JP2991689B2 - Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same - Google Patents
Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the sameInfo
- Publication number
- JP2991689B2 JP2991689B2 JP10027102A JP2710298A JP2991689B2 JP 2991689 B2 JP2991689 B2 JP 2991689B2 JP 10027102 A JP10027102 A JP 10027102A JP 2710298 A JP2710298 A JP 2710298A JP 2991689 B2 JP2991689 B2 JP 2991689B2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic recording
- magnetic
- medium
- recording medium
- thin film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、コンピュータの補
助記憶装置などに用いる磁気記録再生装置及びそれに用
いる磁気記録媒体に係る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus used for an auxiliary storage device of a computer and a magnetic recording medium used therefor.
【０００２】[0002]
【従来の技術】情報化時代の進行により、日常的に扱う
情報量は増加の一途を辿っている。これに伴い、磁気記
録再生装置に対する高記録密度化と大容量化の要求が強
くなっている。磁気記録媒体の記録密度を高密度化して
いった場合、記録ビット当たりの媒体面積が小さくなる
ため、再生出力が低下し、再生が困難になる。この問題
を解決するため、記録と再生を別のヘッドで行い、再生
用ヘッドとして高い感度を持つ磁気抵抗効果を利用した
ヘッドを用いる方式が実用化されている。さらに、高密
度化を進めるために、より高い感度を持つ巨大磁気抵抗
効果を利用したヘッドも検討されている。このような高
感度の再生ヘッドを用いることにより、再生出力は大き
くできるが、同時にノイズも増幅してしまい、ノイズの
大きな媒体を用いた場合には記録された情報の読みとり
が不可能になる。したがって、高密度の記録と再生を行
うための磁気記録媒体としては、媒体ノイズを低く抑え
ることが必須である。2. Description of the Related Art With the advance of the information age, the amount of information handled on a daily basis has been steadily increasing. Along with this, the demand for higher recording density and higher capacity for magnetic recording / reproducing devices has become stronger. When the recording density of the magnetic recording medium is increased, the medium area per recording bit is reduced, so that the reproduction output is reduced and the reproduction becomes difficult. In order to solve this problem, a system has been put to practical use in which recording and reproduction are performed by different heads, and a head using a magnetoresistive effect having high sensitivity is used as a reproducing head. Further, in order to increase the density, a head using a giant magnetoresistance effect having higher sensitivity is also being studied. By using such a high-sensitivity reproducing head, the reproducing output can be increased, but the noise is also amplified at the same time, and it becomes impossible to read the recorded information when a medium with a large noise is used. Therefore, as a magnetic recording medium for performing high-density recording and reproduction, it is essential to suppress medium noise.
【０００３】現在の磁気ディスクに用いられている面内
磁気記録方式では、媒体ノイズの低減のために、結晶粒
の微細化が不可欠であり、今後保磁力の確保や記録磁化
状態の熱的安定性が問題になることが予想される。これ
に対して、垂直磁気記録方式は記録密度が高くなるにつ
れて反磁界が減少するという特徴があり、高密度に記録
した場合に、記録磁化状態が安定で媒体ノイズも小さ
く、高密度記録に適した方式であると考えられる。ただ
し、垂直磁気記録方式においても、高密度に記録された
情報を再生する場合には出力が小さいために、媒体ノイ
ズの低減は必須である。垂直磁気記録媒体のノイズは、
記録ビット内の逆磁区の大きさと記録ビット境界の乱れ
の大きさに依存すると考えられる。これらを小さくして
ノイズを低減するためには、磁性膜の結晶粒径を小さく
するなどして、磁化反転単位を小さくする必要がある。In the in-plane magnetic recording method used for the current magnetic disk, it is essential to make crystal grains fine in order to reduce medium noise. In the future, it will be necessary to secure coercive force and thermally stabilize the recording magnetization state. Sex is expected to be a problem. On the other hand, the perpendicular magnetic recording method has the characteristic that the demagnetizing field decreases as the recording density increases, and when recording at high density, the recording magnetization state is stable and the medium noise is small, making it suitable for high density recording. It is thought that it is a method. However, even in the perpendicular magnetic recording system, when information recorded at high density is reproduced, the output is small, so that reduction of medium noise is indispensable. The noise of a perpendicular magnetic recording medium is
It is considered that it depends on the magnitude of the reverse magnetic domain in the recording bit and the magnitude of the disturbance of the recording bit boundary. In order to reduce noise by reducing these, it is necessary to reduce the unit of magnetization reversal by reducing the crystal grain size of the magnetic film.
【０００４】従来、垂直磁気記録媒体は連続薄膜型磁気
テープを中心に研究や開発が進められており、この場合
には磁性層の膜厚が１００ｎｍ以上と厚く、またトラッ
ク幅の広いヘッドで記録再生を行うため、再生出力が大
きく、媒体ノイズのレベルをそれほど抑える必要がなか
った。これに対して磁気ディスクとして垂直磁気記録媒
体を用いる場合には、トラック幅方向にも高密度化する
必要があることから、記録ビット面積は小さくなり、再
生出力は非常に小さくなる。この小さな出力を高感度ヘ
ッドにより再生することから、必然的に媒体ノイズに対
する制限は厳しくなり、また出力の減衰も極力抑える必
要がある。垂直磁気ディスク媒体のノイズに関する検討
結果は、例えば、Journal of Magnetism and Magnetic
Materials １３４巻３０４〜３０９頁（１９９４年発
行）に記載されているが、ＣｏＣｒＴａ垂直二層媒体に
ついて、９０ｋＦＣＩにおける媒体Ｓ／Ｎが２３．８ｄ
Ｂと示されており、１平方インチ当たり４ギガビット以
上の高い面記録密度の記録再生は困難であると考えら
れ、さらなる媒体ノイズの低減が必要である。Conventionally, research and development have been conducted on perpendicular magnetic recording media mainly on continuous thin-film magnetic tapes. In this case, recording is performed by a head having a magnetic layer having a thickness as large as 100 nm or more and having a wide track width. Since reproduction is performed, the reproduction output is large, and it is not necessary to suppress the level of medium noise so much. On the other hand, when a perpendicular magnetic recording medium is used as the magnetic disk, it is necessary to increase the density in the track width direction, so that the recording bit area is reduced and the reproduction output is extremely reduced. Since this small output is reproduced by a high-sensitivity head, it is inevitable that the limit to the medium noise becomes severe, and it is necessary to suppress the output attenuation as much as possible. The study results on noise of perpendicular magnetic disk media are described in, for example, Journal of Magnetism and Magnetic
Materials 134, 304-309 (published in 1994). As for the CoCrTa perpendicular double layer medium, the medium S / N at 90 kFCI is 23.8 d.
B, it is considered difficult to perform recording and reproduction at a high areal recording density of 4 gigabits per square inch or more, and it is necessary to further reduce the medium noise.
【０００５】[0005]
【発明が解決しようとする課題】我々の検討によると、
Ｃｏ−Ｃｒ−Ｐｔ磁性膜を非磁性のＣｏ−３５ａｔ％Ｃ
ｒ下地層上にエピタキシャル成長させ、かつ膜厚を薄く
することによって磁性膜の結晶粒を微細化すれば、ノイ
ズを低減できることがわかっている。ただし、膜厚が約
２５ｎｍ以下では膜厚を小さくしてもノイズの低減が見
られず、結晶粒微細化によるノイズの低減には限界があ
る。さらに、膜厚が１５ｎｍ以下になると熱揺らぎによ
る記録磁化の不安定性が問題となってくる。このよう
に、高感度の再生ヘッドに対応する垂直磁気記録媒体と
して、特に高密度記録に適するように媒体Ｓ／Ｎを十分
大きくするためには、記録層の膜厚を小さくして結晶粒
径を微細化することが有効であるが、単純に膜厚を低減
するだけでは媒体Ｓ／Ｎの向上に限界がある。According to our studies,
Co-Cr-Pt magnetic film is made of non-magnetic Co-35 at% C
It has been found that noise can be reduced by making the crystal grains of the magnetic film finer by epitaxially growing it on the r underlayer and reducing the film thickness. However, when the film thickness is about 25 nm or less, no reduction in noise is observed even when the film thickness is reduced, and there is a limit to the reduction in noise due to the refinement of crystal grains. Further, when the film thickness is 15 nm or less, instability of recording magnetization due to thermal fluctuation becomes a problem. As described above, in order to sufficiently increase the medium S / N so as to be particularly suitable for high-density recording as a perpendicular magnetic recording medium corresponding to a high-sensitivity reproducing head, the thickness of the recording layer is reduced and the crystal grain size is reduced. It is effective to reduce the size of the medium, but there is a limit in improving the medium S / N by simply reducing the film thickness.
【０００６】本発明は、このような垂直磁気記録媒体の
現状を打開するためになされたものであり、１平方イン
チ当たり４ギガビット以上の高密度記録に適するよう
な、十分に高い媒体Ｓ／Ｎを持ち、かつ記録情報の長期
間保持が可能な垂直磁気記録媒体及びそれを応用した磁
気記録再生装置を提供することを目的とする。The present invention has been made to overcome the current situation of such a perpendicular magnetic recording medium, and has a sufficiently high medium S / N ratio suitable for high-density recording of 4 gigabits per square inch or more. It is an object of the present invention to provide a perpendicular magnetic recording medium having the above characteristics and capable of holding recorded information for a long period of time, and a magnetic recording / reproducing apparatus using the same.
【０００７】[0007]
【課題を解決するための手段】上記目的は、媒体表面に
垂直な方向に磁界を印加して直流消磁したときに媒体表
面に現れる反転磁区の平均直径が媒体表面で測定した結
晶粒の平均直径の２倍以下である媒体を作製することで
達成される。このような特徴を持つ垂直磁気記録媒体を
作製するためには、磁気記録層として膜厚が１００ｎｍ
以下でかつＣｏとＣｒを主たる成分とする強磁性薄膜を
用い、前記磁気記録層に隣接する下地層としてＣｒを３
０ａｔ％以上含有する多結晶薄膜を用いるのがよい。さ
らに好ましくは、下地層と磁気記録層を形成した後に４
００℃〜６００℃の温度、より好ましくは４５０℃〜５
５０℃の温度で熱処理することにより、媒体表面に垂直
な方向に磁界を印加して測定した磁気記録層の保磁力を
３０００エルステッド以上にするのがよい。An object of the present invention is to provide a magnetic recording medium in which a magnetic field is applied in a direction perpendicular to the surface of a medium and the average diameter of reversal magnetic domains appearing on the surface of the medium when a direct current is demagnetized is determined by the average diameter of crystal grains measured on the surface of the medium. This is achieved by producing a medium that is no more than twice as large as In order to produce a perpendicular magnetic recording medium having such characteristics, a film thickness of 100 nm is required for the magnetic recording layer.
A ferromagnetic thin film containing Co and Cr as main components is used as a base layer adjacent to the magnetic recording layer.
It is preferable to use a polycrystalline thin film containing 0 at% or more. More preferably, after forming the underlayer and the magnetic recording layer,
Temperature of 00 ° C to 600 ° C, more preferably 450 ° C to 5 ° C
The coercive force of the magnetic recording layer measured by applying a magnetic field in a direction perpendicular to the medium surface by heat treatment at a temperature of 50 ° C. is preferably 3000 Oe or more.
【０００８】すなわち、本発明による垂直磁気記録媒体
は、媒体表面に垂直な方向に磁界を印加して直流消磁し
たときに媒体表面に現れる反転磁区の面積を円に換算し
たときの平均直径が媒体表面で測定した結晶粒の平均直
径の２倍以下であることを特徴とする。媒体表面に現れ
る反転磁区の形状は、典型的には略円状である。磁気記
録層としては、Ｃｒを３０ａｔ％以上含有する多結晶薄
膜下地層上に形成し、４００〜６００℃で真空中熱処理
した、ＣｏとＣｒを主たる成分とする膜厚１００ｎｍ以
下の強磁性薄膜を用いることができる。前記強磁性薄膜
は、媒体表面に垂直な方向に磁界を印加して測定したと
きの保磁力が３０００エルステッド以上であることが好
ましい。That is, in the perpendicular magnetic recording medium according to the present invention, when the magnetic field is applied in a direction perpendicular to the medium surface and DC degaussing is performed, the average diameter of the inverted magnetic domain appearing on the medium surface when converted into a circle has an average diameter. The average diameter of the crystal grains measured on the surface is twice or less. The shape of the reversed magnetic domain appearing on the medium surface is typically substantially circular. As the magnetic recording layer, a ferromagnetic thin film having Co and Cr as main components and having a thickness of 100 nm or less, which is formed on a polycrystalline thin film underlayer containing Cr at 30 at% or more and heat-treated in a vacuum at 400 to 600 ° C. Can be used. The ferromagnetic thin film preferably has a coercive force of 3000 Oe or more when measured by applying a magnetic field in a direction perpendicular to the medium surface.
【０００９】本発明による磁気記録再生装置は、磁気記
録媒体と、磁気記録媒体を駆動する媒体駆動部と、磁気
ヘッドと、磁気ヘッドを駆動する磁気ヘッド駆動部と、
記録再生信号処理系とを含む磁気記録再生装置におい
て、磁気記録媒体として前記した本発明による垂直磁気
記録媒体を用い、磁気ヘッドは再生部として磁気抵抗効
果型磁気ヘッド又は巨大磁気抵抗効果型ヘッドを備える
ことを特徴とする。A magnetic recording / reproducing apparatus according to the present invention includes a magnetic recording medium, a medium driving unit for driving the magnetic recording medium, a magnetic head, a magnetic head driving unit for driving the magnetic head,
In a magnetic recording / reproducing apparatus including a recording / reproducing signal processing system, the above-described perpendicular magnetic recording medium according to the present invention is used as a magnetic recording medium, and the magnetic head is a magnetoresistive head or a giant magnetoresistive head as a reproducing unit. It is characterized by having.
【００１０】また、本発明による垂直磁気記録媒体の製
造方法は、媒体表面に垂直な方向に磁界を印加して直流
消磁したときに媒体表面に現れる反転磁区の面積を円に
換算したときの平均直径が媒体表面で測定した結晶粒の
平均直径の２倍以下である垂直磁気記録媒体の製造方法
であって、Ｃｒを３０ａｔ％以上含有する多結晶薄膜を
スパッタ法により形成するステップと、２００℃以下の
基板温度において前記多結晶薄膜上にＣｏとＣｒを主た
る成分とする膜厚１００ｎｍ以下の強磁性薄膜をスパッ
タ法により形成するステップと、基板を真空中で４００
〜６００℃において熱処理するステップとを含むことを
特徴とする。In the method for manufacturing a perpendicular magnetic recording medium according to the present invention, the area of a reversed magnetic domain appearing on the medium surface when a magnetic field is applied in a direction perpendicular to the medium surface and subjected to DC demagnetization is converted into an average when converted into a circle. A method for manufacturing a perpendicular magnetic recording medium having a diameter of not more than twice the average diameter of crystal grains measured on the medium surface, wherein a polycrystalline thin film containing 30 at% or more of Cr is formed by a sputtering method; Forming a ferromagnetic thin film having a thickness of 100 nm or less containing Co and Cr as main components by sputtering on the polycrystalline thin film at the following substrate temperature;
And heat treating at a temperature of up to 600 ° C.
【００１１】なお、本明細書でいう結晶粒あるいは反転
磁区の平均直径とは、個々の結晶粒あるいは反転磁区の
占有面積から、それらが円であると考えたときの直径を
求め、その直径の分布を占有面積の積算で表したときの
積算占有面積が総占有面積の２分の１になる直径をい
う。The average diameter of a crystal grain or a reversal magnetic domain referred to in the present specification is obtained from the area occupied by each crystal grain or the reversal magnetic domain. When the distribution is represented by the sum of the occupied areas, the diameter is such that the integrated occupied area becomes half of the total occupied area.
【００１２】[0012]
【発明の実施の形態】以下、図面を参照して本発明の実
施の形態を説明する。図１は、本発明による垂直磁気記
録媒体の基本的な構成を示す略断面図である。この垂直
磁気記録媒体は、基板１１上に第１下地層１２及び第２
下地層１３を形成し、その上に磁気記録層１４、保護潤
滑層１５を積層した構造を有する。基板１１は、強化ガ
ラス、シリコン、カーボン、セラミックス、チタン合
金、有機樹脂、Ｎｉ−Ｐ合金メッキアルミ合金基板など
の非磁性基板である。第１下地層１２は磁気記録膜をｃ
軸垂直配向させるためのチタンあるいはチタン合金など
の薄膜であり、第２下地層１３はクロムを３０ａｔ％以
上含有する合金で構成される常磁性あるいは常磁性に近
い磁気特性の多結晶薄膜である。磁気記録層１４は、コ
バルトとクロムを主成分とする強磁性薄膜であり、例え
ばＣｏ−Ｃｒ−Ｔａ、Ｃｏ−Ｃｒ−Ｐｔ、Ｃｏ−Ｃｒ−
Ｐｔ−Ｔａ、Ｃｏ−Ｃｒ−Ｎｂ、Ｃｏ−Ｃｒ−Ｗなどの
強磁性薄膜である。保護潤滑層１５はカーボン、シリコ
ン−カーボン、ボロン−カーボンなどの保護膜と有機系
潤滑膜とからなる層である。Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing a basic configuration of a perpendicular magnetic recording medium according to the present invention. This perpendicular magnetic recording medium includes a first underlayer 12 and a second
It has a structure in which an underlayer 13 is formed, and a magnetic recording layer 14 and a protective lubrication layer 15 are stacked thereon. The substrate 11 is a non-magnetic substrate such as a tempered glass, silicon, carbon, ceramics, titanium alloy, organic resin, Ni-P alloy-plated aluminum alloy substrate, or the like. The first underlayer 12 has a magnetic recording film of c
The second underlayer 13 is a polycrystalline thin film having paramagnetic or near-paramagnetic magnetic properties and made of an alloy containing 30 at% or more of chromium. The magnetic recording layer 14 is a ferromagnetic thin film containing cobalt and chromium as main components, for example, Co-Cr-Ta, Co-Cr-Pt, Co-Cr-.
It is a ferromagnetic thin film of Pt-Ta, Co-Cr-Nb, Co-Cr-W or the like. The protective lubricating layer 15 is a layer composed of a protective film of carbon, silicon-carbon, boron-carbon or the like and an organic lubricating film.
【００１３】（実施例１）非磁性基板１１として基板表
面粗さＲaが３ｎｍ以下の直径２．５インチの強化ガラ
ス製ディスクを用い、下地層１２，１３、磁気記録層１
４及び保護潤滑層１５の膜形成は直流マグネトロンスパ
ッタ法により、以下の条件で行った。スパッタ装置内の
到達真空度は１×１０-8Ｔｏｒｒ以下、放電用アルゴン
ガス圧力は３×１０-3Ｔｏｒｒ、投入電力は直径６イン
チのターゲットに対して１ｋＷとした。下地層として
は、厚さ３０ｎｍのＴｉ又はＴｉ−１０ａｔ％Ｃｒの第
１下地層１２上に厚さ２０ｎｍのＣｏ−３５ａｔ％Ｃｒ
第２下地層１３を積層した２層膜を形成した。２層膜下
地１２，１３は磁気記録層１４の初期成長層の粒径制御
に役立ち、媒体ノイズの低減と再生出力減衰の抑制に効
果がある。磁気記録層１４としては、厚さ２５ｎｍのＣ
ｏ−１９ａｔ％Ｃｒ−１２ａｔ％Ｐｔを形成した。保護
潤滑層１５としては厚さ５ｎｍのカーボン膜と厚さ５ｎ
ｍの有機系潤滑膜を形成した。(Example 1) As a non-magnetic substrate 11, a 2.5-inch diameter tempered glass disk having a substrate surface roughness Ra of 3 nm or less was used.
4 and the protective lubrication layer 15 were formed under the following conditions by a DC magnetron sputtering method. The ultimate degree of vacuum in the sputtering apparatus was 1 × 10 −8 Torr or less, the discharge argon gas pressure was 3 × 10 −3 Torr, and the input power was 1 kW for a target having a diameter of 6 inches. As a base layer, a 20 nm thick Co-35 at% Cr layer is formed on a 30 nm thick first base layer 12 of Ti or Ti-10 at% Cr.
A two-layer film in which the second underlayer 13 was laminated was formed. The two-layer film bases 12 and 13 are useful for controlling the grain size of the initial growth layer of the magnetic recording layer 14, and are effective in reducing medium noise and suppressing reproduction output attenuation. As the magnetic recording layer 14, a 25 nm thick C
An o-19 at% Cr-12 at% Pt was formed. As the protective lubricating layer 15, a carbon film having a thickness of 5 nm and a thickness of 5 n
m of an organic lubricating film was formed.
【００１４】ここでは、条件を変えて代表的な３種類の
垂直磁気記録媒体を作製した。本発明による垂直磁気記
録媒体である試料Ａは、厚さ２５ｎｍの磁気記録層１４
を加熱をしないで約３０℃の基板温度で形成した後、５
００℃で１０分間の真空中熱処理を行ったものである。
比較用の試料Ｂは、厚さ２５ｎｍの磁気記録層１４を３
００℃の基板温度で形成したもので、熱処理は行ってい
ない。また、比較用の試料Ｃは、厚さ１５ｎｍの磁気記
録層１４を３００℃の基板温度で形成したもので、熱処
理は行っていない。Here, three typical types of perpendicular magnetic recording media were manufactured under different conditions. The sample A, which is a perpendicular magnetic recording medium according to the present invention, has a magnetic recording layer 14 having a thickness of 25 nm.
After forming at a substrate temperature of about 30 ° C. without heating,
Heat treatment was performed in a vacuum at 00 ° C. for 10 minutes.
Sample B for comparison has three magnetic recording layers 14 each having a thickness of 25 nm.
It was formed at a substrate temperature of 00 ° C., and was not subjected to heat treatment. The sample C for comparison had a magnetic recording layer 14 of 15 nm thickness formed at a substrate temperature of 300 ° C., and was not subjected to heat treatment.
【００１５】作製した磁気ディスク媒体は、スピンスタ
ンドにおいて記録再生特性の評価を行い、媒体Ｓ／Ｎと
再生出力の経時変化を調べた。評価の条件としては、ギ
ャップ長０．２μｍ、トラック幅１μｍ、巻線数２０タ
ーンの誘導電磁型ヘッドにより記録し、シールド間隔
０．２μｍ、トラック幅０．９μｍの磁気抵抗効果型ヘ
ッドにより再生を行った。ヘッドと媒体の磁気スペーシ
ングは４０ｎｍとした。再生出力Ｓは線記録密度２ｋＦ
ＣＩの孤立波出力を、媒体ノイズＮは３００ｋＦＣＩを
記録した場合の０〜５０ＭＨｚの積算ノイズを測定して
求め、これらの比を媒体Ｓ／Ｎとして評価した。また、
線記録密度５０ｋＦＣＩの信号を記録してから５秒後か
ら１時間後まで再生出力を測定し、時間の対数に対して
プロットして直線で近似したときの５秒後に対する１時
間後の再生出力の比を求め、再生出力の経時変化の指標
とした。The recording / reproducing characteristics of the manufactured magnetic disk medium were evaluated using a spin stand, and the changes over time in the medium S / N and the reproduction output were examined. The evaluation conditions were as follows. Recording was performed by an induction electromagnetic head having a gap length of 0.2 μm, track width of 1 μm, and 20 turns, and reproduction was performed by a magnetoresistive head having a shield interval of 0.2 μm and a track width of 0.9 μm. went. The magnetic spacing between the head and the medium was 40 nm. The reproduction output S has a linear recording density of 2 kF.
The solitary wave output of CI was obtained by measuring integrated noise of 0 to 50 MHz when the medium noise N was recorded at 300 kFCI, and these ratios were evaluated as the medium S / N. Also,
The reproduction output was measured from 5 seconds to 1 hour after recording the signal at a linear recording density of 50 kFCI, plotted against the logarithm of time, and reproduced output 1 hour after 5 seconds when approximated by a straight line. Was determined and used as an index of the change over time in the reproduction output.
【００１６】結晶粒径は、原子間力顕微鏡で媒体表面を
観察して求めた。また、反転磁区像は、電磁石で膜面垂
直方向に１５キロエルステッドの磁界を印加して直流消
磁した後、磁気力顕微鏡で媒体表面を走査して観察し
た。図２は、原子間力顕微鏡で観察した媒体表面の形態
像（ａ）と、磁気力顕微鏡で観察した反転磁区像（ｂ）
を同一視野で示した図である。図３は、直流消磁状態の
磁気記録層での結晶粒と反転磁区の様子を説明する模式
図である。結晶粒及び反転磁区のサイズを求めるために
は、少なくとも１００個以上の結晶粒又は反転磁区が観
察できるようにいくつかの視野で像を撮り、結晶粒３１
の占める面積３４と反転磁区３２の占める面積３５を求
め、各々を等円直径と考えて結晶粒及び反転磁区の直径
を算出した。図中の領域３３は直流消磁の磁場印加方向
に磁化された領域である。The crystal grain size was determined by observing the medium surface with an atomic force microscope. The inverted magnetic domain image was observed by scanning the medium surface with a magnetic force microscope after applying a magnetic field of 15 kOe in the direction perpendicular to the film surface with an electromagnet to perform DC demagnetization. FIG. 2 shows a morphological image (a) of the medium surface observed with an atomic force microscope and an inverted magnetic domain image (b) observed with a magnetic force microscope.
It is the figure which showed in the same visual field. FIG. 3 is a schematic diagram illustrating the state of crystal grains and reversal magnetic domains in the magnetic recording layer in a DC demagnetized state. In order to determine the sizes of the crystal grains and the reversal magnetic domains, images are taken in several fields so that at least 100 crystal grains or reversal domains can be observed, and the crystal grains 31 are obtained.
And the area 35 occupied by the inverted magnetic domains 32 were determined, and the diameters of the crystal grains and the inverted magnetic domains were calculated by assuming each area to be of equal circular diameter. The region 33 in the figure is a region magnetized in the direction of applying a magnetic field for DC demagnetization.
【００１７】図４及び図５に、測定結果の一例を示す。
図４は、試料Ａについて、結晶粒及び反転磁区の直径を
横軸に、その大きさの結晶粒が占める面積を全面積を１
として規格化した値を縦軸にしてプロットした図であ
る。黒丸で示した分布４１は試料Ａについて測定した結
晶粒の直径分布を表し、白丸で示した分布４２は試料Ａ
について測定した反転磁区の直径分布を表す。この図か
らわかるように結晶粒径及び反転磁区径にはかなりの分
布があり、平均値を正確に求めることは難しい。この図
のピークがほぼ平均直径と考えられるが、ここではさら
に正確な評価のために、この占有面積を積算して０．５
となる直径を平均直径とした。図５に、積算した規格化
結晶粒面積を示した。黒丸で示した積算曲線５１は試料
Ａについて測定した結晶粒の直径分布の積算曲線であ
り、白丸で示した積算曲線５２は試料Ａについて測定し
た反転磁化の直径分布の積算曲線である。図５から、試
料Ａにおける結晶粒の平均直径は約１６ｎｍ、反転磁区
の平均直径は約２０ｎｍと求められる。FIGS. 4 and 5 show examples of the measurement results.
FIG. 4 shows that, for the sample A, the area occupied by crystal grains of that size is 1 area, with the horizontal axis representing the diameters of the crystal grains and the reversed magnetic domains.
It is the figure which plotted the value normalized as "" on the vertical axis. The distribution 41 shown by a black circle represents the diameter distribution of the crystal grains measured for the sample A, and the distribution 42 shown by a white circle represents the distribution of the sample A.
2 shows the diameter distribution of the reversal magnetic domain measured with respect to. As can be seen from this figure, there is a considerable distribution in the crystal grain size and the reversal magnetic domain diameter, and it is difficult to accurately determine the average value. Although the peak in this figure is considered to be approximately the average diameter, here, for more accurate evaluation, this occupied area is integrated to 0.5
Was taken as the average diameter. FIG. 5 shows the integrated normalized crystal grain area. The integration curve 51 indicated by a black circle is the integration curve of the diameter distribution of the crystal grains measured for the sample A, and the integration curve 52 indicated by the white circle is the integration curve of the diameter distribution of the reversal magnetization measured for the sample A. From FIG. 5, the average diameter of the crystal grains in Sample A is about 16 nm, and the average diameter of the reversal domain is about 20 nm.
【００１８】図６は、試料Ｂについて測定した結晶粒の
直径分布６１と、反転磁区の直径分布６２を表し、図７
は試料Ｃについて測定した結晶粒の直径分布７１と反転
磁区の直径分布７２を表す。図６及び図７より得られる
直径分布の積算曲線から、試料Ｂに対しては結晶粒の平
均粒径が１６．３ｎｍ、反転磁区の平均直径が４２．３
と求められ、試料Ｃに対しては結晶粒の平均直径が９．
７ｎｍ、反転磁区の平均直径が２０．５ｎｍと求められ
た。FIG. 6 shows the diameter distribution 61 of the crystal grains measured for the sample B and the diameter distribution 62 of the reversed magnetic domains.
Represents the diameter distribution 71 of the crystal grains and the diameter distribution 72 of the reversed magnetic domains measured for the sample C. From the integrated curves of the diameter distribution obtained from FIG. 6 and FIG. 7, the average grain size of the crystal grains is 16.3 nm and the average diameter of the reversal domain is 42.3 for the sample B.
For sample C, the average diameter of the crystal grains is 9.
It was determined that the average diameter of the inverted magnetic domains was 70.5 nm and 20.5 nm.
【００１９】前記３種類の垂直磁気記録媒体試料Ａ，
Ｂ，Ｃの記録再生特性と結晶粒径及び反転磁区径の測定
結果を表１に示す。媒体Ｓ／Ｎと再生出力の経時変化の
両方を考慮に入れると、記録再生特性の優れた試料は試
料Ａである。試料Ａは他の試料と比較しても、結晶粒径
は小さくなく、反転磁区径は試料Ｃと同程度である。た
だし、結晶粒径と反転磁区径の関係で比べてみると、反
転磁区径は結晶粒径の１．２４倍と小さくなっていた。The three types of perpendicular magnetic recording medium samples A,
Table 1 shows the recording / reproducing characteristics of B and C, and the measurement results of the crystal grain size and the reversed magnetic domain diameter. Taking both the medium S / N and the change over time in the reproduction output into consideration, the sample having excellent recording and reproduction characteristics is the sample A. Sample A does not have a small crystal grain size even when compared with the other samples, and the reversal magnetic domain diameter is almost the same as that of Sample C. However, comparing the relationship between the crystal grain size and the reversal magnetic domain diameter, the reversal magnetic domain diameter was as small as 1.24 times the crystal grain size.
【００２０】[0020]
【表１】 [Table 1]
【００２１】この関係を詳しく調べてみると、反転磁区
と結晶粒の直径比と媒体Ｓ／Ｎの関係を表す図８に示す
ように、反転磁区径が結晶粒径の２倍以下の試料はノイ
ズが小さく、媒体Ｓ／Ｎが少なくとも３６ｄＢ以上であ
った。これに対して、試料Ｃのように、たとえ結晶粒径
が小さくても、反転磁区が結晶粒径の２倍以上の試料は
ノイズが比較的大きく、媒体Ｓ／Ｎが３６ｄＢ以下であ
った。Examining this relationship in detail, as shown in FIG. 8, which shows the relationship between the median S / N and the ratio of the diameter of the reversal magnetic domain to the crystal grain, the sample having the reversal magnetic domain diameter of twice or less the crystal grain size was obtained. The noise was small, and the medium S / N was at least 36 dB. On the other hand, even if the crystal grain size is small, such as the sample C, the sample in which the reversal domain is twice or more the crystal grain size has relatively large noise, and the medium S / N is 36 dB or less.
【００２２】媒体ノイズの大きさは反転磁区の大きさに
関係すると考えられるが、結晶粒を小さくしただけでは
反転磁区は小さくならず、かえって反転磁区の大きさに
ばらつきを生じさせ、これが新たな媒体ノイズの原因を
作っていると考えられる。したがって、ノイズを小さく
するためには、各結晶粒を磁気的に孤立させ、結晶粒単
位で磁区が反転することが理想的であると考えられる。
少なくともこれに近い状態を実現することはノイズの低
減に非常に有効である。ただし、従来の媒体では、特に
結晶粒を小さくした場合には、反転磁区径は少なくとも
結晶粒の２〜３倍程度の大きさがあり、そのために十分
大きな媒体Ｓ／Ｎが得られなかった。It is considered that the magnitude of the medium noise is related to the size of the reversal magnetic domain. However, merely reducing the crystal grain size does not make the reversal magnetic domain smaller, but rather causes a variation in the size of the reversal magnetic domain. This is considered to be the cause of the medium noise. Therefore, in order to reduce noise, it is considered ideal that each crystal grain is magnetically isolated and the magnetic domain is inverted in units of the crystal grain.
Realizing at least a state close to this is very effective in reducing noise. However, in the conventional medium, especially when the crystal grains are made small, the reversal magnetic domain diameter is at least about 2 to 3 times as large as the crystal grains, and therefore, a sufficiently large medium S / N cannot be obtained.
【００２３】本発明では、ＣｏとＣｒを主な成分とする
磁気記録層に接する下地としてＣｒを３０ａｔ％以上含
有する下地層を用いて、さらにこれらを形成後に４００
〜６００℃で真空中熱処理することにより、垂直方向に
磁場を印加して測定した保磁力が３０００エルステッド
以上で、反転磁区径が結晶粒径の２倍以下の垂直磁気記
録媒体を作製することができた。下地にＣｒの含有量が
３０ａｔ％以下の材料を用いても、熱処理の効果はほと
んど見られなかった。また、図８に示すように、保磁力
が３０００エルステッド以下の場合も、十分高い媒体Ｓ
／Ｎの値が得られなかった。磁気記録層の材料として、
Ｃｏ−Ｃｒ−Ｔａ、Ｃｏ−Ｃｒ−Ｐｔ−Ｔａ、Ｃｏ−Ｃ
ｒ−Ｎｂ、Ｃｏ−Ｃｒ−Ｗなどを選び、また組成を変え
て同様の比較実験を行ったところ同様の傾向を示す結果
が得られた。In the present invention, an underlayer containing 30 at% or more of Cr is used as an underlayer in contact with a magnetic recording layer containing Co and Cr as main components.
By performing a heat treatment in a vacuum at ~ 600 ° C., a perpendicular magnetic recording medium having a coercive force measured by applying a magnetic field in the perpendicular direction of not less than 3000 Oersted and a reversal domain diameter of not more than twice the crystal grain size can be produced. did it. Even when a material having a Cr content of 30 at% or less was used for the underlayer, the effect of the heat treatment was hardly observed. Also, as shown in FIG. 8, when the coercive force is 3000 Oe or less, the sufficiently high medium S
/ N value could not be obtained. As a material for the magnetic recording layer,
Co-Cr-Ta, Co-Cr-Pt-Ta, Co-C
A similar comparison experiment was performed by selecting r-Nb, Co-Cr-W, etc., and changing the composition. As a result, a result showing a similar tendency was obtained.
【００２４】（実施例２）実施例１において作製した垂
直磁気記録媒体の中から媒体Ｓ／Ｎが３６ｄＢ以上の媒
体Ａを選び、これを用いた磁気ディスク装置を作製し
た。図９は磁気ディスク装置の構造を示す概略図であ
り、（ａ）は平面図、（ｂ）はそのＡＡ断面図である。
この磁気ディスク装置は、磁気記録媒体９１と、磁気記
録媒体を駆動する媒体駆動部９２と、磁気ヘッド９３
と、磁気ヘッドを駆動する磁気ヘッド駆動部９４と、記
録再生信号処理系６５とを備える周知の構造の磁気ディ
スク装置である。再生ヘッドとしては、実施例１で使用
したものと同様の磁気抵抗効果型ヘッドを用い、ヘッド
と媒体の間の磁気スペーシングは５０ｎｍ以下となるよ
うに調整した。その結果、１平方インチ当たり４ギガビ
ット以上の面記録密度での情報の記録と再生が可能であ
ることを確認できた。これに対して、媒体Ｓ／Ｎが３６
ｄＢに満たない試料Ｂあるいは試料Ｃの媒体を用いた場
合は、高記録密度での再生が困難であった。(Example 2) A medium A having a medium S / N of 36 dB or more was selected from the perpendicular magnetic recording medium manufactured in Example 1, and a magnetic disk drive using this medium was manufactured. 9A and 9B are schematic views showing the structure of the magnetic disk drive, wherein FIG. 9A is a plan view and FIG.
This magnetic disk device includes a magnetic recording medium 91, a medium driving unit 92 for driving the magnetic recording medium, and a magnetic head 93.
And a magnetic disk drive having a known structure including a magnetic head driving unit 94 for driving the magnetic head, and a recording / reproducing signal processing system 65. As the reproducing head, a magnetoresistive head similar to that used in Example 1 was used, and the magnetic spacing between the head and the medium was adjusted to be 50 nm or less. As a result, it was confirmed that information could be recorded and reproduced at an areal recording density of 4 gigabits per square inch or more. In contrast, the medium S / N is 36
When the medium of Sample B or Sample C having less than dB was used, reproduction at a high recording density was difficult.
【００２５】再生ヘッドとして、誘導電磁型ヘッドを用
いた場合には、本実施例で見られるような媒体間の媒体
Ｓ／Ｎの差異が見られず、また高密度に記録された情報
の再生も不可能であった。再生ヘッドとして、巨大磁気
抵抗効果を利用したヘッドを用いた場合には、本実施例
において見られた媒体Ｓ／Ｎの違いがより明確に現れ、
本発明が有効であることが確認された。When an inductive electromagnetic head is used as a reproducing head, there is no difference in medium S / N between the media as seen in the present embodiment, and reproduction of information recorded at high density is performed. Was also impossible. When a head utilizing the giant magnetoresistance effect is used as the reproducing head, the difference in the medium S / N seen in the present embodiment appears more clearly.
It was confirmed that the present invention was effective.
【００２６】[0026]
【発明の効果】本発明によると、高密度記録に適した十
分に高い媒体Ｓ／Ｎを持ち、かつ記録情報の長期間保持
が可能な垂直磁気記録媒体を得ることができる。According to the present invention, it is possible to obtain a perpendicular magnetic recording medium having a sufficiently high medium S / N suitable for high-density recording and capable of holding recorded information for a long period of time.
【図１】本発明による垂直磁気記録媒体の断面構造を示
す模式図。FIG. 1 is a schematic diagram showing a cross-sectional structure of a perpendicular magnetic recording medium according to the present invention.
【図２】原子間力顕微鏡で観察した媒体表面の形態像
（ａ）と、磁気力顕微鏡で観察した反転磁区像（ｂ）を
同一視野で示した図。FIG. 2 is a diagram showing a morphological image (a) of a medium surface observed by an atomic force microscope and a reversed magnetic domain image (b) observed by a magnetic force microscope in the same field of view.
【図３】直流消磁状態の磁気記録層での結晶粒と反転磁
区の様子を説明する模式図。FIG. 3 is a schematic diagram illustrating a state of crystal grains and reversal magnetic domains in a magnetic recording layer in a DC demagnetized state.
【図４】試料Ａについて測定した結晶粒と反転磁区の直
径分布を示す図。FIG. 4 is a view showing a distribution of diameters of crystal grains and inverted magnetic domains measured for a sample A;
【図５】試料Ａについて測定した結晶粒と反転磁区の直
径分布を積算面積で示した図。FIG. 5 is a diagram showing a distribution of diameters of crystal grains and reversal magnetic domains measured for a sample A by an integrated area.
【図６】試料Ｂについて測定した結晶粒と反転磁区の直
径分布を示す図。FIG. 6 is a diagram showing a distribution of diameters of crystal grains and inverted magnetic domains measured for a sample B;
【図７】試料Ｃについて測定した結晶粒と反転磁区の直
径分布を示す図。FIG. 7 is a diagram showing a distribution of diameters of crystal grains and reversed magnetic domains measured for a sample C;
【図８】反転磁区と結晶粒の直径比と媒体Ｓ／Ｎの関係
を表す図。FIG. 8 is a diagram showing the relationship between the median S / N and the diameter ratio between the reversed magnetic domain and the crystal grains.
【図９】磁気記録再生装置の構造を示す図。FIG. 9 is a diagram showing a structure of a magnetic recording / reproducing device.
１１…非磁性基板、１２…磁気記録層をｃ軸配向させる
ための下地層、１３…Ｃｒを含有する下地層、１４…磁
気記録層、１５…保護潤滑層、３１…結晶粒、３２…反
転磁区、３３…直流消磁の磁場印加方向に磁化された領
域、３４…結晶粒の占める面積、３５…反転磁区の占め
る面積、４１…試料Ａについて測定した結晶粒の直径分
布、４２…試料Ａについて測定した反転磁区の直径分
布、５１…試料Ａについて測定した結晶粒の直径分布、
５２…試料Ａについて測定した反転磁区の直径分布、６
１…試料Ｂについて測定した結晶粒の直径分布、６２…
試料Ｂについて測定した反転磁区の直径分布、７１…試
料Ｃについて測定した結晶粒の直径分布、７２…試料Ｃ
について測定した反転磁区の直径分布、９１…磁気記録
媒体、９２…磁気記録媒体駆動部、９３…磁気ヘッド、
９４…磁気ヘッド駆動部、９５…記録再生信号処理系DESCRIPTION OF SYMBOLS 11 ... Non-magnetic board | substrate, 12 ... Underlayer for making a magnetic recording layer c-axis orientation, 13 ... Underlayer containing Cr, 14 ... Magnetic recording layer, 15 ... Protective lubrication layer, 31 ... Crystal grain, 32 ... Inversion Magnetic domain, 33: region magnetized in the direction of application of the magnetic field of DC demagnetization, 34: area occupied by crystal grains, 35: area occupied by reversal magnetic domains, 41: diameter distribution of crystal grains measured for sample A, 42: sample A Diameter distribution of reversed magnetic domains measured, 51: diameter distribution of crystal grains measured for sample A,
52: Diameter distribution of reversed magnetic domains measured for sample A, 6
1 ... diameter distribution of crystal grains measured for sample B, 62 ...
Diameter distribution of reversed magnetic domains measured for Sample B, 71: Diameter distribution of crystal grains measured for Sample C, 72: Sample C
Diameter distribution of the reversal magnetic domain measured for: 91: magnetic recording medium, 92: magnetic recording medium drive, 93: magnetic head,
94: magnetic head drive unit, 95: recording / reproducing signal processing system
───────────────────────────────────────────────────── フロントページの続き (72)発明者 伊藤 研也 東京都国分寺市東恋ヶ窪一丁目280番地 株式会社 日立製作所 中央研究所内 (58)調査した分野(Int.Cl.6，ＤＢ名) G11B 5/66 G11B 5/84 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenya Ito 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (58) Field surveyed (Int. Cl. 6 , DB name) G11B 5 / 66 G11B 5/84
Claims (6)
直流消磁したときに媒体表面に現れる反転磁区の平均直
径が媒体表面で測定した結晶粒の平均直径の２倍以下で
あることを特徴とする垂直磁気記録媒体。An average diameter of a reversal domain appearing on a medium surface when a magnetic field is applied in a direction perpendicular to the medium surface and subjected to DC demagnetization is not more than twice an average diameter of crystal grains measured on the medium surface. Characteristic perpendicular magnetic recording medium.
であることを特徴とする請求項１記載の垂直磁気記録媒
体。2. The perpendicular magnetic recording medium according to claim 1, wherein the inverted magnetic domains appearing on the surface of the medium are substantially circular.
上含有する多結晶薄膜下地層上に形成し、４００〜６０
０℃で真空中熱処理した、ＣｏとＣｒを主たる成分とす
る膜厚１００ｎｍ以下の強磁性薄膜を用いることを特徴
とする請求項１又は２記載の垂直磁気記録媒体。3. A magnetic recording layer, which is formed on a polycrystalline thin film underlayer containing 30 at% or more of Cr, and
3. The perpendicular magnetic recording medium according to claim 1, wherein a ferromagnetic thin film having a film thickness of 100 nm or less containing Co and Cr as main components and heat-treated in a vacuum at 0 ° C. is used.
向に磁界を印加して測定したときの保磁力が３０００エ
ルステッド以上であることを特徴とする請求項３記載の
垂直磁気記録媒体。4. The perpendicular magnetic recording medium according to claim 3, wherein the ferromagnetic thin film has a coercive force of 3000 Oe or more when measured by applying a magnetic field in a direction perpendicular to the medium surface.
動する媒体駆動部と、磁気ヘッドと、前記磁気ヘッドを
駆動する磁気ヘッド駆動部と、記録再生信号処理系とを
含む磁気記録再生装置において、前記磁気記録媒体とし
て請求項１〜４のいずれか１項に記載の垂直磁気記録媒
体を用い、前記磁気ヘッドは再生部として磁気抵抗効果
型磁気ヘッド又は巨大磁気抵抗効果型ヘッドを備えるこ
とを特徴とする磁気記録再生装置。5. A magnetic recording / reproducing apparatus including a magnetic recording medium, a medium driving unit for driving the magnetic recording medium, a magnetic head, a magnetic head driving unit for driving the magnetic head, and a recording / reproducing signal processing system. 5. The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording medium includes a magnetoresistive head or a giant magnetoresistive head as a reproducing unit. A magnetic recording / reproducing apparatus characterized by the above-mentioned.
直流消磁したときに媒体表面に現れる反転磁区の面積を
円に換算したときの平均直径が媒体表面で測定した結晶
粒の平均直径の２倍以下である垂直磁気記録媒体の製造
方法であって、 Ｃｒを３０ａｔ％以上含有する多結晶薄膜をスパッタ法
により形成するステップと、２００℃以下の基板温度に
おいて前記多結晶薄膜上にＣｏとＣｒを主たる成分とす
る膜厚１００ｎｍ以下の強磁性薄膜をスパッタ法により
形成するステップと、前記基板を真空中で４００〜６０
０℃において熱処理するステップとを含むことを特徴と
する垂直磁気記録媒体の製造方法。6. The average diameter of a reversal domain appearing on the medium surface when a magnetic field is applied in a direction perpendicular to the medium surface and subjected to DC demagnetization is converted into a circle, and the average diameter is the average diameter of crystal grains measured on the medium surface. Forming a polycrystalline thin film containing 30 at% or more of Cr by sputtering, and forming a thin film of Co on the polycrystalline thin film at a substrate temperature of 200 ° C. or less. Forming a ferromagnetic thin film having a film thickness of 100 nm or less containing Cr and Cr as main components by a sputtering method;
Heat-treating at 0 ° C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10027102A JP2991689B2 (en) | 1998-02-09 | 1998-02-09 | Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10027102A JP2991689B2 (en) | 1998-02-09 | 1998-02-09 | Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11232633A JPH11232633A (en) | 1999-08-27 |
| JP2991689B2 true JP2991689B2 (en) | 1999-12-20 |
Family
ID=12211730
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10027102A Expired - Fee Related JP2991689B2 (en) | 1998-02-09 | 1998-02-09 | Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2991689B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3647031B2 (en) * | 2000-03-17 | 2005-05-11 | 高橋 研 | Method for controlling film formation of perpendicular magnetic recording medium |
| KR100374792B1 (en) | 2000-12-29 | 2003-03-04 | 삼성전자주식회사 | Perpendicular magnetic recording disks |
| WO2005006311A1 (en) * | 2003-07-10 | 2005-01-20 | Fujitsu Limited | Multilayer structure film and method for manufacture thereof |
-
1998
- 1998-02-09 JP JP10027102A patent/JP2991689B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11232633A (en) | 1999-08-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3143611B2 (en) | Ultrathin nucleation layer for magnetic thin film media and method of making the layer | |
| JP2524514B2 (en) | Magnetic recording media | |
| US6403242B1 (en) | Magnetic recording medium and magnetic recording system using such a magnetic recording medium | |
| JP2007317304A (en) | Magnetic recording medium and magnetic recording system | |
| JP2005032353A (en) | Magnetic recording medium, magnetic storage, and method of recording of magnetic recording medium | |
| JP3011918B2 (en) | Perpendicular magnetic recording medium and magnetic storage device | |
| JP3764833B2 (en) | Magnetic recording medium and magnetic storage device | |
| US6083599A (en) | Perpendicular magnetic recording media and magnetic recording and reproducing apparatus using the same | |
| US6156422A (en) | High density magnetic recording medium with high Hr and low Mrt | |
| JP2991689B2 (en) | Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same | |
| US6706426B1 (en) | Longitudinal magnetic recording media | |
| JP3867351B2 (en) | Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same | |
| JP3041273B2 (en) | Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same | |
| JP3138453B2 (en) | Perpendicular magnetic recording medium and magnetic storage device using the same | |
| JP2002063714A (en) | Perpendicular magnetic recording medium and perpendicular magnetic recording and reproducing apparatus | |
| JPH0773433A (en) | Magnetic recording medium, its production and magnetic recorder | |
| US4939045A (en) | Magnetic recording medium | |
| JP3102638B2 (en) | Magnetic recording / reproducing device | |
| JP3136133B2 (en) | Magnetic recording media | |
| JP2001101643A (en) | Magnetic recording medium | |
| US6749956B1 (en) | Magnetic recording medium | |
| JP3670798B2 (en) | Perpendicular magnetic recording medium | |
| JP2000339657A (en) | Magnetic recording medium | |
| JP3697469B2 (en) | Perpendicular magnetic recording medium and magnetic storage device using the same | |
| US6572988B1 (en) | Magnetic recording medium and magnetic recording apparatus |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313115 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313115 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20071015 Year of fee payment: 8 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20081015 Year of fee payment: 9 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20091015 Year of fee payment: 10 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20091015 Year of fee payment: 10 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20101015 Year of fee payment: 11 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111015 Year of fee payment: 12 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111015 Year of fee payment: 12 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313117 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111015 Year of fee payment: 12 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121015 Year of fee payment: 13 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121015 Year of fee payment: 13 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| LAPS | Cancellation because of no payment of annual fees |