JP4283934B2 - Magnetic recording medium and magnetic storage device - Google Patents

Description

【００２１】
ここで、下地層の平均粒径は、磁気記録媒体を表面側（カーボン保護膜側）からイオンミリングし、カーボン保護膜、及び磁性層を削除した磁気記録媒体のTEM観察を行うことによって求めた。尚、磁性層の削除はオージェ測定によって、Co、またはPtが検出されなくなることによって確認した。また、規格化媒体ノイズは、線記録密度350kFCIで記録したときの媒体ノイズNdを、孤立再生波出力E0で規格化した値Nd/E0と定義し、分解能は該記録密度での再生出力E350kFCIと孤立再生波出力E0の比E350k/E0×100 (%)と定義した。下地層の平均粒径が20nm以上と大きい比較例媒体では、バイクリスタル面積比率は70％以上であり、保磁力が低い。これに対し、本実施例媒体では下地層の平均粒径が14nm以下で、かつ該クラスター面積比率が50％以下となり、2.8kOe以上の高い保磁力が得られている。また、バイクリスタル面積比率が30％以下となる実施例媒体1C-1Fでは、媒体ノイズが特に低減されており、該面積比率が更に20％以下の実施例磁気記録媒体1E、1Fではそれらに加え、高い分解能を示した。
【００２２】
本実施例磁気記録媒体に潤滑剤56を塗布したのち、上記磁気ヘッドとともに磁気記憶装置に組み込み、一平方インチ当たり10ギガビットの条件で記録再生特性を評価したところ、2.2という高い装置S/Nが得られた。また、コンタクト・スタート・ストップ試験（CSS試験）を行ったところ、３万回のCSSを行っても摩擦係数は0.2以下であった。
【００２３】
＜実施例２＞
カーボン基板上に室温でTaシード層を20nm形成したのち、ランプヒーターにより300℃まで加熱し、10nmのCr-30at％V-3at％C下地層、17nmのCo-19at%Cr-8at%Pt-3at%Ta磁性層、12nmのカーボン保護膜を連続的に成膜した。Taシード層の成膜は、ArにN2を2％添加した混合ガス雰囲気中で行い、ガス圧を5から15mTorrまで変化させた。その他の層は全て5mTorrの純Arガス雰囲気中で形成した。また、比較例としてTaシード層を、30〜50mTorrのArにN2を20％添加した混合ガス雰囲気中で形成した磁気記録媒体を作製した。本実施例及び比較例における磁気ディスク媒体の特性について表２に示す。
【００２４】
【表２】

【００２５】
本実施例、及び比較例磁気記録媒体のいずれも、磁性層の平均粒径は11〜14nmと大きな差はなく、またバイクリスタル面積比率も全て50％以下であった。X線回折測定を行ったところ、磁性層からの回折ピークは、すべての磁気記録媒体に於いて、CoCrPtTa(11.0)ピークとCoCrPtTa(00.2)ピークのみであった。しかし、本実施例磁気記録媒体では両者のピーク強度比ICo(11.0)/ICo(00.2)は2.0以上と、磁性層は強い(11.0)配向を示していたのに対し、比較例磁気記録媒体では磁性層は、強い(00.2)配向を示し、該強度比は2.0未満であった。これは、本実施例磁気記録媒体のTaシード層が主としてベータ構造であったのに対し、比較例磁気記録媒体のTaシード層は主としてアルファ構造であったためと考えられる。本実施例磁気記録媒体はいずれも2.8kOe以上の高い保磁力と、0.02μVrms/μVpp以下の低い媒体ノイズを示した。よって以上より、バイクリスタル面積比率が50％以下の磁気記録媒体では、磁性層に(11.0)配向以外の結晶粒が混在していても、(11.0)面からの回折ピーク強度が他の面からのピーク強度の2倍以上であれば、良好な磁気特性が得られることが明らかになった。
【００２６】
本実施例磁気記録媒体に潤滑剤を塗布したのち、上記磁気ヘッドとともに磁気記憶装置に組み込み、一平方インチ当たり10ギガビットの条件で記録再生特性を評価したところ、2.0という高い装置S/Nが得られた。
【００２７】
＜実施例３＞
アルカリ洗浄を施した化学強化ガラス基板を150℃まで加熱した後、Ni-30at%Taシード層を20nm、Cr-Xat％Mo-5at％B下地層(X=20, 30, 40, 50)を40nm、Co-23at%Cr-12at%Pt-2at%Ta磁性層を14nm、カーボン保護膜を12nm、連続的に成膜した。カーボン保護膜以外は、全て10mTorrのArガス雰囲気中で形成し、下地層、及び磁性層形成時にそれぞれ、-100V、-300Vの基板バイアスを印加した。カーボン保護膜は、Arガスにメタンを10％添加した混合ガス中で形成した。また、比較例としてCr-50at％Mo-5at％B下地層を用い、下地層、磁性層ともに基板バイアスを印加せずに形成した磁気記録媒体を作製した。
【００２８】
X線回折測定を行ったところ、実施例磁気記録媒体、比較例磁気記録媒体とも磁性層からのhcp(11.0)ピーク、及び下地層からのbcc(200)ピークのみが観察された。また、TEM観察より求めた磁性層の平均粒径は、いずれの磁気記録媒体も12〜14nm程度であった。表3に各磁気記録媒体のバイクリスタル面積比率、格子ミスフィット、媒体ノイズ、及び再生出力の減衰率を示す。
【００２９】
【表３】

【００３０】
ここで、格子ミスフィットは、X線回折スペクトラムのピーク位置より算出したCo合金(11.0)面間隔dCo(11.0)と、Cr合金(200)面間隔dCr(200)を用いて[√3・dCo(11.0) - √2・dCr(200)] / √2・dCr(200)×100 (%)と定義された値である。また、再生出力の減衰率は、記録直後の再生出力E0と48時間後の再生出力E48hを用いて(E48h-E0)/E0×100(%)と定義された値である。尚、本実施例では、熱揺らぎによる記録磁化の減衰を顕著にするため、意図的に膜厚が薄く、かつ高Cr濃度の磁性層を用いた。
【００３１】
本実施例磁気記録媒体では、いずれもバイクリスタル面積比率は50％以下であり、0.02μVrms/μVpp以下の低い媒体ノイズを示している。これに対し、バイアスを印加せずに成膜した比較例磁気記録媒体のバイクリスタル面積比率は50％を上回り、媒体ノイズが大きい。一方、実施例磁気記録媒体のうち、格子ミスフィットが8％以下である実施例3Cと実施例3Dは低ノイズであるのに加え、再生出力の減衰率がより低減されていた。よって、格子ミスフィットを8％以下とすることにより、低ノイズ化に加え、熱揺らぎによる再生出力の減衰を抑制できることがわかった。
【００３２】
本実施例磁気記録媒体に潤滑剤を塗布したのち、上記磁気ヘッドとともに磁気記憶装置に組み込み、一平方インチ当たり10ギガビットの条件で記録再生特性を評価したところ、2.0という高い装置S/Nが得られた。また、コンタクト・スタート・ストップ試験（CSS試験）を行ったところ、３万回のCSSを行っても摩擦係数は0.2以下であった。
【００３３】
＜実施例４＞
表面に超平滑処理を施したNiPメッキAl-Mg合金基板上に、第一のシード層として50nmのCo-30at%Cr-8at%Zr合金、第二のシード層としてTaを10nm室温で形成し、次いで260℃まで加熱した後、Cr-20at%Ti合金下地層を30nm、Co-22at%Cr-12at%Pt磁性層を18nm、カーボン保護膜を10nm、DCスパッタにより、10mTorrのArガス雰囲気中で連続的に成膜した。また、比較例としてTa/CoCrZr二層シード層の代わりに50nmのNiAl合金シード層を用いた磁気記録媒体を同一成膜条件で形成した。
【００３４】
本実施例磁気記録媒体のX線回折スペクトラムでは、強いCoCrPt(11.0)ピークが観測され、バイクリスタル面積比率は28％であった。これに対し、比較例磁気記録媒体の磁性層、下地層からはそれぞれ、強いCoCrPt(10.0)ピーク、CrTi(211)ピークが観測され、(211)配向した下地層上に、磁性層が(10.0)配向をとってエピタキシャル成長していることがわかった。表4に本実施例磁気記録媒体、及び比較例磁気記録媒体の粒径パラメーターを示す。
【００３５】
【表４】

【００３６】
両者の磁性層の平均粒径はほぼ同程度であったが、比較例磁気記録媒体の磁性層のTEM像中には、粒径が30nm以上の巨大な結晶粒がいくつか観察された。これは、該磁性結晶が、不可避的に形成された粒径30nm以上の巨大な下地粒径上に形成されたためと考えられる。これに対し、実施例磁気記録媒体ではこのような巨大な磁性結晶粒は観察されず、粒径分散を表わす標準偏差値は、比較例磁気記録媒体に対し30％程度低かった。また、表4には保磁力、及び記録再生特性の値も示してあるが、本実施例磁気記録媒体は、保磁力はやや低いものの、0.02μVrms/μVpp以下の低い媒体ノイズと、10％以上の高い分解能を示している。即ち、磁性層の平均粒径が同程度でも、磁性層が(11.0)配向をとり、低頻度でバイクリスタルクラスターが形成された磁気記録媒体の方が、磁性層が(10.0)配向をとり、バイクリスタルクラスターを形成しない磁気記録媒体よりも保磁力は若干低いが、より低ノイズで、かつ高分解能であることが明らかになった。
【００３７】
本実施例磁気記録媒体に潤滑剤を塗布したのち、上記磁気ヘッドとともに磁気記憶装置に組み込み、一平方インチ当たり10ギガビットの条件で記録再生特性を評価したところ、2.3という高い装置S/Nが得られた。
【００３８】
【発明の効果】
本発明の磁気記録媒体は、高保磁力化、高分解能化、及びノイズ低減効果を持つ。本発明の磁気記録媒体とスピンバルブ型磁気ヘッドを用いることにより、一平方インチ当たり10ギガビット以上の記録密度を有し、かつ平均故障回数が30万時間以上の磁気記憶装置の実現が可能となる。
【図面の簡単な説明】
【図１】本発明の一実施例の磁気記録媒体の磁性層の平面TEM像を示す模式図である。
【図２】 (a)および(b)は、それぞれ、本発明の一実施例の磁気記憶装置の平面模式図およびそのA-A' 断面図である。
【図３】本発明の磁気記憶装置における、磁気ヘッドの断面構造の一例を示す斜視図である。
【図４】本発明の磁気記憶装置における、磁気ヘッドの磁気抵抗センサ部の断面構造の一例を示す模式図である。
【図５】本発明の一実施例の磁気記録媒体の断面構造の一例を示す模式図である。
【符号の説明】
21...磁気ヘッド
22...磁気ヘッド駆動部
23...記録再生信号処理系
24...磁気記録媒体
25...磁気記録媒体駆動部
31...基体
32...コイル
33...上部記録磁極
34...下部記録磁極兼上部シールド層
35...磁気抵抗センサ
36...導体層
37...下部シールド層
41...信号検出領域
42...シールド層と磁気抵抗センサの間のギャップ層
43...バッファ層
44...第一の磁性層
45...中間層
46...第二の磁性層
47...反強磁性層
48...テーパー部
49...永久磁石層
51..基板
52...シード層
53...下地層
54...磁性層
55...保護膜
56...潤滑剤。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic storage device, specifically a magnetic storage device having a recording density of 10 gigabits per square inch or more, low noise for realizing this, and suppression of attenuation of reproduction output due to thermal magnetic relaxation. The present invention also relates to a thin film magnetic recording medium having high stability.
[0002]
[Prior art]
In the in-plane magnetic recording medium, in order to realize high coercive force and high resolution, the magnetic layer has an orientation in which the (11.0) plane is substantially parallel to the substrate surface (hereinafter abbreviated as (11.0) orientation) and is magnetized. It is preferable that the c-axis which is an easy axis is directed in the in-plane direction. In order to realize this, a Cr underlayer is formed on the substrate and between the magnetic layers. This is because Cr formed on a conventional Al-Mg alloy substrate coated with NiP plating (hereinafter referred to as an Al substrate) takes an orientation in which the (100) plane is substantially parallel to the substrate surface. This is because the formed magnetic layer has an (11.0) orientation by epitaxial growth. In addition, when the magnetic layer contains Pt with a large atomic radius in a high concentration, the lattice matching is enhanced and maintained by using an underlayer in which the lattice constant is increased by adding V, Ti, or the like to Cr. JP-A-62-257618 and JP-A-63-197018 disclose that the magnetic force is improved. On the other hand, when glass is used for the substrate, the Cr or Cr alloy underlayer formed on the substrate does not have the (100) orientation as described above. Therefore, a new layer called a seed layer or the like is further formed between the substrate and the base layer in order to make the base layer take (100) orientation. Examples of such a seed layer include Ta (Japanese Patent Laid-Open No. 4-188427) and MgO (J. Appl. Phys. 67, 3638 (1995)).
[0003]
However, it has been reported that the above-mentioned medium has a bicrystal structure in which a plurality of Co alloys with the c-axis perpendicular to each other are grown on one Cr alloy base crystal (J. Appl. Phys., Vol. 73, 418 (1993), J. Appl. Phys., Vol. 73, 5566 (1993)). By adopting such a bicrystal structure, the magnetic grain size is made finer than the base grain size and the medium noise is reduced, but on the other hand, it is effective due to the exchange interaction between adjacent magnetic grains. Magnetic anisotropy is offset and there is a drawback that a significant decrease in coercive force is caused. In order to improve this, introduction of a seed layer made of a Ni2 alloy having a B2 structure has been proposed (IEEE Trans. Magn. Vol. 30, 3099 (1992)). Since the Cr underlayer is (211) oriented on the NiAl seed layer, a medium in which the magnetic layer is (10.0) oriented by epitaxial growth can be obtained. In such a medium, the c-axis of the magnetic layer is oriented in the in-plane direction, similar to the (11.0) -oriented magnetic layer, and does not have the bicrystal structure as described above, but on one underlying crystal grain. One magnetic crystal grain is growing. For this reason, a high coercive force is obtained without causing a decrease in effective magnetic anisotropy.
[0004]
However, the average particle size in the Cr alloy underlayer formed on the NiAl seed layer is about 15 nm, and the magnetic crystal grains have the same particle size. This is not sufficient to obtain a low noise medium capable of realizing a recording density of 10 Gb / in 2 or more. In addition, the magnetic crystal grains grown on the inevitably generated enlarged base crystal grains are enlarged to the same extent as the base crystal grains, which causes a significant increase in noise.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a magnetic recording medium that suppresses the formation of bicrystal clusters while keeping the (11.0) orientation in the magnetic layer, thereby reducing noise and suppressing thermomagnetic relaxation. is there. Furthermore, by combining this with a high-sensitivity spin valve magnetic head and optimizing the conditions, a highly reliable magnetic storage device having a recording density of 10 gigabits per square inch or more can be provided.
[0006]
[Means for Solving the Problems]
The above-described object is that the magnetic layer is made of an alloy mainly composed of Co having an hcp structure, the magnetic layer has an orientation in which the (11.0) plane is substantially parallel to the substrate surface, and the magnetic layer Co alloy crystal grains having an average grain size of 8 nm or more and 14 nm or less and a c-axis relative angle of 0 ° or more, 10 ° or less, or 80 ° or more and 90 ° or less are adjacent to one cluster. When considered, the total area of the planes substantially parallel to the substrate of the crystal grains forming the cluster is 50% or less of the total area of planes substantially parallel to the substrates of all the crystal grains in the magnetic layer. A magnetic recording medium, a drive unit for driving the magnetic recording medium in a recording direction, a magnetic head composed of a recording unit and a reproducing unit, means for moving the magnetic head relative to the magnetic recording medium, and Recording / reproduction signal processing for performing signal input to the magnetic head and output signal reproduction from the magnetic head Wherein the magnetic storage apparatus having means reproducing portion of the magnetic head is achieved by a magnetic storage device constituted by the magnetoresistive head.
[0007]
The magnetoresistive sensor portion of the magnetic head used in the magnetic recording apparatus includes a plurality of conductive magnetic layers that cause a large resistance change due to relative changes in the magnetization directions of each other by an external magnetic field, and the conductive magnetic layers. It is assumed that the spin valve effect formed by the conductive nonmagnetic layer disposed between the two is utilized. The distance between the two shield layers sandwiching the resistance sensor portion (shield distance) is preferably 0.25 μm or less. This is because when the shield interval is 0.25 μm or more, the resolution is lowered and the phase jitter of the signal is increased.
[0008]
The magnetic layer of the magnetic recording medium is made of a Co alloy having an hcp structure and has an orientation in which the (11.0) plane is substantially parallel to the substrate surface. A stripe pattern representing the c-plane of the Co alloy was observed in the lattice image obtained by surface TEM observation of the magnetic layer. FIG. 1 shows a schematic diagram of the lattice image. The straight line in the figure represents the c-plane report (perpendicular to the c-axis) of each crystal grain. In the lattice image, the relative angle of each c-plane (c-axis), called a bicrystal cluster, such as the area surrounded by diagonal lines in the figure, is 0 degree or more, 10 degrees or less, or 80 degrees or more Co alloy grain groups adjacent to each other at 90 degrees or less were observed. The ratio of the total area of all the crystal grain groups forming such a cluster to the total area of all the observed crystal grains is hereinafter defined as a bicrystal area ratio. In the case of the lattice image in FIG. 1, lattice fringes representing the c-plane were observed in all the observed regions, so the bicrystal area ratio is the area ratio of the shaded area to the total area of all crystal grains in the lattice image. It becomes. In order to eliminate statistical errors, it is preferable to use 100 to 150 or more crystal grains in the calculation of the area ratio. In addition, when lattice fringes representing the c-plane are not observed due to deterioration of the (11.0) orientation of the magnetic layer or an increase in dispersion of the (11.0) -oriented plane, the area ratio is determined by symmetric only the region where the c-plane is observed. Is calculated.
[0009]
By setting the bicrystal area ratio to 50% or less, a magnetic recording medium having a high coercive force of 2.8 kOe or more can be obtained. If the area ratio exceeds 50%, the effect of canceling out magnetic anisotropy between Co crystal grains forming a bicrystal cluster becomes remarkable, which causes a significant reduction in coercive force. Further, it is preferable that the bicrystal area ratio is further 30% or less because noise can be further reduced. Furthermore, when the area ratio is set to 20% or less, in addition to the improvement of these characteristics, a significant improvement in resolution can be obtained, which is further preferable. If the bicrystal area ratio is less than 5%, the effect of refining the magnetic crystal grown on the inevitably formed giant crystal grains is impaired, which is not preferable. If the average grain size of the magnetic crystal grains is smaller than 8 nm, the influence of thermal magnetic relaxation becomes remarkable, and if it exceeds 14 nm, the medium noise increases, which is not preferable. It is preferable that the average particle size is further 9 nm or more and 12 nm or less because a magnetic recording medium with even lower noise and high overwrite characteristics can be obtained. In addition, the crystal orientation of the magnetic layer of the magnetic recording medium is mainly an orientation in which the (11.0) plane is parallel to the substrate surface, but crystal grains having other orientations such as (00.2) orientation and (10.1) orientation. If the diffraction peak intensity from these planes in the X-ray diffraction spectrum is less than 50% of the diffraction peak intensity from the (11.0) plane, the above effect can be obtained. Also, using the Co alloy (11.0) surface spacing dCo (11.0) calculated from the peak position of the X-ray diffraction spectrum and the Cr alloy (200) surface spacing dCr (200), [√3 · dCo (11.0)-√2・ The lattice misfit defined as dCr (200)] / √2 · dCr (200) × 100 (%) is preferably 0% or more and 8% or less. This is because when the misfit exceeds 8%, many defects are generated in the magnetic crystal, and magnetization reversal is easily caused by thermal fluctuation. When the misfit is less than 0%, tensile stress acts on the magnetic crystal grain, This is because the coercive force is lowered.
[0010]
The bicrystal area ratio strongly depends on the average particle size of the underlayer, and can be reduced particularly effectively by setting the particle size to 15 nm or less. However, if the grain size is less than 5 nm, the crystal grain size of the magnetic layer is remarkably increased, which causes an increase in noise. In addition to the average grain size of the underlayer, the bicrystal area ratio is affected by the lattice misfit between the magnetic layer and the underlayer, the (100) orientation degree of the underlayer, the film formation process such as the substrate bias, etc. These can also be reduced by controlling them.
[0011]
For the underlayer, an alloy mainly composed of an element having a body-centered cubic structure such as Cr is used. The base alloy may contain additive elements such as Ti, Mo, V, and W for the purpose of improving the lattice constant. Further, B, C, Si or the like may be added for the purpose of further reducing the particle size, or a multilayer structure combining these may be used.
[0012]
The seed layer is preferably made of MgO, Ta, NiP, CoCrZr, NiTa, NiNb, or a material containing these as a main component in order to orient the (100) orientation of the underlying layer made of a Cr alloy. Further, a layer for forming irregularities for the purpose of improving circumferential resistance or a layer for improving adhesion may be formed between the seed layer and the substrate.
[0013]
As the substrate, in addition to an Al—Mg alloy substrate plated with NiP, a chemically strengthened glass substrate, a crystallized glass substrate, an amorphous carbon substrate, or the like can be used. As a protective layer of the magnetic layer, carbon is formed to a thickness of 3 nm to 20 nm, and a lubricating layer such as an adsorptive perfluoroalkyl polyether is provided to a thickness of 2 nm to 10 nm. A recording medium is obtained. The protective layer is a carbon film to which hydrogen or nitrogen is added, a film made of a compound such as silicon carbide, tungsten carbide, (W-Mo) -C, (Zr-Nb) -N, or these compounds. A carbon mixed film may be used.
[0014]
The magnetic characteristics of the magnetic recording medium are as follows: the coercivity measured in the easy axis direction is 2800 oersted or more, and the product Br × t of residual magnetic flux density Br and film thickness t is 30 gauss microns or more and 80 gauss microns or less. This is preferable because good recording / reproducing characteristics can be obtained in a recording density region of 10 gigabits or more per square inch. If the coercive force in the circumferential direction is smaller than 2800 Oersted, the output at a high recording density (350 kFCI or more) becomes small, which is not preferable. Further, when Br × t is larger than 80 gauss microns, the resolution is lowered, and when it is smaller than 30 gauss microns, the reproduction output is undesirably small.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
<Example 1>
An embodiment of the present invention will be described with reference to FIG. 2, FIG. 3, and FIG. FIG. 2 (a) and FIG. 2 (b) show a schematic plan view and a schematic sectional view of the magnetic memory device of this example. This device is a magnetic storage device having a known structure comprising a magnetic head 21, a drive unit 22 thereof, a recording / reproduction signal processing means 23 of the magnetic head, a magnetic recording medium 24, and a drive unit 25 for rotating the magnetic recording medium 24. .
[0016]
The structure of the magnetic head is shown in FIG. This magnetic head is a composite head having both a recording electromagnetic induction type magnetic head formed on a substrate 31 and a reproducing spin valve type magnetic head. The recording head comprises an upper recording magnetic pole 33 and a lower recording magnetic pole / upper shield layer 34 sandwiching the coil 32, and the gap layer thickness between the recording magnetic poles was 0.30 μm. Further, Cu having a thickness of 3 μm was used for the coil. The reproducing head comprises a magnetoresistive sensor 35 and electrode patterns 36 at both ends thereof. Both magnetoresistive sensors are sandwiched between a 1 μm thick lower recording magnetic pole / upper shield layer and a lower shield layer 37, and the shield interlayer distance is 0.22 μm. It is. In FIG. 3, the gap layer between the recording magnetic poles and the gap layer between the shield layer and the magnetoresistive sensor are omitted.
[0017]
FIG. 4 shows a cross-sectional structure of the magnetoresistive sensor. The signal detection region 41 of the sensor has a 5 nm Ta buffer layer 43, a 7 nm first magnetic layer 44, a 1.5 nm Cu intermediate layer 45, a 3 nm second magnetic layer 46 on an Al oxide gap layer 42. In this structure, a 10-50 nm Fe-50 at% Mn antiferromagnetic alloy layer 47 is sequentially formed. Ni-20at% Fe alloy was used for the first magnetic layer, and Co was used for the second magnetic layer. The magnetization of the second magnetic layer is fixed in one direction by the exchange magnetic field from the antiferromagnetic layer. On the other hand, the direction of magnetization of the first magnetic layer that is in contact with the second magnetic layer via the nonmagnetic layer changes due to the leakage magnetic field from the magnetic recording medium, so that a resistance change occurs. As the reproducing head, a spin-valve magnetic head using a change in resistance accompanying a change in the relative direction of magnetization of the two magnetic layers was used. At both ends of the signal detection region, there are tapered portions 48 processed into a tapered shape. The tapered portion is composed of a permanent magnet layer 49 for making the magnetoresistive ferromagnetic layer into a single magnetic domain, and a pair of electrodes 11 for taking out signals formed thereon. The permanent magnet layer needs to have a large coercive force and the magnetization direction does not easily change, and CoCr, CoCrPt alloy or the like is used.
[0018]
FIG. 5 shows the layer structure of the magnetic recording medium of the present invention. After heating the chemically tempered glass substrate 51 subjected to alkali cleaning to 200 ° C, the MgO seed layer 52 was changed to 30 nm and the Cr concentration was changed from 2 to 10 at% with a Cr-20at% Ti-Xat% B alloy underlayer (X = 2-10) 53 was continuously formed in a vacuum at 30 nm, Co-22 at% Cr-10 at% Pt magnetic layer 54 at 18 nm, and carbon protective film 55 at 10 nm. The substrate was heated using a lamp heater, only the MgO seed layer was formed by RF sputtering, and the other layers were all formed by DC sputtering in an Ar gas atmosphere of 10 mTorr. As a comparative example medium, a magnetic recording medium using a Cr-20 at% Ti alloy underlayer without addition of B was prepared.
[0019]
Table 1 shows the average particle diameter, bicrystal area ratio, coercive force, medium noise, and resolution values of the underlayer and magnetic layer of each magnetic recording medium.
[0020]
[Table 1]

[0021]
Here, the average particle diameter of the underlayer was obtained by ion milling the magnetic recording medium from the surface side (carbon protective film side) and performing TEM observation of the magnetic recording medium from which the carbon protective film and the magnetic layer were deleted. . The deletion of the magnetic layer was confirmed by the fact that Co or Pt was not detected by Auger measurement. The standardized medium noise is defined as a value Nd / E0 obtained by normalizing the medium noise Nd when recording at a linear recording density of 350 kFCI, and the resolution is a reproduction output E350 kFCI at the recording density. The ratio of solitary regenerative wave output E0 was defined as E350k / E0 × 100 (%). In the comparative medium having a large average particle size of the underlayer of 20 nm or more, the bicrystal area ratio is 70% or more and the coercive force is low. In contrast, in the medium of this example, the average particle size of the underlayer is 14 nm or less, the cluster area ratio is 50% or less, and a high coercive force of 2.8 kOe or more is obtained. Further, in the example medium 1C-1F in which the bicrystal area ratio is 30% or less, the medium noise is particularly reduced, and in the example magnetic recording media 1E and 1F in which the area ratio is further 20% or less, in addition to them Showed high resolution.
[0022]
After applying the lubricant 56 to the magnetic recording medium of this example, it was incorporated into the magnetic storage device together with the magnetic head, and the recording / reproducing characteristics were evaluated under the condition of 10 gigabits per square inch. Obtained. In addition, when a contact start / stop test (CSS test) was performed, the coefficient of friction was 0.2 or less even after 30,000 CSS tests.
[0023]
<Example 2>
A 20nm Ta seed layer is formed on a carbon substrate at room temperature, then heated to 300 ° C with a lamp heater, 10nm Cr-30at% V-3at% C underlayer, 17nm Co-19at% Cr-8at% Pt- A 3 at% Ta magnetic layer and a 12 nm carbon protective film were continuously formed. The Ta seed layer was formed in a mixed gas atmosphere in which 2% of N2 was added to Ar, and the gas pressure was changed from 5 to 15 mTorr. All other layers were formed in a pure Ar gas atmosphere of 5 mTorr. As a comparative example, a magnetic recording medium in which a Ta seed layer was formed in a mixed gas atmosphere in which 20% N2 was added to 30 to 50 mTorr of Ar was manufactured. Table 2 shows the characteristics of the magnetic disk media in this example and the comparative example.
[0024]
[Table 2]

[0025]
In both of the present example and the comparative example magnetic recording medium, the average particle size of the magnetic layer was not significantly different from 11 to 14 nm, and the bicrystal area ratios were all 50% or less. When X-ray diffraction measurement was performed, the diffraction peaks from the magnetic layer were only the CoCrPtTa (11.0) peak and the CoCrPtTa (00.2) peak in all magnetic recording media. However, in the magnetic recording medium of this example, the peak intensity ratio ICo (11.0) / ICo (00.2) of both was 2.0 or more, and the magnetic layer showed a strong (11.0) orientation, whereas in the comparative magnetic recording medium The magnetic layer exhibited strong (00.2) orientation and the intensity ratio was less than 2.0. This is presumably because the Ta seed layer of the magnetic recording medium of this example mainly has a beta structure, whereas the Ta seed layer of the comparative magnetic recording medium has mainly an alpha structure. All of the magnetic recording media of this example showed a high coercive force of 2.8 kOe or more and a low medium noise of 0.02 μVrms / μVpp or less. Therefore, from the above, in the magnetic recording medium having a bicrystal area ratio of 50% or less, even if crystal grains other than (11.0) orientation are mixed in the magnetic layer, the diffraction peak intensity from the (11.0) plane is different from that of the other plane. It has been clarified that good magnetic properties can be obtained when the peak intensity is 2 times or more.
[0026]
After applying a lubricant to the magnetic recording medium of this example and incorporating it in the magnetic storage device together with the above magnetic head, and evaluating the recording / reproducing characteristics under the condition of 10 gigabits per square inch, an apparatus S / N as high as 2.0 was obtained. It was.
[0027]
<Example 3>
After heating the alkali-cleaned chemically strengthened glass substrate to 150 ° C, the Ni-30at% Ta seed layer is 20nm, Cr-Xat% Mo-5at% B underlayer (X = 20, 30, 40, 50) A 40 nm, Co-23 at% Cr-12 at% Pt-2 at% Ta magnetic layer was continuously formed at 14 nm and a carbon protective film at 12 nm. Except for the carbon protective film, all were formed in an Ar gas atmosphere of 10 mTorr, and substrate biases of −100 V and −300 V were applied when forming the underlayer and the magnetic layer, respectively. The carbon protective film was formed in a mixed gas obtained by adding 10% of methane to Ar gas. As a comparative example, a Cr-50at% Mo-5at% B underlayer was used, and a magnetic recording medium was produced in which both the underlayer and the magnetic layer were formed without applying a substrate bias.
[0028]
As a result of X-ray diffraction measurement, only the hcp (11.0) peak from the magnetic layer and the bcc (200) peak from the underlayer were observed in both the example magnetic recording medium and the comparative example magnetic recording medium. The average particle size of the magnetic layer determined by TEM observation was about 12 to 14 nm for all magnetic recording media. Table 3 shows the bicrystal area ratio, lattice misfit, medium noise, and reproduction output attenuation rate of each magnetic recording medium.
[0029]
[Table 3]

[0030]
Here, the lattice misfit is [√3 · dCo using the Co alloy (11.0) plane spacing dCo (11.0) calculated from the peak position of the X-ray diffraction spectrum and the Cr alloy (200) plane spacing dCr (200). (11.0)-√2 · dCr (200)] / √2 · dCr (200) × 100 (%). The attenuation rate of the reproduction output is a value defined as (E48h-E0) / E0 × 100 (%) using the reproduction output E0 immediately after recording and the reproduction output E48h after 48 hours. In this example, a magnetic layer having a small thickness and a high Cr concentration was intentionally used in order to make the recording magnetization attenuate due to thermal fluctuation.
[0031]
In all of the magnetic recording media of this example, the bicrystal area ratio is 50% or less, and low medium noise of 0.02 μVrms / μVpp or less is shown. In contrast, the bicrystal area ratio of the comparative example magnetic recording medium formed without applying a bias exceeds 50%, and the medium noise is large. On the other hand, among the magnetic recording media of Examples, Examples 3C and 3D in which the lattice misfit was 8% or less were low noise, and the attenuation rate of the reproduction output was further reduced. Therefore, it was found that by setting the lattice misfit to 8% or less, in addition to reducing noise, attenuation of reproduction output due to thermal fluctuation can be suppressed.
[0032]
After applying a lubricant to the magnetic recording medium of this example and incorporating it in the magnetic storage device together with the above magnetic head, and evaluating the recording / reproducing characteristics under the condition of 10 gigabits per square inch, an apparatus S / N as high as 2.0 was obtained. It was. In addition, when a contact start / stop test (CSS test) was performed, the coefficient of friction was 0.2 or less even after 30,000 CSS tests.
[0033]
<Example 4>
On a NiP-plated Al-Mg alloy substrate with ultra-smooth surface treatment, 50nm Co-30at% Cr-8at% Zr alloy is formed as the first seed layer, and Ta is formed as the second seed layer at 10nm at room temperature. Then, after heating to 260 ° C, Cr-20at% Ti alloy underlayer is 30nm, Co-22at% Cr-12at% Pt magnetic layer is 18nm, carbon protective film is 10nm, and DC sputtering is used in an Ar gas atmosphere of 10mTorr. The film was continuously formed. As a comparative example, a magnetic recording medium using a 50 nm NiAl alloy seed layer instead of the Ta / CoCrZr bilayer seed layer was formed under the same film formation conditions.
[0034]
In the X-ray diffraction spectrum of the magnetic recording medium of this example, a strong CoCrPt (11.0) peak was observed, and the bicrystal area ratio was 28%. In contrast, strong CoCrPt (10.0) peak and CrTi (211) peak were observed from the magnetic layer and the underlayer of the comparative magnetic recording medium, respectively, and the magnetic layer was (10.0) on the (211) -oriented underlayer. ) It was found that epitaxial growth occurred with orientation. Table 4 shows the particle size parameters of the magnetic recording medium of this example and the comparative magnetic recording medium.
[0035]
[Table 4]

[0036]
Although the average grain sizes of the two magnetic layers were almost the same, some huge crystal grains having a grain size of 30 nm or more were observed in the TEM image of the magnetic layer of the comparative magnetic recording medium. This is presumably because the magnetic crystal was inevitably formed on a huge base particle diameter of 30 nm or more. On the other hand, in the example magnetic recording medium, such huge magnetic crystal grains were not observed, and the standard deviation value representing the particle size dispersion was about 30% lower than that of the comparative example magnetic recording medium. Table 4 also shows values of coercive force and recording / reproducing characteristics. Although the magnetic recording medium of this example has a slightly low coercive force, it has a low medium noise of 0.02 μVrms / μVpp and 10% or more. High resolution is shown. That is, even if the average grain size of the magnetic layer is the same, the magnetic layer has a (11.0) orientation, and the magnetic recording medium in which the bicrystal cluster is formed less frequently has the (10.0) orientation of the magnetic layer. It was found that the coercive force is slightly lower than that of a magnetic recording medium that does not form a bicrystal cluster, but it has lower noise and higher resolution.
[0037]
After applying a lubricant to the magnetic recording medium of this example and incorporating it in the magnetic storage device together with the above magnetic head, and evaluating the recording / reproducing characteristics under the condition of 10 gigabits per square inch, an apparatus S / N as high as 2.3 was obtained. It was.
[0038]
【The invention's effect】
The magnetic recording medium of the present invention has high coercive force, high resolution, and noise reduction effect. By using the magnetic recording medium of the present invention and the spin valve magnetic head, it is possible to realize a magnetic storage device having a recording density of 10 gigabits per square inch or more and an average failure frequency of 300,000 hours or more. .
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a planar TEM image of a magnetic layer of a magnetic recording medium according to an embodiment of the present invention.
FIGS. 2A and 2B are a schematic plan view and a sectional view taken along line AA ′ of a magnetic memory device according to an embodiment of the present invention, respectively.
FIG. 3 is a perspective view showing an example of a cross-sectional structure of a magnetic head in the magnetic storage device of the present invention.
FIG. 4 is a schematic diagram showing an example of a cross-sectional structure of a magnetoresistive sensor portion of a magnetic head in the magnetic storage device of the present invention.
FIG. 5 is a schematic diagram showing an example of a cross-sectional structure of a magnetic recording medium according to an embodiment of the present invention.
[Explanation of symbols]
21 ... Magnetic head
22 ... Magnetic head drive
23.Recording and playback signal processing system
24 ... Magnetic recording media
25 ... Magnetic recording medium drive
31 ... Substrate
32 ... coil
33 ... Upper recording magnetic pole
34 ... Lower magnetic pole and upper shield layer
35 ... Magnetoresistive sensor
36 ... conductor layer
37 ... Lower shield layer
41 ... Signal detection area
42 ... Gap layer between shield layer and magnetoresistive sensor
43 ... Buffer layer
44 ... First magnetic layer
45 ... Middle layer
46 ... Second magnetic layer
47 ... Antiferromagnetic layer
48 ... Taper part
49 ... Permanent magnet layer
51 .. Board
52 ... Seed layer
53 ... Underlayer
54 ... Magnetic layer
55 ... Protective film
56. Lubricant.

Claims (8)

It consists of a Cr alloy with a body-centered cubic structure, an average grain size of 5 nm or more and 15 nm or less, and an alloy whose main component is Co with an hcp structure, and has an average grain size in the in-plane direction. A magnetic layer having a diameter of 8 nm to 14 nm,
The magnetic layer is oriented so that the (11.0) plane is substantially parallel to the substrate surface, and the diffraction peak intensity from the (11.0) plane of the magnetic layer is the diffraction peak from any other plane of the magnetic layer. It is more than twice the strength,
In addition, when the Co alloy crystal grain groups adjacent to each other with the c-axis relative angle of 0 ° to 10 ° or 80 ° to 90 ° are regarded as one cluster, A magnetic recording medium characterized in that the total area of substantially parallel planes to the substrate is 50% or less of the total area of substantially parallel planes to all crystal grains in the magnetic layer.   The total area of the planes substantially parallel to the substrate of the crystal grains forming the cluster is 30% or less of the total area of the planes substantially parallel to the substrates of all the crystal grains in the magnetic layer. The magnetic recording medium according to claim 1.   The total area of the planes substantially parallel to the substrate of the crystal grains forming the cluster is 20% or less of the total area of the planes substantially parallel to the substrates of all the crystal grains in the magnetic layer. The magnetic recording medium according to claim 1.   2. The magnetic recording medium according to claim 1, wherein the average grain size of the crystal grains is 9 nm or more and 12 nm or less. The magnetic recording medium according to claim 1, wherein said magnetic layer is formed in a substantially (100) plane of the bcc structure having orientation which is substantially parallel to the substrate surface underlying layer.   The magnetic layer is formed on a base layer having a bcc structure having an orientation in which the (100) plane is substantially parallel to the substrate surface, and (200) of the base layer calculated from the peak position of the X-ray diffraction spectrum is formed. (√3 · dCo (11.0)-√2 · dCr (200)) / √2 · dCr (200) using the interplanar spacing dCr (200) and the (11.0) interplanar spacing dCo (11.0) of the magnetic layer 2. The magnetic recording medium according to claim 1, wherein a lattice misfit defined as x100 (%) is not less than 0% and not more than 8%. A magnetic recording medium; a drive unit for driving the magnetic recording medium in a recording direction; a magnetic head including a recording unit and a reproducing unit; means for moving the magnetic head relative to the magnetic recording medium; and a signal to the magnetic head In a magnetic storage device having recording / reproduction signal processing means for performing input and output signal reproduction from the magnetic head,
A plurality of conductive magnetic layers in which a reproducing portion of the magnetic head causes a resistance change due to a relative change in magnetization direction by an external magnetic field, and a conductive nonmagnetic layer disposed between the conductive magnetic layers Is composed of a spin valve type magnetic head composed of a magnetoresistive sensor including
A magnetic storage device comprising the magnetic recording medium according to any one of claims 1 to 6 . The magnetoresistive sensor part of the spin valve magnetic head is formed between two shield layers made of a soft magnetic material separated from each other by a distance of 0.25 μm or less, and the thickness t of the magnetic film And the product Br × t of the residual magnetic flux density Br measured by applying a magnetic field in the direction of travel of the magnetic head relative to the magnetic recording medium during recording is not less than 30 gauss microns and not more than 90 gauss microns. 8. The magnetic storage device according to claim 7 , wherein the coercive force of the magnetic recording medium measured by applying a magnetic field in the same direction as the magnetic field application direction is 2800 oersted or more.

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