JPH0628091B2 - Perpendicular magnetic recording medium - Google Patents
Perpendicular magnetic recording mediumInfo
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- JPH0628091B2 JPH0628091B2 JP13219285A JP13219285A JPH0628091B2 JP H0628091 B2 JPH0628091 B2 JP H0628091B2 JP 13219285 A JP13219285 A JP 13219285A JP 13219285 A JP13219285 A JP 13219285A JP H0628091 B2 JPH0628091 B2 JP H0628091B2
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- layer
- magnetic
- coercive force
- crystal layer
- magnetization
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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係り、特に垂直磁気特性を
向上し得る垂直磁気記録媒体に関する。TECHNICAL FIELD The present invention relates to a perpendicular magnetic recording medium, and more particularly to a perpendicular magnetic recording medium capable of improving perpendicular magnetic characteristics.
従来の技術 一般に、磁気ヘツドにより磁気記録媒体に記録,再生を
行なうには、磁気ヘツドにより磁気記録媒体の磁性層に
その媒体長手方向(面内方向)の磁化を行なわせて記録
し、これを再生するものが汎用されている。しかるに、
これによれば記録が高密度になるに従つて減磁界が大き
くなり減磁作用が高密度記録に悪影響を及ぼすことが知
られている。そこで近年上記悪影響を解消するものとし
て、磁気記録媒体の磁性層に垂直方向に磁化を行なう垂
直磁気記録方式が提案されている。これによれば記録密
度を向上させるに従い減磁界が小さくなり理論的には残
留磁化の減少がない良好な高密度記録を行なうことがで
きる。2. Description of the Related Art Generally, in order to record / reproduce on / from a magnetic recording medium by using a magnetic head, the magnetic layer of the magnetic recording medium is magnetized in the longitudinal direction (in-plane direction) of the magnetic recording medium and recorded. The thing to reproduce is general-purpose. However,
According to this, it is known that the demagnetizing field increases as the recording density increases, and the demagnetizing action adversely affects the high density recording. Therefore, in recent years, as a means for eliminating the above-mentioned adverse effects, a perpendicular magnetic recording system has been proposed in which the magnetic layer of the magnetic recording medium is magnetized in the perpendicular direction. According to this, as the recording density is improved, the demagnetizing field becomes smaller, and theoretically good high density recording in which the residual magnetization does not decrease can be performed.
従来この垂直磁気記録方式に用いる垂直磁気記録媒体と
しては、ベースフイルム上にCo −Cr 膜をスパツタリ
ングにより被膜形成したものがあつた。周知の如く、C
o −Cr 膜は比較的高い飽和磁化(Ms )を有し、かつ
膜面に対し垂直な磁化容易軸を持つ(すなわち膜面に対
し垂直方向の抗磁力Hc ⊥が大である)ため垂直磁気記
録媒体としては極めて有望な材質であることが知られて
いる。ただし上記の如くスパツタリングによりCo −C
r 膜を単層形成した構造の垂直磁気記録媒体の場合、垂
直磁気記録媒体上の所定磁気記録位置に磁束を集中させ
ることができず(特にリングコアヘツドを用いた場合顕
著である)、垂直磁気記録媒体に分布が鋭くかつ強い垂
直磁化ができないという問題点があつた。Conventionally, as a perpendicular magnetic recording medium used in this perpendicular magnetic recording system, there is one in which a Co-Cr film is formed on the base film by sputtering. As is well known, C
The o-Cr film has a relatively high saturation magnetization (Ms) and an easy axis of magnetization perpendicular to the film surface (that is, the coercive force Hc ⊥ in the direction perpendicular to the film surface is large). It is known that the recording medium is an extremely promising material. However, as described above, Co-C
In the case of a perpendicular magnetic recording medium having a single r film structure, the magnetic flux cannot be concentrated at a predetermined magnetic recording position on the perpendicular magnetic recording medium (especially when a ring core head is used). The recording medium has a problem that the distribution is sharp and strong perpendicular magnetization cannot be performed.
また上記問題点を解決するため、Co −Cr 膜とベース
フイルムとの間に、いわゆる裏打ち層である高透磁率層
(すなわち抗磁力Hc が小なる層。例えばNi −Fe)
を別個形成して二層構造とし高透磁率層内で広がつてい
る磁束を所定磁気記録位置にて磁気ヘツドの磁極に向け
集中させて吸い込まれることにより分布が鋭くかつ強い
垂直磁化を行ない得る構成の垂直磁気記録媒体があつ
た。In order to solve the above problems, a high magnetic permeability layer (that is, a layer having a small coercive force Hc, that is, a so-called backing layer, for example, Ni-Fe) is provided between the Co-Cr film and the base film.
Is formed separately to form a two-layer structure, and the magnetic flux spreading in the high-permeability layer is concentrated toward the magnetic pole of the magnetic head at a predetermined magnetic recording position and is absorbed, so that a sharp distribution and strong perpendicular magnetization can be performed. A perpendicular magnetic recording medium having a structure has been obtained.
発明が解決しようとする問題点 しかるに上記従来の垂直磁気記録媒体,例えばCo −C
r 単層媒体にリングコアヘツドで記録する場合、その磁
界分布は面内方向成分をかなり有しているので記録時に
磁化が傾きやすい。磁化を垂直に維持するために、垂直
磁気記録媒体は高い垂直異方性磁界(Hk )を有し、飽
和磁化(Ms )はある程度小さい値に抑える必要があつ
た。また高い再生出力を実現しようとすると垂直方向の
抗磁力(Hc ⊥)を大きくし垂直磁気記録媒体の厚さ寸
法を大とする必要があつた。また厚さ寸法を大とした場
合には垂直磁気記録媒体の磁気ヘツドのいわゆる当たり
(垂直磁気記録媒体と磁気ヘツドの摺接部における摺接
条件)が悪くなり、垂直磁気記録媒体を損傷したり磁気
ヘツドに悪影響が生じ良好な垂直磁気記録再生ができな
いという問題点があつた。DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the above-mentioned conventional perpendicular magnetic recording medium such as Co-C
r When recording on a single-layer medium with a ring core head, the magnetic field distribution has a considerable in-plane component, so the magnetization tends to tilt during recording. In order to keep the magnetization perpendicular, the perpendicular magnetic recording medium has a high perpendicular anisotropy field (Hk), and the saturation magnetization (Ms) needs to be suppressed to a small value to some extent. Further, in order to realize a high reproduction output, it was necessary to increase the coercive force (Hc ⊥ ) in the vertical direction and increase the thickness of the perpendicular magnetic recording medium. When the thickness is large, the so-called hit of the magnetic head of the perpendicular magnetic recording medium (sliding contact condition at the sliding contact portion between the perpendicular magnetic recording medium and the magnetic head) is deteriorated, and the perpendicular magnetic recording medium is damaged. There is a problem that the magnetic head is adversely affected and good perpendicular magnetic recording / reproduction cannot be performed.
またCo −Cr 膜に加え高透磁率層を裏打ち層として形
成された二層構造の垂直磁気記録媒体の場合、Co −C
r 膜の抗磁力Hc (700 Oe 以上)に対して高透磁率層
の抗磁力Hc は極めて小(10Oe 以下)となつていたた
め、衝撃性のバルクアウゼンノイズが発生するという問
題点があつた。これに加えて二層構造の垂直磁気記録媒
体を得るには、まず高透磁率層を形成するに適した所定
条件にてベースフイルム上に例えばFe −Ni/アモル
フアス等をスパツタリングにより被膜し、次にCo −C
r 膜を形成するに適した所定条件にてCo −Cr をスパ
ツタリングにより被膜する必要があり、各層の形成毎に
スパツタリング条件及びターゲツトを変える必要があり
連続スパツタリングを行なうことができず、製造工程が
複雑になると共に量産性にも劣るという問題点があつ
た。In addition, in the case of a perpendicular magnetic recording medium having a two-layer structure in which a high magnetic permeability layer is used as a backing layer in addition to the Co-Cr film, Co-C
Since the coercive force Hc of the high-permeability layer was extremely small (10 Oe or less) with respect to the coercive force Hc (700 Oe or more) of the r film, there was a problem in that shock-induced bulk Ausen noise was generated. . In addition to this, in order to obtain a perpendicular magnetic recording medium having a two-layer structure, first, Fe-Ni / amorphous or the like is coated on the base film by spattering under predetermined conditions suitable for forming a high magnetic permeability layer, and then, To Co-C
It is necessary to coat Co-Cr by spattering under a predetermined condition suitable for forming the r film, and it is necessary to change the spattering condition and the target every time each layer is formed. There was a problem that it became complicated and the mass productivity was poor.
そこで本発明では、上層と下層とにより形成された磁性
層の各層の有する抗磁力の比を所定範囲内に選定するこ
とにより上記問題点を解決した垂直磁気記録媒体を提供
することを目的とする。Therefore, an object of the present invention is to provide a perpendicular magnetic recording medium which solves the above problems by selecting the ratio of the coercive force of each layer of the magnetic layers formed by the upper layer and the lower layer within a predetermined range. .
問題点を解決するための手段 上記問題点を解決するために本発明では、上層と下層と
により形成された磁性層を有する垂直磁気記録媒体の、
上層の垂直方向の抗磁力をHc ⊥とし、該下層の面内方
向の抗磁力をHc とした際、比 の値が となるよう選定した。Means for Solving the Problems In order to solve the above problems, the present invention provides a perpendicular magnetic recording medium having a magnetic layer formed by an upper layer and a lower layer,
When the vertical coercive force of the upper layer is Hc ⊥ and the in-plane coercive force of the lower layer is Hc, The value of Was selected.
実施例 本発明になる垂直磁気記録媒体(以下単に記録媒体とい
う)は、ベースとなるポリイミド基板上に例えばコバル
ト(Co ),クロム(Cr )にニオブ(Nb )及びタン
タル(Ta )のうち少なくとも一方を加えてなる磁性材
をターゲツトとしてスパツタリングすることによつて得
られる。EXAMPLE A perpendicular magnetic recording medium (hereinafter simply referred to as a recording medium) according to the present invention has, for example, at least one of cobalt (Co), chromium (Cr), niobium (Nb) and tantalum (Ta) on a base polyimide substrate. It is obtained by sputtering the magnetic material obtained by adding as a target.
従来より金属等(例えばCo −Cr 合金)をベース上に
スパツタリングした際、被膜形成された薄膜はその膜面
に垂直方向に対して同一結晶構造を形成するのではな
く、ベース近傍の極めて薄い部分にまず小粒径の第一の
結晶層を形成し、その上部に続いて大粒径の第二の結晶
層が形成されることが各種の実験(例えば走査型電子顕
微鏡による写真撮影)により明らかになつてきている
(Edward R.Wuori and Professor J.H.J
udy:“INITIAL LAYER EFFECT
IN CO−OR FILMS”,IEEE Tran
s.,VOL.MAG−20,No.5,SEPTEMBE
R 1984,P 774〜P 775またはWilliam G.Haine
s:“VSMPROFILING OF Co CrFIL
MS:A NEW ANALYTICAL TECHN
IQUE”IEEE Trans.,VOL,MAG−2
0,No.5,SEPTEMBER1984,P 812〜P 81
4)。本発明者は上記観点に注目しCo −Cr 合金を基
とし、またこれに第三元素を添加した金属を各種スパツ
タリングし、形成される小粒径の結晶層とその上部に形
成された大粒径の結晶層との物理的性質を測定した結
果、特に第三元素としてNb またはTa を添加した場
合、小粒径結晶層の抗磁力か大粒径結晶層よりも非常に
小であることがわかつた。本発明ではこの低抗磁力を有
する小粒径結晶層を高透磁率層として用い高抗磁力を有
する大粒径結晶層を垂直磁化層として用いることを特徴
とする。Conventionally, when a metal or the like (for example, Co-Cr alloy) is sputtered on a base, the thin film formed does not form the same crystal structure in the vertical direction on the film surface, but an extremely thin portion near the base. First, a small crystal grain first crystal layer was formed, and then a large crystal grain second crystal layer was formed on top of it, by various experiments (eg, scanning electron microscope photography). (Edward R. Wuori and Professor JHJ
udy: "INITIAL LAYER EFFECT
IN CO-OR FILMS ", IEEE Tran
s., VOL. MAG-20, No.5, SEPTEMBE
R 1984, P 774-P 775 or William G. Haine
s: "VSMPROFILING OF Co CrFIL
MS: A NEW ANALYTICAL TECHN
IQUE "IEEE Trans., VOL, MAG-2
0, No. 5, SEPTEMBER 1984, P 812 to P 81
Four). The present inventor pays attention to the above point of view, and based on a Co--Cr alloy, and by various sputtering of a metal to which a third element is added, a crystal layer having a small grain size and a large grain formed on the crystal layer are formed. As a result of measuring the physical properties of the crystal layer with a large diameter, especially when Nb or Ta is added as the third element, the coercive force of the small grain crystal layer is much smaller than that of the large grain crystal layer. Wakatsuta. The present invention is characterized in that the small grain size crystal layer having the low coercive force is used as the high magnetic permeability layer and the large grain size crystal layer having the high coercive force is used as the perpendicular magnetization layer.
以下本発明者が行なつたスパツタリングにより形成され
た小粒径結晶層及び大粒径結晶層の抗磁力を測定した実
験結果を詳述する。Co −Cr 薄膜,Co −Cr −Nb
薄膜及びCo −Cr −Ta 薄膜をスパツタリングするに
際し、スパツタリング条件は下記の如く設定した(Nb
またはTa を添加した各場合においてスパツタリング条
件は共に等しく設定した)。The experimental results of measuring the coercive force of the small grain size crystal layer and the large grain size crystal layer formed by the sputtering by the inventor will be described in detail below. Co-Cr thin film, Co-Cr-Nb
When the thin film and the Co-Cr-Ta thin film were sputtered, the sputtering conditions were set as follows (Nb
Alternatively, the spattering conditions were set equal in each case when Ta was added).
*スパツタ装置 RFマグネトロンスパツタ装置 *スパツタリング方法 連続スパツタリング。予め予備排気圧1×10-6Torrま
で排気した後Ar ガスを導入した1×10-3Torrとした *ベース ポリイミド(厚さ20μm) *ターゲツト Co −Cr 合金上にNb あるいはTa の小片を載置した
複合ターゲツト *ターゲツト基板間距離 110mm なお薄膜の磁気特性は振動試料型磁力計(理研電子製,
以下VSMと略称する)にて、薄膜の組成はエネルギー
分散型マイクロアナライザ(KEVEX社製,以下ED
Xと略称する)にて、また結晶配向性はX線回折装置
(理学電機製)にて夫々測定した。* Sputter device RF magnetron sputter device * Sputtering method Continuous sputtering. Preliminary exhaust pressure was set to 1 × 10 -6 Torr and then Ar gas was introduced to 1 × 10 -3 Torr * Base polyimide (thickness: 20 μm) * A small piece of Nb or Ta was placed on the target Co-Cr alloy. Placed composite target * Target-to-substrate distance 110mm Note that the magnetic properties of the thin film are the vibrating sample magnetometer (manufactured by Riken Denshi,
The composition of the thin film is an energy dispersive microanalyzer (KEVEX, hereinafter ED).
(Abbreviated as X) and the crystal orientation was measured by an X-ray diffractometer (manufactured by Rigaku Denki).
Co −Cr に第三元素としてNb を添加(2〜10at%
添加範囲において同一現象が生ずる)し、ポリイミドベ
ースに 0.2μmの膜厚でスパツタリングした記録媒体に
15KOe 磁界を印加した場合の面内方向のヒステリシ
ス曲線を第1図に示す。同図より面内方向の抗磁力(記
号Hc で示す)がゼロ近傍部分でヒステリシス曲線は
急激に変則的に立ち上がり(図中矢印Aで示す)、いわ
ゆる磁化ジヤンプが生じていることがわかる。スパツタ
リングされたCo −Cr −Nb 薄膜がスパツタリング時
に常に均一の結晶成長を行なつたと仮定した場合、第1
図に示された磁化ジヤンプは生ずるはずはなく、これよ
りCo −Cr −Nb 薄膜内に磁気的性質の異なる複数の
結晶層が存在することが推測される。Addition of Nb as a third element to Co-Cr (2-10 at%
The same phenomenon occurs in the addition range), and a hysteresis curve in the in-plane direction when a 15 KOe magnetic field is applied to a recording medium obtained by sputtering a polyimide base with a film thickness of 0.2 μm is shown in FIG. From the figure, it can be seen that the hysteresis curve abruptly and irregularly rises (indicated by arrow A in the figure) in the portion where the coercive force (indicated by symbol Hc) in the in-plane direction is near zero, and so-called magnetization jump occurs. If it is assumed that the sputtered Co-Cr-Nb thin film always performs uniform crystal growth during the sputtering, the first
The magnetization jump shown in the figure should not occur, which suggests that a plurality of crystal layers having different magnetic properties are present in the Co-Cr-Nb thin film.
続いて第1図に示した実験条件と同一条件にてCo −C
r −Nb をポリイミドベースに 0.05μmの膜厚でスパ
ツタリングした記録媒体に15KOeの磁界を印加した
場合の面内方向にヒステリシス曲線を第2図に示す。同
図においては第1図に見られたようなヒステリシス曲線
の磁化ジヤンプは生じておらず 0.05μm程度の膜厚に
おけるCo −Cr −Nb 薄膜は略均一な結晶となつてい
ることが理解される。これに加えて同図より 0.05μm
程度の膜厚における抗磁力Hc に注目するに、抗磁力
Hc は極めて小なる値となつており面内方向に対する
透磁率が大であることが理解される。上記結果よりスパ
ツタリングによりベース近傍位置にはじめに成長する初
期層は抗磁力Hc が小であり、この初期層は走査型電
子顕微鏡写真で確かめられている(前記資料参照)ベー
ス近傍位置に成長する小粒径の結晶層であると考えられ
る。また初期層の上方に成長する層は、初期層の抗磁力
Hc より大なる抗磁力Hc を有し、この層は同じく
走査型電子顕微鏡写真で確かめられている大粒径の結晶
層であると考えられる。Then, under the same experimental conditions as shown in FIG.
FIG. 2 shows a hysteresis curve in the in-plane direction when a magnetic field of 15 KOe was applied to a recording medium obtained by sputtering r-Nb on a polyimide base with a film thickness of 0.05 μm. In this figure, it is understood that the magnetization jump of the hysteresis curve as shown in FIG. 1 does not occur, and the Co-Cr-Nb thin film at a film thickness of about 0.05 μm is a substantially uniform crystal. . In addition to this, 0.05 μm from the figure
Focusing on the coercive force Hc at a certain film thickness, it is understood that the coercive force Hc has an extremely small value and the magnetic permeability in the in-plane direction is large. From the above results, the coercive force Hc of the initial layer that grows near the base by spattering is small, and this initial layer has been confirmed by scanning electron micrographs (see the above reference). It is considered to be a crystal layer having a diameter. Further, the layer grown above the initial layer has a coercive force Hc larger than the coercive force Hc of the initial layer, and this layer is also a large grain crystal layer confirmed by a scanning electron micrograph. Conceivable.
小粒径結晶層と大粒径結晶層が併存するCo −Cr −N
b 薄膜において磁化ジヤンプが生ずる理由を第3図から
第5図に用いて以下述べる。なお後述する如く、磁化ジ
ヤンプは組成率及びスパツタリング条件に関し全てのC
o −Cr −Nb 薄膜に対して発生するものではない。所
定の条件下においてCo −Cr −Nb 薄膜をスパツタリ
ングにより形成しこの薄膜のヒステリシス曲線を測定に
より描くと第3図に示す如く磁化ジヤンプが現われたヒ
ステリシス曲線となる。また小粒径結晶層のみからなる
ヒステリシス曲線は膜厚寸法を小としたスパツタリング
(約 0.075μm以下、これについては後述する)を行な
い、これを測定することにより得ることができる(第4
図に示す)。また大粒径結晶層は均一結晶構造を有して
いると考えられ、かつ第3図に示すヒステリシス曲線は
小粒径結晶層のヒステリシス曲線と大粒径結晶層のヒス
テリシス曲線を合成したものと考えられるため第5図に
示す如く抗磁力Hc が小粒径結晶層よりも大であり、
磁化ジヤンプのない滑らかなヒステリシス曲線を形成す
ると考えられる。すなわち第3図において示されている
磁化ジヤンプの存在は、磁気特性の異なる二層が同一の
薄膜内に形成されていることを示しており、従つて第1
図に示されたCo −Cr −Nb 薄膜にも磁気特性の異な
る二層が形成されていることが理解できる。なお大粒径
結晶層の抗磁力は、小粒径結晶層と大粒径結晶層が併存
するCo −Cr −Nb 薄膜のヒステリシス曲線から小粒
径結晶層のみのCo −Cr −Nb 薄膜のヒステリシス曲
線を差引いて得られるヒステリシス曲線より求めること
ができる。上記各実験結果によりCo −Cr −Nb 薄膜
のヒステリシス曲線に磁化ジヤンプが生じている時、磁
気特性の異なる二層が形成されていることが証明された
ことになる。Co-Cr-N in which a small grain size crystal layer and a large grain size crystal layer coexist
b The reason why the magnetization jump occurs in the thin film will be described below with reference to FIGS. 3 to 5. As will be described later, the magnetizing jump is a C composition with respect to the composition ratio and the sputtering condition.
It does not occur for o-Cr-Nb thin films. When a Co-Cr-Nb thin film is formed by sputtering under predetermined conditions and a hysteresis curve of this thin film is drawn by measurement, a hysteresis curve in which a magnetization jump appears appears as shown in FIG. A hysteresis curve consisting of a small grain crystal layer can be obtained by performing spattering with a small film thickness dimension (about 0.075 μm or less, which will be described later) and measuring it (4th step).
(Shown in the figure). The large crystal grain layer is considered to have a uniform crystal structure, and the hysteresis curve shown in FIG. 3 is a combination of the hysteresis curve of the small crystal grain layer and the hysteresis curve of the large crystal grain layer. It is considered that the coercive force Hc is larger than that of the small grain crystal layer as shown in FIG.
It is considered to form a smooth hysteresis curve without a magnetization jump. That is, the presence of the magnetization jump shown in FIG. 3 indicates that two layers having different magnetic properties are formed in the same thin film, and accordingly, the first
It can be understood that the Co-Cr-Nb thin film shown in the figure also has two layers having different magnetic properties. The coercive force of the large grain crystal layer is determined by the hysteresis curve of the Co-Cr-Nb thin film in which the small grain crystal layer and the large grain crystal layer coexist. It can be obtained from the hysteresis curve obtained by subtracting the curve. From the above experimental results, it is proved that two layers having different magnetic properties are formed when the magnetization jump occurs in the hysteresis curve of the Co-Cr-Nb thin film.
続いてCo −Cr −Nb 薄膜のベース上へのスパツタリ
ングの際形成される上記二層の夫々の磁気的性質をCo
−Cr −Nb 薄膜の厚さ寸法に関連させつつ第6図を用
いて以下説明する。第6図はCo −Cr −Nb 薄膜の膜
厚寸法をスパツタリング時間を変えることにより制御
し、各膜厚寸法における面内方向の抗磁力Hc ,垂直
方向の抗磁力Hc ⊥,磁化ジヤンプ量σjを夫々描いた
ものである。The magnetic properties of each of the two layers formed during the sputtering of the Co-Cr-Nb thin film on the base are described below.
It will be described below with reference to FIG. 6 in relation to the thickness of the -Cr-Nb thin film. In FIG. 6, the film thickness dimension of the Co-Cr-Nb thin film is controlled by changing the sputtering time, and the coercive force Hc in the in-plane direction, the coercive force Hc ⊥ in the vertical direction, and the magnetization jump amount σj at each film thickness dimension are controlled. They are drawn respectively.
まず面内方向の抗磁力Hc に注目するに、膜厚寸法が
0.08μm以下においては極めて小なる値(150Oe以
下)となつており、面内方向に対する透磁率は高いと考
えられる。また膜厚寸法が大となつても抗磁力Hc は
大きく変化するようにことはない。また磁化ジヤンプ量
σjに注目すると、磁化ジヤンプ量は膜厚寸法が 0.075
μmにて急激に立ち上がり、 0.075μm以上の膜厚にお
いては滑らかな下に凸の放物線形状を描く。更に垂直方
向の抗磁力Hc ⊥に注目すると、抗磁力Hc ⊥は膜厚寸
法 0.05μm〜 0.1μmで急激に立ち上がり、 0.1μm
以上の膜厚寸法では900 Oe 以上の高い抗磁力を示す。
これらの結果より小粒径結晶層と大粒径結晶層の境は略
0.075μmの膜厚寸法のところにあり、膜厚寸法が 0.0
75μm以下の小粒径結晶層は面内方向及び垂直方向に対
する抗磁力Hc ,Hc ⊥が低い、いわゆる低抗磁力層
となつており、また膜厚寸法が 0.075μm以上の大粒径
結晶層は面内方向の抗磁力Hc は低いものの垂直方向
に対する抗磁力Hc ⊥は非常に高い値を有する、いわゆ
る高抗磁力層となつており垂直磁気記録に適した層とな
つている。更に磁化ジヤンプが生じない膜厚寸法( 0.0
75μm以下)においては、面内方向及び垂直方向に対す
る抗磁力Hc ,Hc ⊥は低く、これより大なる膜厚寸
法( 0.075μm以上)においては垂直方向に対する抗磁
力Hc ⊥が急増する。これによつても磁化ジヤンプが生
じている場合、Co −Cr −Nb 薄膜に磁気特性の異な
る二層が形成されていることが推測される。First, paying attention to the coercive force Hc in the in-plane direction,
At 0.08 μm or less, the value is extremely small (150 Oe or less), and it is considered that the magnetic permeability in the in-plane direction is high. Further, the coercive force Hc does not change significantly even if the film thickness is large. Also, paying attention to the amount of magnetization jump σj, the amount of magnetization jump is 0.075
It sharply rises at μm and draws a smooth downward convex parabola shape at a film thickness of 0.075 μm or more. Still focusing on the vertical coercive force Hc ⊥, coercive force Hc ⊥ rises rapidly with thickness dimensions 0.05 micrometers to 0.1 [mu] m, 0.1 [mu] m
The above film thickness dimension shows a high coercive force of 900 Oe or more.
From these results, the boundary between the small grain size crystal layer and the large grain size crystal layer is almost
The thickness is 0.075 μm, and the thickness is 0.0
The small grain size crystal layer of 75 μm or less is a so-called low coercive force layer with low coercive force Hc and Hc ⊥ in the in -plane direction and the vertical direction, and the large grain size crystal layer of 0.075 μm or more is The coercive force Hc in the in-plane direction is low, but the coercive force Hc ⊥ in the vertical direction is very high, which is a so-called high coercive force layer, which is a layer suitable for perpendicular magnetic recording. Furthermore, the film thickness dimension (0.0
(75 μm or less), the coercive forces Hc and Hc ⊥ in the in-plane direction and the vertical direction are low, and the coercive force Hc ⊥ in the vertical direction sharply increases at larger film thicknesses (0.075 μm or more). Even if the magnetization jump occurs due to this, it is presumed that two layers having different magnetic properties are formed in the Co-Cr-Nb thin film.
次にCo −Cr に第三元素としてTa を添加(1〜10
at%添加範囲において同一現象が生ずる)し、上記した
Nb 添加した場合と同一の実験を行なつた結果を第7図
に示す。第7図はCo −Cr −Ta 薄膜の膜厚寸法をス
パツタリング時間を変えることにより制御し、各膜厚寸
法における面内方向の抗磁力Hc ,垂直方向の抗磁力
Hc ⊥,磁化ジヤンプ量σjを夫々描いたものである。
同図よりCo −Cr にTa を添加した場合も、Co −C
r にNb を添加した場合と略同様な結果が得られ、小粒
径結晶層と大粒径結晶層の境は略 0.075μmの膜厚寸法
のところにあり、膜厚寸法が 0.075μm以下の小粒径結
晶層は面内方向及び垂直方向に対する抗磁力Hc ,H
c ⊥が低い(Hc ,Hc ⊥共に170Oe 以下)、いわ
ゆる低抗磁力層となつており、また膜厚寸法が 0.075μ
m以上の大粒径結晶層は面内方向の抗磁力Hc は低い
ものの垂直方向に対する抗磁力Hc ⊥は非常に高い値
(750Oe以上)となつている。Next, Ta is added as a third element to Co-Cr (1 to 10).
The same phenomenon occurs in the range of addition of at%), and the results of the same experiment as in the case of adding Nb are shown in FIG. Figure 7 is controlled by varying the Supatsutaringu time the thickness dimensions of Co -Cr -Ta film, the coercive force Hc in the in-plane direction of each film thickness dimension, vertical coercive force Hc ⊥, the magnetization jump amount σj They are drawn respectively.
As shown in the figure, when Ta is added to Co-Cr, Co-C
Almost the same result as when Nb was added to r was obtained, and the boundary between the small grain size crystal layer and the large grain size crystal layer was at a film thickness dimension of about 0.075 μm. The small grain size crystal layer has coercive forces Hc and H in the in-plane and vertical directions.
Low c ⊥ (both Hc and Hc ⊥ 170Oe or less), so-called low coercive force layer, and thickness of 0.075μ.
m or more large crystal grain layer coercive force Hc ⊥ with respect to the vertical direction of the low coercive force Hc in the in-plane direction that is summer very high values (higher 750Oe).
なお上記実験で注意すべきことは、スパツタリング条件
及びNb ,Ta の添加量を前記した値(Nb :2〜10
at%,Ta :1〜10at%)より変えた場合磁化ジヤン
プは生じないが、しかるに磁化ジヤンプが生じないCo
−Cr −Nb 薄膜,Co −Cr −Ta 薄膜においても小
粒径結晶層及び大粒径結晶層が形成されていることであ
る(前記資料参照)。磁化ジヤンプが生じないCo −C
r −Nb 薄膜のヒステリシス曲線の一例を第8図に示
す。第8図(A)は小粒径結晶層及び大粒径結晶層を含
む面内方向のヒステリシス曲線であり、第8図(B)は
小粒径結晶層のみの面内方向のヒステリシス曲線,第8
図(C)は大粒径結晶層のみの面内方向のヒステリシス
曲線である。各図より小粒径結晶層の面内方向の残留磁
化Mr Bは大粒径結晶層の残留磁化Mr Cよりも大で
あるため、両結晶層を含む残留磁化Mr Aは大粒径結
晶層の残留磁化Mr Cのみの時よりも不利となり異方
性磁界Hk が小さくなる。また小粒径結晶層は配向が悪
いこと(Δθ50が大)が知られており、また面内方向の
抗磁力Hc も大で垂直磁気記録には適さない。It should be noted that in the above experiment, the spattering conditions and the amounts of Nb and Ta added are the above-mentioned values (Nb: 2 to 10).
At%, Ta: 1 to 10 at%), the magnetization jump does not occur, but the magnetization jump does not occur.
This means that the small grain size crystal layer and the large grain size crystal layer are also formed in the -Cr-Nb thin film and the Co-Cr-Ta thin film (see the above-mentioned reference). Magnetization jump does not occur Co-C
An example of the hysteresis curve of the r-Nb thin film is shown in FIG. FIG. 8 (A) is an in-plane direction hysteresis curve including a small grain size crystal layer and a large grain size crystal layer, and FIG. 8 (B) is an in-plane direction hysteresis curve of only the small grain size crystal layer, 8th
FIG. 6C is an in-plane hysteresis curve of only the large grain crystal layer. From each figure, the remanent magnetization Mr B in the in-plane direction of the small grain crystal layer is larger than the remanent magnetization Mr C of the large grain crystal layer, so the remanent magnetization Mr A including both crystal layers is the large grain crystal layer. Of the residual magnetization Mr C alone is more disadvantageous and the anisotropic magnetic field Hk becomes smaller. It is also known that the small grain crystal layer has a poor orientation (large Δθ50), and the coercive force Hc in the in-plane direction is also large, which is not suitable for perpendicular magnetic recording.
ここで上記の如く小粒径結晶層と大粒径結晶層を有する
Co −Cr −Nb 薄膜及びCo −Cr −Ta 薄膜を垂直
磁気記録媒体として考えた場合、Co −Cr −Nb 薄膜
及びCo −Cr −Ta 薄膜をその膜面に対し垂直方向に
膜厚の全てに亘つて垂直磁化を行なおうとすると、小粒
径結晶層の存在は垂直磁化に対し極めて不利な要因とな
る(磁化ジヤンプが生じている場合及び磁化ジヤンプが
生じていない場合の相方において不利な要因となる)。
すなわち磁化ジヤンプが生じている場合の小粒径結晶層
は、面内方向及び垂直方向に対する抗磁力Hc ,Hc
⊥が共に極めて低く(170Oe以下)、この層においては
垂直磁化はほとんどされないと考えられる。また磁化ジ
ヤンプが生じていない場合の小粒径結晶層においても、
面内方向の抗磁力Hc は磁化ジヤンプの生じている場
合の抗磁力Hc よりは大であるが垂直方向の抗磁力H
c ⊥は垂直磁気記録を実現し得る程の抗磁力はなくやは
り良好な垂直磁化は行なわれないと考えられる。従つて
膜面に対して垂直方向に磁化を行なつても小粒径結晶層
における垂直磁化はほとんど行なわれず、磁性膜全体と
しての垂直磁化効率が低下してしまう。この影響はリン
グコアヘツドのような磁束の面内成分を多く含む磁気ヘ
ツドにおいては顕著である。また膜厚寸法に注目するに
上記Co −Cr −Nb 薄膜及びCo −Cr −Ta 薄膜を
垂直磁気記録媒体として実用に足る膜厚寸法(約 0.3μ
m以下)にすると、小粒径結晶層の厚さ寸法は 0.1μm
以下で略一定であるため(実験においては小粒径及び大
粒径結晶層を含む膜厚寸法を小とすると小粒径結晶層の
厚さ寸法は若干大となる傾向を示す)、薄膜の膜厚寸法
に対する小粒径結晶層の相対的厚さ寸法が大となり更に
垂直磁化特性が劣化してしまう。When the Co-Cr-Nb thin film and the Co-Cr-Ta thin film having the small grain size crystal layer and the large grain size crystal layer as described above are considered as the perpendicular magnetic recording medium, the Co-Cr-Nb thin film and the Co- If the Cr-Ta thin film is to be perpendicularly magnetized in the direction perpendicular to the film surface over the entire film thickness, the existence of the small grain size crystal layer is a very disadvantageous factor for the perpendicular magnetization (the magnetization jump is It becomes a disadvantageous factor in the case where it occurs and the case where the magnetization jump does not occur).
That is, when the magnetization jump is generated, the small grain size crystal layer has coercive forces Hc and Hc in the in-plane direction and the vertical direction.
Both ⊥ are extremely low (170 Oe or less), and it is considered that perpendicular magnetization is scarcely done in this layer. Also in the small grain crystal layer when the magnetization jump does not occur,
The coercive force Hc in the in-plane direction is larger than the coercive force Hc in the case where the magnetization jump is generated, but the coercive force Hc in the vertical direction.
c⊥ does not have a coercive force enough to realize perpendicular magnetic recording, and it is considered that good perpendicular magnetization cannot be achieved. Therefore, even if the magnetization is performed in the direction perpendicular to the film surface, the perpendicular magnetization in the small grain crystal layer is hardly performed, and the perpendicular magnetization efficiency of the entire magnetic film is reduced. This effect is remarkable in a magnetic head such as a ring core head, which contains a large amount of in-plane components of magnetic flux. Also, paying attention to the film thickness, the Co-Cr-Nb thin film and the Co-Cr-Ta thin film can be practically used as a perpendicular magnetic recording medium (about 0.3 .mu.m).
m or less), the thickness dimension of the small grain crystal layer is 0.1 μm
Since it is almost constant below (in the experiment, when the film thickness dimension including the small grain size and large grain size crystal layers is made small, the thickness dimension of the small grain size crystal layer tends to be slightly large). The relative thickness dimension of the small grain size crystal layer with respect to the thickness dimension becomes large, and the perpendicular magnetization characteristic further deteriorates.
しかるに小粒径結晶層の磁気特性は、面内方向に対する
抗磁力Hc が小であり比較的高い透磁率を有してお
り、これは従来Co −Cr 薄膜とベース間に配設した裏
打ち層(例えばFe −Ni 薄膜)と似た特性を有してい
る。つまりCo −Cr −Nb 薄膜及びCo −Cr −Ta
薄膜の単一磁性膜において、低抗磁力Hc を有する小
粒径結晶層をいわゆる裏打ち層である高透磁率層として
用い、垂直方向に高抗磁力Hc ⊥を有する大粒径結晶層
を垂直磁化層として用いることにより単一膜構造におい
て二層膜構造の垂直磁気記録媒体と等しい機能を実現す
ることが可能であると考えられる。However, the magnetic characteristics of the small grain size crystal layer are such that the coercive force Hc in the in-plane direction is small and the magnetic permeability is relatively high, which is due to the backing layer (conventionally disposed between the Co-Cr thin film and the base). For example, Fe-Ni thin film) has similar characteristics. That is, Co-Cr-Nb thin film and Co-Cr-Ta
In a single thin magnetic film, a small grain size crystal layer having a low coercive force Hc is used as a so-called backing layer having a high magnetic permeability, and a large grain size crystal layer having a high coercive force Hc ⊥ in the vertical direction is perpendicularly magnetized. It is considered that by using it as a layer, it is possible to realize the same function in a single film structure as in a perpendicular magnetic recording medium having a double layer structure.
この点に鑑み、Co −Cr −Nb 薄膜及びCo −Cr −
Ta 薄膜の組成率を変化させた場合、各薄膜の厚さ寸法
を変化させた場合における磁気特性の変化及び再生出力
の相異を第9図から第16図を用いて以下説明する。第
9図はCo −Cr −Nb 薄膜の組成率を変化させた場合
における各種磁気特性を示す図で、第10図及び第11
図は第9図に示した各薄膜に垂直磁気記録再生を行なつ
た時の記録波長と再生出力の関係を示したものである。
なお第9図に示した各薄膜を区別して第10図及び第1
1図に示すのに、第9図の左端に記載したNo.を第10
図,第11図に付することにより区別した。第9図より
Co −Cr に第三元素としてNb またはTa を添加した
際、磁化ジヤンプが生じている時は垂直磁化に寄与する
垂直方向の抗磁力Hc ⊥は高い値となるが磁化ジヤンプ
が生じていない時は抗磁力Hc ⊥は低い値となつてい
る。また磁化ジヤンプが生じている時は垂直異方性磁界
Hk が小さく、Mr /Ms はCo −Cr 薄膜に比べて
大であるこれは面内方向に磁束分布が大であるリングコ
アヘツドを用いる際不利な条件と考えられていた。しか
るに上記各Co −Cr −Nb 及びCo −Cr Ta 薄膜
(以下Co −Cr −Nb 薄膜とCo −Cr −Ta 薄膜を
総称する場合Co −Cr −Nb (Ta )薄膜という)を
垂直磁気記録媒体として用いた際の記録波長−再生出力
特性(第10図及び第11図に示す)を見ると、磁化ジ
ヤンプが生じているCo −Cr −Nb (Ta )薄膜の再
生出力の方が磁化ジヤンプの生じていないCo −Cr −
Nb 薄膜及びCo −Cr 薄膜の再生出力よりも良好とな
つており、特に記録波長の短波長領域において顕著であ
る。短波長領域(記録波長が 0.2μm〜 1.0μm程度の
領域)においてはCo −Cr 薄膜及び磁化ジヤンプの生
じていないCo −Cr −Nb 薄膜においても再生出力は
増加している。しかるに磁化ジヤンプの生じているCo
−Cr Nb (Ta )薄膜は、上記各薄膜の再生出力増加
率に対して、それよりも高い再生出力増加率を示してお
り、磁化ジヤンプの生じているCo −Cr −Nb (Ta
)薄膜は特に記録波長の垂直磁化に適しているという
ことができる。特にNo.III,IVに示すCo −Cr −Nb
薄膜においては第9図に示す如く、磁化ジヤンプが生
じていないNo.V,VIに示す薄膜に対して飽和磁化Ms
が100emu/cc以上も小さいにもかかわらず、短波長領域
における出力特性が良好である。上記短波長領域におい
ては再生出力曲線は上に凸の放物線形状をとるが、その
全域において磁化ジヤンプの生じているCo −Cr −N
b 薄膜はCo −Cr 薄膜及び磁化ジヤンプの生じていな
いCo −Cr −Nb 薄膜より大なる再生出力を得ること
ができた。In view of this point, Co-Cr-Nb thin film and Co-Cr-
The change in magnetic characteristics and the difference in reproduction output when the composition ratio of the Ta thin film is changed and the thickness of each thin film is changed will be described below with reference to FIGS. 9 to 16. FIG. 9 is a diagram showing various magnetic characteristics when the composition ratio of the Co-Cr-Nb thin film is changed.
The figure shows the relationship between the recording wavelength and the reproduction output when perpendicular magnetic recording / reproduction is performed on each thin film shown in FIG.
It should be noted that the thin films shown in FIG.
As shown in FIG. 1, the No. described at the left end of FIG.
They are distinguished by attaching them to FIG. 11 and FIG. From FIG. 9, when Nb or Ta is added as a third element to Co-Cr, when the magnetization jump is generated, the coercive force Hc ⊥ in the vertical direction that contributes to the perpendicular magnetization has a high value, but the magnetization jump is generated. When not, the coercive force Hc ⊥ is low. Further, the perpendicular anisotropic magnetic field Hk is small when the magnetization jump is generated, and Mr / Ms is larger than that of the Co-Cr thin film. This is disadvantageous when using a ring core head having a large magnetic flux distribution in the in-plane direction. Was considered to be a condition. However, the above Co-Cr-Nb and Co-Cr Ta thin films (hereinafter Co-Cr-Nb thin films and Co-Cr-Ta thin films are collectively referred to as Co-Cr-Nb (Ta) thin films) are used as perpendicular magnetic recording media. Looking at the recording wavelength-reproduction output characteristics (shown in FIGS. 10 and 11) when used, the reproduction output of the Co-Cr-Nb (Ta) thin film in which the magnetization jump has occurred is more likely to cause the magnetization jump. Not Co-Cr-
It is better than the reproduction output of the Nb thin film and the Co-Cr thin film, and is particularly remarkable in the short wavelength region of the recording wavelength. In the short wavelength region (the recording wavelength is in the range of 0.2 μm to 1.0 μm), the reproduction output is increased even in the Co-Cr thin film and the Co-Cr-Nb thin film in which the magnetization jump is not generated. However, the Co that has a magnetic jump
The -CrNb (Ta) thin film shows a higher reproduction output increase rate than the reproduction output increase rate of each of the above-mentioned thin films, and Co-Cr-Nb (Ta) where the magnetization jump occurs.
It can be said that the thin film is particularly suitable for perpendicular magnetization at the recording wavelength. In particular, Co-Cr-Nb shown in Nos. III and IV
As shown in FIG. 9, in the thin film, the saturation magnetization Ms was obtained for the thin films shown in No. V and VI in which no magnetization jump was generated.
Is as low as 100 emu / cc or more, the output characteristics are good in the short wavelength region. In the above short wavelength region, the reproduction output curve has a parabolic shape that is convex upward, but Co-Cr-N in which the magnetization jump is generated in the entire region.
The b thin film was able to obtain a larger reproduction output than the Co-Cr thin film and the Co-Cr-Nb thin film in which no magnetization jump occurred.
上述の如く、短波長領域における出力特性の向上は磁化
ジヤンプの発生に起因していると考えられる。磁化ジヤ
ンプが生じている磁性層に形成される小粒径結晶層の面
内方向の抗磁力Hc は、磁化ジヤンプの生じていない
磁性層に形成された小粒径結晶層の抗磁力Hc より小
である。As described above, it is considered that the improvement of the output characteristics in the short wavelength region is caused by the occurrence of the magnetization jump. The coercive force Hc in the in-plane direction of the small grain crystal layer formed in the magnetic layer having the magnetization jump is smaller than the coercive force Hc of the small grain crystal layer formed in the magnetic layer having no magnetization jump. Is.
ここで大粒径結晶層の垂直方向の抗磁力Hc ⊥に対する
小粒径結晶層の面内方向の抗磁力Hc の比 (以下この比 を抗磁力比という)に注目する。第9図に示す如く磁化
ジヤンプの生じている磁性層を有する薄膜は抗磁力比 の値が1/5以下となつている。しかるに磁化ジヤンプ
の生じていない磁性層を有する薄膜においては、抗磁力
比 の値が1/ 1.6程度の大なる値となつている。本発明者
の実験によれば、磁化ジヤンプが発生する抗磁力比 の上限値は1/5近傍の値であると思われる。また一般
に垂直磁気記録再生を行なうに適当な垂直磁化層の垂直
方向の抗磁力Hc ⊥は約 1500 Oe 程度までであり、ま
た磁化ジヤンプの発生している小粒径結晶層がいわゆる
裏打ち層として適宜に機能する面内方向の抗磁力Hc
は平均して 30 Oe 程度であると考えられるため抗磁力
比 の下限値は1/50近傍の値であると思われる。すなわ
ち磁性層を形成する際、抗磁力比 の値が となるよう選定することにより、磁化ジヤンプが生じ
る、従つて短波長領域において特に再生出力の良好な垂
直磁気記録媒体を実現することができる。なお抗磁力比 の値は、磁性材の組成率を変化させることにより、また
スパツタリング条件を適宜選定することにより調整する
ことが可能である。Here, the ratio of the coercive force Hc in the in-plane direction of the small grain crystal layer to the vertical coercive force Hc ⊥ of the large grain crystal layer. (Hereafter this ratio Is called the coercive force ratio). As shown in FIG. 9, a thin film having a magnetic layer in which a magnetization jump is generated has a coercive force ratio. The value of is less than 1/5. However, in a thin film having a magnetic layer with no magnetic jump, the coercive force ratio The value of is as large as about 1 / 1.6. According to the experiment by the present inventor, the coercive force ratio at which the magnetization jump occurs It seems that the upper limit value of is about 1/5. Generally, the perpendicular coercive force Hc ⊥ of the perpendicular magnetic layer suitable for performing perpendicular magnetic recording and reproduction is up to about 1500 Oe, and the small grain crystal layer in which the magnetization jump occurs is appropriately used as a so-called backing layer. In-plane coercive force Hc
Is considered to be about 30 Oe on average, so the coercive force ratio It seems that the lower limit value of is around 1/50. That is, when forming the magnetic layer, the coercive force ratio The value of By selecting such a value, it is possible to realize a perpendicular magnetic recording medium in which a magnetization jump occurs, and thus a reproduction output is particularly good in a short wavelength region. Coercive force ratio The value of can be adjusted by changing the composition ratio of the magnetic material and by appropriately selecting spattering conditions.
次に磁化ジヤンプが発生している磁性層において、再生
出力が向上する理由を以下説明する。Next, the reason why the reproduction output is improved in the magnetic layer in which the magnetization jump is generated will be described below.
Co −Cr −Nb (Ta )薄膜はスパツタリングによる
磁性層の薄膜形成時に第12図に示す如くベース1近傍
に低抗磁力を有する小粒径結晶層2とその上方に特に垂
直方向に高い抗磁力を有する大粒径結晶層3と二層構造
を形成し、かつ各層2,3の抗磁力比 の値は となるように選定されていため、各層2,3より形成さ
れる磁性層は磁化ジヤンプの生じた磁性層となる。よつ
て、磁気ヘツド4から放れた磁束線は大粒径結晶層3を
貫通して小粒径結晶層2に到り、低抗磁力でかつ高透磁
率を有する小粒径結晶層2内で磁束は面内方向に進行
し、磁気ヘツド4の磁極部分で急激に磁束が吸い込まれ
ることにより大粒径結晶層3に垂直磁化がされると考え
られる。よつて磁束が形成する磁気ループは第12図に
矢印で示す如く、馬蹄形状となり所定垂直記録位置にお
いて大粒径結晶層3に磁束が鋭く貫通するため、大粒径
結晶層3には残留磁化の大なる垂直磁化が行なわれる。
ここで磁化ジヤンプが生じている場合と生じていない場
合における小粒径結晶層2の面内方向の抗磁力Hc に
注目すると、第9図に示される如く磁化ジヤンプが生じ
ている場合の面内方向の抗磁力Hc は磁化ジヤンプが
生じていない場合の抗磁力Hc より小なる値となつて
いる。周知の如く小粒径結晶層2がいわゆる裏打ち層と
して機能するためには抵抗磁力,高透磁率を有すること
が望ましく、よつて磁化ジヤンプの生じているCo −C
r −Nb (Ta )薄膜の方が再生出力が良好であると推
測される。また小粒径結晶層2は、その有する抗磁力H
c が完全にゼロではなく所定の抗磁力は有しているた
め、この抗磁力に対応する磁化を行なうことができる。
垂直磁気記録が行なわれると大粒径結晶層3には第14
図に示す如く所定ビツト間隔に対応し磁化方向を逆にし
た複数の磁石が交互に形成される。そして、この形成さ
れた複数の磁石下端部の小粒径結晶層2には、相隣接し
て形成された磁石の上記下端部を連通する磁束(第14
図中矢印で示す)が形成されこれが磁化される。これに
より各隣接する磁石の減磁作用はなくなり、特にこの現
象は各隣接する磁石の密度の高い、すなわち記録波長の
小なる垂直磁気記録において顕著であるため短波長領域
における再生出力を増加させることができる。更にCo
−Cr −Nb (Ta )薄膜の膜厚寸法に注目すると、膜
厚寸法を大とすることは大粒径結晶層3の厚さ寸法を大
とすることであり(小粒径結晶層2の厚さ寸法は略一定
である)、これを大とすることにより磁気ヘツド4と小
粒径結晶層2の距離が大となり、小粒径結晶層2による
磁束の吸込み効果はわずかで第13図に矢印で示す如く
磁気ヘツド4から放れた磁力線は小粒径結晶層2に到る
ことなく大粒径結晶層3を横切つて磁気ヘツド4の磁極
に吸い込まれる。従つて垂直方向に対する磁化は分散さ
れた弱いものとなり良好な垂直磁化は行なわれない。し
かるにCo −Cr −Nb (Ta )薄膜の膜厚寸法を小と
すると、磁気ヘツド4と小粒径結晶層2の距離が小とな
り、小粒径結晶層2による磁束の吸込み効果が大となり
磁気ヘツド4から放れた磁束は小粒径結晶層2に確実に
進行し上記馬蹄形の磁気ループを形成する。即ち、垂直
磁化に寄与する磁束は馬蹄形の極めて鋭い磁界であるの
で残留磁化は大となり良好な垂直磁化が行なわれると考
えられる。すなわちCo −Cr −Nb (Ta )薄膜の膜
厚寸法を小とした方が(記録媒体の厚さを薄くした方
が)良好な垂直磁化を行なうことができ、これにより磁
気ヘツド4とのいわゆる当たりの良好な薄い記録媒体を
実現することができる(本発明者の実験によると膜厚寸
法が 0.1μm〜 0.3μm程度の寸法まで高出力を保持で
きた)。これに加えて上記の如く高抗磁力を有する層と
低抗磁力を有する層を形成するCo −Cr −Nb (Ta
)薄膜は連続スパツタリングにより形成されるため、
二層構造を形成させるためにわざわざスパツタリング条
件を変えたりターゲツトを取換える作業等は不用でCo
−Cr −Nb (Ta )薄膜の形成工程を容易にし得ると
共にスパツタリング時間を短くし得、低コストでかつ量
産性をもつて垂直磁気記録媒体を製造することができ
る。更に抗磁力比 の値は に選定されており小粒径結晶層2の面内方向の抗磁力H
c は大粒径結晶層3の抗磁力Hc ⊥に対して極端に小
なる値ではないため衝撃性のバルクハウゼンノイズが発
生することもなく良好な垂直磁気記録再生を行ない得
る。The Co-Cr-Nb (Ta) thin film has a small grain size crystal layer 2 having a low coercive force in the vicinity of the base 1 and a high coercive force particularly in the vertical direction above the base layer 1 as shown in FIG. 12 when the magnetic layer is formed by sputtering. Forming a two-layer structure with a large grain crystal layer 3 having The value of Therefore, the magnetic layer formed by the layers 2 and 3 is a magnetic layer in which a magnetic jump is generated. Therefore, the magnetic flux lines emitted from the magnetic head 4 reach the small grain size crystal layer 2 through the large grain size crystal layer 3, and within the small grain size crystal layer 2 having low coercive force and high magnetic permeability. It is considered that the magnetic flux travels in the in-plane direction and is abruptly absorbed by the magnetic pole portion of the magnetic head 4 so that the large grain crystal layer 3 is perpendicularly magnetized. Therefore, the magnetic loop formed by the magnetic flux has a horseshoe shape as shown by an arrow in FIG. 12, and the magnetic flux sharply penetrates through the large grain crystal layer 3 at a predetermined perpendicular recording position. A large perpendicular magnetization is performed.
Here, focusing on the coercive force Hc in the in-plane direction of the small grain crystal layer 2 with and without the magnetization jump, the in-plane with the magnetization jump as shown in FIG. 9 is obtained. The coercive force Hc in the direction is smaller than the coercive force Hc when the magnetization jump is not generated. As is well known, in order for the small grain size crystal layer 2 to function as a so-called backing layer, it is desirable that it has a resistance magnetic force and a high magnetic permeability, and thus Co-C in which a magnetization jump occurs.
It is presumed that the r-Nb (Ta) thin film has a better reproduction output. The small grain size crystal layer 2 has a coercive force H
Since c is not completely zero and has a predetermined coercive force, the magnetization corresponding to this coercive force can be performed.
When perpendicular magnetic recording is performed, the large grain crystal layer 3 has a 14th
As shown in the figure, a plurality of magnets corresponding to a predetermined bit interval and having opposite magnetization directions are alternately formed. Then, to the small grain size crystal layers 2 at the lower ends of the formed magnets, the magnetic flux (the 14th
(Indicated by an arrow in the figure) is formed and this is magnetized. As a result, the demagnetizing action of each adjacent magnet is eliminated, and this phenomenon is particularly noticeable in perpendicular magnetic recording where the density of each adjacent magnet is high, that is, the recording wavelength is small, so increase the reproduction output in the short wavelength region. You can Further Co
Focusing on the film thickness dimension of the -Cr-Nb (Ta) thin film, increasing the film thickness dimension means increasing the thickness dimension of the large grain crystal layer 3 (the small grain crystal layer 2). (The thickness dimension is substantially constant.) By increasing this, the distance between the magnetic head 4 and the small grain crystal layer 2 becomes large, and the effect of absorbing the magnetic flux by the small grain crystal layer 2 is slight, and FIG. The magnetic force lines emitted from the magnetic head 4 as shown by the arrows cross the large grain crystal layer 3 without reaching the small grain crystal layer 2 and are drawn into the magnetic poles of the magnetic head 4. Therefore, the magnetization in the perpendicular direction becomes dispersed and weak, and good perpendicular magnetization cannot be performed. However, if the film thickness of the Co-Cr-Nb (Ta) thin film is made small, the distance between the magnetic head 4 and the small grain crystal layer 2 becomes small, and the effect of absorbing the magnetic flux by the small grain crystal layer 2 becomes large, and The magnetic flux emitted from the head 4 surely advances to the small grain crystal layer 2 to form the horseshoe-shaped magnetic loop. That is, since the magnetic flux that contributes to the perpendicular magnetization is a horseshoe-shaped extremely sharp magnetic field, it is considered that the residual magnetization becomes large and good perpendicular magnetization is performed. That is, the smaller the thickness of the Co-Cr-Nb (Ta) thin film is (the thinner the recording medium is), the better the perpendicular magnetization can be performed. It is possible to realize a thin recording medium having a good hit (according to the experiments of the present inventor, high output can be maintained up to a thickness of about 0.1 μm to 0.3 μm). In addition to this, Co-Cr-Nb (Ta which forms a layer having a high coercive force and a layer having a low coercive force as described above
) Since the thin film is formed by continuous sputtering,
It is unnecessary to change the spattering conditions or change the target in order to form a two-layer structure.
The step of forming a -Cr-Nb (Ta) thin film can be facilitated, the sputtering time can be shortened, and the perpendicular magnetic recording medium can be manufactured at low cost and with mass productivity. Further coercive force ratio The value of The coercive force H in the in-plane direction of the small grain crystal layer 2 is selected as
Since c is not an extremely small value with respect to the coercive force Hc ⊥ of the large-grain-diameter crystal layer 3, good perpendicular magnetic recording / reproduction can be performed without generating shocking Barkhausen noise.
発明の効果 上述の如く本発明になる垂直磁気記録媒体によれば、上
層と下層とにより形成された磁性層を有する垂直磁気記
録媒体の、上記上層の垂直方向の抗磁力をHc ⊥とし、
下層の面内方向の抗磁力をHc とした際、比 の値が となるよう選定することにより、垂直磁気記録媒体の有
する磁性層は磁化ジヤンプを有する磁性層となり磁気ヘ
ツドより放れた磁束は容易に低抗磁力を有する下層に進
入した水平方向へ進行した後磁気ヘツドの磁極にて急激
にかつ鋭く高抗磁力を有する上層を貫通して磁気ヘツド
の磁極に吸い込まれるため、上層には強い残留磁化が生
じ高い再生出力を実現し得る垂直磁気記録再生を行なう
ことができ、これに加え記録波長が短い時に特にすぐれ
た垂直磁化が行なわれ良好な再生出力を得ることがで
き、また下層は磁化ジヤンプが生じている、すなわち面
内方向に対する抗磁力が小で、かつ高透磁率を有する層
であるため、いわゆる裏打ち層として確実に機能すると
共にその抗磁力は上層の抗磁力に対して極端に小なる値
ではないため衝撃性のバルクハウゼンノイズが発生する
こともなく良好な垂直磁気記録再生を行うことが、でき
ると等の特長を有する。As described above, according to the perpendicular magnetic recording medium of the present invention, in the perpendicular magnetic recording medium having the magnetic layer formed by the upper layer and the lower layer, the coercive force of the upper layer in the vertical direction is Hc ⊥ ,
When the coercive force in the in-plane direction of the lower layer is Hc, The value of By selecting so that the magnetic layer of the perpendicular magnetic recording medium becomes a magnetic layer having a magnetization jump, the magnetic flux emitted from the magnetic head easily enters the lower layer having a low coercive force and then advances in the horizontal direction, and then the magnetic head. Since the magnetic pole of the magnetic field rapidly penetrates the upper layer having a high coercive force and is absorbed by the magnetic pole of the magnetic head, perpendicular magnetic recording and reproduction capable of achieving high reproduction output can be performed due to strong residual magnetization in the upper layer. In addition to this, especially when the recording wavelength is short, particularly excellent perpendicular magnetization is performed and a good reproduction output can be obtained, and the lower layer has a magnetization jump, that is, the coercive force in the in-plane direction is small, and Since it is a layer with high magnetic permeability, it reliably functions as a so-called backing layer and its coercive force is not extremely small compared to the coercive force of the upper layer, so it has impact resistance. The Barkhausen noise perform good perpendicular magnetic recording reproducing without occur has the features of equal if possible.
第1図は本発明になる垂直磁気記録媒体の一実施例の磁
性膜であるCo −Cr −Nb 薄膜のヒステリシス曲線を
示す図、第2図は小粒径結晶層のヒステリシス曲線を示
す図、第3図から第5図は磁化ジヤンプが生ずる理由を
説明するための図、第6図はCo −Cr −Nb 薄膜が二
層構造となつていること及び各層の磁気特性を示す図、
第7図はCo −Cr −Ta 薄膜が二層構造となつている
こと及び各層の磁気特性を示す図、第8図は磁化ジヤン
プが生じていないCo −Cr −Nb の薄膜のヒステリシ
ス曲線の一例を示す図、第9図は磁化ジヤンプが生じて
いるCo −Cr −Nb 薄膜及びCo −Cr −Ta 薄膜に
おける各種磁気特性を磁化ジヤンプの生じていないCo
−Cr −Nb 薄膜及びCo −Cr 薄膜の磁気特性と比較
して示す図、第10図及び第11図は第9図に示した各
薄膜に垂直磁気記録再生を行なつた時の記録波長と再生
出力の関係を示す図、第12図は本発明記録媒体の厚さ
寸法を小とした場合に磁束が形成する磁気ループを示す
図、第13図は本発明記録媒体の厚さ寸法を大とした場
合に磁束が形成する磁気ループを示す図、第14図は小
粒径結晶層に形成され大粒径結晶層に磁化形成された複
数の磁石の下端部間を連通する磁束を説明するための図
である。 1……ベース、2……小粒径結晶層、3……大粒径結晶
層、4……磁気ヘツド。FIG. 1 is a diagram showing a hysteresis curve of a Co--Cr--Nb thin film which is a magnetic film of one embodiment of a perpendicular magnetic recording medium according to the present invention, and FIG. 2 is a diagram showing a hysteresis curve of a small grain crystal layer, 3 to 5 are views for explaining the reason why the magnetization jump occurs, and FIG. 6 is a view showing that the Co-Cr-Nb thin film has a two-layer structure and the magnetic characteristics of each layer,
FIG. 7 is a diagram showing that the Co-Cr-Ta thin film has a two-layer structure and the magnetic characteristics of each layer, and FIG. 8 is an example of the hysteresis curve of the Co-Cr-Nb thin film in which no magnetization jump occurs. And FIG. 9 show various magnetic characteristics of the Co-Cr-Nb thin film and the Co-Cr-Ta thin film in which the magnetization jump is generated, and Co in which the magnetization jump is not generated.
-Compared with the magnetic characteristics of the -Cr-Nb thin film and the Co-Cr thin film, FIGS. 10 and 11 show the recording wavelength when perpendicular magnetic recording and reproduction were performed on each thin film shown in FIG. FIG. 12 is a diagram showing a relationship of reproduction output, FIG. 12 is a diagram showing a magnetic loop formed by magnetic flux when the thickness dimension of the recording medium of the present invention is small, and FIG. 13 is a thickness dimension of the recording medium of the present invention being large. FIG. 14 is a diagram showing a magnetic loop formed by a magnetic flux in the above case, and FIG. 14 illustrates the magnetic flux that communicates between the lower end portions of a plurality of magnets formed in the small grain size crystal layer and magnetized in the large grain size crystal layer. FIG. 1 ... Base, 2 ... Small grain crystal layer, 3 ... Large grain crystal layer, 4 ... Magnetic head.
フロントページの続き (72)発明者 今岡 英一郎 神奈川県横浜市神奈川区守屋町3丁目12番 地 日本ビクター株式会社内 (56)参考文献 特開 昭60−21507(JP,A) 特開 昭59−98321(JP,A) 特開 昭60−101710(JP,A)Front Page Continuation (72) Inventor Eiichiro Imaoka 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Company of Japan (56) References JP-A-60-21507 (JP, A) JP-A-59- 98321 (JP, A) JP-A-60-101710 (JP, A)
Claims (1)
する垂直磁気記録媒体であつて、該上層の垂直方向の抗
磁力をHc ⊥とし、該下層の面内方向の抗磁力をHc
とすると、比 の値が であるよう選定されていることを特徴とする垂直磁気記
録媒体。1. A perpendicular magnetic recording medium having a magnetic layer formed of an upper layer and a lower layer, wherein the coercive force of the upper layer in the vertical direction is Hc ⊥ and the coercive force of the lower layer in the in-plane direction is Hc.
Then, the ratio The value of A perpendicular magnetic recording medium characterized by being selected as follows.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP13219285A JPH0628091B2 (en) | 1985-06-18 | 1985-06-18 | Perpendicular magnetic recording medium |
US06/834,236 US4731300A (en) | 1985-03-07 | 1986-02-26 | Perpendicular magnetic recording medium and manufacturing method thereof |
DE19863607500 DE3607500A1 (en) | 1985-03-07 | 1986-03-07 | CROSS-MAGNETIZING RECORDING MEDIUM AND METHOD FOR PRODUCING A CROSS-MAGNETIZING RECORDING MEDIUM |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP13219285A JPH0628091B2 (en) | 1985-06-18 | 1985-06-18 | Perpendicular magnetic recording medium |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS61292220A JPS61292220A (en) | 1986-12-23 |
JPH0628091B2 true JPH0628091B2 (en) | 1994-04-13 |
Family
ID=15075544
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP13219285A Expired - Lifetime JPH0628091B2 (en) | 1985-03-07 | 1985-06-18 | Perpendicular magnetic recording medium |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH0628091B2 (en) |
-
1985
- 1985-06-18 JP JP13219285A patent/JPH0628091B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JPS61292220A (en) | 1986-12-23 |
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