was appropriately used. The interference layer, the intermediate layer, and the protective layer are not necessarily provided in the practice of the present invention. However, the interference layer is provided for controlling the magnetic interaction between the layers and the reproducing layer and the recording layer for enhancing the reproduction signal. In order to control the temperature difference, the protective layer has a function for preventing the medium from being oxidized, as the name implies. In the first embodiment, the thickness of the interference layer is 100 n
m, a 15 nm-thick SiN film as an intermediate layer,
A 100 nm-thick SiN film was used as each protective layer. The medium shown in FIG. 1 can be created, for example, by the following procedure.
【0020】基板は通常のマスタリングプロセスにより
原盤を作成した後、Ni電鋳プロセスでスタンパーを形
成、射出成形プロセスでポリカーボネイト基板を得る事
が出来る。トラックピッチの調整はマスタリングプロセ
スにおけるレーザパワー調整と波長調整で行った。基板
は多室スパッタリング装置のホルダーにセットし真空排
気後、各層の形成を順次実施した。各磁性層は磁性合金
ターゲットをArガス中でDCマグネトロンスパッタし
て得る事が出来、光導電層は本実施例ではCuOターゲ
ットをAr−O2混合ガス中でRFマグネトロンスパッ
タして得た。SiN膜はBドープSiターゲットをAr
−N2ガス中でDC反応性スパッタして得る事が出来
る。成膜後、保護膜上にUV硬化樹脂を接着層として塗
布しチルトを防止する為の対向基板(本発明の実施例で
は膜の付いていないダミー基板を用いた)を貼り合せ
た。その後、電磁石を用いて初期磁化方向の設定を行っ
た。各層の保磁力は元素及び組成の選び方で制御可能で
あり、後記する様に、本実施例では室温付近で再生層は
面内磁化、記録層は保磁力8kOeの垂直磁化、磁石層
は保磁力4kOeの垂直磁化に設定したので、初期化は
先ず膜面に垂直に図1で下向きに12kOeの磁界を印
加して記録層、磁石層共に磁化を下向きに向けた後、膜
面に垂直に上向きに6kOeの磁界を印加して、磁石層
の磁化の向きだけを上向きに揃えた。再生層は室温付近
では面内に磁化されているので、電磁石から取出した後
の磁化の向きは面内でランダムである。各磁性層の初期
磁化の向きは概略図1に示した。After a master is prepared by a normal mastering process, a stamper is formed by a Ni electroforming process, and a polycarbonate substrate can be obtained by an injection molding process. The track pitch was adjusted by adjusting the laser power and the wavelength in the mastering process. The substrate was set in a holder of a multi-chamber sputtering apparatus, and after evacuation, the layers were sequentially formed. Each magnetic layer can be obtained by DC magnetron sputtering of a magnetic alloy target in Ar gas, and the photoconductive layer in this embodiment is obtained by RF magnetron sputtering of a CuO target in an Ar-O2 mixed gas. For the SiN film, a B-doped Si target is Ar
It can be obtained by DC reactive sputtering in -N2 gas. After the film formation, a UV curable resin was applied as an adhesive layer on the protective film, and a counter substrate (a dummy substrate without a film was used in the embodiment of the present invention) for preventing tilt was attached. Thereafter, the initial magnetization direction was set using an electromagnet. The coercive force of each layer can be controlled by selecting the element and composition. As described later, in this embodiment, the in-plane magnetization of the reproducing layer, the perpendicular magnetization of 8 kOe of the coercive force of the recording layer, and the coercive force of the magnet layer at around room temperature in this embodiment. Since the magnetization was set to 4 kOe perpendicular magnetization, first, a magnetic field of 12 kOe was applied perpendicularly to the film surface and downward in FIG. 1 to direct the magnetization of both the recording layer and the magnet layer downward, and then upwardly perpendicular to the film surface. Then, a magnetic field of 6 kOe was applied to adjust the magnetization direction of the magnet layer upward. Since the reproducing layer is magnetized in the plane near room temperature, the direction of the magnetization after being extracted from the electromagnet is random in the plane. The direction of the initial magnetization of each magnetic layer is schematically shown in FIG.
【0021】上記に従って作成した本発明の図1の光磁
気記録媒体を以下の手順で評価した。先ず、図1を形成
したのと同一の条件で予め作成した石英基盤上のCuO
光導電膜を電極状にパターニングして波長488nm
(2.54eV)のArイオンレーザを照射して光導電
特性を調べた。CuO電極パターンに電圧を印加して光
の照射パワー(フォトン数:Np)を変えながら光電流
を調べ、光導電率(σ)を導出した。又、別途形成した
記録層、光導電層、磁石層を積層した試料に波長488
nm(2.54eV)のArイオンレーザを照射しなが
ら加熱し、VSMを用いて磁化曲線を調べ、記録層と磁
石層の間の交換磁界(Hexg)と記録層の保磁力を調
べた。照射パワーと媒体膜温度の関係はArイオンレー
ザを後述のディスク動作と同程度に集光照射した条件で
熱解析して換算した。これらの結果を図3に纏めて示
す。光導電率σはフォトン数Npの増加と共に増加し、
熱解析からは記録層のキューリー点(Tcw)付近では
高い一定値を示した。この様なσ−T(解析上の膜温
度)の元で、VSMの熱磁気特性から導出した交換磁界
Hexgと記録層の保磁力Hcwは膜温度に対して図3
の挙動を示す事が判った。煩雑を避ける為に図には示し
ていないが、光照射の無い場合にはHexgは全温度領
域に亘り零で有った。これは光導電膜がオフで伝導電子
が無い場合には、光導電膜は単純に非磁性中間層として
作用する為に、記録層と磁石層間には交換相互作用が働
かない為である。σを調べた場合と同等のパワーの光を
照射した場合には図3のHexgが得られた。σが小さ
い場合(熱解析上の換算温度が低い場合に相当)は、H
exgが作用しないが、σの増加に伴ってHexgは増
加し、Tcw付近でHexgがHcwを上回り、Tcw
ではHexg,Hcw共零になる。ここでHexgは交
換エネルギー(光導電膜が存在せずに記録層と磁石層が
直接積層されている場合には界面磁壁エネルギーに相
当)をEw、記録層の磁化をMsw、記録層の膜厚をd
wとすると、Hexg=Ew/(Msw×dw)で与え
られる。参考の為、光導電膜が無い記録層と磁石層を直
接積層した比較用試料のVSM温度測定から得られたH
exgを図3に併記した。σが大きな一定値に至った以
上のパワー領域でのHexgの振舞いはHexgに類似
し、σが小さい値を示す領域ではHexgはHexgよ
りも小さい値を示す事が判る。図3の特性から本発明の
記録原理が基本的に成立する事が証明された。The magneto-optical recording medium of the present invention prepared as described above and shown in FIG. 1 was evaluated according to the following procedure. First, CuO on a quartz substrate prepared in advance under the same conditions as those for forming FIG.
The photoconductive film is patterned into an electrode shape, and the wavelength is 488 nm.
(2.54 eV) was irradiated with an Ar ion laser to examine the photoconductive characteristics. The photocurrent was examined while applying a voltage to the CuO electrode pattern to change the light irradiation power (the number of photons: Np), and the photoconductivity (σ) was derived. A wavelength of 488 was applied to a sample in which a recording layer, a photoconductive layer, and a magnet layer separately formed were laminated.
Heating was performed while irradiating an Ar ion laser of nm (2.54 eV), the magnetization curve was examined using a VSM, and the exchange magnetic field (Hexg) between the recording layer and the magnet layer and the coercive force of the recording layer were examined. The relationship between the irradiation power and the medium film temperature was converted by thermal analysis under the condition that the Ar ion laser was condensed and irradiated to the same degree as the disk operation described later. These results are summarized in FIG. The photoconductivity σ increases as the number of photons Np increases,
Thermal analysis showed a high constant value near the Curie point (Tcw) of the recording layer. Under such σ-T (analytical film temperature), the exchange magnetic field Hexg and the coercive force Hcw of the recording layer derived from the thermomagnetic characteristics of the VSM are shown in FIG.
Was found to behave. Although not shown in the figure to avoid complication, Hexg was zero over the entire temperature range without light irradiation. This is because when the photoconductive film is off and there are no conduction electrons, the photoconductive film simply acts as a non-magnetic intermediate layer, so that no exchange interaction works between the recording layer and the magnet layer. Hexg shown in FIG. 3 was obtained when light having the same power as that when σ was examined was irradiated. When σ is small (corresponding to the case where the converted temperature in thermal analysis is low), H
exg does not act, but Hexg increases with an increase in σ, and Hexg exceeds Hcw near Tcw, and Tcw
In this case, both Hexg and Hcw become zero. Here, Hexg is the exchange energy (equivalent to the interface domain wall energy when the recording layer and the magnet layer are directly laminated without a photoconductive film), Ew is the magnetization of the recording layer, Msw is the film thickness of the recording layer. To d
If w, Hexg = Ew / (Msw × dw). For reference, H obtained from VSM temperature measurement of a comparative sample in which a recording layer without a photoconductive film and a magnet layer were directly laminated was used.
exg is also shown in FIG. It can be seen that the behavior of Hexg in a power region where σ reaches a large constant value is similar to Hexg, and that Hexg shows a smaller value than Hexg in a region where σ shows a small value. It has been proved from the characteristics of FIG. 3 that the recording principle of the present invention basically holds.
【0022】図4は図1の媒体に使用した再生層、記録
層、磁石層の熱磁気特性を示す図であり、図4[a]は
磁化(Ms)の温度特性、図4[b]は保磁力(Hc)
の温度特性である。磁化は垂直方向の磁化を意味し面内
磁化は零として示してある。図4において、Rが再生
層、Wが記録層、Pが磁石層を各々示し、Tcompは
補償点、Tcはキューリー点、各々の末尾の符号は再生
層、記録層、磁石層に対応している。本実施例で選択し
た磁性層は全てRE−TM膜であるが、RE−TM膜は
REの副格子磁化とTMの副格子磁化が逆向きを向くフ
ェリ磁性膜である。低温ではREの副格子磁化が優勢で
ネットの磁化(Ms)はRE磁化と同じ向きに揃い大き
さはRE磁化からTM磁化を差引いた大きさとなる。補
償点でRE磁化とTM磁化の大きさが一致して見掛け上
Msは零を示す。補償点よりも高い温度ではTM磁化が
優勢となり、MsはTM磁化と同じ向きに揃い大きさは
TM磁化からRE磁化を差引いたものとなる。キューリ
ー点ではRE磁化、TM磁化共消失する。補償点、キュ
ーリー点はRE元素とTM元素の選び方で制御可能であ
り、RE組成比が高い程補償点は高くなり、RE組成比
が非常に高いとRE優勢のまま補償点を示さずにキュー
リー点に至る組成範囲も存在する。キューリー点はRE
中ではGd>Tb>Dyの関係で、TM中ではCo>F
eの関係にある。HcはRE中でTb>Dy>Gdの関
係にある。Gdが多いと垂直磁気異方性が小さく(その
為Hcが小さい)、補償点付近のMsが小さくなる温度
範囲以外は反磁界の影響で膜は面内に磁化する。図3で
再生層の特性が補償点付近でしか書いていないのはその
為である(面内磁化から垂直磁化への遷移領域を細かい
破線で示した)。FIG. 4 is a diagram showing the thermomagnetic characteristics of the reproducing layer, the recording layer, and the magnet layer used in the medium of FIG. 1. FIG. 4A shows the temperature characteristics of the magnetization (Ms), and FIG. Is the coercive force (Hc)
Is the temperature characteristic. The magnetization means the magnetization in the perpendicular direction, and the in-plane magnetization is shown as zero. In FIG. 4, R represents a reproducing layer, W represents a recording layer, and P represents a magnet layer, Tcomp represents a compensation point, Tc represents a Curie point, and the suffixes of the respective symbols correspond to the reproducing layer, the recording layer, and the magnet layer. I have. The magnetic layers selected in this embodiment are all RE-TM films, but the RE-TM film is a ferrimagnetic film in which the sub-lattice magnetization of RE and the sub-lattice magnetization of TM are in opposite directions. At a low temperature, the sublattice magnetization of the RE is dominant, and the magnetization (Ms) of the net is aligned in the same direction as the RE magnetization, and the magnitude is the magnitude obtained by subtracting the TM magnetization from the RE magnetization. At the compensation point, the magnitudes of the RE magnetization and the TM magnetization match, and apparently Ms is zero. At a temperature higher than the compensation point, the TM magnetization becomes dominant, Ms is aligned in the same direction as the TM magnetization, and the magnitude thereof is obtained by subtracting the RE magnetization from the TM magnetization. At the Curie point, both RE magnetization and TM magnetization disappear. The compensation point and the Curie point can be controlled by the selection of the RE element and the TM element. The higher the RE composition ratio, the higher the compensation point. There is also a composition range up to the point. Curie point is RE
In the relationship of Gd>Tb> Dy, in TM, Co> F
e. Hc has a relationship of Tb>Dy> Gd in the RE. If the Gd is large, the perpendicular magnetic anisotropy is small (Hc is small), and the film is magnetized in-plane by the influence of the demagnetizing field except in the temperature range where Ms near the compensation point is small. That is why the characteristics of the reproducing layer are shown only in the vicinity of the compensation point in FIG. 3 (the transition region from the in-plane magnetization to the perpendicular magnetization is shown by a fine broken line).
【0023】図3,4を参照しながら本発明の記録再生
方法を説明する。記録過程は前述した様にフォトンモー
ド主体である。即ち記録光照射時にスポット中央部付近
のフォトン数の多い部分の光導電膜中に多量の伝導電子
が生成し、その部分の交換磁界Hexgが図3に示され
る様に記録層の保磁力Hcwを上回り、Hexgの他に
他の層から記録層に印加する漏洩磁界、必要に応じて印
加される外部磁界が有るが、Hexgがドミナントで磁
界のベクトル和(実効磁界)が図1の上向きで大きさが
Hcw以上である場合に記録層の磁化は上向きに揃う。
記録マークサイズは原理的に記録時に光導電膜のσが大
きくなる部分で決まるので、σに起因するHexg特性
とHcw特性で決定され、レーザスポットのFWHMよ
りも小さいサイズのマークが形成可能であり、結果とし
て高密度記録を実現する。The recording / reproducing method of the present invention will be described with reference to FIGS. The recording process is mainly in the photon mode as described above. That is, during irradiation of the recording light, a large amount of conduction electrons are generated in the photoconductive film in the portion having a large number of photons near the center of the spot, and the exchange magnetic field Hexg in that portion reduces the coercive force Hcw of the recording layer as shown in FIG. There is a leakage magnetic field applied from another layer to the recording layer in addition to Hexg, and an external magnetic field applied as necessary. Hexg is dominant, and the vector sum (effective magnetic field) of the magnetic field is large in the upward direction in FIG. When is equal to or higher than Hcw, the magnetization of the recording layer is aligned upward.
Since the recording mark size is determined in principle by the portion where σ of the photoconductive film increases during recording, it is determined by the Hexg characteristic and Hcw characteristic caused by σ, and a mark smaller than the FWHM of the laser spot can be formed. As a result, high density recording is realized.
【0024】消去過程は記録時と消去時の外部磁界を変
える非オーバライトの実施態様では簡単で、単に消去時
は記録時よりも下向きに大きな外部磁界を印加して、記
録層がキューリー点付近に加熱されている領域に印加す
る実効磁界を下向きにしたやれば良い。非オーバライト
タイプでは、再生層、記録層、磁石層共にそれらの熱磁
気特性には自由度が高い。記録時も消去時も同一の外部
磁界を用いる光変調オーバライトの実施では、実効磁界
をパワーで制御する必要がある。この場合は特に記録層
に他の層から印加する漏洩磁界を利用する事になるの
で、記録層の特性に合わせて他の磁性層の熱磁気特性を
設計する必要がある。図4の特性では主に磁石層から発
生する漏洩磁界を利用する事が出来る。磁石層の磁化の
向きは室温では一様に同向きで膜の外部に漏洩磁界を供
給しないが、加熱によって磁化の空間分布を形成すると
膜外部に漏洩磁界を発生する。図1の様に上向きに磁化
されている磁石層をレーザ光で局所的に加熱すると、図
4の特性から加熱部の磁化Mspが周囲よりも低下し
て、Tcompp以上で見掛け上反転する。ここで注意
を要するのはMspの向きが見掛け上反転しただけでR
E,TM各々の磁化の向きは変っていないので、交換磁
界の向きは補償点前後で上向きのままである。このMs
pの空間分布に従って磁石層からは下向きに漏洩磁界が
発生して記録層に印加する。消去パワーレベルの設定に
は色々なバリエーションが挙げられるが、例えば実効磁
界のパワー変調を各層の温度差の利用で行う場合には、
消去パワーを記録パワーよりも高く設定する実施態様が
挙げられる。記録層は磁石層よりも光ビーム入射側に近
く、記録層と磁石層の間にある光導電層は熱的には温度
差形成層として作用するので、光照射による昇温過程と
最高温度到達時には、記録層温度を磁石層温度よりも高
く設定し、冷却過程では層間の熱拡散により記録層と磁
石層の温度をほぼ同一に出来る。そこで記録パワーを消
去パワーよりらも低く設定すると、記録時には、記録層
がTcw付近にいる時、磁石層はTcwよりも低く漏洩
磁界が小さい温度に有って、漏洩磁界よりも交換磁界が
ドミナントで記録層は上向きに磁化され、消去時には、
記録層がTcw付近にいる時(より高い温度から冷却し
てきた時)、磁石層はTcw付近の記録時よりも漏洩磁
界の大きな温度に有って、交換磁界よりも漏洩磁界ドミ
ナントで記録層は下向きに磁化される、事が可能とな
る。温度差の利用の他に記録層の磁化反転には有限な時
間を有する事を利用して、記録時と消去時で記録層がキ
ューリー点付近の磁化反転温度帯を通過する時間に差を
設けても光変調オーバライトが成立し得る。The erasing process is simple in a non-overwrite embodiment in which an external magnetic field is changed between recording and erasing. In erasing, a larger external magnetic field is simply applied downward than during recording, and the recording layer is moved near the Curie point. What is necessary is just to make the effective magnetic field applied to the area heated in the downward direction downward. In the non-overwrite type, the reproducing layer, the recording layer, and the magnet layer have a high degree of freedom in their thermomagnetic properties. In performing the light modulation overwrite using the same external magnetic field during recording and erasing, it is necessary to control the effective magnetic field with power. In this case, in particular, a leakage magnetic field applied to the recording layer from another layer is used, so it is necessary to design the thermomagnetic characteristics of the other magnetic layer according to the characteristics of the recording layer. In the characteristic of FIG. 4, a leakage magnetic field mainly generated from the magnet layer can be used. At room temperature, the direction of magnetization of the magnet layer is uniform and does not supply a leakage magnetic field to the outside of the film. However, if a spatial distribution of magnetization is formed by heating, a leakage magnetic field is generated outside the film. When the magnet layer magnetized upward as shown in FIG. 1 is locally heated by the laser beam, the magnetization Msp of the heating portion is lower than the surroundings from the characteristics of FIG. 4, and apparently reverses at Tcompp or more. It should be noted here that the direction of Msp is apparently reversed,
Since the directions of the magnetizations of E and TM are not changed, the direction of the exchange magnetic field remains upward before and after the compensation point. This Ms
A leakage magnetic field is generated downward from the magnet layer according to the spatial distribution of p and is applied to the recording layer. There are various variations in the setting of the erasing power level. For example, when power modulation of the effective magnetic field is performed by using the temperature difference of each layer,
There is an embodiment in which the erasing power is set higher than the recording power. The recording layer is closer to the light beam incident side than the magnet layer, and the photoconductive layer between the recording layer and the magnet layer thermally acts as a temperature difference forming layer. Sometimes, the temperature of the recording layer is set higher than the temperature of the magnet layer, and in the cooling process, the temperatures of the recording layer and the magnet layer can be made almost the same due to thermal diffusion between the layers. Therefore, if the recording power is set lower than the erasing power, during recording, when the recording layer is near Tcw, the magnet layer is at a temperature lower than Tcw and the leakage magnetic field is small, and the exchange magnetic field is more dominant than the leakage magnetic field. The recording layer is magnetized upward, and when erasing,
When the recording layer is near Tcw (when cooled from a higher temperature), the magnet layer is at a temperature where the leakage magnetic field is larger than during recording near Tcw, and the recording layer is dominant in the leakage magnetic field rather than the exchange magnetic field. It can be magnetized downward. In addition to utilizing the temperature difference, the fact that the recording layer has a finite time for the magnetization reversal of the recording layer makes use of the fact that there is a difference in the time that the recording layer passes through the magnetization reversal temperature zone near the Curie point between recording and erasing. However, light modulation overwriting can be achieved.
【0025】次に図1と図4を参照しながら本発明の再
生過程を説明する。再生層は本実施例の様な室温付近で
面内磁化の膜を用いてもそうで無くても構わないが、こ
こでは面名磁化の場合を例示する。再生層はその補償点
TcompR付近のMsRが小さい温度帯で垂直に磁化
して、記録層の磁化に揃う。記録層と再生層が直接積層
されている場合には、キロ区層と再生層間には交換力が
作用するので、再生層が垂直磁化になる温度帯では再生
層の磁化は記録層からの交換磁界で記録層の磁化の向き
に揃い、図1に示した様に再生層と記録層間に非磁性層
が介在する場合には、記録層の磁化の分布に対応する漏
洩磁界が再生層に作用して再生層の磁化は漏洩磁界によ
ってやはり記録層の磁化に揃う。いづれの場合でも光を
照射していない部分は面内磁化でカー効果を原理とする
光磁気再生には寄与しないので、再生光照射部のみに記
録層の磁化が転写される。転写領域の大きさは再生層の
熱磁気特性と、記録層からの交換磁界あるいは漏洩磁界
に依存するが、転写領域をレーザスポットサイズよりも
小さく出来るので、本発明で記録した微小な記録マーク
を高分解能で再生出来る(MSR再生)。又、再生層と
して磁壁エネルギーが反磁界エネルギーよりも小さく、
又、磁壁移動速度の速い膜材料を用いると、記録層から
再生層に転写した微小なマークは再生層で拡大して高C
/N再生を実現する。Next, the reproducing process of the present invention will be described with reference to FIGS. The reproducing layer may or may not be a film having an in-plane magnetization near room temperature as in the present embodiment. The reproducing layer is vertically magnetized in a temperature range where the MsR near the compensation point TcompR is small, and is aligned with the magnetization of the recording layer. When the recording layer and the reproducing layer are directly laminated, an exchange force acts between the kilo-layer and the reproducing layer. Therefore, in the temperature range where the reproducing layer is perpendicularly magnetized, the magnetization of the reproducing layer is exchanged from the recording layer. When the magnetization direction of the recording layer is aligned by the magnetic field, and a non-magnetic layer is interposed between the reproducing layer and the recording layer as shown in FIG. 1, a leakage magnetic field corresponding to the magnetization distribution of the recording layer acts on the reproducing layer. Then, the magnetization of the reproducing layer is also aligned with the magnetization of the recording layer due to the leakage magnetic field. In any case, since the portion not irradiated with light does not contribute to magneto-optical reproduction based on the Kerr effect due to in-plane magnetization, the magnetization of the recording layer is transferred only to the reproduction light irradiated portion. Although the size of the transfer area depends on the thermomagnetic characteristics of the reproducing layer and the exchange magnetic field or the leakage magnetic field from the recording layer, the transfer area can be made smaller than the laser spot size. High resolution playback (MSR playback). Also, the domain wall energy as the reproducing layer is smaller than the demagnetizing field energy,
Further, when a film material having a high domain wall moving speed is used, a minute mark transferred from the recording layer to the reproducing layer is enlarged in the reproducing layer and has a high C value.
/ N reproduction.
【0026】上記した記録再生プロセスをディスク動作
で検証し、本発明の効果を明確にする目的で実施例1の
ディスクを試作した実験用ドライブに設置して記録再生
動作を行った。実験用ドライブは光源としてArイオン
レーザを有するAOMモジュレータを使用する光変調記
録用の実験機であり、媒体面上でのスポットサイズは、
記録に関連するFWHMが0.38μm、再生に関連す
るe−2径が0.68μmである。The above-mentioned recording / reproducing process was verified by a disk operation, and for the purpose of clarifying the effect of the present invention, the disk of the first embodiment was installed in a prototype experimental drive to perform a recording / reproducing operation. The experimental drive is an experimental device for optical modulation recording using an AOM modulator having an Ar ion laser as a light source. The spot size on the medium surface is:
The FWHM related to recording is 0.38 μm, and the e-2 diameter related to reproduction is 0.68 μm.
【0027】このスポットサイズを有する記録装置で
は、磁性層としてRE−TM記録層のみを有する通常の
光磁気記録媒体では、再生C/Nとして45dB以上の
値が得られる記録マーク長は0.35μm以上、トラッ
クピッチは0.46μm以上で、これよりも小さいマー
クの記録はパワーマージンが無く不安定であり、又、安
定したマークサイズが得られる記録パワーでマークピッ
チを上記した値よりも詰めると符号間干渉とクロストー
クの影響が大きくC/Nは著しく劣化した。又、当然の
事ながら従来の光磁気記録媒体を使用した際には光変調
オーバライトは出来ず、消去時は記録時とは逆向きに外
部磁界を印加して一括消去する必要が有った。さらに記
録データ転送速度は媒体の熱応答で制限される為、線速
を15m/s程度以上に高速化すると記録感度の低下と
熱干渉の影響によるC/Nの劣化を呈した。In a recording apparatus having this spot size, in a normal magneto-optical recording medium having only an RE-TM recording layer as a magnetic layer, a recording mark length at which a value of 45 dB or more is obtained as a reproduction C / N is 0.35 μm. As described above, when the track pitch is 0.46 μm or more, recording of a mark smaller than this is unstable without a power margin, and when the mark pitch is narrowed from the above value at a recording power capable of obtaining a stable mark size. The influence of intersymbol interference and crosstalk was large, and C / N was significantly degraded. Naturally, when using a conventional magneto-optical recording medium, optical modulation overwriting was not possible, and it was necessary to apply an external magnetic field in the opposite direction to the recording to erase the data at the time of erasing. . Furthermore, since the recording data transfer speed is limited by the thermal response of the medium, increasing the linear velocity to about 15 m / s or more causes a decrease in recording sensitivity and a deterioration in C / N due to the influence of thermal interference.
【0028】一方で本発明の光磁気記録媒体では、再生
層として実施例1のGdFe−MSR膜を採用した場合
においても、再生C/Nとして45dBの値が得られる
記録マーク長は0.25μm、トラックピッチも0.2
5μmに短縮する事が出来た。再生層の組成比を調整し
て転写後に拡大再生(MAMMOS)が可能な様にする
と、C/N:45dBを示すマーク長とトラックピッチ
は共に0.2μmまで、さらに短縮する事が可能であ
る。これらの数値は線速:15m/s、光変調オーバラ
イトで得られた値である。さらに本発明の記録原理は高
速のフォトンモードプロセスがドミナントである事に起
因して、線速を30m/sまで増加させても良好な記録
感度と高いC/Nを得た。ここで、記録/消去/再生パ
ワーはC/N、消去率等を基準に最適化し、線速が15
m/sでは各々12/6/2mWであった。DC外部磁
界も最適化を行った結果、十分な消去比を得る上では図
1の下向き即ち消去向きに200Oe程度の磁界を印加
する必要が有った。 [実施例2]前記実施例では、比較的短波長で光導電性
を示すCuOを光導電膜に選び、波長488nmのAr
イオンレーザを用いた実験機で本発明の効果を検証した
例を述べたが、本実施例では波長650nmの赤色LD
での実用的な動作を試みた。図2に本実施例2に使用し
た光磁気記録媒体の構成を示す。図2において、21は
再生層、22は記録層、23は光導電層、24は磁石
層、25は基板、26は干渉層、27はゲート層、28
保護層、29は下部バリア層、210は上部バリア層で
ある。実施例1との構造上の差異は、非磁性中間層17
の代りに面内磁化のゲート層27を用いゲート層を介し
て記録層と再生層を交換結合させた点、光導電層と記録
層、及び磁石層との二つの界面にバリア層を使用した点
である。この実施例2では、再生層として膜厚25nm
のGdDyFeCo膜、記録層として膜厚60nmのT
bFeCo膜、光導電層として膜厚100nmの非晶質
Si膜(光学ギャップ:1.2eV)、磁石層として膜
厚50nmのGdTbFeCo膜、ゲート層として膜厚
10nmのGdDyFe膜、上部、下部バリア層として
各々膜厚10nmのTiN膜を用いた。On the other hand, in the magneto-optical recording medium of the present invention, even when the GdFe-MSR film of Example 1 is employed as the reproducing layer, the recording mark length at which a value of 45 dB is obtained as the reproducing C / N is 0.25 μm. , Track pitch 0.2
It could be reduced to 5 μm. If the composition ratio of the reproduction layer is adjusted to enable enlarged reproduction (MAMMOS) after transfer, the mark length and track pitch indicating C / N: 45 dB can both be further reduced to 0.2 μm. . These numerical values are values obtained by linear velocity: 15 m / s and light modulation overwriting. Further, the recording principle of the present invention is that, because the high-speed photon mode process is dominant, good recording sensitivity and high C / N were obtained even when the linear velocity was increased to 30 m / s. Here, the recording / erasing / reproducing power is optimized based on the C / N, the erasing rate, etc.
At m / s, they were 12/6/2 mW, respectively. As a result of optimizing the DC external magnetic field, it was necessary to apply a magnetic field of about 200 Oe downward in FIG. [Embodiment 2] In the above embodiment, CuO having photoconductivity at a relatively short wavelength was selected as a photoconductive film, and ArO having a wavelength of 488 nm was selected.
An example in which the effect of the present invention was verified using an experimental machine using an ion laser was described. In this embodiment, a red LD having a wavelength of 650 nm is used.
Tried a practical operation in. FIG. 2 shows the configuration of the magneto-optical recording medium used in the second embodiment. In FIG. 2, 21 is a reproducing layer, 22 is a recording layer, 23 is a photoconductive layer, 24 is a magnet layer, 25 is a substrate, 26 is an interference layer, 27 is a gate layer, 28
A protective layer, 29 is a lower barrier layer, and 210 is an upper barrier layer. The structural difference from the first embodiment is that the nonmagnetic intermediate layer 17
Instead of using a gate layer 27 having an in-plane magnetization, the recording layer and the reproducing layer were exchange-coupled through the gate layer, and a barrier layer was used at two interfaces between the photoconductive layer, the recording layer, and the magnet layer. Is a point. In Example 2, the thickness of the reproducing layer was 25 nm.
GdDyFeCo film, 60 nm thick T as a recording layer
bFeCo film, 100 nm-thick amorphous Si film (optical gap: 1.2 eV) as a photoconductive layer, 50 nm-thick GdTbFeCo film as a magnet layer, 10 nm-thick GdDyFe film as a gate layer, upper and lower barrier layers Used are TiN films each having a thickness of 10 nm.
【0029】本実施例では光導電膜として長波長感応性
の非晶質Siを用いたので、バリア層が存在しない場合
は、Siと磁性層の界面にFeシリサイド層を形成し、
記録層と磁石層間に作用する交換磁界を低下させた(記
録層と磁石層が直接積層されている試料比)。バリア層
を設けた場合には特には交換磁界の低下は見られなかっ
た。バリア層としては導電性材料ならば何でも良いが、
半導体、磁性体に反応性の少ないものが好ましく、本実
施例で用いたTiNの他ITOが好適である。ITOを
用いた場合、ITOは光を通すので、下部バリア層を厚
くしても光導電膜の光導電特性を損なう事はない。In this embodiment, since a long-wavelength-sensitive amorphous Si is used as the photoconductive film, if there is no barrier layer, an Fe silicide layer is formed at the interface between Si and the magnetic layer.
The exchange magnetic field acting between the recording layer and the magnet layer was reduced (compared to a sample in which the recording layer and the magnet layer were directly laminated). When the barrier layer was provided, no decrease in the exchange magnetic field was observed. As the barrier layer, any conductive material may be used,
Those having low reactivity to the semiconductor and the magnetic material are preferable, and ITO other than TiN used in this embodiment is preferable. When ITO is used, since the ITO transmits light, the photoconductive characteristics of the photoconductive film are not impaired even if the lower barrier layer is thickened.
【0030】基板としては実施例1と同じグルーブ(ト
ラッキングガイド用の溝)の設けられたポリカーボネイ
ト基板を用いた。干渉層、保護層は実施例1と同一と
し、ディスク試料の形成も実施例1と同様にマグネトロ
ンスパッタリング法を採用した。波長650nmの光ビ
ームを照射して調べた光導電特性と、光導電時の記録層
と磁石層間に作用する交換磁界、記録層の保磁力の関係
は、図3に示されるのと同等の挙動を示した。As the substrate, a polycarbonate substrate provided with the same groove (groove for tracking guide) as in Example 1 was used. The interference layer and the protective layer were the same as those in Example 1, and the disk samples were formed by the magnetron sputtering method as in Example 1. The relationship between the photoconductivity measured by irradiating a light beam with a wavelength of 650 nm, the exchange magnetic field acting between the recording layer and the magnet layer during photoconduction, and the coercive force of the recording layer is the same as that shown in FIG. showed that.
【0031】図5に再生層とゲート層の熱磁気特性を示
す。記録層と磁石層は実施例1と同様の特性を示した。
図5[a]が垂直方向の磁化Msの温度特性、図5
[b]が保磁力Hcの温度特性である。本実施例に使用
した再生層、ゲート層は共に室温Ta付近では面内に磁
化しており、加熱に伴って磁化が低下し垂直磁気異方性
が発現されて垂直磁化状態に移行する。実施例1に用い
た再生層は補償点付近でのみ垂直磁化だったが、本実施
例2に用いた再生層とゲート層は補償点からキューリー
点の間で垂直磁化を保持した。これらの特性の違いは再
生層に関しては実施例1の材料に実施例2ではDy,G
dを添加した事に起因して得られたものである。再生層
のキューリー点TcRは記録層のそれTcwに近い値に
設定し、ゲート層のキューリー点はTcwよりも低い値
に設定した。FIG. 5 shows the thermomagnetic characteristics of the reproducing layer and the gate layer. The recording layer and the magnet layer exhibited the same characteristics as in Example 1.
FIG. 5A shows the temperature characteristic of the magnetization Ms in the vertical direction.
[B] is the temperature characteristic of the coercive force Hc. Both the reproducing layer and the gate layer used in the present embodiment are magnetized in-plane near room temperature Ta, and the magnetization decreases with heating, the perpendicular magnetic anisotropy is developed, and the state shifts to the perpendicular magnetization state. The reproducing layer used in Example 1 had perpendicular magnetization only near the compensation point, but the reproducing layer and the gate layer used in Example 2 maintained perpendicular magnetization between the compensation point and the Curie point. The difference between these characteristics is that the reproducing layer is made of the material of Example 1 and the reproducing layer is made of Dy, G
This was obtained due to the addition of d. The Curie point TcR of the reproducing layer was set to a value close to that of the recording layer Tcw, and the Curie point of the gate layer was set to a value lower than Tcw.
【0032】記録再生プロセスの詳細は実施例1で述べ
たので、ここでは実施例1と異なる部分についてのみ記
述する。実施例1では消去動作において記録層に消去向
きの漏洩磁界を印加する膜は磁石層だけで有り、その為
十分な消去比を得る為には消去側に200Oeの外部磁
界を印加する必要が有った。この消去向きのが外部磁界
は光変調オーバライト動作においては記録時も印加され
続ける事になるので、実効的な記録磁界を低下させる作
用を持っていた。本実施例2では消去向きの漏洩磁界を
記録層に印加する膜は磁石層の他に再生層がある。基本
的には、再生層は再生パワーレベルではその補償点前後
の比較的Hcの低い温度に加熱され、ゲート層を介して
加熱部が記録層と交換結合して記録層中の微小記録磁区
を転写し拡大再生する作用を有する。再生層の付加的効
果は前記した記録層への漏洩磁界の生成である。消去パ
ワーレベルの光照射時に記録層がそのキューリー点付近
の磁化反転可能な温度帯にある時、再生層はやはりキュ
リー点付近で加熱領域の大半の部分は垂直磁化配向を為
す。一方ゲート層の加熱部はキューリー点以上に加熱さ
れているので記録層と再生層の間には交換磁界は作用し
ない。従って、再生層の加熱部の磁化は磁石層からの漏
洩磁界もしくは必要に応じて印加される比較的小さな下
向きの外部磁界の向きに揃う。再生層の磁化の空間分布
は冷却部は面内、加熱部は下向きとなるので、記録層に
対して下向き即ち消去向きの漏洩磁界を印加して消去プ
ロセスをアシストする。記録プロセスは消去プロセスと
はパワーが異なるので、各層間の温度差の昇温過程と冷
却過程での違い、記録層が磁化反転可能な温度帯を通過
する時間の違いなどを利用する事により、記録プロセス
では再生層から記録層に印加する消去向き磁界は消去プ
ロセスよりも小さく設定である。同様の事が磁石層から
の漏洩磁界にも言える事は実施例1中にも記述した。Since the details of the recording / reproducing process have been described in the first embodiment, only the parts different from the first embodiment will be described here. In the first embodiment, in the erasing operation, only the magnet layer applies the leakage magnetic field in the erasing direction to the recording layer. Therefore, it is necessary to apply an external magnetic field of 200 Oe to the erasing side in order to obtain a sufficient erasing ratio. Was. Since the external magnetic field in the erasing direction is continuously applied even during recording in the light modulation overwrite operation, the external magnetic field has an effect of reducing the effective recording magnetic field. In the second embodiment, the film for applying the leakage magnetic field in the erasing direction to the recording layer includes a reproducing layer in addition to the magnet layer. Basically, the reproducing layer is heated to a relatively low temperature of Hc before and after the compensation point at the reproducing power level, and the heating section exchange-couples with the recording layer via the gate layer to form the minute recording magnetic domain in the recording layer. It has the function of transferring and expanding and reproducing. An additional effect of the reproducing layer is the above-described generation of a stray magnetic field to the recording layer. When the recording layer is in the temperature range where the magnetization can be reversed near the Curie point at the time of irradiating light at the erasing power level, the reproducing layer still has a perpendicular magnetization orientation near the Curie point for most of the heated region. On the other hand, since the heating portion of the gate layer is heated above the Curie point, no exchange magnetic field acts between the recording layer and the reproducing layer. Therefore, the magnetization of the heating portion of the reproducing layer is aligned with the direction of the leakage magnetic field from the magnet layer or the relatively small downward external magnetic field applied as necessary. The spatial distribution of the magnetization of the reproducing layer is such that the cooling portion is in-plane in the cooling portion and the heating portion is in the downward direction. Therefore, a downward or erasing-oriented leakage magnetic field is applied to the recording layer to assist the erasing process. Since the power of the recording process is different from that of the erasing process, the difference in the temperature difference between each layer between the heating process and the cooling process, and the difference in the time during which the recording layer passes through the temperature zone where the magnetization can be reversed can be used. In the recording process, the erasing magnetic field applied from the reproducing layer to the recording layer is set smaller than in the erasing process. The same can be said for the leakage magnetic field from the magnet layer as described in Example 1.
【0033】上記した記録再生プロセスをディスク動作
で検証し、本発明の効果を明確にする目的で実施例2の
ディスクを光変調オーバライトモードの実験用光磁気ド
ライブに設置して記録再生動作を行った。光源は波長6
50nmのLDで、媒体面上でのスポットサイズは、記
録に関連するFWHMが0.5μm、再生に関連するe
−2径が0.9μmである。The above-described recording / reproducing process was verified by disk operation, and for the purpose of clarifying the effect of the present invention, the disk of Example 2 was installed in an experimental magneto-optical drive in the optical modulation overwrite mode to perform the recording / reproducing operation. went. Light source is wavelength 6
With a 50 nm LD, the spot size on the medium surface is 0.5 μm for FWHM related to recording, and e
-2 diameter is 0.9 μm.
【0034】このスポットサイズを有する記録装置で
は、磁性層としてRE−TM記録層のみを有する通常の
光磁気記録媒体では、再生C/Nとして45dB以上の
値が得られる記録マーク長は0.42μm以上、トラッ
クピッチは0.6μm以上で、これよりも小さいマーク
の記録はパワーマージンが無く不安定であり、又、安定
したマークサイズが得られる記録パワーでマークピッチ
を上記した値よりも詰めると符号間干渉とクロストーク
の影響が大きくC/Nは著しく劣化した。又、当然の事
ながら従来の光磁気記録媒体を使用した際には光変調オ
ーバライトは出来ず、消去時は記録時とは逆向きに外部
磁界を印加して一括消去する必要が有った。さらに記録
データ転送速度は媒体の熱応答で制限される為、線速を
15m/s程度以上に高速化すると記録感度の低下と熱
干渉の影響によるC/Nの劣化を呈した。In a recording apparatus having this spot size, in a normal magneto-optical recording medium having only a RE-TM recording layer as a magnetic layer, a recording mark length at which a value of 45 dB or more is obtained as a reproduction C / N is 0.42 μm. As described above, when the track pitch is 0.6 μm or more, recording of a mark smaller than this is unstable without a power margin, and when the mark pitch is narrowed from the above value at the recording power at which a stable mark size is obtained. The influence of intersymbol interference and crosstalk was large, and C / N was significantly degraded. Naturally, when using a conventional magneto-optical recording medium, optical modulation overwriting was not possible, and it was necessary to apply an external magnetic field in the opposite direction to the recording to erase the data at the time of erasing. . Furthermore, since the recording data transfer speed is limited by the thermal response of the medium, increasing the linear velocity to about 15 m / s or more causes a decrease in recording sensitivity and a deterioration in C / N due to the influence of thermal interference.
【0035】一方で本発明の光磁気記録媒体では、再生
C/Nとして45dBの値が得られる記録マーク長は
0.27μm、トラックピッチも0.27μmに短縮す
る事が出来た。これは実施例1で用いた波長488nm
に換算すると各々0.2μmとなり、実質的に本実施例
2の媒体は前記した実施例1の媒体よりも高密度記録が
可能であると言える。上記した数値は線速:15m/
s、光変調オーバライトで得られた値である。さらに本
発明の記録原理は高速のフォトンモードプロセスがドミ
ナントである事に起因して、線速を30m/sまで増加
させても良好な記録感度と高いC/Nを得た。ここで、
記録/消去/再生パワーはC/N、消去率等を基準に最
適化し、線速が15m/sでは各々12/6/2mWで
あった。DC外部磁界も最適化を行った結果、十分な消
去比を得る上では図1の下向き即ち消去向きに50−1
00Oe程度の磁界を印加するだけで十分であり、実施
例2では消去プロセスにおいて再生層から記録層へ消去
向きの漏洩磁界が印加されている事が立証された。On the other hand, in the magneto-optical recording medium of the present invention, the recording mark length at which a value of 45 dB was obtained as the reproduction C / N was reduced to 0.27 μm, and the track pitch was reduced to 0.27 μm. This is the wavelength of 488 nm used in Example 1.
In other words, it can be said that the medium of the second embodiment can substantially perform higher-density recording than the medium of the first embodiment. The above value is the linear velocity: 15m /
s is a value obtained by light modulation overwriting. Further, the recording principle of the present invention is that, because the high-speed photon mode process is dominant, good recording sensitivity and high C / N were obtained even when the linear velocity was increased to 30 m / s. here,
The recording / erasing / reproducing power was optimized on the basis of C / N, erasing rate, etc., and was 12/6/2 mW at a linear velocity of 15 m / s. As a result of optimizing the DC external magnetic field, in order to obtain a sufficient erasing ratio, 50-1 in the downward direction in FIG.
It is sufficient to apply a magnetic field of about 00 Oe. In Example 2, it was proved that a leakage magnetic field for erasing was applied from the reproducing layer to the recording layer in the erasing process.
【0036】上記した実施例1,2では再生層として室
温で面内磁化の膜を用いた例を述べたが、再生層は室温
で垂直磁化でも構わず、又、再生層自身が実施例2に示
した様に磁性多層膜構造を為していても良い。磁性膜材
料、光導電膜材料、バリア膜材料、干渉膜材料、保護膜
材料も本発明の主旨を逸脱しない範囲で幅広く選択出来
る。本発明は基本的に、記録光照射によって光導電層中
に生成した伝導電子により、光導電膜の上下の少なくも
二つの磁性膜が交換相互作用を及ぼし合ってスポットサ
イズよりも小さな記録マークの形成が行われ、この小さ
な記録マークを記録層から再生層への磁化転写、もしく
は磁化転写と磁区拡大によって高分解能かつ高C/Nで
再生する光磁気記録媒体、光磁気記録再生方法、光磁気
記録再生装置を提供するものであり、実施例以外にも数
多くの変形例を挙げる事も可能である。In Embodiments 1 and 2 described above, an example was described in which a film having in-plane magnetization at room temperature was used as a reproducing layer. However, the reproducing layer may have perpendicular magnetization at room temperature. As shown in the above, a magnetic multilayer structure may be formed. The material of the magnetic film, the material of the photoconductive film, the material of the barrier film, the material of the interference film, and the material of the protective film can be widely selected without departing from the gist of the present invention. The present invention is basically based on conduction electrons generated in a photoconductive layer by irradiation of recording light, so that at least two magnetic films above and below a photoconductive film exert an exchange interaction and a recording mark smaller than a spot size is formed. A magneto-optical recording medium, a magneto-optical recording / reproducing method, a magneto-optical recording / reproducing method, which reproduces the small recording mark with high resolution and high C / N by magnetizing transcription from the recording layer to the reproducing layer or by magnetizing transcription and magnetic domain expansion. A recording / reproducing apparatus is provided, and a number of modified examples other than the embodiment can be given.
【0037】[0037]
【発明の効果】本発明によれば、光スポットサイズより
も小さな記録マーク列を高速に記録する事が出来、又、
微細記録マーク列を高分解能、高C/Nで再生出来るの
で、光磁気記録システムの記録面密度・記憶容量の格段
な向上とデータ転送速度の高速化が実現出来る。According to the present invention, a record mark array smaller than the light spot size can be recorded at a high speed.
Since a fine recording mark array can be reproduced with a high resolution and a high C / N, a remarkable improvement in the recording surface density and storage capacity of the magneto-optical recording system and an increase in the data transfer speed can be realized.
【図1】本発明の光磁気記録媒体の第一の実施例の断面
構成図。FIG. 1 is a sectional configuration view of a first embodiment of a magneto-optical recording medium according to the present invention.
【図2】本発明の光磁気記録媒体の第二の実施例の断面
構成図。FIG. 2 is a sectional configuration diagram of a second embodiment of the magneto-optical recording medium of the present invention.
【図3】本発明の記録過程を説明する図。FIG. 3 is a diagram illustrating a recording process of the present invention.
【図4】本発明の光磁気記録媒体の第一の実施例に使用
される各層の熱磁気特性の一例。FIG. 4 shows an example of thermomagnetic characteristics of each layer used in the first embodiment of the magneto-optical recording medium of the present invention.
【図5】本発明の光磁気記録媒体の第二の実施例に使用
される各層の熱磁気特性の一例。FIG. 5 is an example of the thermomagnetic characteristics of each layer used in the second embodiment of the magneto-optical recording medium of the present invention.
11:再生層、 12:記録層、 13:光導電層、 14:磁石層、 15:基板、 16:干渉層、 17:非磁性中間層、 18:保護層、 21:再生層、 22:記録層、 23:光導電層、 24:磁石層、 25:基板、 26:干渉層、 27:ゲート層、 28:保護層、 29:下部バリア層、 210:上部バリア層 11: reproducing layer, 12: recording layer, 13: photoconductive layer, 14: magnet layer, 15: substrate, 16: interference layer, 17: non-magnetic intermediate layer, 18: protective layer, 21: reproducing layer, 22: recording Layer, 23: photoconductive layer, 24: magnet layer, 25: substrate, 26: interference layer, 27: gate layer, 28: protective layer, 29: lower barrier layer, 210: upper barrier layer
Claims (8)
磁性層、光導電層、磁石層の順に積層してなる事を特徴
とする光磁気記録媒体。1. A magneto-optical recording medium comprising a reproducing magnetic layer, a recording magnetic layer, a photoconductive layer, and a magnet layer laminated in this order from the light beam incident side.
磁石層の間から選ばれた少なくも一つの界面に導電層が
設けられている事を特徴とする請求項[1]に記載の光
磁気記録媒体。2. The method according to claim 1, wherein a conductive layer is provided on at least one interface selected between the recording magnetic layer and the photoconductive layer and between the photoconductive layer and the magnet layer. 3. The magneto-optical recording medium according to claim 1.
に対して垂直な方向に一様に同じ向きに磁化されている
事を特徴とする請求項[1],[2]に記載の光磁気記
録媒体。3. The light according to claim 1, wherein the magnet layer is uniformly magnetized in the same direction perpendicular to the film surface at the memory holding temperature. Magnetic recording medium.
面内に磁化されている事を特徴とする請求項[1]、
[2]、[3]のいずれかに記載の光磁気記録媒体。4. The reproducing magnetic layer has a memory holding temperature,
3. The method according to claim 1, wherein the surface is magnetized.
The magneto-optical recording medium according to any one of [2] and [3].
のいずれかに記載された光磁気記録媒体に記録パワーレ
ベルの光ビームを照射して、照射部の光導電層を導電性
にスイッチングし、伝導電子を介し記録磁性層と磁石層
を交換結合状態にして、磁石層の磁化の向きに記録磁性
層の磁化の向きを揃えて記録を行い、前記光磁気記録媒
体に再生パワーレベルの光ビームを照射して、照射部の
記録磁性層の磁化を再生磁性層に転写して再生を行う事
を特徴とする光磁気記録再生方法。5. Claims [1], [2], [3] and [4]
Irradiates the magneto-optical recording medium described in any of the above with a light beam of a recording power level, switches the photoconductive layer of the irradiated portion to conductive, and exchanges the recording magnetic layer and the magnet layer through conduction electrons. Then, recording is performed by aligning the direction of magnetization of the recording magnetic layer with the direction of magnetization of the magnet layer, and irradiating the magneto-optical recording medium with a light beam having a reproduction power level, thereby changing the magnetization of the recording magnetic layer of the irradiated portion. A magneto-optical recording / reproducing method, wherein reproduction is performed by transferring the data to a reproducing magnetic layer.
再生する事を特徴とする請求項[5]に記載の光磁気記
録再生方法。6. The magneto-optical recording / reproducing method according to claim 5, wherein the magnetic domain transferred to the reproducing magnetic layer is reproduced while being enlarged.
て、記録磁性層に対し、記録時に印加される交換磁界の
向きとは逆向きの磁界を印加して、消去動作を行う事を
特徴とする請求項[5]、[6]のいずれかに記載の光
磁気記録再生方法。7. The erasing operation is performed by irradiating a light beam having an erasing power level and applying a magnetic field in a direction opposite to a direction of an exchange magnetic field applied at the time of recording to the recording magnetic layer. The magneto-optical recording / reproducing method according to any one of claims [5] and [6].
のいずれかに記載された光磁気記録媒体に記録パワーレ
ベルの光ビームを照射して、照射部の光導電層を導電性
にスイッチングし、伝導電子を介し記録磁性層と磁石層
を交換結合状態にして、磁石層の磁化の向きに記録磁性
層の磁化の向きを揃えて記録を行い、前記光磁気記録媒
体に再生パワーレベルの光ビームを照射して、照射部の
記録磁性層の磁化を再生磁性層に転写して再生を行う事
を特徴とする光磁気記録再生装置。8. Claims [1], [2], [3], [4]
Irradiates the magneto-optical recording medium described in any of the above with a light beam of a recording power level, switches the photoconductive layer of the irradiated portion to conductive, and exchanges the recording magnetic layer and the magnet layer through conduction electrons. Then, recording is performed by aligning the direction of magnetization of the recording magnetic layer with the direction of magnetization of the magnet layer, and irradiating the magneto-optical recording medium with a light beam having a reproduction power level, thereby changing the magnetization of the recording magnetic layer of the irradiated portion. A magneto-optical recording / reproducing apparatus characterized in that reproduction is performed by transferring to a reproducing magnetic layer.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP11018207A JP2000215533A (en) | 1999-01-27 | 1999-01-27 | Magneto-optical recording medium, magneto-optical recording and reproducing method using the same, and magneto-optical recording and reproducing device |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP11018207A JP2000215533A (en) | 1999-01-27 | 1999-01-27 | Magneto-optical recording medium, magneto-optical recording and reproducing method using the same, and magneto-optical recording and reproducing device |
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Publication Number | Publication Date |
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JP2000215533A true JP2000215533A (en) | 2000-08-04 |
Family
ID=11965213
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JP11018207A Pending JP2000215533A (en) | 1999-01-27 | 1999-01-27 | Magneto-optical recording medium, magneto-optical recording and reproducing method using the same, and magneto-optical recording and reproducing device |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2016181340A1 (en) * | 2015-05-12 | 2016-11-17 | Ecole Polytechnique Federale De Lausanne (Epfl) | Magnetic-photoconductive material, magneto-optical data storage device, magneto-optical data storage system, and light-tunable microwave components comprising a photoconductive-ferromagnetic device |
-
1999
- 1999-01-27 JP JP11018207A patent/JP2000215533A/en active Pending
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2016181340A1 (en) * | 2015-05-12 | 2016-11-17 | Ecole Polytechnique Federale De Lausanne (Epfl) | Magnetic-photoconductive material, magneto-optical data storage device, magneto-optical data storage system, and light-tunable microwave components comprising a photoconductive-ferromagnetic device |
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