JPS6163919A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve recording and reproducing efficiency without generating spiky noise by providing a soft magnetic lining layer which has the uniaxial anisotropy to make the direction of the axis of easy magnetization approximately in the track width direction and is controlled in anisotropic magnetic field and coercive force. CONSTITUTION:The soft magnetic lining layer (e.g.; 'Permalloy(R)') having the uniaxial anisotropy to make the direction of the axis of easy magnetization approximately into the track width direction, having the anisotropic magnetic field of <=1.8 times the coercive force of the direction of the axis of easy magnet ization and having 1.2 Oe coercive force in the direction of the axis of easy magnetization is formed on a heat-resistant high-polymer base film. A vertical anisotropic film (e.g.; Co-Cr vertical anisotropic film) is then formed thereon by which the intended magnetic recording medium is obtd.

Description

【発明の詳細な説明】 産業上の利用分野 本発明は垂直磁気記録媒体に関するものである。[Detailed description of the invention] Industrial applications The present invention relates to perpendicular magnetic recording media.

従来例の構成とその問題点 短波長記録特性の優れた磁気記録方式として、垂直磁気
記録方式がある。この方式においては、垂直磁気異方性
を有する磁性薄膜を磁性層とした垂直磁気記録媒体が必
要となる。このような媒体に信号を記録すると残留磁化
は媒体の膜面に略垂百雪面仝面咎　−従。イ■ゴ易が嬉
辿易［％　入ｐ♀〃リイ太内反磁界は減少し、優れた再
生出力が得られる。Conventional Structure and Problems There is a perpendicular magnetic recording system as a magnetic recording system with excellent short wavelength recording characteristics. This method requires a perpendicular magnetic recording medium whose magnetic layer is a magnetic thin film having perpendicular magnetic anisotropy. When a signal is recorded on such a medium, the residual magnetization will be approximately equal to the surface of the medium. The demagnetizing field within the inner diameter is reduced and excellent playback output can be obtained.

ところで、非磁性基板上に直接垂直磁気異方性膜が形成
された単層膜媒体に対し、非磁性基板と垂直磁気異方性
膜との間に、軟磁性裏打ち層を設けた二層膜媒体は、記
録再生効率の大幅な向上が認められる。By the way, in contrast to single-layer media in which a perpendicular magnetic anisotropic film is formed directly on a non-magnetic substrate, there is a double-layer film in which a soft magnetic underlayer is provided between the non-magnetic substrate and the perpendicular magnetic anisotropic film. The medium is recognized to have significantly improved recording and reproducing efficiency.

二層膜媒体の記録再生効率には、軟磁性裏打ち層の磁気
特性が大きな影響を及ぼし、軟磁性裏打ち層の保磁力が
小さい程、記録再生効率が高いことが知られている。と
ころが、軟磁性裏打ち層の保磁力を小さくすると、軟磁
性裏打ち層のバルクハウゼン効果に起因するスパイク状
ノイズが発生する。このスパイク状ノイズの発生を防止
するためには、軟磁性裏打ち層の保磁力を高くする必要
があり、具体的には約３０＠Ｉ以上の値が必要である。It is known that the magnetic properties of the soft magnetic underlayer have a large influence on the recording and reproducing efficiency of a two-layer film medium, and the smaller the coercive force of the soft magnetic underlayer, the higher the recording and reproducing efficiency. However, when the coercive force of the soft magnetic underlayer is reduced, spike-like noise occurs due to the Barkhausen effect of the soft magnetic underlayer. In order to prevent the occurrence of this spike-like noise, it is necessary to increase the coercive force of the soft magnetic underlayer, and specifically, a value of about 30@I or more is required.

しかし軟磁性裏打ち層の保磁力を３０．以上にすると、
記録再生効率が低下してしまう。例えばｏ、ａ　Ｏ，の
保磁力の軟磁性裏打ち層に対し、３ｏ８の場合にはあら
ゆる記録密度において、約７ｄＢの効率低下がある。こ
のことを、具体的な実験結果に基づいて説明する。第１
図は二層膜媒体における軟磁性裏打ち層の保磁力と再生
出力及びスパイク状ノイズの関係を示すグラフである。However, the coercive force of the soft magnetic underlayer is 30. If above,
Recording and reproducing efficiency decreases. For example, for a soft magnetic underlayer with a coercive force of o, a O, and a coercive force of 3o8, there is a decrease in efficiency of about 7 dB at all recording densities. This will be explained based on specific experimental results. 1st
The figure is a graph showing the relationship between the coercive force of the soft magnetic underlayer, reproduction output, and spike noise in a two-layer film medium.

二層膜媒体は、高分子ベースフィルム上に膜厚４０００
人の軟磁性裏打ち層としてのパーマロイ膜を介して、膜
厚１８０Ｑ入のＣｏ　−Ｃｒ垂直異方性膜が形成された
ものである。なおこの軟磁性膜ち σ層は膜面内においてほぼ等方である。記録再生には、
主磁極厚０．３μｍの補助磁極励磁型垂直ヘッドを用い
、記録密度は５０ＫＦＲＰＩである。ここで５０ＫＦＲ
ＰＩとは１インチ当たり５００００回磁化反転のある記
録状態である。測定はテープ状媒体により行ない、テー
プ走行速度は４．８　ｔｙｎ　７秒であ祝記録密度を変
えても第１図に示される結果は殆ど変わらない。第１図
曲線１（黒丸）は軟磁性裏打ち層の保磁力と再生出力の
関係を示し・曲線２（白丸）は軟磁性裏打ち層の保磁力
と１秒間に発生するスパイク状ノイズの数との関係を示
す。第１図から明らかな様に、軟磁性裏打ち層の保磁力
を小さくすると、再生出力は増加するが、スパイク状ノ
イズの発生を伴なう。スパイク状ノイズは信号のエラー
に結び付くので好ましくない。The two-layer film medium has a film thickness of 4000 mm on a polymeric base film.
A Co--Cr perpendicular anisotropic film with a film thickness of 180Q was formed via a permalloy film as a soft magnetic underlayer. Note that this soft magnetic film, σ layer, is approximately isotropic within the film plane. For recording and playback,
An auxiliary pole excitation type vertical head with a main pole thickness of 0.3 μm is used, and the recording density is 50 KFRPI. 50KFR here
PI is a recording state in which magnetization is reversed 50,000 times per inch. The measurement was carried out using a tape-like medium, and the tape running speed was 4.8 tyn 7 seconds.Even if the recording density was changed, the results shown in FIG. 1 did not change much. Curve 1 (black circle) in Figure 1 shows the relationship between the coercive force of the soft magnetic underlayer and the reproduction output.Curve 2 (white circle) shows the relationship between the coercive force of the soft magnetic underlayer and the number of spike noises generated per second. Show relationships. As is clear from FIG. 1, when the coercive force of the soft magnetic underlayer is reduced, the reproduction output increases, but this is accompanied by the generation of spike-like noise. Spiked noise is undesirable because it leads to signal errors.

軟磁性裏打ち層が膜面内において等方の場合には、スパ
イク状ノイズを無くするために、保磁力を３０８以上に
しなければならず、大きな再生出力が得られない。また
、記録再生系においては相反定理が成り立つために、再
生出力が低い場合には記録効率も悪い。If the soft magnetic underlayer is isotropic in the film plane, the coercive force must be set to 308 or more in order to eliminate spike-like noise, and a large reproduction output cannot be obtained. Furthermore, since the reciprocity theorem holds true in the recording/reproducing system, when the reproduction output is low, the recording efficiency is also poor.

以上の様に、二層膜媒体は単層膜媒体に対し、優れた記
録再生効率を有するが、効率向上のために軟磁性裏打“
ち層の保磁力を小さくすると、スパイク状ノイズが発生
するという問題があり、この解決が望まれていた。As mentioned above, double-layer media have superior recording and reproducing efficiency compared to single-layer media, but in order to improve efficiency, a soft magnetic backing is used.
There is a problem in that when the coercive force of the first layer is reduced, spike-like noise occurs, and a solution to this problem has been desired.

発明の目的 本発明は、記録再生効率が優れかつスパイク状ノイズの
無い軟磁性裏打ち層を備えた二層膜垂直記録媒体を提供
することを目的とする。OBJECTS OF THE INVENTION An object of the present invention is to provide a two-layer perpendicular recording medium that has a soft magnetic underlayer that has excellent recording and reproducing efficiency and is free from spike-like noise.

発明の構成 垂直磁気記録用二層膜媒体における軟磁性裏打ち層が、
膜面内において磁化容易軸方向を略トラック幅方向とす
る一軸異方性を有し、異方性磁界が磁化容易軸方向の保
磁力の１．８倍以下であり、かつ磁化容易軸方向の保磁
力が１．２０゜以上である。Structure of the Invention The soft magnetic underlayer in the double-layer film medium for perpendicular magnetic recording is
It has uniaxial anisotropy in the film plane with the direction of the easy axis of magnetization approximately in the track width direction, the anisotropic magnetic field is 1.8 times or less of the coercive force in the direction of the easy axis of magnetization, and Coercive force is 1.20° or more.

実施例の説明 第２図〜第４図を用いて本発明の詳細な説明を行なう。Description of examples The present invention will be explained in detail using FIGS. 2 to 4.

二層膜媒体における軟磁性裏打ち層が膜面内で等方では
なく、−軸異方性を有する場合について第２図を用いて
説明する。第２図は軟磁性裏打ち層のＨＫ、’Ｈｃ（Ｔ
Ｄ）と１秒間に発生するスパイク状ノイズの数との関係
を示す。ここでＨＫは、膜面内における異方性磁界であ
り、Ｈｃ（ＴＤ）はテープの幅方向の保磁力である。−
軸異方性を有する軟磁性膜のＨＫは第３図に示される様
に、磁化困難軸方向めヒステリンス曲線３の中心を通る
直線４が（磁化Ｍ）＝（飽和磁化ＭＳ）の直線と交わる
点にほぼ等しい。第３図の曲線５は磁化容易軸方向のヒ
ステリンス曲線である。なお媒体の構成、測定条件は前
記の等方軟磁性裏打ち層の場合と同一である。軟磁性裏
打ち層は、テープの幅方向すなわちトラック幅方向が磁
化容易軸方向であり、テープ走行方向すなわち磁化困難
軸方向の保磁力Ｈｃ（ＭＤ）はｏ、ｓ　Ｏ，、ＨｃＣＴ
Ｄ）は２００である。第２図から、ＨＫ　／　Ｈａ　（
ＴＤ　）が１．８以下になると、Ｈｃ（ＭＤ　）　　が
○、ａ　Ｏ，と小さくても、スパイク状ノイズが発生し
なくなることがわかる。ＨＫ　／　ＨＣ（ＴＤ　）　　
が１．８を越える場合には、トラック幅方向が磁化容易
軸の一軸異方性があっても、スパイク状ノイズが発生す
る。なおＨｃ（ＭＤ）　は０．８００であるので、大き
な再生出力が得られ、第１図においてＨｃ＜−０，８０
，の場合と同程度である。A case in which the soft magnetic underlayer in a two-layer film medium is not isotropic within the film plane but has -axis anisotropy will be described with reference to FIG. Figure 2 shows the soft magnetic underlayer HK, 'Hc(T
The relationship between D) and the number of spike-like noises generated per second is shown. Here, HK is the anisotropic magnetic field in the film plane, and Hc (TD) is the coercive force in the width direction of the tape. −
As shown in Fig. 3, the HK of a soft magnetic film having axial anisotropy is such that a straight line 4 passing through the center of the hysteresis curve 3 in the direction of the hard magnetization axis intersects with the straight line of (magnetization M) = (saturation magnetization MS). approximately equal to a point. Curve 5 in FIG. 3 is a hysteresis curve in the direction of the easy axis of magnetization. Note that the configuration of the medium and measurement conditions are the same as in the case of the isotropic soft magnetic underlayer described above. In the soft magnetic underlayer, the tape width direction, that is, the track width direction, is the easy magnetization axis direction, and the coercive force Hc (MD) in the tape running direction, that is, the hard magnetization axis direction, is o, s O,, HcCT
D) is 200. From Figure 2, HK / Ha (
It can be seen that when TD) becomes 1.8 or less, no spike-like noise occurs even if Hc(MD) is as small as ◯ or aO. HK/HC(TD)
If exceeds 1.8, spike-like noise will occur even if there is uniaxial anisotropy with the easy axis of magnetization in the track width direction. Note that since Hc(MD) is 0.800, a large reproduction output can be obtained, and in Fig. 1, Hc<-0,80
, which is about the same as in the case of .

以上ではＨｃ（ＴＤ）が２００の場合について説明した
が、次にスパイク状ノイズのＨｃ（ＴＤ）依存性につい
て説明する。第４図は、ＨＫ／　ＨＣ（ＴＤ）く１．８
なる条件のもとての、Ｈｃ（ＴＤ）　　と１秒間に発生
するスパイク状ノイズの数との関係を示す。The case where Hc (TD) is 200 has been described above, and next, the dependence of spike noise on Hc (TD) will be described. Figure 4 shows HK/HC(TD) 1.8
The relationship between Hc(TD) and the number of spike noises generated per second is shown under the following conditions.

ただし、媒体構成、測定条件は前記と同様である。However, the medium configuration and measurement conditions are the same as above.

Ｈｃ（ＴＤ）が１．２ｏｏ以上の場合には、スパイク状
ノイズは全く見られないが、１．２０８よりも小さくな
ると、たとえＨＫ／Ｈｃ（ＴＤ）く１．８なる条件を満
たしていても、スパイク状ノイズが発生する。なおＨｃ
（ＴＤ）は再生出方には殆ど影響を及ぼさない。When Hc(TD) is 1.2oo or more, no spike-like noise is observed, but when it becomes smaller than 1.208, even if the condition of HK/Hc(TD) = 1.8 is satisfied. , spike-like noise occurs. Furthermore, Hc
(TD) has almost no effect on the playback.

以上まとめると、二層膜媒体における軟磁性裏打ち智と
して、略トラック幅方向を磁化容易軸とし、Ｈｙ、がＨ
ｃ（ＴＤ）の１．８倍以下で、かっＨｃ（ＴＤ）が１．
２０゜以上の膜を用いることにより、スパイク状ノイズ
が全く発生せず、大きな再生出力を有する垂直磁気記録
媒体が得られる。また、記録再生系において相反定理が
成立するので、本発明の媒体は記録効率も優れている。In summary, as a soft magnetic backing force in a double-layered film medium, the axis of easy magnetization is approximately in the track width direction, and Hy is H.
c(TD) is 1.8 times or less, and Hc(TD) is 1.8 times or less.
By using a film with an angle of 20° or more, a perpendicular magnetic recording medium that does not generate any spike noise and has a large reproduction output can be obtained. Furthermore, since the reciprocity theorem holds true in the recording/reproduction system, the medium of the present invention also has excellent recording efficiency.

以上では高分子ベースフィルム上に軟磁性裏打ち層を介
して、垂直異方性膜が形成された二層膜媒体について説
明したが、軟磁性裏打ち層と垂直異方性膜との間に非磁
性層があっても、また軟磁性裏打ち層が多層構造になっ
ていても、以上の説明は全く変わらない。The above describes a two-layer film medium in which a perpendicular anisotropic film is formed on a polymer base film with a soft magnetic backing layer in between. The above explanation does not change at all even if there are layers or even if the soft magnetic underlayer has a multilayer structure.

次に、より具体的な実施例について説明する。Next, a more specific example will be described.

耐熱性高分子ベースフィルム上に＊空蒸着法により、第
６図ａ及びｂに示される２種のヒステリシス曲線を有す
る軟磁性裏打ち層としての膜厚３０００人のパーマロイ
膜を形成し、その上に膜厚８０人のＴｉ膜を介して、膜
厚１５ｏＯ人のＣｏ−Ｃτ垂直異方性膜を形成した。第
６図のヒステリシス曲線６，８は磁化容易軸方向のもの
でちり、７，９は磁化困難軸方向のものである。これら
の２種の二層膜媒体を主磁極厚０．３μｍの補助磁極励
磁型垂直ヘッドで、パーマロイ裏打ち層の磁化容易軸方
向をトラック幅方向として、記録再生を行なった。第５
図ａのパーマロイ膜のＨＫ。A permalloy film with a thickness of 3,000 mm as a soft magnetic backing layer having two types of hysteresis curves shown in Figure 6 a and b is formed on a heat-resistant polymer base film by the air vapor deposition method, and then A Co-Cτ vertically anisotropic film with a thickness of 150 mm was formed via a Ti film with a thickness of 80 mm. Hysteresis curves 6 and 8 in FIG. 6 are along the easy axis of magnetization, and curves 7 and 9 are along the hard axis of magnetization. Recording and reproduction were performed on these two types of dual-layer media using an auxiliary pole-excited vertical head with a main pole thickness of 0.3 μm, with the easy axis of magnetization of the permalloy underlayer set as the track width direction. Fifth
HK of permalloy membrane in figure a.

Ｈｃ（ＭＤ）、Ｈｃ（ＴＤ）　　はそれぞれ、２．２．
１及び２０．であり本発明の条件を満足しており、第５
図すのパーマロイ膜のＨＫ　、　Ｈａ　（ＭＤ　）　、
　Ｈｃ（ＴＤ）はそれぞれ、２　、０．８及び１０８で
あり本発明の条件を満足していない。第５図ａのノく一
マロイ膜を有する二層膜媒体と、第５図すのノく−マロ
イ膜を有する二層膜媒体を有する二層膜媒体とはほぼ同
じ再生出力であるが、前者はスノくイク状ノイズが全く
見られず、後者はスノくイク状ノイズが発生した。Hc(MD) and Hc(TD) are respectively 2.2.
1 and 20. This satisfies the conditions of the present invention, and the fifth
HK, Ha (MD) of the permalloy film shown in the figure.
Hc (TD) is 2, 0.8, and 108, respectively, which do not satisfy the conditions of the present invention. Although the two-layer film medium having the No. 1 Malloy film in FIG. 5a and the two-layer film medium having the No. 1 Malloy film in FIG. In the former case, no snow-like noise was observed, and in the latter case, a snow-like sound noise occurred.

発明の効果 本発明によれば、優れた再生出力を有し、かつスパイク
状ノイズが無い垂直磁気記録媒体が得られる。Effects of the Invention According to the present invention, a perpendicular magnetic recording medium having excellent reproduction output and free from spike noise can be obtained.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は従来の等方性軟磁性裏打ち層を有する二層膜媒
体の再生出力及びスパイク状ノイズ数と軟磁性裏打ち層
の保磁力との関係を示す図、第２図は、トラック幅方向
に磁化容易軸のある一軸異方性軟磁性裏打ち層を有する
二層膜媒体の、スパイク状ノイズ数と軟磁性裏打ち層の
ＨＫ　／　Ｈｃ（ＴＤ）との関係を示す図、＃３図は一
軸異方性軟磁性膜の異方性磁界ＨＫを説明するための図
、第４図はトラ、り幅方向に磁化容易軸のある一軸異方
性軟磁性裏打ち層を有する二層膜媒体の、スパイク状ノ
イズ数と軟磁性裏打ち層のＨｃ（ＴＤ）との関係を示す
図、第６図は、軟磁性裏打ち層のヒステリシス曲線を示
す図であり、同図ａは本発明の一実繞αＩＩＷ　　七１
ンセ　７、　ｄ、ｉ）か　　　斤ｌ民ハ　ｋｋ十太どト
日日ａ）名仕デｈ　へ外れるものを示す。　　′ 代理人の氏名　弁理士　中　尾　敏　男　ほか１名第１
図 第　２　ロ 第　３　図 り 第４図 第５図 博 弯 ヰ （ａ）Figure 1 is a diagram showing the relationship between the reproduction output and the number of spike-like noises of a conventional two-layer film medium having an isotropic soft magnetic underlayer and the coercive force of the soft magnetic underlayer, and Figure 2 is a diagram showing the relationship in the track width direction. Figure #3 shows the relationship between the number of spike-like noises and the HK/Hc (TD) of the soft magnetic underlayer for a two-layer film medium having a uniaxial anisotropic soft magnetic underlayer with an easy axis of magnetization. Figure 4 is a diagram for explaining the anisotropic magnetic field HK of an anisotropic soft magnetic film. FIG. 6 is a diagram showing the relationship between the number of spike noises and Hc (TD) of the soft magnetic underlayer, and FIG. 6 is a diagram showing the hysteresis curve of the soft magnetic underlayer. Seventy one
7. d. ′ Name of agent Patent attorney Toshio Nakao and 1 other person 1st
Figure 2 B Figure 3 Figure 4 Figure 5 Hiroki (a)

Claims (1)

【特許請求の範囲】[Claims] 垂直磁気記録用二層膜媒体における軟磁性裏打ち層が、
膜面内において磁化容易軸方向を略トラック幅方向とす
る一軸異方性を有し、異方性磁界が磁化容易軸方向の保
磁力の１．８倍以下であり、かつ磁化容易軸方向の保磁
力が１．２Ｏ＿ｅ以上であることを特徴とする垂直磁気
記録媒体。The soft magnetic underlayer in a double-layer film medium for perpendicular magnetic recording is
It has uniaxial anisotropy in the film plane with the direction of the easy axis of magnetization approximately in the track width direction, the anisotropic magnetic field is 1.8 times or less of the coercive force in the direction of the easy axis of magnetization, and A perpendicular magnetic recording medium characterized by having a coercive force of 1.2 O_e or more.