JP2004335068A - Perpendicular magnetic recording medium, its manufacturing method, and perpendicular magnetic recording/reproducing device - Google Patents
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Abstract
Description
本発明は、垂直磁気記録媒体、その製造方法、及び垂直磁気記憶装置に関し、特に、基板に垂直方向に磁化容易軸が配向する磁化膜を記録層にもつ垂直磁気記録媒体に関する。 The present invention relates to a perpendicular magnetic recording medium, a method for manufacturing the same, and a perpendicular magnetic storage device, and more particularly to a perpendicular magnetic recording medium having a recording layer having a magnetization film whose easy axis is oriented in a direction perpendicular to a substrate.
実用に供されている磁気記録方式は、基板面に平行な方向に磁化容易軸をもつ磁性膜を利用した長手記録方式である。しかしながら、この方式では、信号の源となる隣り合った磁区の磁化方向が反対方向となり、互いに反発し合い弱め合うので、高密度記録になるとその弊害が露呈してくる。 The magnetic recording method used in practice is a longitudinal recording method using a magnetic film having an easy axis of magnetization in a direction parallel to the substrate surface. However, in this method, the magnetization directions of adjacent magnetic domains serving as signal sources are opposite to each other, and repel each other and weaken each other.
更に、高密度化を可能とするためには磁区を構成する磁性粒子を微細化することが不可欠となるが、その微細化に伴う磁性粒子の体積減少が起因となって発現する熱擾乱による減磁効果が無視できなくなり、熱安定性が劣化してくる。 Furthermore, it is indispensable to reduce the size of the magnetic particles constituting the magnetic domain in order to enable high density, but the reduction due to thermal disturbance that occurs due to the reduction in the volume of the magnetic particles accompanying the reduction in size. The magnetic effect cannot be ignored and thermal stability deteriorates.
高密度記録化に伴うその弊害を回避できる方法として、一例として、大きな磁気異方性エネルギーＫｕをもつ磁性体を基板面の垂直方向に磁化容易軸を配向させた磁性膜を利用した垂直磁気記録方式が試行されている。この方式では、隣り合って反対方向に向いている磁化が静磁気学エネルギー的に有利となるので安定し、高密度になればなるほどその特長が顕著になる。また、反対方向に磁化されている隣り合った磁区が静磁気学エネルギーに関して有利に安定する。 As a method of avoiding the adverse effects associated with high-density recording, as an example, perpendicular magnetic recording using a magnetic film having a magnetic material having a large magnetic anisotropic energy Ku with an easy axis of magnetization oriented in the direction perpendicular to the substrate surface. The method is being tried. In this method, adjacent magnetizations directed in opposite directions are advantageous in terms of magnetostatic energy, so that they are stable. The higher the density, the more remarkable their features. Also, adjacent magnetic domains magnetized in opposite directions are advantageously stable with respect to magnetostatic energy.
一般に、磁気記録層に信号を書き込むためには、磁気ヘッドから漏れてくる磁界により磁気記録層の磁区中の磁性粒子を飽和磁化しなければならないが、長手記録方式ではそれを完全に行うためには磁気記録層をなるべく薄くした方がよいことが知られている。 Generally, in order to write a signal to the magnetic recording layer, the magnetic particles in the magnetic domain of the magnetic recording layer must be saturated with the magnetic field leaking from the magnetic head. It is known that it is better to make the magnetic recording layer as thin as possible.
これに対して垂直磁気記録方式では、垂直磁気記録層の下に高飽和磁束密度を有する軟磁性膜を付与した重畳型媒体と単磁極ヘッドを用いれば、下地膜となる軟磁性膜が磁気ヘッドから漏洩した磁界を強力に引き込み更に磁気ヘッドに戻す役割を担うことになり、磁気記録層を薄くしなくとも磁気記録層の飽和記録が容易となる。 On the other hand, in the perpendicular magnetic recording method, if a single-pole head and a superposition type medium having a soft magnetic film having a high saturation magnetic flux density provided under the perpendicular magnetic recording layer are used, the soft magnetic film serving as an underlayer becomes a magnetic head. The magnetic recording layer has a role of strongly drawing in the magnetic field leaked from the magnetic recording layer and returning the magnetic field to the magnetic head, thereby facilitating the saturation recording of the magnetic recording layer without making the magnetic recording layer thin.
上述した軟磁性膜には、高透磁率かつ高飽和磁束密度のものが好ましいが、一般的には軟磁性膜自体には磁壁が生じてしまうために磁壁移動や磁壁の揺らぎによるスパイクノイズの発生、及び外部浮遊磁界による磁壁移動に起因する記録の消磁、減磁等の記録磁化が不安定になる等の問題があった（例えば、特許文献１、特許文献２、特許文献３、特許文献４、非特許文献１、非特許文献２参照。）。
The soft magnetic film described above preferably has a high magnetic permeability and a high saturation magnetic flux density. However, in general, a domain wall is generated in the soft magnetic film itself, and thus spike noise is generated due to domain wall movement or domain wall fluctuation. And the recording magnetization becomes unstable such as demagnetization and demagnetization of the recording due to domain wall movement caused by an external floating magnetic field (for example, Patent Document 1,
さらに、特許文献５にはめっき法による縞状磁区についての記載がされており垂直磁化膜について作製方法が記載されているが、無電解めっき法により作製した薄膜においては、基板に対して垂直方向に磁化容易軸を有する薄膜作製の報告はなく、また、一般には基板に対し平行方向に磁化容易軸が形成されやすい。
尚、本発明で言う下地膜は一般的に述べられる磁性膜の下地膜のことではなく、通常、裏打ち層（膜）と称されるもののことを指す。
Further,
It should be noted that the underlayer referred to in the present invention does not refer to the underlayer of the magnetic film generally described, but refers to what is usually called a backing layer (film).
本発明は、上記事情に鑑みなされたものであり、磁壁の発生が無く、低ノイズの下地膜を有する垂直磁気記録媒体を提供することにある。 SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a perpendicular magnetic recording medium having no low-noise underlayer and no domain wall.
本発明者は、上記目的を達成するため鋭意検討を重ねた結果、非磁性基板上に金属核又はシード層が形成され、その上に無電解メッキ法により形成された、例えばリン（Ｐ）またはホウ素（Ｂ）を含有する軟磁性膜であること、さらにこの軟磁性膜の磁気特性が、特に、基板の面内方向においては磁気的に等方性であること、あるいは基板の垂直方向に磁化容易軸を有するものであれば磁壁に関連する上記課題を解決する事を見い出し、本発明をなすに至った。即ち本発明は以下に関する。
（１）非磁性基板上に、少なくとも、軟磁性材料からなる軟磁性下地膜と、直上の膜の配向性を制御する配向制御膜と、磁化容易軸が基板に対し主に垂直に配向した垂直磁性膜と、保護層が設けられた垂直磁気記録媒体であって、前記軟磁性下地膜が磁気的に等方性を示すことを特徴とする垂直磁気記録媒体。
（２）軟磁性下地膜が基板の面内方向において磁気的に等方性を示すことを特徴とする（１）に記載の垂直磁気記録媒体。
（３）軟磁性下地膜を円盤状非磁性基板に形成した際に、その円周方向のＨｓ（飽和磁束密度測定時に得られる印加磁界の最低強度）と半径方向のＨｓの比率＝等方性度が、１．０±０．２以内であることを特徴とする（１）または（２）に記載の垂直磁気記録媒体。
（４）非磁性基板上に、少なくとも、軟磁性材料からなる軟磁性下地膜と、直上の膜の配向性を制御する配向制御膜と、磁化容易軸が基板に対し主に垂直に配向した垂直磁性膜と、保護層が設けられた垂直磁気記録媒体であって、前記軟磁性下地膜が基板に対して垂直方向に磁化容易軸を有すことを特徴とする垂直磁気記録媒体。
（５）軟磁性下地膜の垂直磁気異方性の異方性磁界（Ｈｋ）が３９５Ａ／ｍ〜３９５０Ａ／ｍ（５Ｏｅ〜５０Ｏｅ）の範囲内であることを特徴とする（４）に記載の垂直磁気記録媒体。
（６）軟磁性下地膜の飽和磁束密度（Ｂｓ）が、０．２Ｔ〜１．７Ｔの範囲内であること特徴とする（１）〜（５）の何れか１項に記載の垂直磁気記録媒体。
（７）軟磁性下地膜の結晶粒子径が、５ｎｍ以下の微結晶もしくはアモルファス構造であることを特徴とする（１）〜（６）の何れか１項に記載の垂直磁気記録媒体。
（８）磁性下地膜の膜厚が、５０ｎｍ〜５０００ｎｍの範囲内であることを特徴とする（１）〜（７）の何れか１項に記載の垂直磁気記録媒体。
（９）軟磁性下地膜の垂直磁気記録層を積層する側の平均面粗さＲａが、０．８ｎｍ以下であることを特徴とする（１）〜（８）の何れか１項に記載の垂直磁気記録媒体。
（１０）軟磁性下地膜が、リンを含むことを特徴とする（１）〜（９）の何れか１項に記載の垂直磁気記録媒体。
（１１）軟磁性下地膜が、ホウ素を含むことを特徴とする（１）〜（１０）の何れか１項に記載の垂直磁気記録媒体。
（１２）非磁性基板がシリコン基板であることを特徴とする（１）〜（１１）の何れか１項に記載の垂直磁気記録媒体。
（１３）非磁性基板上に金属核又はシード層を形成し、その上に無電解メッキ法により軟磁性下地膜を形成する工程を含む垂直磁気記録媒体の製造方法であって、非磁性基板に外部から平行磁場を印加し、平行磁場に対して平行、かつ回転させながら軟磁性下地膜を形成することを特徴とする垂直磁気記録媒体の製造方法。
（１４）（１３）に記載の垂直磁気記録媒体の製造方法により製造した垂直磁気記録媒体。
（１５）（１）〜（１２）および（１４）の何れか１項に記載の垂直磁気記録媒体と、該磁気記録媒体に情報を記録再生する磁気ヘッドとを備えた垂直磁気記録再生装置。
（１６）軟磁性下地膜を有する非磁性基板であって、非磁性基板が円盤状であり、その円周方向のＨｓ（飽和磁束密度測定時に得られる印加磁界の最低強度）と半径方向のＨｓの比率＝等方性度が、１．０±０．２以内であることを特徴とする軟磁性下地膜を有する非磁性基板。
（１７）軟磁性下地膜の飽和磁束密度（Ｂｓ）が、０．２Ｔ〜１．７Ｔの範囲内であること特徴とする（１６）に記載の軟磁性下地膜を有する非磁性基板。
（１８）軟磁性下地膜を有する非磁性基板であって、非磁性基板が円盤状であり、磁化容易軸が基板に対して垂直方向に有すことを特徴とする非磁性基板。
（１９）軟磁性下地膜の垂直磁気異方性の異方性磁界（Ｈｋ）が３９５Ａ／ｍ〜３９５０Ａ／ｍ（５Ｏｅ〜５０Ｏｅ）の範囲内であることを特徴とする（１８）に記載の軟磁性下地膜を有することを特徴とする非磁性基板。
（２０）非磁性基板上に金属核又はシード層を形成し、その上に無電解メッキ法により軟磁性下地膜を形成させる非磁性基板の製造方法であって、軟磁性下地膜を形成する前、あるいは形成した後に、基板表面を研磨する工程を含むことを特徴とする非磁性基板の製造方法。
（２１）非磁性基板上に金属核又はシード層を形成し、その上に無電解メッキ法により軟磁性下地膜を形成させる非磁性基板の製造方法であって、軟磁性下地膜を形成する前後に基板表面を研磨する工程を含むことを特徴とする非磁性基板の製造方法。
（２２）基板表面を研磨する工程の前に、１００℃〜３５０℃の範囲内で熱処理を行う工程を含むことを特徴とする（２０）または（２１）に記載の非磁性基板の製造方法。
The present inventor has conducted intensive studies to achieve the above object, and as a result, a metal nucleus or a seed layer was formed on a nonmagnetic substrate, and then formed by an electroless plating method, for example, phosphorus (P) or It is a soft magnetic film containing boron (B), and the magnetic properties of the soft magnetic film are magnetically isotropic, especially in the in-plane direction of the substrate, or are magnetized in the direction perpendicular to the substrate. It has been found that any object having an easy axis can solve the above-mentioned problems relating to the domain wall, and has accomplished the present invention. That is, the present invention relates to the following.
(1) On a non-magnetic substrate, at least a soft magnetic underlayer made of a soft magnetic material, an orientation control film for controlling the orientation of the film immediately above, and a perpendicular direction in which the axis of easy magnetization is mainly perpendicular to the substrate. A perpendicular magnetic recording medium provided with a magnetic film and a protective layer, wherein the soft magnetic underlayer shows magnetic isotropy.
(2) The perpendicular magnetic recording medium according to (1), wherein the soft magnetic underlayer shows magnetic isotropy in an in-plane direction of the substrate.
(3) When the soft magnetic underlayer is formed on a disc-shaped non-magnetic substrate, the ratio of Hs in the circumferential direction (minimum intensity of the applied magnetic field obtained at the time of measuring the saturation magnetic flux density) to Hs in the radial direction = isotropic. The perpendicular magnetic recording medium according to (1) or (2), wherein the degree is within 1.0 ± 0.2.
(4) On a non-magnetic substrate, at least a soft magnetic underlayer made of a soft magnetic material, an orientation control film for controlling the orientation of the film immediately above, and a perpendicular direction in which the axis of easy magnetization is mainly perpendicular to the substrate. A perpendicular magnetic recording medium provided with a magnetic film and a protective layer, wherein the soft magnetic underlayer has an easy axis of magnetization in a direction perpendicular to a substrate.
(5) The anisotropic magnetic field (Hk) of perpendicular magnetic anisotropy of the soft magnetic underlayer is in the range of 395 A / m to 3950 A / m (5 Oe to 50 Oe). Perpendicular magnetic recording medium.
(6) The perpendicular magnetic recording according to any one of (1) to (5), wherein the saturation magnetic flux density (Bs) of the soft magnetic underlayer is in the range of 0.2T to 1.7T. Medium.
(7) The perpendicular magnetic recording medium according to any one of (1) to (6), wherein the soft magnetic underlayer has a crystal grain diameter of 5 nm or less in a microcrystalline or amorphous structure.
(8) The perpendicular magnetic recording medium according to any one of (1) to (7), wherein the thickness of the magnetic underlayer is in the range of 50 nm to 5000 nm.
(9) The soft magnetic underlayer according to any one of (1) to (8), wherein the average surface roughness Ra of the side on which the perpendicular magnetic recording layer is laminated is 0.8 nm or less. Perpendicular magnetic recording medium.
(10) The perpendicular magnetic recording medium according to any one of (1) to (9), wherein the soft magnetic underlayer contains phosphorus.
(11) The perpendicular magnetic recording medium according to any one of (1) to (10), wherein the soft magnetic underlayer contains boron.
(12) The perpendicular magnetic recording medium according to any one of (1) to (11), wherein the nonmagnetic substrate is a silicon substrate.
(13) A method for manufacturing a perpendicular magnetic recording medium, comprising a step of forming a metal nucleus or a seed layer on a nonmagnetic substrate and forming a soft magnetic underlayer thereon by electroless plating. A method for manufacturing a perpendicular magnetic recording medium, comprising applying a parallel magnetic field from the outside, and forming a soft magnetic underlayer while rotating and parallel to the parallel magnetic field.
(14) A perpendicular magnetic recording medium manufactured by the method for manufacturing a perpendicular magnetic recording medium according to (13).
(15) A perpendicular magnetic recording / reproducing apparatus comprising: the perpendicular magnetic recording medium according to any one of (1) to (12) and (14); and a magnetic head for recording / reproducing information on / from the magnetic recording medium.
(16) A non-magnetic substrate having a soft magnetic underlayer, wherein the non-magnetic substrate has a disk shape, and Hs in the circumferential direction (minimum intensity of the applied magnetic field obtained at the time of measuring the saturation magnetic flux density) and Hs in the radial direction. A non-magnetic substrate having a soft magnetic underlayer, wherein the ratio of isotropic is within 1.0 ± 0.2.
(17) The non-magnetic substrate having a soft magnetic underlayer according to (16), wherein the saturation magnetic flux density (Bs) of the soft magnetic underlayer is in the range of 0.2T to 1.7T.
(18) A non-magnetic substrate having a soft magnetic underlayer, wherein the non-magnetic substrate has a disk shape and has an easy axis of magnetization perpendicular to the substrate.
(19) The soft magnetic underlayer according to (18), wherein the anisotropic magnetic field (Hk) of perpendicular magnetic anisotropy is in the range of 395 A / m to 3950 A / m (5 Oe to 50 Oe). A non-magnetic substrate having a soft magnetic underlayer.
(20) A method for manufacturing a non-magnetic substrate in which a metal core or a seed layer is formed on a non-magnetic substrate, and a soft magnetic under film is formed thereon by electroless plating, wherein the soft magnetic under film is formed. Or a method of manufacturing a non-magnetic substrate, comprising a step of polishing a substrate surface after forming.
(21) A method of manufacturing a non-magnetic substrate in which a metal nucleus or a seed layer is formed on a non-magnetic substrate, and a soft magnetic under film is formed thereon by an electroless plating method. A method of manufacturing a non-magnetic substrate, the method further comprising a step of polishing the surface of the substrate.
(22) The method for manufacturing a nonmagnetic substrate according to (20) or (21), further comprising, before the step of polishing the substrate surface, a step of performing a heat treatment within a range of 100 ° C to 350 ° C.
本発明によれば、磁壁が観察されない下地膜を得ることが出来、これを用いることで熱安定性が高く、ノイズ特性に優れ、高密度記録が可能な垂直磁気記録媒体及び垂直磁気記憶再生装置を提供することができる。 According to the present invention, a perpendicular magnetic recording medium and a perpendicular magnetic recording / reproducing apparatus capable of obtaining a base film in which domain walls are not observed and having high thermal stability, excellent noise characteristics, and capable of high-density recording can be obtained. Can be provided.
以下、本発明につき更に詳しく説明する。図１（ａ）（ｂ）は、本発明の一実施例に係る磁気記録媒体を示す断面図である。図１（ａ）に示されている磁気記録媒体は、非磁性基板１上に軟磁性下地膜２と、配向制御膜３と、中間膜４と、垂直磁気記録膜５と、保護膜６と、潤滑膜７とが順次積層された構成となっている。以下、非磁性基板１側から順次にその構成を説明する。
Hereinafter, the present invention will be described in more detail. 1A and 1B are cross-sectional views showing a magnetic recording medium according to one embodiment of the present invention. The magnetic recording medium shown in FIG. 1A has a soft
本発明の軟磁性下地膜は、例えば、図１（ｂ）に示すように非磁性基板上に金属核又はシード層８が形成され、その上に無電解メッキ法により形成された軟磁性膜からなるものであり、かつその下地膜が磁気的に等方性を示すものである。
また本発明の垂直磁気記録媒体は、軟磁性下地膜が基板の面内方向において磁気的に等方性を示すのが好ましい。
より具体的には、前記下地膜を円盤状基材に形成した際に、その円周方向のＨｓと半径方向のＨｓの比率（等方性度）が１．０±０．２以内であるのが好ましい。
As shown in FIG. 1B, the soft magnetic underlayer of the present invention comprises a metal nucleus or a
Further, in the perpendicular magnetic recording medium of the present invention, it is preferable that the soft magnetic underlayer exhibit magnetic isotropy in the in-plane direction of the substrate.
More specifically, when the base film is formed on a disc-shaped base material, the ratio (isotropy) of Hs in the circumferential direction to Hs in the radial direction is within 1.0 ± 0.2. Is preferred.
図２は、本発明である軟磁性下地膜の磁気特性の概念図を示したものである。該下地膜の磁気特性をＶＳＭ（振動資料測定型磁力計；Ｖｉｂｒａｔｉｎｇ Ｓａｍｐｌｅ Ｍａｇｎｅｔｏｍｅｔｅｒ）で測定し、このようなヒステリシスループを得、その飽和磁束密度（Ｂｓ）からＨｓを求める。 FIG. 2 is a conceptual diagram showing the magnetic properties of the soft magnetic underlayer according to the present invention. The magnetic properties of the underlayer are measured with a VSM (vibrating sample magnetometer), such a hysteresis loop is obtained, and Hs is obtained from the saturation magnetic flux density (Bs).
通常、無電解メッキにおいて軟磁性膜を成膜すると配向、例えば、異方性結晶配向が生じ、これが磁壁となって現れてくるので、これまで垂直磁気記録用の下地膜に用いるにはスパイクノイズ等の発生があり十分ではなかった。 Ordinarily, when a soft magnetic film is formed by electroless plating, an orientation, for example, anisotropic crystal orientation is generated, and this appears as a domain wall. Therefore, spike noise has been conventionally used as a base film for perpendicular magnetic recording. Etc. were not enough.
本発明者らは、外部から印加された平行磁場中で軟磁性膜を無電解メッキ法により成膜することで、軟磁性膜の配向を無くし、等方性にすることを可能とし本発明に至った。まず、ＶＳＭ測定において、Ｂｓが得られた時の測定印加磁場の強さをＨｓと定義（図２参照）する。このＨｓは磁化容易方向を判断するための指標となる。Ｈｓが小さいほどその方向に磁化容易軸をもっていることになり、９０°異なる方向でのそれらの比（等方性度）は膜全体の磁気的配向性（等方性）を示すことになる。その値が１．０に近いほど磁気的に等方性と見なすことが出来る。従来の無電解メッキ法で成膜された軟磁性膜は配向があるために上記ＶＳＭで測定すると半径方向と、円周方向で同じＢｓ値が得られるが、このＢｓ値を得ることが出来る測定印加磁場には差が認められる。そこで、円盤状の非磁性基板上に形成された下地膜を図３のように基板ごと切出して、円周方向と半径方向でそれぞれＨｓを求め次式にしたがって、等方性の程度を判定した。 The present inventors have made it possible to eliminate the orientation of the soft magnetic film and to make it isotropic by forming the soft magnetic film by an electroless plating method in a parallel magnetic field applied from the outside. Reached. First, in the VSM measurement, the strength of the measured applied magnetic field when Bs is obtained is defined as Hs (see FIG. 2). This Hs is an index for determining the easy magnetization direction. The smaller the Hs, the easier the axis of magnetization in that direction, and the ratio (isotropy) in directions different by 90 ° indicates the magnetic orientation (isotropic) of the entire film. The closer the value is to 1.0, the more magnetically isotropic. Since the soft magnetic film formed by the conventional electroless plating method has an orientation, the same Bs value is obtained in the radial direction and the circumferential direction when measured by the above VSM when measured with the above VSM. There is a difference in the applied magnetic field. Therefore, the base film formed on the disc-shaped non-magnetic substrate was cut out together with the substrate as shown in FIG. 3, Hs was obtained in the circumferential direction and the radial direction, and the degree of isotropic was determined according to the following equation. .
等方性度＝Ｈｓ（円周方向）／Ｈｓ（半径方向）
一般的にはＢｓ近傍では印加磁場の変化してもＢの変化は小さいので、便宜上ＨｓをＢｓ値の９５％の様にある一定係数値のＢの値から算出するＨとしても何ら差しつかえない。
Isotropy = Hs (circumferential direction) / Hs (radial direction)
Generally, even when the applied magnetic field changes near Bs, the change in B is small. Therefore, for the sake of convenience, Hs can be used as H calculated from the value of B having a certain constant coefficient, such as 95% of the Bs value. .
通常の無電解メッキにより軟磁性膜を成膜すると膜は配向しているために、それぞれのＢｓ値が得られた時のＨｓは異なる。例えば、円周方向に配向していれば、円周方向に磁化容易軸が向いている為にＨｓ（半径方向）＞Ｈｓ（円周方向）となる。 When a soft magnetic film is formed by ordinary electroless plating, the film is oriented, so that Hs when each Bs value is obtained is different. For example, if oriented in the circumferential direction, Hs (radial direction)> Hs (circumferential direction) because the axis of easy magnetization is oriented in the circumferential direction.
本発明において、基板として用いることのできるものとしては、非磁性であればよく、結晶構造としては、単結晶、多結晶又はアモルファス状のものであればよい。例えば、ガラスウェハ、シリコンウェハ、アルミディスクなどが挙げられる。特に、シリコンウエハ、ガラスウエハが好ましい。また、これらの基板に別途、Ｎｉ−Ｐなどの非磁性物質があらかじめ成膜されたものであっても、本発明にはいっこうに差し支えない。 In the present invention, what can be used as the substrate only needs to be non-magnetic, and the crystal structure need only be a single crystal, polycrystal or amorphous. For example, a glass wafer, a silicon wafer, an aluminum disk and the like can be mentioned. Particularly, a silicon wafer and a glass wafer are preferable. Further, even if a non-magnetic substance such as Ni-P is separately formed on these substrates in advance, the present invention is not impeded.
本発明において、下地膜の例えば、Ｐを含有する軟磁性材は、無電解メッキ法により形成されるが、重要なのは無電解メッキ中に基板の面内方向に平行に外部から平行な磁場をあらかじめ印加するようにし、その平行面内でさらに基板を回転させることである。すなわち、あらかじめ常に基板の半径方向に外部から磁場が影響している状況を作りだし、その条件下でメッキを行うことにより、磁気的に等方性にすることが出来る。その平行の程度については概ね基板に対し±２０°以内が好ましい。図４には、メッキ方法の概念図を示した。 In the present invention, a soft magnetic material containing P, for example, of a base film is formed by an electroless plating method. It is important that a magnetic field parallel to the in-plane direction of the substrate is applied from the outside during the electroless plating. And rotating the substrate further in the parallel plane. That is, a situation is created in which a magnetic field is always exerted from the outside in the radial direction of the substrate, and plating can be performed under such conditions to make the substrate magnetically isotropic. The degree of the parallelism is preferably within ± 20 ° with respect to the substrate. FIG. 4 shows a conceptual diagram of the plating method.
本発明で用いることの出来る、メッキ用の外部磁場の強さは基板中心付近において、磁束密度が１０Ｇ〜５００Ｇ（１００００Ｇ＝１Ｔ）程度が好ましく、さらに好ましくは２５Ｇ〜１５０Ｇである。また、この磁場強度を得るために用いることが可能な磁石は、フェライト系、ネオジ−鉄−ボロン系、サマリウム−コバルト系等の永久磁石、あるいは電磁石を用いることが出来、特に制限すべきものではない。さらに本発明では、磁石が固定されて基板が回転しているが、基板を固定し磁石を回転させても本発明と全く同様の効果が得られる。あるいは、図４に示した様に平行磁界中で基板が上下に揺動しても何ら差し支えない。 The intensity of the external magnetic field for plating that can be used in the present invention is preferably about 10 G to 500 G (10000 G = 1 T), more preferably 25 G to 150 G, near the center of the substrate. In addition, a magnet that can be used to obtain this magnetic field strength can be a permanent magnet such as a ferrite-based, neodymium-iron-boron-based, samarium-cobalt-based, or electromagnet, and is not particularly limited. . Furthermore, in the present invention, the magnet is fixed and the substrate is rotated. However, even when the substrate is fixed and the magnet is rotated, exactly the same effects as those of the present invention can be obtained. Alternatively, there is no problem if the substrate swings up and down in a parallel magnetic field as shown in FIG.
本発明で用いられる、例えば、Ｐを含有する軟磁性材としては、Ｃｏ−Ｎｉ−Ｐ、Ｃｏ−Ｆｅ−Ｐ、Ｃｏ−Ｎｉ−Ｆｅ−Ｐなどが好んで用いられる、これらのうち特に高Ｂｓを有する組成がさらに好適である。あるいはＢ系のＣｏ−Ｎｉ−Ｆｅ−Ｂも好ましい。 For example, as the soft magnetic material containing P used in the present invention, Co-Ni-P, Co-Fe-P, Co-Ni-Fe-P and the like are preferably used. Among them, particularly high Bs Is more preferable. Alternatively, B-based Co-Ni-Fe-B is also preferable.
また、基板上に該軟磁性膜を成膜する前には、成膜促進のために、無電解メッキに触媒活性を有する表面を形成する必要がある。触媒活性を有する表面を形成するには、慣用の触媒化処理や基板に金属核を形成又はシード層を形成する方法が挙げられる。このような表面を形成する方法は基板により異なり、適宜選択する必要性があるが、下地膜の軟磁性膜の無電解反応を均一に開始させられるものであれば特に制限はない。 In addition, before forming the soft magnetic film on the substrate, it is necessary to form a surface having catalytic activity in electroless plating in order to promote film formation. In order to form a surface having catalytic activity, a conventional catalyzing treatment or a method of forming a metal nucleus or a seed layer on a substrate may be used. The method of forming such a surface varies depending on the substrate and needs to be selected as appropriate. However, there is no particular limitation as long as the electroless reaction of the soft magnetic film as the underlayer can be uniformly started.
触媒化処理としては、慣用の一液型Ｐｄ触媒化法や二液型Ｐｄ触媒化法、置換によるＰｄ触媒化法などが挙げられる。また、活性化処理の前にリン酸処理、酸処理などの公知の前処理、酸素プラズマなどによるアッシング処理を施してもよい。上記金属核としては、例えば、表面にＮｉ核、Ｃｕ核などの金属核が挙げられるが、Ｎｉ核やＣｕ核を付与する方法としては、Ｓｉウェハ上に直接ＮｉやＣｕを析出させる方法などで形成することが可能である。なお、上記金属核は非磁性であることが好ましい。 Examples of the catalyzing treatment include a conventional one-part Pd catalyzing method, a two-part Pd catalyzing method, and a Pd catalyzing method by substitution. Prior to the activation treatment, a known pretreatment such as a phosphoric acid treatment or an acid treatment, or an ashing treatment using oxygen plasma or the like may be performed. Examples of the metal nucleus include a metal nucleus such as a Ni nucleus and a Cu nucleus on the surface. Examples of a method for providing the Ni nucleus and the Cu nucleus include a method of depositing Ni or Cu directly on a Si wafer. It is possible to form. The metal nucleus is preferably non-magnetic.
一方、シード層を形成する場合は、後述する下地膜の無電解メッキ浴（メッキ液）中の還元剤に対して活性を有する金属で形成することが好ましく、例えば、Ｎｉ、Ｃｕ又はそれらの合金からなる好ましくは厚さ５〜１００ｎｍ、特に好ましくは１０〜５０ｎｍのシード層を形成することが好ましい。なお、上記シード層を形成する場合、基板とシード層との密着性を向上させるために、シード層にＺｎを添加することが好ましい。 On the other hand, when the seed layer is formed, it is preferable that the seed layer is formed of a metal having an activity with respect to a reducing agent in an electroless plating bath (plating solution) for an underlayer described later, for example, Ni, Cu, or an alloy thereof. It is preferable to form a seed layer having a thickness of preferably 5 to 100 nm, particularly preferably 10 to 50 nm. When forming the seed layer, it is preferable to add Zn to the seed layer in order to improve the adhesion between the substrate and the seed layer.
シード層の形成方法としては、スパッタ、蒸着などの乾式法や、置換メッキ、無電解メッキなどの湿式法が挙げられる。なお、無電解メッキにてシード層を形成する場合は、シード層を形成する前に金属核を形成する必要がある。この場合慣用のＰｄ活性化処理により形成することが望ましい。また、この場合も、金属核を形成する前に、リン酸処理、酸処理などの公知の前処理、酸素プラズマなどによるアッシング処理を施してもよい。 Examples of the method for forming the seed layer include a dry method such as sputtering and vapor deposition, and a wet method such as displacement plating and electroless plating. When forming a seed layer by electroless plating, it is necessary to form a metal nucleus before forming the seed layer. In this case, it is desirable to form by a conventional Pd activation process. Also in this case, a known pretreatment such as a phosphoric acid treatment or an acid treatment, or an ashing treatment using oxygen plasma or the like may be performed before forming the metal nucleus.
なお、上記シード層を形成する場合、基板とシード層との密着性を向上させるために、基板とシード層との間にスパッタリング等公知の方法でＴｉ、Ｃｒなどの密着層を形成することが好ましい。この場合、上記密着層の厚さは５〜５０ｎｍ、特に１０〜３０ｎｍが好ましい。 When the seed layer is formed, in order to improve the adhesion between the substrate and the seed layer, an adhesion layer such as Ti or Cr may be formed between the substrate and the seed layer by a known method such as sputtering. preferable. In this case, the thickness of the adhesion layer is preferably 5 to 50 nm, particularly preferably 10 to 30 nm.
本発明において、下地膜を形成するための無電解メッキ浴としては、例えば、コバルトイオン、ニッケルイオン及び鉄イオンなどの金属イオン、次亜リン酸、もしくは次亜リン酸ナトリウム等のリン系還元剤あるいはジメチルアミンボラン等のボロン系還元材、並びに上記金属イオンの錯化剤を含むものが用いられる。 In the present invention, examples of the electroless plating bath for forming the base film include metal ions such as cobalt ions, nickel ions and iron ions, hypophosphorous acid, and phosphorus-based reducing agents such as sodium hypophosphite. Alternatively, a material containing a boron-based reducing agent such as dimethylamine borane, and a complexing agent for the above-mentioned metal ion is used.
金属イオンの供給源としては、硫酸コバルト、硫酸ニッケル、硫酸鉄等の水溶性のコバルト塩、ニッケル塩、鉄塩等が挙げられ、その組成比（コバルト、ニッケル及び鉄の組成比）は、所望の磁気特性が得られるように選択すればよく、また、メッキ浴中の金属塩の濃度も適宜選定されるが、総金属塩濃度を０．０１〜３．０ｍｏｌ／ｄｍ3、特に０．０５〜０．３ｍｏｌ／ｄｍ3とすることが好ましい。 Examples of the supply source of metal ions include water-soluble cobalt salts such as cobalt sulfate, nickel sulfate, and iron sulfate, nickel salts, and iron salts. The composition ratio (composition ratio of cobalt, nickel, and iron) is desired. And the concentration of the metal salt in the plating bath may be appropriately selected. The total metal salt concentration may be 0.01 to 3.0 mol / dm 3 , especially 0.05 It is preferable to set it to ０．３0.3 mol / dm 3 .
また、還元剤の濃度も適宜選定されるが、メッキ浴中０．０１〜０．５ｍｏｌ／ｄｍ3、特に０．０１〜０．２ｍｏｌ／ｄｍ3とすることが好ましい。 Further, the concentration of the reducing agent is also appropriately selected, plating bath 0.01 to 0.5 mol / dm 3, it is preferable that the particular 0.01~0.2mol / dm 3.
一方、錯化剤としては、クエン酸ナトリウム、酒石酸ナトリウム等のカルボン酸塩、硫酸アンモニウム等のアンモニウム塩など、上記金属イオンの公知の錯化剤が使用され、その濃度は、メッキ浴中０．０５ｍｏｌ／ｄｍ3以上が好ましく、０．１〜１．０ｍｏｌ／ｄｍ3とすることがより好ましい。また、メッキ浴には亜リン酸等の結晶調整剤を用いることが好ましく、特に、０．０１ｍｏｌ／ｄｍ3以上の濃度で用いることが好ましい。 On the other hand, as the complexing agent, known complexing agents for the above metal ions such as sodium citrate, carboxylate such as sodium tartrate, and ammonium salt such as ammonium sulfate are used, and the concentration thereof is 0.05 mol in the plating bath. / Dm 3 or more, more preferably 0.1 to 1.0 mol / dm 3 . Further, it is preferable to use a crystal modifier such as phosphorous acid in the plating bath, and it is particularly preferable to use a concentration of 0.01 mol / dm 3 or more.
上記メッキ浴には、ホウ酸などのｐＨ緩衝剤を用いてもよい。また、無電解メッキ膜の均一性を向上させるために界面活性剤を用いてもよく、界面活性剤としては、ドデシル硫酸ナトリウム、ポリエチレングリコールが好ましい。更に、膜の平滑性を向上させるために慣用の添加剤（イオウ系など）を用いてもよい。膜の平滑性を向上させるために、サッカリンなどの慣用の第１種光沢剤や、チオ尿素などの慣用の第２種光沢剤を単独もしくは複合で用いても良い。特にイオウ系光沢剤が好んで用いられる。
A pH buffer such as boric acid may be used in the plating bath. In addition, a surfactant may be used to improve the uniformity of the electroless plating film. As the surfactant, sodium dodecyl sulfate and polyethylene glycol are preferable. Further, a conventional additive (such as a sulfur-based additive) may be used to improve the smoothness of the film. In order to improve the smoothness of the film, a conventional type 1 brightener such as saccharin or a
また、上記メッキ浴の温度、ｐＨは、浴組成により適宜決定されるが、浴温は、５０℃以上が好ましく、ｐＨは８以上が好ましい。特に、好ましいのは７０℃〜９５℃、ｐＨ９前後である。更に、上記無電解メッキ浴により形成された下地膜は、軟磁気特性の向上のために熱処理してもよい。この場合、熱処理温度は、１５０〜３００℃が好ましい。 The temperature and pH of the plating bath are appropriately determined depending on the bath composition. The bath temperature is preferably 50 ° C. or higher, and the pH is preferably 8 or higher. Particularly preferred are 70 ° C to 95 ° C and pH around 9. Further, the base film formed by the electroless plating bath may be heat-treated to improve soft magnetic properties. In this case, the heat treatment temperature is preferably from 150 to 300C.
本発明の下地膜は、等方性度が１．０±０．２以内であることが好ましく、より好ましいのは１．０±０．１５以内である。また、飽和磁束密度Ｂｓは０．２Ｔ以上１．７Ｔ以下が好ましく、０．８Ｔ以上１．５Ｔ以下がより好ましい。またその厚さ（ｔ）は５０ｎｍ以上５０００ｎｍ以下が好ましく、２００ｎｍ以上３０００ｎｍ以下がより好ましい。さらに、軟磁性下地膜の結晶粒子径は、５ｎｍ以下、より好ましくは３ｎｍ以下の微結晶、もしくはアモルファス構造であるのが好ましい。 The undercoat film of the present invention preferably has an isotropic degree of 1.0 ± 0.2 or less, more preferably 1.0 ± 0.15 or less. Further, the saturation magnetic flux density Bs is preferably 0.2T or more and 1.7T or less, more preferably 0.8T or more and 1.5T or less. The thickness (t) is preferably 50 nm or more and 5000 nm or less, more preferably 200 nm or more and 3000 nm or less. Further, the soft magnetic underlayer preferably has a crystal grain diameter of 5 nm or less, more preferably 3 nm or less, or a microcrystalline or amorphous structure.
本発明により形成された下地膜は、基板に対し垂直方向に磁化容易軸を有しても良い。垂直方向の磁化容易軸は磁壁を形成しにくくするために大変有効である。このときの垂直方向への磁化容易軸すなわち垂直磁気異方性の異方性磁界（Ｈｋ）は５〜５０Ｏｅが好ましく、１０〜３０Ｏｅがより好ましい。なお、１Ｏｅは約７９Ａ／ｍである。 The base film formed according to the present invention may have an easy axis of magnetization perpendicular to the substrate. The easy axis of magnetization in the vertical direction is very effective for making it difficult to form a domain wall. At this time, the axis of easy magnetization in the vertical direction, that is, the anisotropic magnetic field (Hk) of perpendicular magnetic anisotropy is preferably 5 to 50 Oe, more preferably 10 to 30 Oe. Note that 1 Oe is about 79 A / m.
垂直磁気異方性が認められる際には、この異方性磁界（Ｈｋ）は、先述した様にＶＳＭのヒステリシスループよりＢｓが得られた磁界となる（図９参照）。 When perpendicular magnetic anisotropy is recognized, the anisotropic magnetic field (Hk) is a magnetic field in which Bs is obtained from the hysteresis loop of the VSM as described above (see FIG. 9).
このように、下地膜の磁気特性を等方性にすることにより、磁壁が発生しなくなり、低ノイズである高性能な垂直磁気記録媒体となり、Ｓ／Ｎ比やオーバーライト特性を向上させることできる。尚、下地膜の軟磁性膜の保磁力Ｈｃは、特に限定されないが、４０Ｏｅ（１Ｏｅ＝約７９Ａ／ｍ）以下が好ましく、１０Ｏｅ以下がより好ましい。 As described above, by making the magnetic characteristics of the underlayer isotropic, domain walls are not generated, and a low-noise, high-performance perpendicular magnetic recording medium is obtained, and the S / N ratio and the overwrite characteristics can be improved. . The coercive force Hc of the soft magnetic film as the base film is not particularly limited, but is preferably 40 Oe (1 Oe = about 79 A / m) or less, and more preferably 10 Oe or less.
本発明の下地膜を有した基材を用いてさらに常法により表面の平滑化、及び垂直磁気記録層を形成等により高性能な垂直磁気記録媒体を得ることが出来る。以下にその例を示す。 Using the substrate having the base film of the present invention, a high-performance perpendicular magnetic recording medium can be obtained by smoothing the surface and forming a perpendicular magnetic recording layer by a conventional method. An example is shown below.
基板表面の平滑化工程は、軟磁性下地膜の成膜後に行う方法、軟磁性膜の成膜前にシード層を平滑化して次に軟磁性下地膜を成膜し、さらに軟磁性下地膜を平滑化する方法、シード層のみを平滑化する方法、およびそれらを併用する方法などがあるが、何れの方法も本発明において好適に用いることができる。特にこれらの方法を併用し、基板表面をより高度に平滑化するのが好ましい。 The step of smoothing the surface of the substrate is a method performed after the formation of the soft magnetic underlayer film, the seed layer is smoothed before the formation of the soft magnetic film, the soft magnetic underlayer is formed next, and the soft magnetic underlayer is further formed. There are a method of smoothing, a method of smoothing only the seed layer, and a method of using them in combination, and any method can be suitably used in the present invention. In particular, it is preferable to use these methods in combination to smooth the substrate surface to a higher degree.
また、平滑化工程の直前に基板全体に加熱処理を施して、基板および膜の歪などを除去する操作をすることも好ましい。熱処理温度としては１００℃〜３５０℃の範囲が好ましく、処理時間は１０分〜６０分程度が好ましい。
平滑化工程の具体的な例としてはアルミナもしくはシリカ（コロイダルシリカ）等が主成分である研磨材を含有する研磨液を用いた化学機械研磨法により行うことが好ましい。その際、表面平滑度としてはその平均高さ（Ｒａ）が２ｎｍ〜０．０５ｎｍであることが好ましく、０．８ｎｍ〜０．０５ｎｍであることがより好ましい。
It is also preferable to perform an operation of performing heat treatment on the entire substrate immediately before the smoothing step to remove distortion and the like of the substrate and the film. The heat treatment temperature is preferably in the range of 100 ° C. to 350 ° C., and the treatment time is preferably about 10 minutes to 60 minutes.
As a specific example of the smoothing step, it is preferable to perform the chemical mechanical polishing method using a polishing liquid containing an abrasive mainly composed of alumina or silica (colloidal silica). At that time, the average height (Ra) of the surface smoothness is preferably 2 nm to 0.05 nm, and more preferably 0.8 nm to 0.05 nm.
垂直磁性膜は、その磁化容易軸が基板に対して主に垂直方向に向いた磁性膜であれば良く、特に組成が限定されるものではない。一般的には、Ｃｏ系合金（例えば、ＣｏＣｒＰｔ、ＣｏＣｒＰｔＢ、ＣｏＣｒＰｔ−ＳｉＯ2、Ｃｏ／Ｐｄ多層、ＣｏＢ／ＰｄＢ多層、ＣｏＳｉＯ2／ＰｄＳｉＯ2多層等。）などが好んで用いられる。
The perpendicular magnetic film may be any magnetic film whose easy axis of magnetization is oriented mainly in the direction perpendicular to the substrate, and the composition is not particularly limited. In general, Co-based alloys (e.g., CoCrPt, CoCrPtB, CoCrPt-
垂直磁性膜は、上記Ｃｏ系材料からなる１層構造とすることもできるし、Ｃｏ系合金材料からなる層と、Ｃｏ系合金材料とは異なる材料からなる層とを含む２層以上の構造とすることもできる。 The perpendicular magnetic film may have a single-layer structure made of the above-mentioned Co-based material, or may have a structure of two or more layers including a layer made of a Co-based alloy material and a layer made of a material different from the Co-based alloy material. You can also.
また、Ｃｏ系合金層とＰｄ系合金層を積層した構造や、ＴｂＦｅＣｏ等のアモルファス材料層とＣｏＣｒＰｔ系合金材料層とを含む複層構造とすることも好ましい。 It is also preferable to have a structure in which a Co-based alloy layer and a Pd-based alloy layer are stacked, or a multilayer structure including an amorphous material layer such as TbFeCo and a CoCrPt-based alloy material layer.
垂直磁性膜の厚さは、３〜６０ｎｍ（より好ましくは５〜４０ｎｍ）とするのが好ましい。垂直磁性膜の厚さが上記範囲未満であると、十分な磁束が得られず、再生出力が低下する。また、垂直磁性膜の厚さが上記範囲を超えると、垂直磁性膜内の磁性粒子の粗大化が起き、記録再生特性が低下するため好ましくない。 The thickness of the perpendicular magnetic film is preferably 3 to 60 nm (more preferably, 5 to 40 nm). If the thickness of the perpendicular magnetic film is less than the above range, sufficient magnetic flux cannot be obtained, and the reproduction output decreases. On the other hand, if the thickness of the perpendicular magnetic film exceeds the above range, the magnetic particles in the perpendicular magnetic film become coarse and the recording / reproducing characteristics deteriorate, which is not preferable.
垂直磁性膜の保磁力Ｈｃは、３０００Ｏｅ以上とすることが好ましい。この保磁力が３０００Ｏｅ未満の磁気記録媒体は、高記録密度化に不適であり、また熱揺らぎ耐性にも劣るため好ましくない。 The coercive force Hc of the perpendicular magnetic film is preferably 3000 Oe or more. A magnetic recording medium having a coercive force of less than 3000 Oe is not suitable for increasing the recording density and is also inferior in resistance to thermal fluctuation, which is not preferable.
垂直磁性膜の残留磁化（Ｍｒ）と飽和磁化（Ｍｓ）の比Ｍｒ／Ｍｓは、０．９以上であることが好ましい。このＭｒ／Ｍｓが０．９未満の磁気記録媒体は、熱揺らぎ耐性に劣るため好ましくない。 The ratio Mr / Ms of the residual magnetization (Mr) to the saturation magnetization (Ms) of the perpendicular magnetic film is preferably 0.9 or more. A magnetic recording medium having an Mr / Ms of less than 0.9 is not preferable because of poor thermal fluctuation resistance.
垂直磁性膜の逆磁区核形成磁界（−Ｈｎ）は、０Ｏｅ以上２５００Ｏｅ以下であることが好ましい。この逆磁区核形成磁界（−Ｈｎ）が０Ｏｅ未満の磁気記録媒体は、熱揺らぎ耐性に劣るため好ましくない。
以下、逆磁区核形成磁界（−Ｈｎ）について説明する。
It is preferable that the reverse domain nucleation magnetic field (-Hn) of the perpendicular magnetic film is not less than 0 Oe and not more than 2500 Oe. A magnetic recording medium having a reverse magnetic domain nucleation magnetic field (-Hn) of less than 0 Oe is not preferable because of poor thermal fluctuation resistance.
Hereinafter, the reverse magnetic domain nucleation magnetic field (-Hn) will be described.
図６に示すように、ＭＨ曲線において、磁化が飽和した状態から外部磁界を減少させる過程で外部磁界が０となる点をａとし、磁化が０になった点をｂとし、点ｂでのＭＨ曲線の接線と飽和磁化を示す直線との交点をｃとすると、逆磁区核形成磁界（−Ｈｎ）は、点ａと点ｃとの距離（Ｏｅ）で表すことができる。 As shown in FIG. 6, in the MH curve, a point at which the external magnetic field becomes 0 in the process of reducing the external magnetic field from a state where the magnetization is saturated is a, a point at which the magnetization becomes 0 is b, and a point b at the point b Assuming that an intersection between a tangent line of the MH curve and a line indicating the saturation magnetization is c, the reverse domain nucleation magnetic field (-Hn) can be represented by a distance (Oe) between the points a and c.
なお、逆磁区核形成磁界（−Ｈｎ）は、外部磁界が負となる領域に点ｃがある場合に正の値をとり（図６を参照）、逆に、外部磁界が正となる領域に点ｃがある場合に負の値をとる（図７を参照）。 Note that the reverse magnetic domain nucleation magnetic field (-Hn) takes a positive value when the point c is in a region where the external magnetic field is negative (see FIG. 6), and conversely, in a region where the external magnetic field is positive. It takes a negative value when there is a point c (see FIG. 7).
この磁気記録媒体では、配向制御膜がＮｉを３３〜８０ａｔ％含み、Ｓｃ、Ｙ、Ｔｉ、Ｚｒ、Ｈｆ、Ｎｂ、Ｔａのうち１種または２種以上含む非磁性材料からなるものとすることにより、優れたエラーレート、熱揺らぎ耐性を得ることができる。 In this magnetic recording medium, the orientation control film is made of a non-magnetic material containing 33 to 80 at% of Ni and one or more of Sc, Y, Ti, Zr, Hf, Nb, and Ta. , Excellent error rate, and resistance to thermal fluctuation.
また、本発明の下地膜を用いた磁気記録媒体を公知の複合型ヘッドと組み合わせることにより磁気記憶装置を構成することができる。この場合、複合型記録ヘッドは３．０ｋＯｅ以上の書き込み磁界を発生できることが好ましい。図８に本発明の垂直磁気記録媒体を用いた垂直磁気記録再生装置の概念図を示す。 Further, a magnetic storage device can be configured by combining a magnetic recording medium using the underlayer film of the present invention with a known composite type head. In this case, it is preferable that the composite recording head can generate a write magnetic field of 3.0 kOe or more. FIG. 8 shows a conceptual diagram of a perpendicular magnetic recording / reproducing apparatus using the perpendicular magnetic recording medium of the present invention.
以下、実施例及び比較例を挙げて本発明を具体的に説明するが、本発明は下記実施例に限定されるものではない。 Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
平均粗さＲａが０．５ｎｍ以下のガラス基板を化学洗浄した後、ＤＣマグネトロンスパッタリング法により、膜厚１０ｎｍのＴｉ膜からなる密着層と膜厚２０ｎｍのＮｉ膜からなるシード層を続けて成膜した。次に、慣用の前処理を行ったのち、下記表１に示された無電解メッキ浴により下地膜として膜厚３０００ｎｍのＣｏＮｉＦｅＰの軟磁性膜を成膜した。この時、ガラス基板の半径方向に外部磁界がかかる様にメッキ槽の両側にフェライト磁石をセットした（図５参照）。図５は、本発明に用いる、メッキ装置の一例を示す説明図である。上記軟磁性膜を成膜したメッキ装置２１の一例であり、メッキ液が満たされたメッキ槽２８は、水槽２２の中に設置され、メッキ槽２８の中に、回転機構（図示せず）を備えた基板保持治具２９に保持された上記シード層を成膜したガラス基板３０が浸漬している。上記基板保持治具２９は、基板保持治具２７により上下に揺動可能に支持されている。また、上記シード層を成膜したガラス基板の半径方向に外部磁界を印加するため、メッキ槽２８を挟んでＮ極磁石２５とＳ極磁石２６が設けられている。更に、水槽２２内の水温を一定にするため、下端に撹拌翼２３を備えた撹拌棒２４が水槽２２に設けられている。上記メッキ装置を用い、ガラス基板中心には、３５Ｇの磁束を印加し、ガラス基板の回転数は６．５ｒ．ｐ．ｍとして、軟磁性膜をガラス基板上に成膜した。
After chemically cleaning a glass substrate having an average roughness Ra of 0.5 nm or less, an adhesion layer made of a 10 nm-thick Ti film and a seed layer made of a 20 nm-thick Ni film are successively formed by DC magnetron sputtering. did. Next, after performing a conventional pretreatment, a 3000 nm-thick soft magnetic film of CoNiFeP was formed as a base film using an electroless plating bath shown in Table 1 below. At this time, ferrite magnets were set on both sides of the plating tank so that an external magnetic field was applied in the radial direction of the glass substrate (see FIG. 5). FIG. 5 is an explanatory diagram illustrating an example of a plating apparatus used in the present invention. This is an example of the
次に、得られた下地膜に、アルミナおよびシリカを主成分とする研磨液を用いて化学機械研磨を施した。これにより、下地膜の平均粗さＲａを０．６〜０．８ｎｍとした（Ｖｅｅｃｏ社製ＴＭＳ２０００（Texture Measurement System)で測定）。ＴＥＭ観察から下地膜中の粒子サイズは２〜５ｎｍであり、Ｘ線回折からこの粒子はアモルファス状であることが判明した。なお研磨後の下地膜の膜厚は３００ｎｍ、飽和磁束密度Ｂｓは１．３Ｔであった。またＶＳＭ測定により、円周方向と半径方向のＨｓを測定し等方性度を求めたところ１．１１であった。また、前述したように垂直方向に磁化容易軸が認められヒステリシスループからもとめた垂直磁気異方性は１０Ｏｅであった。さらに、ＯＳＡ（Ｏｐｔｉｃａｌ Ｓｕｒｆａｃｅ Ａｎａｌｙｚｅｒ）にて磁壁の有無を観察したところ、磁壁が発生していないことが判明した。 Next, the obtained base film was subjected to chemical mechanical polishing using a polishing liquid containing alumina and silica as main components. As a result, the average roughness Ra of the underlayer was set to 0.6 to 0.8 nm (measured by TMS2000 (Texture Measurement System) manufactured by Veeco). The particle size in the base film was 2 to 5 nm from TEM observation, and the particles were found to be amorphous from X-ray diffraction. The thickness of the ground film after polishing was 300 nm, and the saturation magnetic flux density Bs was 1.3T. Further, Hs in the circumferential direction and in the radial direction were measured by VSM measurement to determine the degree of isotropicity, which was 1.11. As described above, the axis of easy magnetization was observed in the perpendicular direction, and the perpendicular magnetic anisotropy determined from the hysteresis loop was 10 Oe. Further, when the presence or absence of a domain wall was observed by OSA (Optical Surface Analyzer), it was found that no domain wall was generated.
次に、清浄環境下で乾燥させた下地膜の上に、ＤＣマグネトロンスパッタリング法により膜厚５ｎｍのＳｉ膜と膜厚５ｎｍのＰｄ膜を室温にて成膜して中間層を形成した。なお、このＳｉ膜とＰｄ膜との積層膜は、ＳｉとＰｄとが部分的に相互拡散した構造をもっている。 Next, a 5-nm-thick Si film and a 5-nm-thick Pd film were formed at room temperature on the base film dried in a clean environment by DC magnetron sputtering to form an intermediate layer. The stacked film of the Si film and the Pd film has a structure in which Si and Pd are partially diffused.
次に、中間層を成膜した後、厚さ０．２ｎｍのＣｏ層と厚さ０．８ｎｍのＰｄ層を交互に１０層積層させ、総膜厚１０ｎｍの垂直磁気記録層を成膜した。 Next, after an intermediate layer was formed, a Co layer having a thickness of 0.2 nm and a Pd layer having a thickness of 0.8 nm were alternately laminated to form a perpendicular magnetic recording layer having a total film thickness of 10 nm.
更に、垂直磁気記録層を成膜後、保護層として、膜厚５ｎｍのＣ膜を成膜して磁気記録媒体を得た。得られた磁気記録媒体は、書き込み部が単磁極型ヘッド、読み込み部がシールド型磁気抵抗ヘッドにより構成される複合型ヘッドを用い電磁変換特性を測定してＭＦ−Ｓ／Ｎ比を評価した。結果を磁壁の結果と共に表４に併記した。 Further, after forming a perpendicular magnetic recording layer, a C film having a thickness of 5 nm was formed as a protective layer to obtain a magnetic recording medium. The MF-S / N ratio of the obtained magnetic recording medium was evaluated by measuring the electromagnetic conversion characteristics using a composite type head in which the writing section was a single pole type head and the reading section was a shield type magnetoresistive head. The results are shown in Table 4 together with the results of the domain walls.
実施例１において、メッキ時に外部から印加する磁場の強さを３５Ｇから１００Ｇ（ネオジム−鉄−ボロン磁石）にした以外は実施例１と同様にした。Ｂｓ、等方性度、垂直磁気異方性、ＭＦ−Ｓ／Ｎ比、磁壁の有無を表４に示した。 Example 1 was the same as Example 1 except that the intensity of the magnetic field applied from the outside during plating was changed from 35 G to 100 G (neodymium-iron-boron magnet). Table 4 shows Bs, degree of isotropy, perpendicular magnetic anisotropy, MF-S / N ratio, and presence or absence of a domain wall.
実施例１において、メッキ浴の組成を表２のように変更した以外は実施例１と同様にした。Ｂｓ、等方性度、垂直磁気異方性、ＭＦ−Ｓ／Ｎ比、磁壁の有無を表４に示した。 Example 1 was the same as Example 1 except that the composition of the plating bath was changed as shown in Table 2. Table 4 shows Bs, degree of isotropy, perpendicular magnetic anisotropy, MF-S / N ratio, and presence or absence of a domain wall.
実施例１において、ＦｅＳＯ4を添加しないメッキ浴を用いた以外は、実施例１と同様にした。Ｂｓ、等方性度、垂直磁気異方性、ＭＦ−Ｓ／Ｎ比、磁壁の有無を表４に示した。 Example 1 was the same as Example 1 except that a plating bath to which FeSO 4 was not added was used. Table 4 shows Bs, degree of isotropy, perpendicular magnetic anisotropy, MF-S / N ratio, and presence or absence of a domain wall.
実施例１においてガラス基板の代わりに両面研磨された、平均粗さＲａが０．３ｎｍ以下の１インチシリコンウエハーを基板にした以外は実施例１と同様にした。Ｂｓ、等方性度、垂直磁気異方性、ＭＦ−Ｓ／Ｎ比、磁壁の有無を表４に示した。 Example 1 was repeated except that a glass substrate was replaced with a 1-inch silicon wafer having an average roughness Ra of 0.3 nm or less polished on both sides instead of a glass substrate. Table 4 shows Bs, degree of isotropy, perpendicular magnetic anisotropy, MF-S / N ratio, and presence or absence of a domain wall.
実施例１において、メッキ浴の組成をＢ系の表３のように変更した以外は実施例１と同様にした。Ｂｓ、等方性度、垂直磁気異方性、ＭＦ−Ｓ／Ｎ比、磁壁の有無を表４に示した。 Example 1 was the same as Example 1 except that the composition of the plating bath was changed as shown in Table 3 for B system. Table 4 shows Bs, degree of isotropy, perpendicular magnetic anisotropy, MF-S / N ratio, and presence or absence of a domain wall.
実施例１においてガラス基板の代わりに２．５インチＡｌ基板を用いた。定法により両面研磨、活性化処理して、シード層として膜厚１２μｍのＮｉＰメッキを施した。次に２５０℃、３０分間熱処理を行いメッキ膜の歪を取り除いた後、アルミナ系研磨材を主成分とする研磨液を用いて約２μｍ研磨して平均粗さＲａを２ｎｍとした。引続き実施例１と同様の条件で無電解メッキ浴により下地膜として膜厚６００ｎｍのＣｏＮｉＦｅＰの軟磁性膜を成膜した。さらに１５０℃、１５分間の熱処理を施した後、シリカを主成分とする研磨液を用いて約３００ｎｍ研磨して下地膜の平均粗さＲａを０．１〜０．３ｎｍとした。これ以降、実施例１と同じ操作を行った。Ｂｓ、等方性度、垂直磁気異方性、ＭＦ−Ｓ／Ｎ比、磁壁の有無を表４に示した。 In Example 1, a 2.5-inch Al substrate was used instead of a glass substrate. Both sides were polished and activated by a conventional method, and a 12 μm-thick NiP plating was applied as a seed layer. Next, a heat treatment was performed at 250 ° C. for 30 minutes to remove the distortion of the plating film, and then the resultant was polished to about 2 μm using a polishing liquid containing an alumina-based abrasive as a main component to obtain an average roughness Ra of 2 nm. Subsequently, a CoNiFeP soft magnetic film having a thickness of 600 nm was formed as a base film by using an electroless plating bath under the same conditions as in Example 1. After a heat treatment at 150 ° C. for 15 minutes, the base film was polished with a polishing liquid containing silica as a main component to a thickness of about 300 nm so that the average roughness Ra of the base film was 0.1 to 0.3 nm. Thereafter, the same operation as in Example 1 was performed. Table 4 shows Bs, degree of isotropy, perpendicular magnetic anisotropy, MF-S / N ratio, and presence or absence of a domain wall.
（比較例１）
実施例１において、メッキ時にフェライト磁石をセットせずに、外部平行磁場が存在しない状態で、無電解メッキを行い下地膜を成膜した以外は実施例１と同様の作業を行い、垂直磁気記録媒体を得た。Ｂｓは１．３Ｔ、膜厚は３００ｎｍであったが、ＯＳＡにより磁壁が認められた。
(Comparative Example 1)
Perpendicular magnetic recording was performed in the same manner as in Example 1, except that the ferrite magnet was not set at the time of plating, and an underlayer was formed by electroless plating in the absence of an external parallel magnetic field. The medium was obtained. Although Bs was 1.3 T and the film thickness was 300 nm, domain walls were recognized by OSA.
（比較例２）
下地膜としてスパッタリングにより膜厚１００ｎｍ、飽和磁束密度Ｂｓ１．０ＴのＮｉＦｅ軟磁性膜を形成し、平坦化処理を施さずにそのまま用いたこと以外は実施例１と同様の方法で磁気記録媒体を得た。得られた磁気記録媒体について、実施例１と同様に電磁変換特性を測定してＳ／Ｎ比を評価した。また、ＯＳＡ測定で磁壁の有無を観察した。
(Comparative Example 2)
A magnetic recording medium was obtained in the same manner as in Example 1, except that a NiFe soft magnetic film having a thickness of 100 nm and a saturation magnetic flux density of Bs 1.0 T was formed as a base film by sputtering, and used as it was without performing a planarization process. Was. With respect to the obtained magnetic recording medium, the electromagnetic conversion characteristics were measured in the same manner as in Example 1, and the S / N ratio was evaluated. The presence or absence of a domain wall was observed by OSA measurement.
（比較例３）
比較例２においてＮｉＦｅの代わりに、ＣｏＮｉＦｅの軟磁性膜を形成した以外は同様に行った。結果を表４に示した。
(Comparative Example 3)
Comparative Example 2 was performed similarly except that a soft magnetic film of CoNiFe was formed instead of NiFe. The results are shown in Table 4.
表４によれば、比較例に比べ、実施例のＭＦ−Ｓ／Ｎ比が高く、また磁壁が発生していないことがわかる。特に、実施例１の方が高いＳ／Ｎ比を示したのは、下地膜のＢｓ値が高い軟磁性膜を用いたことにより、記録ヘッドの漏洩磁界の高集束化が達成され、これに伴い再生信号が増大したためと推定される。 According to Table 4, the MF-S / N ratio of the example is higher than that of the comparative example, and no domain wall is generated. In particular, Example 1 exhibited a higher S / N ratio because a soft magnetic film having a high Bs value of the underlayer was used to achieve a higher focusing of the leakage magnetic field of the recording head. It is presumed that the reproduction signal increased accordingly.
１ 非磁性基板
２ 軟磁性下地膜
３ 配向制御膜
４ 中間膜
５ 垂直磁性膜
６ 保護膜
７ 潤滑膜
８ 金属核又はシード層
１０ 磁気記録媒体
１１ 媒体駆動部
１２ 磁気ヘッド
１２ａ 主磁極
１２ｂ 補助磁極
１２ｃ 連結部
１２ｄ コイル
１３ ヘッド駆動部
１４ 記録再生信号処理系
２１ メッキ装置
２２ 水槽
２３ 撹拌翼
２４ 撹拌棒
２５ Ｎ極磁石
２６ Ｓ極磁石
２７ 基板保持治具
２８ メッキ槽
２９ 基板保持治具
３０ ガラス基板
DESCRIPTION OF SYMBOLS 1
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| JP2006173403A (en) * | 2004-12-16 | 2006-06-29 | Fujitsu Ltd | Soft magnetic thin film, manufacturing method thereof, perpendicular magnetic recording medium, and magnetic recording / reproducing apparatus |
| JP2006338837A (en) * | 2005-06-06 | 2006-12-14 | Fuji Electric Device Technology Co Ltd | Method of plating on glass substrate, method of manufacturing disk substrate for perpendicular magnetic recording medium, disk substrate for perpendicular magnetic recording medium, and perpendicular magnetic recording medium |
| JP2007018591A (en) * | 2005-07-07 | 2007-01-25 | Fuji Electric Device Technology Co Ltd | Disk substrate for perpendicular magnetic recording medium and perpendicular magnetic recording medium |
| JP2007026513A (en) * | 2005-07-14 | 2007-02-01 | Hoya Corp | Perpendicular magnetic recording medium |
| US7859792B2 (en) | 2007-03-27 | 2010-12-28 | Tdk Corporation | Magnetic head with a recording element including a non-magnetic film and a magnetic pole film of an electrode and plated film formed in a depression of the magnetic pole film |
| WO2012046712A1 (en) * | 2010-10-07 | 2012-04-12 | 東洋鋼鈑株式会社 | Method for producing substrate for hard disk, and substrate for hard disk |
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| JP2006173403A (en) * | 2004-12-16 | 2006-06-29 | Fujitsu Ltd | Soft magnetic thin film, manufacturing method thereof, perpendicular magnetic recording medium, and magnetic recording / reproducing apparatus |
| JP2006338837A (en) * | 2005-06-06 | 2006-12-14 | Fuji Electric Device Technology Co Ltd | Method of plating on glass substrate, method of manufacturing disk substrate for perpendicular magnetic recording medium, disk substrate for perpendicular magnetic recording medium, and perpendicular magnetic recording medium |
| JP2007018591A (en) * | 2005-07-07 | 2007-01-25 | Fuji Electric Device Technology Co Ltd | Disk substrate for perpendicular magnetic recording medium and perpendicular magnetic recording medium |
| JP2007026513A (en) * | 2005-07-14 | 2007-02-01 | Hoya Corp | Perpendicular magnetic recording medium |
| US7983003B2 (en) | 2005-07-14 | 2011-07-19 | WD Media (Singapore) PTE LTD | Magnetic recording medium having soft magnetic layer and perpendicular magnetic recording layer |
| US7859792B2 (en) | 2007-03-27 | 2010-12-28 | Tdk Corporation | Magnetic head with a recording element including a non-magnetic film and a magnetic pole film of an electrode and plated film formed in a depression of the magnetic pole film |
| WO2012046712A1 (en) * | 2010-10-07 | 2012-04-12 | 東洋鋼鈑株式会社 | Method for producing substrate for hard disk, and substrate for hard disk |
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| JP5705230B2 (en) * | 2010-10-07 | 2015-04-22 | 東洋鋼鈑株式会社 | Hard disk substrate manufacturing method and hard disk substrate |
| WO2013153993A1 (en) * | 2012-04-10 | 2013-10-17 | 東洋鋼鈑株式会社 | Method for producing hard disk substrate |
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| JP2013218764A (en) * | 2012-04-10 | 2013-10-24 | Toyo Kohan Co Ltd | Method for producing hard disk substrate |
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