JP3856060B2

JP3856060B2 - Magnetic recording method and magnetic head

Info

Publication number: JP3856060B2
Application number: JP34683497A
Authority: JP
Inventors: 幸治松本
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 1997-12-16
Filing date: 1997-12-16
Publication date: 2006-12-13
Anticipated expiration: 2017-12-16
Also published as: JPH11185235A

Description

【０００１】
【発明の属する技術分野】
本発明は、磁気的に情報を記録する磁気記録方法、及び磁気記録媒体に磁界を印加して情報の記録を行なう磁気ヘッドに関する。
【０００２】
【従来の技術】
磁気ディスクは、コンピュータにおける情報記録装置として普及している。とりわけ、動画像を取り扱うＰＣ（personal computer ）環境においては、さらなる大容量の記録、即ち高密度記録が可能な磁気ディスクが求められている。記録密度を高めるためには、磁気ディスクに形成する記録マーク長を短くするとともに、トラック幅を狭くする。
【０００３】
例えば、基板上にＣｒからなる下地層とＣｏＣｒＴａＰｔからなる記録層が積層された従来の磁気ディスクに情報を記録する。記録層の保磁力は２ｋＯｅ程度である。この磁気ディスクには、通常の磁気ヘッドを用いて交番磁界を印加することにより記録層に情報を記録することができる。この記録層に微小な記録マークを形成した場合には、記録層の粒子サイズに起因するノイズの上昇が生じる。これを解決するためには記録層の結晶粒を小さくすれば良いが、結晶粒を微小化すると記録された磁化方向が乱れやすくなり、記録層の熱的安定性が低下するという問題があった。
【０００４】
【発明が解決しようとする課題】
記録層の熱的安定性を良好にするためには、記録層の保磁力を例えば３ｋＯｅまで大きくすれば良い。しかしながら、磁性層の保持力が大きくなると、記録時に印加する交番磁界を大きくする必要があるという問題があった。また短い記録マーク長を形成する場合には、記録周波数が高いために、大きな交番磁界の印加が記録装置に大きな負担をかけるという問題があった。
【０００５】
本発明は、かかる事情に鑑みてなされたものであり、大きな保磁力を有する磁性層を備える磁気記録媒体に、小さな交番磁界の印加で情報を記録できる磁気記録方法、及びその方法を実現する磁気ヘッドを提供することを目的とする。なお、以下本願において交番磁界とは、「記録すべき情報に応じた磁化の方向を記録再生層に生じせしめる一方向の磁界の有無で構成する磁界」のことを示す。
【０００６】
【課題を解決するための手段】
本発明に係る磁気記録方法は、基板に少なくとも第２の磁性層と第１の磁性層をこの順序で積層し、前記第１の磁性層の保磁力Ｈｃ１と前記第２の磁性層の保磁力Ｈｃ２との間に、Ｈｃ１＜Ｈｃ２の関係を有する磁気記録媒体に情報を記録する磁気記録方法であって、前記第１及び第２の磁性層の各々の磁化の大きさをＭｓ１、Ｍｓ２、各々の膜厚をｔ１、ｔ２とし、前記第１及び第２の磁性層間の界面磁壁エネルギーをσとした際にＨｄａ＝Ｈｃ２−σ／２Ｍｓ２ｔ２、Ｈａｂ＝−Ｈｃ１−σ／２Ｍｓ１ｔ１、Ｈｂｃ＝ - Ｈｃ 2 ＋σ／２Ｍｓ２ｔ２によって定義される各値に対して、情報を記録すべき領域に｜Ｈｄｃ１｜＞｜Ｈｄａ｜の関係を満たす第１の初期化磁界Ｈｄｃ１を印加し、前記第１及び第２の磁性層の磁化方向を同方向に揃える第１初期化過程と、該第１初期化過程後に、前記領域に｜Ｈｂｃ｜＞｜Ｈｄｃ２｜＞｜Ｈａｂ｜の関係を満たす第２の初期化磁界Ｈｄｃ２を印加し、前記第１及び第２の磁性層の磁化方向を相異なる方向にする第２初期化過程と、該第２初期化過程後に、記録すべき情報に応じて極性を変化させた交番磁界Ｈｗを前記領域に印加する記録過程とを有することを特徴とする。
但し、｜Ｈｃ１−σ／２Ｍｓ１ｔ１｜＜｜Ｈｗ｜＜｜Ｈａｂ｜
【０００７】
本発明にあっては、情報を記録保持する第１の磁性層と、該磁性層と交換結合可能な第２の磁性層とを備えており、これらの交換結合領域での磁気特性に基づいて決定された大きさの磁界を印加することにより、記録用交番磁界を印加する直前で第１及び第２の磁性層の磁化方向が所定の方向に向く。この状態の磁性層に交番磁界を印加することにより、第１の磁性層単体の場合よりも小さい磁界の印加で、第１の磁性層の磁化方向を変化させることができる。第１及び第２の磁性層の交換結合領域の磁気特性に基づいて決定された第１の初期化磁界を印加して第１及び第２の磁性層を同方向に揃えた後、第２の初期化磁界を印加して、例えば第１の磁性層の磁化方向を反転させる。この状態の磁性層に交番磁界を印加することにより、第１の磁性層単体に対して必要な大きさよりも小さい磁界の印加で、第１の磁性層の磁化方向を変化させることができる。
【０００８】
本発明に係る磁気ヘッドは、基板に少なくとも第２の磁性層と第１の磁性層をこの順序で積層し、前記第１の磁性層の保磁力Ｈｃ１と前記第２の磁性層の保磁力Ｈｃ２との間に、Ｈｃ１＜Ｈｃ２の関係を有する磁気記録媒体の一面に対向して配され、前記磁気記録媒体に対して相対移動しつつ磁界を印加する磁気ヘッドにおいて、第１の初期化磁界を印加する第１の磁気発生部と第２の初期化磁界を印加する第２の磁気発生部と交番磁界を印加する第３の磁気発生部とを並設してあり、前記磁気発生部の並設方向を前記相対移動の方向と略平行に配すべくなしてあり、前記第１の磁気発生部が印加する前記第１の初期化磁界は、前記第１及び第２の磁性層の各々の磁化の大きさをＭｓ１、Ｍｓ２、各々の膜厚をｔ１、ｔ２とし、前記第１及び第２の磁性層間の界面磁壁エネルギーをσとした際にＨｄａ＝Ｈｃ２−σ／２Ｍｓ２ｔ２、Ｈａｂ＝−Ｈｃ１−σ／２Ｍｓ１ｔ１、Ｈｂｃ＝-Ｈｃ２＋σ／２Ｍｓ２ｔ２によって定義される各値に対して、情報を記録すべき領域に｜Ｈｄｃ１｜＞｜Ｈｄａ｜の関係を満たす磁界Ｈｄｃ１であって、前記第２の磁気発生部が印加する前記第２の初期化磁界は、前記領域に｜Ｈｂｃ｜＞｜Ｈｄｃ２｜＞｜Ｈａｂ｜の関係を満たす磁界Ｈｄｃ２であって、前記第３の磁気発生部が印加する交番磁界Ｈｗは、｜Ｈｃ１−σ／２Ｍｓ１ｔ１｜＜｜Ｈｗ｜＜｜Ｈａｂ｜を満たすことを特徴とする。
【００１５】
本発明にあっては、例えば、上述したような第１の初期化磁界を印加する第１の磁気発生部、第２の初期化磁界を印加する第２の磁気発生部、及び交番磁界を印加する第３の磁気発生部を相対移動方向に並設してあるので、相対移動中の磁気記録媒体の同一領域に、第１の初期化磁界、第２の初期化磁界及び交番磁界を順次印加することができる。
【００１６】
【発明の実施の形態】
以下、本発明をその実施の形態を示す図面に基づき具体的に説明する。
図１は本発明に係る磁気記録媒体及び磁気ヘッドの構成を示す断面図であり、本発明の磁気記録方法の実施態様を示している。図２は図１の平面図である。図中１は本発明に係る磁気ディスクであり、２は本発明に係る磁気ヘッドである。磁気ディスク１は、合成樹脂製の基板１１上に前記第２の磁性層たる制御層１２、及び前記第１の磁性層たる記録再生層１３をＤＣスパッタ法によりこの順に積層して構成されている。制御層１２の保磁力，膜厚，飽和磁化は、夫々、Ｈｃ１，ｔ１及びＭｓ１であり、記録再生層１３の保磁力，膜厚，飽和磁化は、夫々、Ｈｃ２，ｔ２及びＭｓ２である。なお、Ｈｃ１＜Ｈｃ２である。
【００１７】
磁気ディスク１上には、記録再生層１３に対向して磁気ヘッド２が配されている。磁気ヘッド２はスイングアーム３に連結されており、スイングアーム３の移動により磁気ヘッド２は磁気ディスク１の半径方向に移動可能である。磁気ヘッド２は、その内部に第１，第２及び第３のコイル２１，２２，２３を所定長だけ離隔して設けており、夫々のコイルにより異なる大きさの磁界を磁気ディスク１の対向する領域に印加する。また、磁気ヘッド２は、第１，第２及び第３のコイル２１，２２，２３が並設された方向が、磁気ディスク１のトラックの接線方向になるように対向配置される。ここで、第１，第２及び第３のコイル２１，２２，２３は、夫々、第１の初期化磁界Ｈdc１，第２の初期化磁界Ｈdc２，交番磁界Ｈｗを印加する。
【００１８】
このような膜構成の磁気ディスク１に情報を記録する際に、磁気ヘッド２を記録再生層１３の径方向の所定位置に移動させ、磁気ディスク１を回転させる。磁気ディスク１の回転により、磁気ディスク１は磁気ヘッド２に対して移動している。従って、記録再生層１３の記録すべき領域には第１，第２及び第３のコイル２１，２２，２３により、順に磁界が印加される。これらの磁界が印加された時点の制御層１２及び記録再生層１３の磁化状態について、これらの層の磁化曲線に基づいて以下に説明する。
【００１９】
図３は、磁気ディスク１の制御層１２及び記録再生層１３の磁化曲線を示した図である。図３（ａ）は記録再生層１３単体のヒステリシスループである。図３（ｂ）は制御層１２と記録再生層１３との交換結合領域のヒステリシスループであり、記録再生層１３のマイナーループを太線で示している。いずれの図も縦軸は磁化Ｍを示し、横軸は磁界Ｈを示している。制御層１２と記録再生層１３との交換結合領域は印加される磁界の大きさに応じて、図３（ｂ）に示すように、状態Ａ），状態Ｂ），状態Ｃ）及び状態Ｄ）の磁化状態を示す。図中、白抜き矢印及び二重矢印は、夫々、記録再生層１３及び制御層１２の相対的な磁化方向を示している。状態Ａ）及び状態Ｃ）では同じ方向を向いている。状態Ｂ）及び状態Ｄ）では相異なる方向を向き、記録再生層１３及び制御層１２の表面に界面磁壁を形成している。
【００２０】
状態Ａ）から状態Ｂ）に遷移するための磁界Ｈab，状態Ｂ）から状態Ｃ）に遷移するための磁界Ｈbc，状態Ｃ）から状態Ｄ）に遷移するための磁界Ｈcd，及び状態Ｄ）から状態Ａ）に遷移するための磁界Ｈdaは、夫々、
Ｈab＝−Ｈｃ１−σ／２Ｍｓ１ｔ１
Ｈbc＝−Ｈｃ２＋σ／２Ｍｓ２ｔ２
Ｈcd＝Ｈｃ１＋σ／２Ｍｓ１ｔ１
Ｈda＝Ｈｃ２−σ／２Ｍｓ２ｔ２
である。ここで、σは界面磁壁のエネルギーである。
【００２１】
上述した磁気ディスク１に、まず、第１のコイル２１により第１の初期化磁界Ｈｄｃ１が印加される。ここで｜Ｈｄｃ１｜＞｜Ｈｄａ｜である。このとき、磁界が印加された領域は状態Ａ）、即ち、記録再生層１３及び制御層１２の磁化が同方向に向いている状態である。所定時間経過後、第２のコイル２２により、この領域に第２の初期化磁界Ｈdc２が印加される。ここで｜Ｈｂｃ｜＞｜Ｈｄｃ２｜＞｜Ｈａｂ｜である。このとき、磁界が印加された領域は状態Ｂ）、即ち、記録再生層１３及び制御層１２の磁化が逆方向に向いている状態である。
【００２２】
さらに所定時間経過後、第３のコイル２３により交番磁界Ｈｗが印加される。状態Ｂ）から情報が記録された状態に遷移するためには、交番磁界Ｈｗは、｜Ｈｂａ｜＜｜Ｈｗ｜＜｜Ｈａｂ｜である。交番磁界Ｈｗは、記録すべき情報に応じた極性が印加される。交番磁界Ｈｗの絶対値の最小値である｜Ｈｂａ｜は、｜Ｈｂａ｜＝｜Ｈｃ１−σ／２Ｍｓ１ｔ１｜である。従って、本実施の形態の磁気ディスク１では、記録再生層１３単体で記録可能な交番磁界Ｈｃ１よりも（σ／２Ｍｓ１ｔ１）だけ小さな磁界を用いて、情報を記録することが可能である。
【００２３】
以上の如き磁気記録方法により、大きな保磁力の記録再生層１３を備える磁気ディスク１に、記録再生層１３単体に対して必要な磁界よりも小さな交番磁界の印加で情報を記録することができる。
【００２４】
【実施例】
上述の如き特性を有する膜組成の磁気ディスクに、上述の如き記録方法にて情報を記録し、その記録再生特性を調べた。ガラス基板上に、Ｃｒからなる第１の下地層（２０ｎｍ）と、ＮｉＡｌからなる第２の下地層（２０ｎｍ）をＤＣスパッタ法により形成した。スパッタ条件は、投入電力が１ｋＷ、Ａｒガス圧が１Ｐａである。その上にＤＣスパッタ法により、制御層１２及び記録再生層１３を積層した。制御層１２及び記録再生層１３の組成、膜厚及びスパッタ条件を表１に示す。
【００２５】
【表１】

【００２６】
この磁気ディスクのＨab，Ｈba，Ｈbcを調べたところ、Ｈab＝−３ｋＯｅ，Ｈba＝２ｋＯｅ，Ｈbc＝−４ｋＯｅであった。従って、第１の初期化磁界Ｈdc１，第２の初期化磁界Ｈdc２、及び交番磁界Ｈｗは、夫々、
Ｈdc１＞４ｋＯｅ，
−４ｋＯｅ＜Ｈdc２＜−３ｋＯｅ，
２ｋＯｅ＜Ｈｗ＜３ｋＯｅ
である。
【００２７】
磁気ディスクの記録領域に、まず第１のコイル２１により第１の初期化磁界Ｈdc１＝4.5 ｋＯｅを印加することにより状態Ａ）（図３参照）とし、次に第２のコイル２２により、第２の初期化磁界Ｈdc２＝−3.4 ｋＯｅを印加することにより状態Ｂ）（図３参照）とした。交番磁界｜Ｈｗ｜＝2.2 ｋＯｅを情報に応じて極性を変化させて印加し、０．１ミクロン長の記録マークを形成した。このように情報を記録した磁気ディスクについてＳＮＲを測定したところ、３０ｄＢ以上の値を示した。これは実用化に充分な値である。
【００２８】
次に、比較例として制御層１２を設けていない磁気ディスクを作成し、記録再生層１３のみの磁気記録特性を調べた。その他の膜構成は上述の実施例と同様である。その結果、記録再生層１３に情報を記録するために、2.5 ｋＯｅ以上の磁界が必要であった。また、高ノイズのために、ＳＮＲが５ｄＢと低い値を示した。この結果から判るように、比較例の磁気ディスクでは通常よりも大きな保磁力を有しているので記録のために高い交番磁界が必要となり、且つ、良好な記録特性が得られない。これに対して本実施の形態の磁気ディスクは、大きな保磁力を有する記録再生層に、通常と同じか又は小さい交番磁界を印加することにより情報が記録でき、良好な記録再生特性を有すると言える。
【００２９】
【発明の効果】
以上のように、本発明においては、高密度記録を行なうために大きな保磁力を有する磁性層を用いた場合であっても、該磁性層単体に対して必要な記録用磁界の大きさよりも小さな交番磁界で記録を行なうことができ、記録装置に必要以上の負担を与えない等、本発明は優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明に係る磁気記録媒体及び磁気ヘッドの構成を示す断面図である。
【図２】図１の平面図である。
【図３】本実施の形態の磁気ディスクの制御層及び記録再生層の磁化曲線を示した図である。
【符号の説明】
１磁気ディスク
２磁気ヘッド
１１基板
１２制御層（第２の磁性層）
１３記録再生層（第１の磁性層）
２１第１のコイル
２２第２のコイル
２３第３のコイル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording method for recording magnetically information, a magnetic head for applying a magnetic field to 及 beauty magnetic recording medium to record information.
[0002]
[Prior art]
Magnetic disks are widely used as information recording devices in computers. In particular, in a PC (personal computer) environment that handles moving images, there is a demand for a magnetic disk capable of recording a larger capacity, that is, a high-density recording. In order to increase the recording density, the recording mark length formed on the magnetic disk is shortened and the track width is narrowed.
[0003]
For example, information is recorded on a conventional magnetic disk in which a base layer made of Cr and a recording layer made of CoCrTaPt are stacked on a substrate. The coercivity of the recording layer is about 2 kOe. Information can be recorded on the recording layer of this magnetic disk by applying an alternating magnetic field using a normal magnetic head. When a minute recording mark is formed on this recording layer, noise rises due to the particle size of the recording layer. In order to solve this problem, the crystal grain of the recording layer may be made small. However, if the crystal grain is miniaturized, there is a problem that the recorded magnetization direction is likely to be disturbed and the thermal stability of the recording layer is lowered. .
[0004]
[Problems to be solved by the invention]
In order to improve the thermal stability of the recording layer, the coercive force of the recording layer may be increased to, for example, 3 kOe. However, when the coercive force of the magnetic layer is increased, there is a problem that it is necessary to increase the alternating magnetic field applied during recording. When a short recording mark length is formed, there is a problem that application of a large alternating magnetic field places a heavy burden on the recording apparatus because the recording frequency is high.
[0005]
The present invention has been made in view of such circumstances, the magnetic recording medium having a magnetic layer having a large coercive force, realized magnetic recording method capable of recording information by applying a small alternating magnetic field, and the method an object of the present invention is to provide a magnetic head. Hereinafter, the alternating magnetic field in the present application refers to “a magnetic field constituted by the presence or absence of a magnetic field in one direction that causes the recording / reproducing layer to have a magnetization direction corresponding to information to be recorded”.
[0006]
[Means for Solving the Problems]
Magnetic recording method according to the present invention, at least the second magnetic layer and first magnetic layer are laminated in this order, the coercive before Symbol the coercive force Hc1 of the first magnetic layer and the second magnetic layer to the substrate A magnetic recording method for recording information on a magnetic recording medium having a relationship of Hc1 <Hc2 with a magnetic force Hc2 , wherein the magnitudes of magnetizations of the first and second magnetic layers are Ms1, Ms2, each of the film thickness and t1, t2, the Hda the interface wall energy of the first and second magnetic layers upon a σ = Hc2-σ / 2Ms2t2, Hab = -Hc1-σ / 2Ms1t1, Hbc = - Hc For each value defined by 2 + σ / 2Ms2t2, a first initialization magnetic field Hdc1 that satisfies the relationship | Hdc1 |> | Hda | is applied to an area in which information is to be recorded, and the first and second Align the magnetization direction of the magnetic layer in the same direction After the first initialization process and after the first initialization process, a second initialization magnetic field Hdc2 that satisfies the relationship | Hbc |> | Hdc2 |> | Hab | is applied to the region, and the first and second A second initialization process in which the magnetization directions of the magnetic layers are different from each other, and a recording process in which, after the second initialization process, an alternating magnetic field Hw having a polarity changed according to information to be recorded is applied to the area It is characterized by having.
However, | Hc1-σ / 2Ms1t1 | <| Hw | <| Hab |
[0007]
The present invention includes a first magnetic layer for recording and holding information, and a second magnetic layer that can be exchange-coupled to the magnetic layer, and based on the magnetic characteristics in these exchange-coupling regions. By applying the magnetic field having the determined magnitude, the magnetization directions of the first and second magnetic layers are oriented in a predetermined direction immediately before the alternating magnetic field for recording is applied. By applying an alternating magnetic field to the magnetic layer in this state, the magnetization direction of the first magnetic layer can be changed by applying a magnetic field smaller than that of the first magnetic layer alone. After applying the first initialization magnetic field determined based on the magnetic characteristics of the exchange coupling regions of the first and second magnetic layers to align the first and second magnetic layers in the same direction, An initialization magnetic field is applied to reverse the magnetization direction of the first magnetic layer, for example. By applying an alternating magnetic field to the magnetic layer in this state, the magnetization direction of the first magnetic layer can be changed by applying a magnetic field smaller than the required magnitude to the first magnetic layer alone.
[0008]
In the magnetic head according to the present invention, at least the second magnetic layer and the first magnetic layer are stacked in this order on the substrate, and the coercive force Hc1 of the first magnetic layer and the coercive force Hc2 of the second magnetic layer are stacked. Between the magnetic recording medium and the magnetic recording medium having a relationship of Hc1 <Hc2, and applying a magnetic field while moving relative to the magnetic recording medium, a first initialization magnetic field is applied to the magnetic recording medium. A first magnetic generation unit to be applied, a second magnetic generation unit to apply a second initialization magnetic field, and a third magnetic generation unit to apply an alternating magnetic field are arranged in parallel. The direction of installation is arranged substantially parallel to the direction of relative movement, and the first initialization magnetic field applied by the first magnetism generating unit is applied to each of the first and second magnetic layers. The magnitudes of magnetization are Ms1, Ms2, and the respective film thicknesses are t1, t2. For each value defined the interface wall energy of the second magnetic layers upon a sigma by Hda = Hc2-σ / 2Ms2t2, Hab = -Hc1-σ / 2Ms1t1, Hbc = -Hc2 + σ / 2Ms2t2, record information a magnetic field hdc1 that meet the relationships, the second initializing magnetic field second magnetism generating portion is applied, in the region | | hdc1 | |> | Hda to should do region Hbc |> | The magnetic field Hdc2 satisfying the relationship Hdc2 |> | Hab |, and the alternating magnetic field Hw applied by the third magnetism generation unit satisfies | Hc1-σ / 2Ms1t1 | <| Hw | <| Hab |. Features.
[0015]
In the present invention, for example, the first magnetic generation unit that applies the first initialization magnetic field as described above, the second magnetic generation unit that applies the second initialization magnetic field, and the alternating magnetic field are applied. Since the third magnetism generators are arranged in parallel in the relative movement direction, the first initialization magnetic field, the second initialization magnetic field, and the alternating magnetic field are sequentially applied to the same region of the magnetic recording medium that is moving relative to each other. can do.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a cross-sectional view showing the configuration of a magnetic recording medium and a magnetic head according to the present invention, showing an embodiment of the magnetic recording method of the present invention. FIG. 2 is a plan view of FIG. In the figure, 1 is a magnetic disk according to the present invention, and 2 is a magnetic head according to the present invention. The magnetic disk 1 is configured by laminating a control layer 12 as the second magnetic layer and a recording / reproducing layer 13 as the first magnetic layer in this order on a synthetic resin substrate 11 by a DC sputtering method. . The coercivity, film thickness, and saturation magnetization of the control layer 12 are Hc1, t1, and Ms1, respectively, and the coercivity, film thickness, and saturation magnetization of the recording / reproducing layer 13 are Hc2, t2, and Ms2, respectively. Note that Hc1 <Hc2.
[0017]
A magnetic head 2 is disposed on the magnetic disk 1 so as to face the recording / reproducing layer 13. The magnetic head 2 is connected to the swing arm 3, and the magnetic head 2 can move in the radial direction of the magnetic disk 1 by the movement of the swing arm 3. The magnetic head 2 has first, second and

third coils

21, 22, and 23 spaced apart from each other by a predetermined length, and magnetic fields of different magnitudes are opposed to the magnetic disk 1 by the respective coils. Apply to region. The magnetic head 2 is disposed so that the direction in which the first, second, and

third coils

21, 22, and 23 are arranged in parallel is the tangential direction of the track of the magnetic disk 1. Here, the first, second, and

third coils

21, 22, and 23 apply the first initialization magnetic field Hdc1, the second initialization magnetic field Hdc2, and the alternating magnetic field Hw, respectively.
[0018]
When recording information on the magnetic disk 1 having such a film structure, the magnetic head 2 is moved to a predetermined position in the radial direction of the recording / reproducing layer 13 and the magnetic disk 1 is rotated. The magnetic disk 1 is moved relative to the magnetic head 2 by the rotation of the magnetic disk 1. Therefore, a magnetic field is sequentially applied to the area to be recorded in the recording / reproducing layer 13 by the first, second and

third coils

21, 22 and 23. The magnetization states of the control layer 12 and the recording / reproducing layer 13 when these magnetic fields are applied will be described below based on the magnetization curves of these layers.
[0019]
FIG. 3 is a diagram showing magnetization curves of the control layer 12 and the recording / reproducing layer 13 of the magnetic disk 1. FIG. 3A shows a hysteresis loop of the recording / reproducing layer 13 alone. FIG. 3B shows a hysteresis loop in the exchange coupling region between the control layer 12 and the recording / reproducing layer 13, and the minor loop of the recording / reproducing layer 13 is indicated by a bold line. In each figure, the vertical axis indicates the magnetization M, and the horizontal axis indicates the magnetic field H. The exchange coupling region between the control layer 12 and the recording / reproducing layer 13 is in a state A), a state B), a state C) and a state D) as shown in FIG. 3B, depending on the magnitude of the applied magnetic field. The magnetization state of is shown. In the figure, white arrows and double arrows indicate the relative magnetization directions of the recording / reproducing layer 13 and the control layer 12, respectively. In the state A) and the state C), they face the same direction. In the states B) and D), different directions are directed, and interface domain walls are formed on the surfaces of the recording / reproducing layer 13 and the control layer 12.
[0020]
From magnetic field Hab for transition from state A) to state B), magnetic field Hbc for transition from state B) to state C), magnetic field Hcd for transition from state C) to state D), and from state D) Magnetic fields Hda for transitioning to state A) are respectively
Hab = −Hc1−σ / 2Ms1t1
Hbc = −Hc2 + σ / 2Ms2t2
Hcd = Hc1 + σ / 2Ms1t1
Hda = Hc2-σ / 2Ms2t2
It is. Here, σ is the energy of the interface domain wall.
[0021]
First, the first initialization magnetic field Hdc1 is applied to the magnetic disk 1 described above by the first coil 21. Here, | Hdc1 |> | Hda |. At this time, the region to which the magnetic field is applied is in the state A), that is, the magnetization of the recording / reproducing layer 13 and the control layer 12 is directed in the same direction. After a predetermined time has elapsed, the second coil 22 applies a second initialization magnetic field Hdc2 to this region. Here, | Hbc | > | Hdc2 | > | Hab |. At this time, the region to which the magnetic field is applied is in the state B), that is, the state in which the magnetizations of the recording / reproducing layer 13 and the control layer 12 are directed in opposite directions.
[0022]
Further, after a predetermined time has elapsed, an alternating magnetic field Hw is applied by the third coil 23. In order to transition from state B) to a state in which information is recorded, the alternating magnetic field Hw is | Hba | <| Hw | <| Hab |. The alternating magnetic field Hw is applied with a polarity according to the information to be recorded. | Hba | that is the minimum absolute value of the alternating magnetic field Hw is | Hba | = | Hc1-σ / 2Ms1t1 | . Therefore, on the magnetic disk 1 of the present embodiment, information can be recorded using a magnetic field that is smaller by (σ / 2Ms1t1) than the alternating magnetic field Hc1 that can be recorded by the recording / reproducing layer 13 alone.
[0023]
By the magnetic recording method as described above, information can be recorded on the magnetic disk 1 having the recording / reproducing layer 13 having a large coercive force by applying an alternating magnetic field smaller than a necessary magnetic field to the recording / reproducing layer 13 alone.
[0024]
【Example】
Information was recorded on the magnetic disk having a film composition having the above-described characteristics by the recording method as described above, and the recording / reproducing characteristics were examined. A first underlayer (20 nm) made of Cr and a second underlayer (20 nm) made of NiAl were formed on a glass substrate by a DC sputtering method. The sputtering conditions are an input power of 1 kW and an Ar gas pressure of 1 Pa. A control layer 12 and a recording / reproducing layer 13 were laminated thereon by DC sputtering. Table 1 shows the composition, film thickness, and sputtering conditions of the control layer 12 and the recording / reproducing layer 13.
[0025]
[Table 1]

[0026]
When this magnetic disk was examined for Hab, Hba, and Hbc, it was found that Hab = -3 kOe, Hba = 2 kOe, and Hbc = -4 kOe. Therefore, the first initialization magnetic field Hdc1, the second initialization magnetic field Hdc2, and the alternating magnetic field Hw are respectively
Hdc1> 4 kOe,
−4 kOe <Hdc2 <−3 kOe,
2kOe <Hw <3kOe
It is.
[0027]
First, the first initializing magnetic field Hdc1 = 4.5 kOe is applied to the recording area of the magnetic disk by the first coil 21 to obtain the state A) (see FIG. 3). The state B) (see FIG. 3) was established by applying the initializing magnetic field Hdc2 = −3.4 kOe. An alternating magnetic field | Hw | = 2.2 kOe was applied with the polarity changed in accordance with the information to form a recording mark having a length of 0.1 μm. When the SNR was measured for the magnetic disk on which information was recorded in this way, it showed a value of 30 dB or more. This is a value sufficient for practical use.
[0028]
Next, a magnetic disk without the control layer 12 was prepared as a comparative example, and the magnetic recording characteristics of only the recording / reproducing layer 13 were examined. Other film configurations are the same as in the above-described embodiment. As a result, in order to record information on the recording / reproducing layer 13, a magnetic field of 2.5 kOe or more was necessary. Further, because of high noise, the SNR showed a low value of 5 dB. As can be seen from this result, since the magnetic disk of the comparative example has a coercive force larger than usual, a high alternating magnetic field is required for recording, and good recording characteristics cannot be obtained. In contrast, the magnetic disk of this embodiment can record information by applying an alternating magnetic field that is the same as or smaller than that of a recording / reproducing layer having a large coercive force, and can be said to have good recording / reproducing characteristics. .
[0029]
【The invention's effect】
As described above, in the present invention, even when a magnetic layer having a large coercive force is used to perform high-density recording, the magnitude of the recording magnetic field required for the magnetic layer alone is smaller. The present invention has an excellent effect that recording can be performed with an alternating magnetic field, and the recording apparatus is not burdened more than necessary.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a magnetic recording medium and a magnetic head according to the present invention.
2 is a plan view of FIG. 1. FIG.
FIG. 3 is a diagram showing magnetization curves of a control layer and a recording / reproducing layer of the magnetic disk according to the present embodiment.
[Explanation of symbols]
1 Magnetic disk 2 Magnetic head 11 Substrate 12 Control layer (second magnetic layer)
13 Recording / reproducing layer (first magnetic layer)
21 First coil 22 Second coil 23 Third coil

Claims

At least between the second magnetic layer and first magnetic layer are laminated in this order, before Symbol first coercive force of the coercive force Hc1 of the magnetic layer and the second magnetic layer Hc2 on the substrate, Hc1 < A magnetic recording method for recording information on a magnetic recording medium having a relationship of Hc2 ,
When the magnitudes of the magnetizations of the first and second magnetic layers are Ms1 and Ms2, the film thicknesses are t1 and t2, respectively, and the interface domain wall energy between the first and second magnetic layers is σ. hda = Hc2-σ / 2Ms2t2, Hab = -Hc1-σ / 2Ms1t1, Hbc = - for each value defined by Hc 2 + σ / 2Ms2t2, a region in which information is to be recorded | hdc1 |> | hda | of Applying a first initialization magnetic field Hdc1 that satisfies the relationship, the magnetization directions of the first and second magnetic layers are aligned in the same direction, and after the first initialization process, | Applying a second initialization magnetic field Hdc2 satisfying a relationship of Hbc |> | Hdc2 |> | Hab |, and making the magnetization directions of the first and second magnetic layers different from each other; Should be recorded after the second initialization process Magnetic recording method characterized by comprising a recording step of applying an alternating magnetic field Hw of changing the polarity in response to broadcast to the region.
However, | Hc1-σ / 2Ms1t1 | <| Hw | <| Hab |

At least a second magnetic layer and a first magnetic layer are stacked in this order on the substrate, and Hc1 <Hc2 between the coercive force Hc1 of the first magnetic layer and the coercive force Hc2 of the second magnetic layer. In a magnetic head that is arranged to face one surface of a magnetic recording medium having the relationship of and applies a magnetic field while moving relative to the magnetic recording medium,
A first magnetic generation unit that applies a first initialization magnetic field, a second magnetic generation unit that applies a second initialization magnetic field, and a third magnetic generation unit that applies an alternating magnetic field are juxtaposed. The parallel direction of the magnetic generators should be arranged substantially parallel to the direction of relative movement, and the first initialization magnetic field applied by the first magnetic generator is the first and second magnetic fields . When the magnitudes of the magnetizations of the two magnetic layers are Ms1, Ms2, the respective film thicknesses are t1, t2, and the interface domain wall energy between the first and second magnetic layers is σ, Hda = Hc2-σ / 2Ms2t2, Hab = -Hc1-σ / 2Ms1t1, Hbc = -Hc2 + σ / 2Ms2t2 for each value defined by the region in which information is to be recorded | hdc1 |> | Hda | magnetic field satisfying the relationship hdc1 Because
The second initialization magnetic field applied by the second magnetism generator is:
A magnetic field Hdc2 that satisfies the relationship | Hbc |> | Hdc2 |> | Hab |
The alternating magnetic field Hw applied by the third magnetism generator is
| Hc1-σ / 2Ms1t1 | <| Hw | <| Hab |
A magnetic head characterized by satisfying