JP2007257762A

JP2007257762A - Perpendicular magnetic recording medium

Info

Publication number: JP2007257762A
Application number: JP2006082349A
Authority: JP
Inventors: Hiroyuki Suzuki; 博之鈴木; Yoshiyuki Hirayama; 義幸平山
Original assignee: Hitachi Global Storage Technologies Netherlands BV
Current assignee: HGST Netherlands BV
Priority date: 2006-03-24
Filing date: 2006-03-24
Publication date: 2007-10-04

Abstract

<P>PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium in which particle diameter dispersion of crystal grains is reduced while low lamination defect density is maintained. <P>SOLUTION: The perpendicular magnetic recording medium 100 has, on a substrate 101, a non-magnetic underlayer 102, a soft magnetic underlayer 103, a non-magnetic layer 104, a soft magnetic underlayer 105, non-magnetic intermediate layers 106, 107 and 108, a recording layer 109, a protective layer 110, and a lubricant layer 111. The recording layer 109 consists of prismatic crystal grains A having ferromagnetic cobalt as a principal component and a crystal grain boundary B, and the crystal grain boundary B is constituted of a composition containing an oxide of an eutectic composition or an oxide of aluminum, silicon and magnesium and having ≤1,500°C melting point. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、コバルトを主成分とする柱状の磁性結晶粒から構成される記録層を有する垂直磁気記録媒体に関する。 The present invention relates to a perpendicular magnetic recording medium having a recording layer composed of columnar magnetic crystal grains mainly composed of cobalt.

コンピュータ等の情報処理装置の外部記録装置として使用されるハードディスク装置は、大容量化・小型化が進み、それに対応するため記録密度の向上が図られている従来の面内磁気記録方式を用いて高密度化を行うと、媒体上の磁化の転移領域で反磁界が大きいため記録層の膜厚を薄くする必要があり、その結果、熱的な錯乱によって記録されたデータが消えてしまうという問題がある。一方、記録磁化の方向が媒体の膜厚方向である垂直磁気記録方式は、磁化転移領域で反磁界が小さいため媒体の膜厚を薄くする必要が比較的少なく、高記録密度化を達成しやすい。しかしながら、垂直磁気記録方式においても、さらなる高記録密度化のためには、高い保磁力を有し、高い熱安定性を有する媒体が必要である。 Hard disk devices used as external recording devices for information processing devices such as computers use a conventional in-plane magnetic recording method in which the recording density has been improved in response to the increase in capacity and miniaturization. When the density is increased, the demagnetizing field is large in the magnetization transition region on the medium, so it is necessary to reduce the thickness of the recording layer. As a result, the recorded data is lost due to thermal confusion. There is. On the other hand, in the perpendicular magnetic recording method in which the recording magnetization direction is the film thickness direction of the medium, the demagnetizing field is small in the magnetization transition region, so there is relatively little need to reduce the film thickness of the medium and it is easy to achieve high recording density. . However, even in the perpendicular magnetic recording system, a medium having a high coercive force and a high thermal stability is required for further increasing the recording density.

特許文献１には、磁性層の積層欠陥密度と粒径分散の積を０．０２以下とすることにより、高い保磁力を有し、熱ゆらぎに対して十分に安定である垂直磁気記録媒体が開示されている。 Patent Document 1 discloses a perpendicular magnetic recording medium having a high coercive force and sufficiently stable against thermal fluctuation by setting the product of stacking fault density and particle size dispersion of a magnetic layer to 0.02 or less. It is disclosed.

特許文献２には、垂直磁気記録層が、強磁性の結晶粒と非磁性の結晶粒界相とからなり、結晶粒界相が２種類以上の酸化物からなることにより、記録層の磁性粒子を微細化することができ、低ノイズ化を実現し、高密度記録が可能になることが記載されている。 In Patent Document 2, the perpendicular magnetic recording layer is composed of ferromagnetic crystal grains and nonmagnetic grain boundary phases, and the grain boundary phase is composed of two or more kinds of oxides. It is described that the image quality can be reduced, low noise is realized, and high density recording is possible.

特開２００３−１６８２０６号公報JP 2003-168206 A 特開２００５−１００５３７号公報Japanese Patent Laid-Open No. 2005-10057

特許文献１に記載されているように、磁性層の材料積層欠陥が多いと磁性膜の磁気異方性は低下し、保磁力の低下、および記録磁化の熱安定性の低下を招く。したがって、高い熱安定性を実現するためには、磁性層の積層欠陥密度を低減すればよい。積層欠陥密度を低減するためには、磁性層成膜時の温度を低減することが効果的であるが、この場合には、磁性層を構成する結晶粒径分布の分散が広がるため、やはり保磁力の低下および記録磁化の熱安定性の低下を招き、高い熱安定性を実現することはできない。したがって、低い積層欠陥密度を保ったまま同時に粒径分散を小さくすることは困難である。また、特許文献２には、記録層の結晶粒界相を２種類以上の酸化物とすることにより、記録層の磁性粒子を微細化することの記載はあるが、しかしながら、記録層製膜時の温度を低減し、同時に粒径分散を小さくするために最適な酸化物の組成についての記載はない。 As described in Patent Document 1, when there are many material stacking faults in the magnetic layer, the magnetic anisotropy of the magnetic film decreases, leading to a decrease in coercive force and a decrease in thermal stability of recording magnetization. Therefore, in order to realize high thermal stability, the stacking fault density of the magnetic layer may be reduced. In order to reduce the stacking fault density, it is effective to reduce the temperature at the time of forming the magnetic layer. However, in this case, since the dispersion of the crystal grain size distribution constituting the magnetic layer is widened, it is still maintained. A decrease in magnetic force and a decrease in thermal stability of recording magnetization are caused, and high thermal stability cannot be realized. Therefore, it is difficult to reduce the particle size dispersion while maintaining a low stacking fault density. Further, Patent Document 2 describes that the magnetic grain of the recording layer is made finer by using two or more types of oxides as the grain boundary phase of the recording layer. There is no description of an optimal oxide composition for reducing the temperature of the material and simultaneously reducing the particle size dispersion.

本発明の目的は、低い積層欠陥密度を保ったまま、結晶粒の粒径分散を小さくした垂直磁気記録媒体を提供することである。 An object of the present invention is to provide a perpendicular magnetic recording medium in which the grain size dispersion of crystal grains is reduced while maintaining a low stacking fault density.

本発明の垂直磁気記録媒体は、基板上に、少なくとも非磁性下地層と記録層と保護層とを有し、記録層が強磁性のコバルトを主成分とする結晶粒と、前記結晶粒内に比べコバルトの濃度が低い結晶粒界とを有し、結晶粒界が共晶組成の酸化物を含むものである。
また、本発明の垂直磁気記録媒体は、基板上に、少なくとも非磁性下地層と記録層と保護層とを有し、記録層が強磁性のコバルトを主成分とする結晶粒と、前記結晶粒内に比べコバルトの濃度が低い結晶粒界とを有し、結晶粒界がアルミニウムと珪素とマグネシウムの酸化物を含み、その酸化物の融点は１５００°Ｃ以下である。 The perpendicular magnetic recording medium of the present invention has at least a nonmagnetic underlayer, a recording layer, and a protective layer on a substrate, and the recording layer contains ferromagnetic cobalt as a main component, and the crystal grains Compared with a crystal grain boundary having a low cobalt concentration, the crystal grain boundary contains an oxide having a eutectic composition.
The perpendicular magnetic recording medium of the present invention includes a crystal grain having at least a nonmagnetic underlayer, a recording layer, and a protective layer on a substrate, the recording layer comprising ferromagnetic cobalt as a main component, and the crystal grain A crystal grain boundary having a lower cobalt concentration than the inside, and the crystal grain boundary contains an oxide of aluminum, silicon, and magnesium, and the melting point of the oxide is 1500 ° C. or less.

本発明によれば、低い積層欠陥密度を保ったまま、結晶粒の粒径分散を小さくした垂直磁気記録媒体を提供することができる。 According to the present invention, it is possible to provide a perpendicular magnetic recording medium in which the grain size dispersion of crystal grains is reduced while maintaining a low stacking fault density.

以下、図面を参照して、実施例について説明する。図１は実施例による垂直磁気記録ディスク媒体（以下、垂直記録媒体と略す）の構成を示す断面図である。垂直記録媒体１００は、基板１０1上に非磁性下地層１０２、軟磁性下地層１０３、非磁性層１０４、軟磁性下地層１０５、非磁性中間層１０６，１０７，１０８、記録層１０９、保護層１１０および潤滑層１１１を有する。図２に記録層１０９のイメージを断面で示すが、記録層１０９が強磁性のコバルトを主成分とする柱状の結晶粒Ａと、結晶粒内に比べコバルトの濃度が低い結晶粒界Ｂとからなり、結晶粒界Ｂを共晶組成の酸化物を含む組成とするか、またはアルミニウムと珪素とマグネシウムの酸化物を含み、その融点が１５００°Ｃ以下の組成とすれば、結晶粒径の分散の小さな記録層が得られる。これは、結晶粒界を構成する酸化物の融点が、各酸化物の固有の融点、あるいは擬２元系の酸化物の融点に比べ大幅に低くなることにより、薄膜形成時の原子の移動度が高まり、明瞭な粒界が形成されやすくなるためである。 Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a sectional view showing the structure of a perpendicular magnetic recording disk medium (hereinafter abbreviated as a perpendicular recording medium) according to an embodiment. The perpendicular recording medium 100 includes a nonmagnetic underlayer 102, a soft magnetic underlayer 103, a nonmagnetic layer 104, a soft magnetic underlayer 105, nonmagnetic intermediate layers 106, 107, and 108, a recording layer 109, and a protective layer 110 on a substrate 101. And a lubricating layer 111. FIG. 2 shows an image of the recording layer 109 in a cross section. The recording layer 109 includes columnar crystal grains A whose main component is ferromagnetic cobalt and crystal grain boundaries B in which the cobalt concentration is lower than in the crystal grains. If the grain boundary B has a composition containing an oxide having a eutectic composition, or an oxide of aluminum, silicon, and magnesium and has a melting point of 1500 ° C. or less, the dispersion of the crystal grain size A small recording layer. This is because the melting point of the oxide constituting the crystal grain boundary is significantly lower than the melting point of each oxide or the pseudo-binary oxide, so that the mobility of atoms during thin film formation is reduced. This is because clear grain boundaries are easily formed.

次に垂直記録媒体１００の製造方法について説明する。基板１０１には厚さ０．５０８ｍｍ、直径４８ｍｍのガラス基板を用いた。ＤＣマグネトロンスパッタリング装置を用い、基板１０１の加熱は行なわず、全てのチャンバを２×１０^−５Ｐａ以下の真空まで排気後、基板１０１を載せたキャリアを各プロセスチャンバに移動させて、非磁性中間層１０８を除き、Ａｒガス圧０．７Ｐａの条件で以下の薄膜形成を行なった。 Next, a method for manufacturing the perpendicular recording medium 100 will be described. As the substrate 101, a glass substrate having a thickness of 0.508 mm and a diameter of 48 mm was used. Using a DC magnetron sputtering apparatus, the substrate 101 is not heated, and all the chambers are evacuated to a vacuum of 2 × 10 ⁻⁵ Pa or less, and then the carrier on which the substrate 101 is placed is moved to each process chamber. Except for the layer 108, the following thin film was formed under the condition of an Ar gas pressure of 0.7 Pa.

非磁性下地層１０２として厚さ５ｎｍの５０ａｔ．％Ａｌ−５０ａｔ．％Ｔｉ合金膜を形成した。軟磁性層１０３として厚さ３０ｎｍの５１ａｔ．％Ｆｅ−３４ａｔ．％Ｃｏ−１０ａｔ．％Ｔａ−５ａｔ．％Ｚｒ合金膜を形成し、非磁性層１０４として厚さ０．７ｎｍのＲｕ膜を形成後、再び軟磁性下地層１０５として厚さ３０ｎｍの５１ａｔ．％Ｆｅ−３４ａｔ．％Ｃｏ−１０ａｔ．％Ｔａ−５ａｔ．％Ｚｒ合金膜を形成した。非磁性中間層１０６としてＮｉ−８ａｔ．％Ｗ合金膜を８ｎｍ、非磁性中間層１０７としてＲｕを８ｎｍ形成した。非磁性中間層１０８としてＲｕを８ｎｍ形成する際にはＡｒガス圧２Ｐａとした。 As the nonmagnetic underlayer 102, a 50 at. % Al-50 at. % Ti alloy film was formed. As the soft magnetic layer 103, a 51 at. % Fe-34 at. % Co-10 at. % Ta-5 at. % Zr alloy film, a 0.7-nm-thick Ru film as the nonmagnetic layer 104, and a soft-magnetic underlayer 105 with a thickness of 51 at. % Fe-34 at. % Co-10 at. % Ta-5 at. A% Zr alloy film was formed. As the nonmagnetic intermediate layer 106, Ni-8 at. The% W alloy film was formed to 8 nm, and Ru was formed to 8 nm as the nonmagnetic intermediate layer 107. When forming 8 nm of Ru as the nonmagnetic intermediate layer 108, the Ar gas pressure was set to 2 Pa.

その後、図３に示す酸化物Ｏｘ１からＯｘ１１のいずれかと白金（Ｐｔ）を含有したコバルト（Ｃｏ）基合金を記録層１０９として厚さ１２ｎｍとなるように、図４に示す組成のターゲットＡ０１からＡ１５を用いて作製した。非特許文献（窯業協会、窯業工学ハンドブック（新版）、昭和４６年２月１５日、技報堂、2046ページ、付図-32.12）に示されるように、図３で、Ｏｘ３とＯｘ６は共晶(eutectic)組成であり、Ｏｘ９は３元共晶の組成である。図３に示すこれら以外の組成は共晶組成ではないが、Ｏｘ７とＯｘ８ならびにＯｘ１０の融点はいずれも１５００°Ｃ以下である。ここでＯｘ１０は２ＭｇＯ・２Ａｌ_２Ｏ_３・５ＳｉＯ_２からなる斜方晶(cordierite)を構成する組成をとる。Ｏｘ４はＭｇＯ・ＳｉＯ_２からなる単斜晶(clinoenstatite)を構成する組成であり、この組成も共晶組成ではない。また、Ｏｘ１とＯｘ２、Ｏｘ４とＯｘ５は融点が１６００°Ｃ以上のＭｇＯ-ＳｉＯ_２系の酸化物である。さらにＯｘ１１はほぼＡｌ_２Ｏ_３・ＳｉＯ_２の組成をとり、その融点は１８４０°Ｃ以上である。
続いて、化学蒸着法で炭素を主成分とする保護層１１０を厚さ４ｎｍ形成後、大気中に取り出し、パーフルオロポリエーテルを含む潤滑層１１１を形成した。 Thereafter, targets A01 to A15 having the composition shown in FIG. 4 are formed so that the recording layer 109 has a thickness of 12 nm using any of the oxides Ox1 to Ox11 and platinum (Pt) shown in FIG. It was produced using. As shown in non-patent literature (Ceramic Association, Ceramic Engineering Handbook (new edition), February 15, 1971, Gihodo, page 2046, Attached figure -32.12), Ox3 and Ox6 are eutectic in FIG. Ox9 is a ternary eutectic composition. The other compositions shown in FIG. 3 are not eutectic compositions, but the melting points of Ox7, Ox8, and Ox10 are all 1500 ° C. or less. Here, Ox10 has a composition constituting an orthorhombic (cordierite) composed of 2MgO.2Al ₂ O ₃ · 5SiO ₂ . Ox4 is a composition that constitutes the monoclinic (clinoenstatite) consisting of MgO · SiO _2, the composition is not a well eutectic composition. Ox1 and Ox2, and Ox4 and Ox5 are MgO—SiO ₂ oxides having a melting point of 1600 ° C. or higher. Further, Ox11 has a composition of almost Al ₂ O ₃ .SiO ₂ and has a melting point of 1840 ° C. or higher.
Subsequently, a protective layer 110 containing carbon as a main component was formed with a thickness of 4 nm by a chemical vapor deposition method, and then taken out into the atmosphere to form a lubricating layer 111 containing perfluoropolyether.

以下の説明において、平均結晶粒径＜Ｄ＞と粒径分散σ／＜Ｄ＞は透過電子顕微鏡(ＴＥＭ)像から算出した。まず、基板面に平行な方向の記録層の結晶粒像を透過電子顕微鏡により撮影する。次に得られた写真をスキャナで取り込み、画像のコントラストが観察されるコア部分を結晶粒と定義し、各結晶粒に存在するピクセル数を計算した。ピクセル数とスケールとの換算から、各結晶の面積を求め、得られた各結晶粒の面積と同じ面積の真円の直径として結晶粒径を定義し、個々の結晶粒の粒径Ｄｉを求めた。この計算を３００個程度の結晶粒について行ない、得られた粒子径の算術平均値を平均結晶粒径＜Ｄ＞とした。また、個々の結晶粒の粒径Ｄｉと平均結晶粒径＜Ｄ＞の差分の二乗和を測定した結晶の個数Ｎで割り、その平方根から標準偏差σを求めた。この標準偏差σを平均結晶粒径＜Ｄ＞で除した量σ／＜Ｄ＞を粒径分散と定義した。 In the following description, the average crystal grain size <D> and the particle size dispersion σ / <D> were calculated from a transmission electron microscope (TEM) image. First, a crystal grain image of the recording layer in a direction parallel to the substrate surface is taken with a transmission electron microscope. Next, the obtained photograph was captured by a scanner, the core portion where the contrast of the image was observed was defined as a crystal grain, and the number of pixels present in each crystal grain was calculated. From the conversion of the number of pixels and the scale, the area of each crystal is obtained, the crystal grain size is defined as the diameter of a perfect circle having the same area as the obtained crystal grain area, and the grain diameter Di of each crystal grain is obtained. It was. This calculation was performed for about 300 crystal grains, and the arithmetic average value of the obtained particle diameters was defined as the average crystal grain diameter <D>. Also, the standard deviation σ was determined from the square root by dividing the square sum of the difference between the grain size Di of each crystal grain and the average crystal grain size <D> by the number N of the measured crystals. An amount σ / <D> obtained by dividing the standard deviation σ by the average crystal grain size <D> was defined as particle size dispersion.

上記の垂直記録媒体１００について、エネルギ分散型蛍光Ｘ線分析装置（ＥＤＸ）の付いた透過電子顕微鏡(ＴＥＭ)により記録層面内の元素濃度分布をマッピングし、平均結晶粒径＜Ｄ＞と粒径分散σ／＜Ｄ＞を評価した。その結果、Ｃｏ−Ｐｔ合金に酸化物の濃度を変えて添加した図４のターゲットを用いた場合、図４に示すような値が得られた。図４に示すいずれの組成のターゲットを用いた場合にも、記録層１０９の結晶粒界でコバルト濃度が低く、かつ図３に示す酸化物を構成する元素の濃度が高く検出された。記録層１０９を単層で形成した試料についてＩＣＰＳ分析をした結果から図４に示すいずれの組成のターゲットを用いた試料でも、記録層１０９の組成はターゲットの組成と概ね一致していた。 For the above-described perpendicular recording medium 100, the element concentration distribution in the recording layer surface is mapped by a transmission electron microscope (TEM) equipped with an energy dispersive X-ray fluorescence spectrometer (EDX), and the average crystal grain size <D> and the grain size The dispersion σ / <D> was evaluated. As a result, when using the target shown in FIG. 4 in which the oxide concentration was added to the Co—Pt alloy, values as shown in FIG. 4 were obtained. When the target having any composition shown in FIG. 4 was used, the cobalt concentration at the crystal grain boundary of the recording layer 109 was low, and the concentration of the element constituting the oxide shown in FIG. 3 was detected high. From the result of the ICPS analysis of the sample in which the recording layer 109 is formed as a single layer, the composition of the recording layer 109 almost coincided with the composition of the target in any sample using the target having any composition shown in FIG.

Ｃｏ−Ｐｔ合金に、図３に示す酸化物を８ｍｏｌ％添加して形成した記録層の平均結晶粒径＜Ｄ＞は、図５に示すように概ね８．２ｎｍ程度であった。これらの添加した酸化物の融点に対して粒径分散σ／＜Ｄ＞を整理すると、図６に示すように融点の低下と共に粒径分散σ／＜Ｄ＞が小さくなることが明らかになった。特にターゲットＡ０３、Ａ０６からＡ１０、並びにＡ１２からＡ１５を用いた場合、σ／＜Ｄ＞を１８．２％以下に小さくすることが可能であった。 The average crystal grain size <D> of the recording layer formed by adding 8 mol% of the oxide shown in FIG. 3 to the Co—Pt alloy was about 8.2 nm as shown in FIG. By arranging the particle size dispersion σ / <D> with respect to the melting point of these added oxides, it became clear that the particle size dispersion σ / <D> became smaller as the melting point decreased as shown in FIG. . In particular, when targets A03, A06 to A10, and A12 to A15 were used, σ / <D> could be reduced to 18.2% or less.

図３に示す酸化物の中で最もσ／＜Ｄ＞を小さくすることができたＯｘ９について、８２ａｔ．％Ｃｏ−１８ａｔ．％Ｐｔ合金に添加する割合を６ｍｏｌ％から１０ｍｏｌ％まで変化させ、ターゲットＡ１２とＡ０９とＡ１３を用いて作製した試料について、平均結晶粒径＜Ｄ＞と粒径分散σ／＜Ｄ＞を比較した。添加する酸化物Ｏｘ９の濃度を増加すると、平均結晶粒径＜Ｄ＞は９．３ｎｍから７．４ｎｍまで減少した。一方、添加する酸化物Ｏｘ９の濃度を増加しても粒径分散σ／＜Ｄ＞はほぼ１６．２％前後で殆ど変化せず、小さな値をとっていた。 As for Ox9 in which σ / <D> could be minimized among the oxides shown in FIG. % Co-18 at. The ratio of addition to the% Pt alloy was changed from 6 mol% to 10 mol%, and the average crystal grain size <D> and the grain size dispersion σ / <D> were compared for samples prepared using the targets A12, A09, and A13. . When the concentration of the added oxide Ox9 was increased, the average crystal grain size <D> decreased from 9.3 nm to 7.4 nm. On the other hand, even when the concentration of the added oxide Ox9 was increased, the particle size dispersion σ / <D> was almost unchanged at around 16.2%, and had a small value.

さらにＯｘ９の添加濃度を８ｍｏｌ％に固定して、コバルトと白金の割合について図４に示すＡ１４とＡ１５のターゲットを用いて比較した。その結果、１６ａｔ．％から２０ａｔ．％まで白金濃度を変化させてコバルトに対して置換しても平均結晶粒径＜Ｄ＞は８．３ｎｍ程度、粒径分散σ／＜Ｄ＞は１６．２％程度の小さな粒径分散を示した。図４に示すターゲットＡ０１を用いた場合を、ターゲットＡ０３とＡ０６のターゲットを用いた場合と比較すると、平均結晶粒径＜Ｄ＞は概ね８．２ｎｍ前後であり、酸化物の融点に依らず略一定であった。一方、粒径分散σ／＜Ｄ＞は２０．４％から１８．２％以下に低減することができた。前記記録層を作製するのに用いたターゲットＡ０３とＡ０６に含有させた酸化物Ｏｘ３とＯｘ６は共晶組成の酸化物を添加した合金ターゲットである。 Furthermore, the addition concentration of Ox9 was fixed at 8 mol%, and the ratio of cobalt and platinum was compared using the targets A14 and A15 shown in FIG. As a result, 16 at. % To 20 at. Even if the platinum concentration is changed up to%, the average crystal grain size <D> is about 8.3 nm and the particle size dispersion σ / <D> is about 16.2%. It was. When the target A01 shown in FIG. 4 is used and the target A03 and the target A06 are used, the average crystal grain size <D> is approximately 8.2 nm, which is almost independent of the melting point of the oxide. It was constant. On the other hand, the particle size dispersion σ / <D> could be reduced from 20.4% to 18.2% or less. The oxides Ox3 and Ox6 contained in the targets A03 and A06 used for producing the recording layer are alloy targets to which an oxide having a eutectic composition is added.

以上の結果を纏めると、（１）共晶組成の酸化物をＣｏ−Ｐｔ合金に添加した場合、平均結晶粒径＜Ｄ＞を大きく変化させずに粒径分散σ／＜Ｄ＞を１８．２％以下に小さくすることができ、（２）融点の低い酸化物をＣｏ−Ｐｔ合金に添加し、その添加濃度を変えた場合、粒径分散σ／＜Ｄ＞を変えずに平均結晶粒径＜Ｄ＞を制御でき、（３）白金の濃度を１６ａｔ．％から２０ａｔ．％まで変化させても粒径分散σ／＜Ｄ＞を小さく保てることが明らかになった。 Summarizing the above results, (1) when an oxide having a eutectic composition is added to the Co—Pt alloy, the grain size dispersion σ / <D> is 18. (2) When an oxide having a low melting point is added to the Co—Pt alloy and the concentration of the addition is changed, the average grain size is not changed without changing the grain size dispersion σ / <D>. The diameter <D> can be controlled, and (3) the concentration of platinum is 16 at. % To 20 at. It was revealed that the particle size dispersion σ / <D> can be kept small even when the content is changed to%.

これらの垂直記録媒体をハードディスクドライブに搭載し、６０°Ｃに加熱後、相対湿度８５％の環境下に１週間暴露し、ランダムシークを継続した。その後、相対湿度を５０％まで低減してから室温に戻し、ハードディスクドライブを分解した。取り出したヘッド並びに垂直記録媒体の表面を、エネルギ分散型蛍光Ｘ線分析装置付きの走査型電子顕微鏡で表面観察並びに元素のマッピング観察を行なった。その結果、ディスク表面で変色などの顕著な変化は認められなかった。また、ランダムシークしたヘッドのスライダ表面で、媒体に起因すると考えられるアルミニウム、マグネシウム、珪素による汚れは元素分析結果から認められなかった。 These perpendicular recording media were mounted on a hard disk drive, heated to 60 ° C., exposed to an environment with a relative humidity of 85% for one week, and random seeking was continued. Thereafter, the relative humidity was reduced to 50%, the temperature was returned to room temperature, and the hard disk drive was disassembled. The head and the surface of the perpendicular recording medium taken out were subjected to surface observation and element mapping observation with a scanning electron microscope equipped with an energy dispersive X-ray fluorescence analyzer. As a result, no significant change such as discoloration was observed on the disk surface. In addition, no contamination due to aluminum, magnesium, or silicon, which is considered to be caused by the medium, was found on the slider surface of the head subjected to random seek from the result of elemental analysis.

なお、上記実施例において、基板１０１には厚さ０．５０８ｍｍ、直径４８ｍｍのガラス基板を用いたが、厚さ０．６３５ｍｍ、直径６５ｍｍのガラス基板でもよく、基板の直径と厚さは限定されない。基板にはクランプするための穴が設けられていても良い。また、軟磁性下地層１０５を形成後にヘリウム等の熱交換用の気体を用いて基板を冷却することは、その後に形成する記録層１０９の粒径分散を低減する上で好ましい。 In the above embodiment, a glass substrate having a thickness of 0.508 mm and a diameter of 48 mm is used as the substrate 101. However, a glass substrate having a thickness of 0.635 mm and a diameter of 65 mm may be used, and the diameter and thickness of the substrate are not limited. . The substrate may be provided with a hole for clamping. In addition, it is preferable to cool the substrate using a heat exchange gas such as helium after forming the soft magnetic underlayer 105 in order to reduce the particle size dispersion of the recording layer 109 formed thereafter.

非磁性中間層１０８を除き、Ａｒガス圧０．７Ｐａの条件で薄膜形成を行なったが、放電ガス圧力は０．７Ｐａに限定されないが、安定して繰り返し放電する圧力を設定する必要がある。非磁性中間層１０７の放電ガス圧力を非磁性中間層１０８よりも低く設定するのは、ｈｃｐ構造をとる非磁性中間層１０７の結晶を膜面の法線方向にｃ軸配向させ、かつ非磁性中間層１０８としてＲｕを８ｎｍ形成する際にＡｒガス圧を２Ｐａとしたのは、薄膜形成時の自己陰影効果（Self Shadowing effect）により、空間的に結晶粒の分離を促進することによりその上に形成する記録層１０９を構成する結晶粒の空間的な分離を促進するためである。非磁性中間層１０８を形成する際に圧力を高くしすぎると、排気能の低下を起こす場合もあるため、非磁性中間層１０7を形成する際の放電圧力に比べ、相対的に高い圧力を設定することが望ましい。 Although the thin film was formed under the condition of Ar gas pressure 0.7 Pa except for the nonmagnetic intermediate layer 108, the discharge gas pressure is not limited to 0.7 Pa, but it is necessary to set the pressure for stable and repeated discharge. The reason why the discharge gas pressure of the nonmagnetic intermediate layer 107 is set lower than that of the nonmagnetic intermediate layer 108 is that the crystals of the nonmagnetic intermediate layer 107 having an hcp structure are c-axis oriented in the normal direction of the film surface and nonmagnetic The reason why the Ar gas pressure is set to 2 Pa when Ru is formed as the intermediate layer 108 is that the separation of crystal grains is spatially promoted by the self shadowing effect at the time of thin film formation. This is to promote spatial separation of crystal grains constituting the recording layer 109 to be formed. If the pressure is too high when forming the nonmagnetic intermediate layer 108, the exhaust capacity may be lowered. Therefore, a relatively high pressure is set compared to the discharge pressure when forming the nonmagnetic intermediate layer 107. It is desirable to do.

非磁性下地層１０２として厚さ５ｎｍの５０ａｔ．％Ａｌ−５０ａｔ．％Ｔｉ合金膜を形成したが、高濃度のＴｉを含有していれば金属間化合物を潜在的に作りやすいため、結晶粒が微細化しかつ接着力が高くなるため、アルミニウム（Ａｌ）に換わる元素としてＣｒ、Ｃｏ、Ｎｉ等を置換或いはＡｌと同時に含有させても良い。非磁性下地層１０２の厚さは１０ｎｍよりも厚くすることができるが、厚くしすぎると耐摺動信頼性が劣化する。一方、非磁性下地層１０２を設けない場合には、基板１０１との接着力が低下する。非磁性下地層１０２の厚さを３ｎｍから１０ｎｍ形成すれば、接着力が向上しかつ耐摺動信頼性が向上するので好ましい。 As the nonmagnetic underlayer 102, a 50 at. % Al-50 at. An element that replaces aluminum (Al) because a Ti alloy film is formed, but if it contains a high concentration of Ti, an intermetallic compound is potentially easily formed, so that the crystal grains become finer and the adhesive strength increases. Cr, Co, Ni, etc. may be substituted or contained simultaneously with Al. Although the thickness of the nonmagnetic underlayer 102 can be made thicker than 10 nm, if it is made too thick, the sliding resistance reliability deteriorates. On the other hand, when the nonmagnetic underlayer 102 is not provided, the adhesive force with the substrate 101 is reduced. If the thickness of the nonmagnetic underlayer 102 is 3 nm to 10 nm, it is preferable because the adhesive strength is improved and the sliding resistance reliability is improved.

軟磁性層１０３として厚さ３０ｎｍの５１ａｔ．％Ｆｅ−３４ａｔ．％Ｃｏ−１０ａｔ．％Ｔａ−５ａｔ．％Ｚｒ合金膜を形成し、非磁性層１０４として厚さ０．７ｎｍのＲｕ膜を形成後、再び軟磁性下地層１０５として厚さ３０ｎｍの５１ａｔ．％Ｆｅ−３４ａｔ．％Ｃｏ−１０ａｔ．％Ｔａ−５ａｔ．％Ｚｒ合金膜を形成したのは、軟磁性下地層を反強磁性結合させ、かつ上部記録層の磁化状態が決まった後で軟磁性下地層の残留磁化に起因したノイズを抑制するためである。非磁性層１０４として厚さ０．７ｎｍのＲｕ膜に代わり、Ｒｕ−５０％Ｆｅ合金等、Ｒｕを含んだ合金或いはＲｕを主成分とする合金を用いることも可能である。非磁性層１０４の厚さを０．７ｎｍとしたのは、反強磁性の結合磁界が大きくなるようにするための膜厚設定であり、Ｒｕを含んだ合金或いはＲｕを主成分とする合金を用いる場合、概ねその膜厚として０．５ｎｍから０．８ｎｍを設定することが好ましい。 As the soft magnetic layer 103, a 51 at. % Fe-34 at. % Co-10 at. % Ta-5 at. % Zr alloy film, a 0.7-nm-thick Ru film as the nonmagnetic layer 104, and a soft-magnetic underlayer 105 with a thickness of 51 at. % Fe-34 at. % Co-10 at. % Ta-5 at. The reason why the% Zr alloy film is formed is to suppress the noise caused by the residual magnetization of the soft magnetic underlayer after the soft magnetic underlayer is antiferromagnetically coupled and after the magnetization state of the upper recording layer is determined. . As the nonmagnetic layer 104, an Ru-containing alloy or an alloy containing Ru as a main component, such as a Ru-50% Fe alloy, may be used instead of the 0.7 nm-thick Ru film. The thickness of the nonmagnetic layer 104 is set to 0.7 nm in order to increase the antiferromagnetic coupling magnetic field, and an alloy containing Ru or an alloy containing Ru as a main component is used. When used, it is preferable to set the film thickness from 0.5 nm to 0.8 nm.

さらに軟磁性層１０３と１０５の組成は前記の組成に限らず、耐食信頼性が得られる軟磁性合金であれば組成は限定されない。軟磁性層１０３と１０５の各層の残留磁束密度と膜厚の積は略等しく、非磁性層１０４を介して反強磁性結合が可能な大きさであることが好ましいが、軟磁性層１０３と１０５を設けなくても記録層１０９の結晶配向性を向上させることによりσ／＜Ｄ＞を小さくすることは可能である。 Further, the composition of the soft magnetic layers 103 and 105 is not limited to the above composition, and the composition is not limited as long as it is a soft magnetic alloy that can provide corrosion resistance reliability. The products of the residual magnetic flux density and the film thickness of each of the soft magnetic layers 103 and 105 are substantially equal and are preferably large enough to allow antiferromagnetic coupling through the nonmagnetic layer 104. It is possible to reduce σ / <D> by improving the crystal orientation of the recording layer 109 even without providing.

非磁性中間層１０６としてＮｉ−８ａｔ．％Ｗ合金膜を８ｎｍ形成したのは、軟磁性下地層上に形成する非磁性中間層１０７としてｈｃｐ構造をとるＲｕのｃ軸を高配向させるためである。非磁性中間層１０８としてＲｕを８ｎｍ形成する際にはＡｒガス圧を２Ｐａとしたのは前述した理由による。 As the nonmagnetic intermediate layer 106, Ni-8 at. The reason why the% W alloy film is formed to 8 nm is to highly orient the c axis of Ru having the hcp structure as the nonmagnetic intermediate layer 107 formed on the soft magnetic underlayer. The reason why the Ar gas pressure is set to 2 Pa when Ru is formed to be 8 nm as the nonmagnetic intermediate layer 108 is as described above.

図３に示す酸化物の中でＯｘ３とＯｘ６からＯｘ１０で示す組成の融点は、図３の右側に記すように１５４３゜Ｃ以下である。酸化物の組成は図３に示す組成に限定されないが、非特許文献（窯業協会、窯業工学ハンドブック（新版）、昭和４６年２月１５日、技報堂、2046ページ、付図-32.53）のＡｌ_２Ｏ_３-ＭｇＯ-ＳｉＯ_２系状態図で融点が１５００゜Ｃ以下の組成領域を有する酸化物を添加することが望ましい。具体的には、下記６組成により囲まれる酸化物の濃度範囲である。
(1)５ｗｔ．％Ａｌ_２Ｏ_３−３０ｗｔ．％ＭｇＯ−６５ｗｔ．％ＳｉＯ_２,（Ｏｘ７の組成）
(2)１２ｗｔ．％Ａｌ_２Ｏ_３−２０ｗｔ．％ＭｇＯ−６８ｗｔ．％ＳｉＯ_２
(3)１７ｗｔ．％Ａｌ_２Ｏ_３−１０ｗｔ．％ＭｇＯ−８３ｗｔ．％ＳｉＯ_２
(4)１５ｗｔ．％Ａｌ_２Ｏ_３−５ｗｔ．％ＭｇＯ−８０ｗｔ．％ＳｉＯ_２
(5)３９ｗｔ．％Ａｌ_２Ｏ_３−１４ｗｔ．％ＭｇＯ−４７ｗｔ．％ＳｉＯ_２
(6)２３ｗｔ．％Ａｌ_２Ｏ_３−３０ｗｔ．％ＭｇＯ−４７ｗｔ．％ＳｉＯ_２
酸化物としてＮａ_２ＯやＷＯ_３を選択して添加した場合には、酸化物を含有した記録層から吸着水に起因して生じたイオンがヘッドと磁気記録媒体の界面に溶出しやすくなるため、耐食信頼性を向上する上で酸化物としてＡｌ_２Ｏ_３-ＭｇＯ-ＳｉＯ_２系を選択することが好ましい。白金の添加量として１６〜２０ａｔ．％となるようにしたのは、２０ａｔ．％よりも白金の濃度を高くすると異方性磁界が大きくなりすぎ、高密度記録する際にオーバーライト性能が劣化するためであり、１６ａｔ．％よりも白金濃度を低くすると所望の媒体の保磁力が得にくくなるためである。 In the oxide shown in FIG. 3, the melting point of the composition represented by Ox3 and Ox6 to Ox10 is 1543 ° C. or less as shown on the right side of FIG. The composition of the oxide is not limited to the composition shown in FIG. 3, but it is Al ₂ O in non-patent literature (Ceramic Association, Ceramic Engineering Handbook (new edition), February 15, 1971, Gihodo, page 2046, Attached Figure -32.53). It is desirable to add an oxide having a composition region having a melting point of 1500 ° C. or lower in the _3- MgO—SiO ₂ phase diagram. Specifically, it is an oxide concentration range surrounded by the following six compositions.
(1) 5 wt. % _Al 2 _O 3 -30wt. % MgO-65 wt. % SiO ₂ (Composition of Ox7)
(2) 12 wt. % _Al 2 _O 3 -20wt. % MgO-68 wt. % SiO ₂
(3) 17 wt. % _Al 2 _O 3 -10wt. % MgO-83 wt. % SiO ₂
(4) 15 wt. % _Al 2 _O 3 -5wt. % MgO-80 wt. % SiO ₂
(5) 39 wt. % _Al 2 _O 3 -14wt. % MgO-47 wt. % SiO ₂
(6) 23 wt. % _Al 2 _O 3 -30wt. % MgO-47 wt. % SiO ₂
When Na ₂ O or WO ₃ is selected and added as an oxide, ions generated due to adsorbed water from the recording layer containing the oxide easily elute at the interface between the head and the magnetic recording medium. In order to improve the corrosion resistance reliability, it is preferable to select an Al ₂ O ₃ —MgO—SiO ₂ system as the oxide. As an addition amount of platinum, 16 to 20 at. % Is 20 at. If the platinum concentration is higher than%, the anisotropic magnetic field becomes too large, and the overwrite performance deteriorates when recording at high density. This is because if the platinum concentration is lower than%, it is difficult to obtain the coercive force of the desired medium.

保護層１１０の厚さは薄い方が電磁変換特性上好ましいが、保護層を設けずに潤滑層を形成すると耐摺動性が劣化するので好ましくは３ｎｍから４ｎｍ程度の厚さで形成することが望ましい。 The thickness of the protective layer 110 is preferably smaller in terms of electromagnetic conversion characteristics. However, if the lubricating layer is formed without providing the protective layer, the sliding resistance deteriorates, so that the protective layer 110 is preferably formed to a thickness of about 3 nm to 4 nm. desirable.

記録層の形成にはＤＣマグネトロンスパッタリング法だけでなく、ＤＣパルススパッタ法、対向ターゲットスパッタ法、高周波（ＲＦ）マグネトロンスパッタ法等の物理蒸着法を用いることも可能である。高周波を用いたスパッタ法による製膜は発熱量が大きいため、粒径分散が大きくなりやすいことから、ＤＣマグネトロンスパッタ法は特に好ましい。 The recording layer can be formed not only by DC magnetron sputtering but also by physical vapor deposition such as DC pulse sputtering, counter target sputtering, and radio frequency (RF) magnetron sputtering. The DC magnetron sputtering method is particularly preferable because film formation by sputtering using a high frequency generates a large amount of heat and tends to increase particle size dispersion.

上記実施例の変形例１として、記録層１０９の合金を、更にＣｒを１２ａｔ．％から２０ａｔ．％添加した（７０〜６２ａｔ．％）Ｃｏ−１８ａｔ．％Ｐｔ−（１２〜２０ａｔ．％）Ｃｒ合金とし、添加する酸化物を図３のＯｘ１とＯｘ９を選択して図７に示すターゲットＢ０１を用いて垂直記録媒体を形成した。平均結晶粒径＜Ｄ＞は８．６ｎｍであり、図４のターゲットＡ０１を用いた場合に比べ、平均結晶粒径＜Ｄ＞が若干大きくなった。酸化物として図３に示すＯｘ９を選択した場合、ターゲットＢ０９とＢ１２とＢ１３を用いて形成した垂直記録媒体の記録層（９０〜９４ｍｏｌ％）ＣｏＰｔＣｒ−（１０〜６ｍｏｌ％）Ｏｘ９を比較すると、酸化物Ｏｘ９の添加濃度が減少するに従い、平均結晶粒径＜Ｄ＞が大きくなった。一方、これらの媒体の記録層について測定した粒径分散σ／＜Ｄ＞は概ね１６％台でターゲットＢ０１を用いた場合に比べ小さな分散を示した。 As a first modification of the above-described embodiment, the alloy of the recording layer 109 is further replaced with 12 at. % To 20 at. % (70-62 at.%) Co-18 at. % Pt- (12 to 20 at.%) Cr alloy, Ox1 and Ox9 in FIG. 3 were selected as oxides to be added, and a perpendicular recording medium was formed using a target B01 shown in FIG. The average crystal grain size <D> was 8.6 nm, and the average crystal grain size <D> was slightly larger than when the target A01 of FIG. 4 was used. When Ox9 shown in FIG. 3 is selected as the oxide, the recording layer (90 to 94 mol%) CoPtCr— (10 to 6 mol%) Ox9 of the perpendicular recording medium formed using the targets B09, B12, and B13 is compared with the oxidation. As the added concentration of the substance Ox9 decreased, the average crystal grain size <D> increased. On the other hand, the particle size dispersion σ / <D> measured for the recording layers of these media was about 16%, which was smaller than that when the target B01 was used.

さらに酸化物Ｏｘ９の添加濃度を８ｍｏｌ％に固定し、白金の濃度を１８ａｔ．％に固定して、コバルトとクロムの割合についてＢ１５とＢ１４のターゲットを用いて形成した垂直記録媒体の記録層１０９について比較した。その結果、１２ａｔ．％から２０ａｔ．％まで白金濃度を変化させると平均結晶粒径＜Ｄ＞は７．８ｎｍから８．９ｎｍに増加するものの、粒径分散σ／＜Ｄ＞は１６．２％程度の小さな粒径分散を示すことが明らかになった。 Furthermore, the addition concentration of the oxide Ox9 was fixed at 8 mol%, and the platinum concentration was 18 at. The recording layer 109 of the perpendicular recording medium formed using B15 and B14 targets was compared with respect to the ratio of cobalt and chromium. As a result, 12 at. % To 20 at. When the platinum concentration is changed to%, the average crystal grain size <D> increases from 7.8 nm to 8.9 nm, but the particle size dispersion σ / <D> shows a small particle size dispersion of about 16.2%. Became clear.

これらの媒体の記録層１０９について、エネルギ分散型蛍光Ｘ線分析装置（ＥＤＸ）の付いた透過電子顕微鏡(ＴＥＭ)により記録層面内の元素濃度分布をマッピングし粒界の組成揺らぎを調べた。その結果、図７に示すいずれの組成のターゲットを用いた場合にも、記録層１０９の結晶粒界でコバルト濃度が低く、図３に示す酸化物を構成する元素の濃度が高く検出された。 Regarding the recording layer 109 of these media, the element concentration distribution in the surface of the recording layer was mapped by a transmission electron microscope (TEM) equipped with an energy dispersive X-ray fluorescence analyzer (EDX), and the composition fluctuation of the grain boundary was examined. As a result, even when the target having any composition shown in FIG. 7 was used, the cobalt concentration was low at the crystal grain boundary of the recording layer 109 and the concentration of the element constituting the oxide shown in FIG. 3 was detected high.

以上の結果を上記実施例と比較する。ターゲットＡ０９とＢ０９、Ａ１２とＢ１２、Ａ１３とＢ１３をそれぞれ比較する。いずれもＣｏにＣｒを１６ａｔ．％添加して置換すると平均結晶粒径＜Ｄ＞は約０．５ｎｍ増加するものの、粒径分散σ／＜Ｄ＞は１６％台の小さな値をとる。一方、ターゲットＡ０１とＢ０１の比較から明らかなように、ＳｉＯ_２だけを単独で添加した場合に平均結晶粒径＜Ｄ＞は酸化物としてＯｘ９を選択した場合と同程度にできるが、粒径分散σ／＜Ｄ＞は２０％台と大きくなった。すなわち、酸化物の組成を適切に選択することにより、Ｃｒが添加された合金でもＣｒが添加されていない合金と同様に粒径分散σ／＜Ｄ＞は小さく制御できる。 The above result is compared with the said Example. The targets A09 and B09, A12 and B12, and A13 and B13 are compared. In either case, Cr is added to Co at 16 at. %, The average grain size <D> increases by about 0.5 nm, but the grain size dispersion σ / <D> takes a small value on the order of 16%. On the other hand, as apparent from the comparison between the targets A01 and B01, when only SiO ₂ is added alone, the average crystal grain size <D> can be made the same as when Ox9 is selected as the oxide, but the grain size dispersion σ / <D> was as high as 20%. That is, by appropriately selecting the composition of the oxide, the particle size dispersion σ / <D> can be controlled to be small as in the alloy to which Cr is added even in the alloy to which Cr is not added.

これらの垂直記録媒体について、上記実施例と同様にハードディスクドライブに搭載して同様の評価を行った結果、ディスク表面で変色などの顕著な変化は認められず、ランダムシークした磁気ヘッドのスライダ表面で、媒体に起因すると考えられるアルミニウム、マグネシウム、珪素による汚れは元素分析結果から認められなかった。 These perpendicular recording media were mounted on a hard disk drive in the same manner as in the above-described embodiment, and as a result of the same evaluation, no noticeable change such as discoloration was observed on the disk surface, and the slider surface of the magnetic head subjected to random seek was observed. As a result of elemental analysis, no contamination due to aluminum, magnesium, or silicon, which was considered to be caused by the medium, was observed.

次に上記実施例の変形例２の垂直記録媒体３００の断面を図８に示す。基板１０1上に非磁性下地層１０２、非磁性中間層１０６，１０７，１０８、記録層１０９、保護層１１０、潤滑層１１１を有する。変形例１の垂直記録媒体において、軟磁性下地層１０３、非磁性層１０４、軟磁性下地層１０５を形成しなかった構成例である。 Next, FIG. 8 shows a cross section of the perpendicular recording medium 300 of the second modification of the above embodiment. A nonmagnetic underlayer 102, nonmagnetic intermediate layers 106, 107, and 108, a recording layer 109, a protective layer 110, and a lubricating layer 111 are provided on a substrate 101. In the perpendicular recording medium of Modification Example 1, the soft magnetic underlayer 103, the nonmagnetic layer 104, and the soft magnetic underlayer 105 are not formed.

基板１０１には厚さ０．５０８ｍｍ、直径４８ｍｍのガラス基板を用いた。基板の加熱は行なわず、非磁性中間層１０８を除き、Ａｒガス圧０．７Ｐａの条件でＤＣマグネトロンスパッタリング法により、以下の薄膜形成を行なった。 As the substrate 101, a glass substrate having a thickness of 0.508 mm and a diameter of 48 mm was used. The substrate was not heated, and the following thin film was formed by DC magnetron sputtering under the condition of Ar gas pressure of 0.7 Pa except for the nonmagnetic intermediate layer.

非磁性下地層１０２として厚さ５ｎｍの５０ａｔ．％Ａｌ−５０ａｔ．％Ｔｉ合金膜を形成した。さらに、非磁性中間層１０６としてＮｉ−８ａｔ．％Ｗ合金膜を８ｎｍ、非磁性中間層１０７としてＲｕを８ｎｍ形成した。非磁性中間層１０８としてＲｕを８ｎｍ形成する際にはＡｒガス圧２Ｐａとした。 As the nonmagnetic underlayer 102, a 50 at. % Al-50 at. % Ti alloy film was formed. Further, Ni-8 at. The% W alloy film was formed to 8 nm, and Ru was formed to 8 nm as the nonmagnetic intermediate layer 107. When forming 8 nm of Ru as the nonmagnetic intermediate layer 108, the Ar gas pressure was set to 2 Pa.

さらに、図３に示す酸化物Ｏｘ１あるいはＯｘ９と白金並びにクロムを含有したコバルト基合金を記録層１０９として厚さ１２ｎｍとなるように、図９に示す組成のターゲットを用いて作製した。その後、化学蒸着法にて炭素を主成分とする保護層１１０を厚さ４ｎｍ形成し、大気中に取り出し、パーフルオロポリエーテルを含む潤滑層１１１を形成した。 Further, a cobalt-based alloy containing oxide Ox1 or Ox9 and platinum and chromium shown in FIG. 3 was prepared as a recording layer 109 using a target having the composition shown in FIG. Thereafter, a protective layer 110 containing carbon as a main component was formed by a chemical vapor deposition method to a thickness of 4 nm, taken out into the atmosphere, and a lubricating layer 111 containing perfluoropolyether was formed.

これらの媒体について、ＴＥＭにより平均結晶粒径＜Ｄ＞と粒径分散σ／＜Ｄ＞を評価した結果、図９に示すような値が得られた。ターゲットＢ１４，Ｂ０９，Ｂ１５を用いて（６２〜７０ａｔ．％）Ｃｏ−１８ａｔ．％Ｐｔ−（２０〜１２）ａｔ．％Ｃｒ合金に酸化物Ｏｘ９の濃度を８ｍｏｌ％添加した記録層１０９についてＴＥＭ観察した結果、平均結晶粒径＜Ｄ＞は８〜９ｎｍでほぼ一定値をとり、粒径分散σ／＜Ｄ＞は１６％台であった。一方、ターゲットＢ１２，Ｂ１３，Ｂ０９を用いて６６ａｔ．％Ｃｏ−１８ａｔ．％Ｐｔ−１６ａｔ．％Ｃｒ合金に酸化物Ｏｘ９の濃度を６〜１０ｍｏｌ％の範囲で添加した記録層１０９についてＴＥＭ観察した結果、平均結晶粒径＜Ｄ＞は７．８〜９．４ｎｍであり、酸化物添加濃度の増加に伴い、平均結晶粒径＜Ｄ＞が減少した。一方、粒径分散σ／＜Ｄ＞は１６％台であり、ＳｉＯ２だけを添加した場合に比べ粒径分散σ／＜Ｄ＞は小さく制御することができた。 For these media, the average crystal grain size <D> and the particle size dispersion σ / <D> were evaluated by TEM. As a result, values as shown in FIG. 9 were obtained. Using targets B14, B09, B15 (62-70 at.%) Co-18 at. % Pt- (20-12) at. As a result of TEM observation of the recording layer 109 in which 8 mol% of the oxide Ox9 was added to the% Cr alloy, the average crystal grain size <D> was almost constant at 8 to 9 nm, and the grain size dispersion σ / <D> was It was 16%. On the other hand, using targets B12, B13, B09, 66 at. % Co-18 at. % Pt-16 at. As a result of TEM observation of the recording layer 109 in which the concentration of the oxide Ox9 was added to the% Cr alloy in the range of 6 to 10 mol%, the average crystal grain size <D> was 7.8 to 9.4 nm. The average crystal grain size <D> decreased with increasing. On the other hand, the particle size dispersion σ / <D> was on the order of 16%, and the particle size dispersion σ / <D> could be controlled to be smaller than when only SiO 2 was added.

さらにこれらの媒体の記録層１０９について、ＥＤＸの付いたＴＥＭを用いて記録層面内の元素濃度分布をマッピングし記録層の粒界について面内方向の組成揺らぎを調べた。その結果、図９に示すいずれの組成のターゲットを用いた記録層１０９でも、記録層１０９の結晶粒界でコバルト濃度が低く、図３に示す酸化物を構成する元素の濃度が高く検出された。 Further, for the recording layer 109 of these media, the element concentration distribution in the recording layer surface was mapped using a TEM with EDX, and the composition fluctuation in the in-plane direction was investigated at the grain boundary of the recording layer. As a result, in the recording layer 109 using the target of any composition shown in FIG. 9, the cobalt concentration was low at the crystal grain boundary of the recording layer 109, and the concentration of the element constituting the oxide shown in FIG. 3 was detected high. .

これらの垂直記録媒体について、上記実施例と同様にハードディスクドライブに搭載して同様の評価を行った結果、ディスク表面で変色などの顕著な変化は認められなかった。また、ランダムシークした磁気ヘッドのスライダ表面で、媒体に起因すると考えられるアルミニウム、マグネシウム、珪素による汚れは元素分析結果から認められなかった。 These perpendicular recording media were mounted on a hard disk drive in the same manner as in the above example and evaluated in the same manner. As a result, no significant change such as discoloration was observed on the disk surface. Also, no contamination due to aluminum, magnesium, or silicon, which is considered to be caused by the medium, was found on the slider surface of the magnetic head subjected to random seek from the result of elemental analysis.

本発明の実施例による垂直記録媒体の構成を示す断面図である。1 is a cross-sectional view illustrating a configuration of a perpendicular recording medium according to an embodiment of the present invention. 記録層のイメージを示す断面図である。It is sectional drawing which shows the image of a recording layer. 検討に用いた酸化物の組成と融点の関係を示す図である。It is a figure which shows the relationship between the composition of the oxide used for examination, and melting | fusing point. ターゲット組成と記録層の平均結晶粒径<Ｄ>並びに粒径分散σ／＜Ｄ＞の関係を示す図である。It is a figure which shows the relationship between a target composition, the average crystal grain diameter <D> of a recording layer, and particle size dispersion | distribution (sigma) / <D>. 平均結晶粒径<Ｄ>とターゲットに添加した酸化物の融点との関係を示す図である。It is a figure which shows the relationship between average crystal grain diameter <D> and melting | fusing point of the oxide added to the target. 粒径分散σ／＜Ｄ＞とターゲットに添加した酸化物の融点との関係を示す図である。It is a figure which shows the relationship between particle size dispersion | distribution (sigma) / <D> and melting | fusing point of the oxide added to the target. 変形例１のターゲット組成と記録層の平均結晶粒径<Ｄ>並びに粒径分散σ／＜Ｄ＞の関係を示す図である。FIG. 10 is a diagram showing the relationship between the target composition of Modification 1 and the average crystal grain size <D> and grain size dispersion σ / <D> of the recording layer. 変形例２の垂直記録媒体の構成を示す断面図である。10 is a cross-sectional view illustrating a configuration of a perpendicular recording medium according to Modification 2. FIG. 変形例２のターゲット組成と記録層の平均結晶粒径<Ｄ>並びに粒径分散σ／＜Ｄ＞の関係を示す図である。FIG. 10 is a diagram showing the relationship between the target composition of Modification 2 and the average crystal grain size <D> and grain size dispersion σ / <D> of the recording layer.

符号の説明Explanation of symbols

１００…垂直記録媒体、
１０１…基板、
１０２…非磁性下地層、
１０３…軟磁性下地層、
１０４…非磁性層、
１０５…軟磁性下地層、
１０６，１０７，１０８…非磁性中間層、
１０９…記録層、
１１０…保護層、
１１１…潤滑層、
３００…垂直記録媒体、
Ａ…強磁性のコバルトを主成分とする柱状の結晶粒、
Ｂ…結晶粒内に比べコバルト濃度が低い結晶粒界。
100 ... perpendicular recording medium,
101 ... substrate,
102 ... nonmagnetic underlayer,
103 ... soft magnetic underlayer,
104 ... nonmagnetic layer,
105: Soft magnetic underlayer,
106, 107, 108 ... nonmagnetic intermediate layer,
109 ... recording layer,
110 ... Protective layer,
111 ... Lubrication layer,
300 ... perpendicular recording medium,
A: Columnar crystal grains mainly composed of ferromagnetic cobalt,
B: A grain boundary having a cobalt concentration lower than that in the crystal grains.

Claims

基板上に、少なくとも非磁性下地層と記録層と保護層とを有する垂直磁気記録媒体であって、前記記録層は、強磁性のコバルトを主成分とする結晶粒と、前記結晶粒内に比べコバルトの濃度が低い結晶粒界とを有し、該結晶粒界が共晶組成の酸化物を含むことを特徴とする垂直磁気記録媒体。 A perpendicular magnetic recording medium having at least a non-magnetic underlayer, a recording layer, and a protective layer on a substrate, wherein the recording layer has a crystal grain mainly composed of ferromagnetic cobalt compared to the inside of the crystal grain. A perpendicular magnetic recording medium comprising: a crystal grain boundary having a low cobalt concentration, wherein the crystal grain boundary contains an oxide having a eutectic composition.

前記記録層が、白金を含有したコバルト基合金であることを特徴とする請求項１記載の垂直磁気記録媒体。 2. The perpendicular magnetic recording medium according to claim 1, wherein the recording layer is a cobalt-based alloy containing platinum.

前記記録層が、白金とクロムを含有したコバルト基合金であることを特徴とする請求項１記載の垂直磁気記録媒体。 2. The perpendicular magnetic recording medium according to claim 1, wherein the recording layer is a cobalt-based alloy containing platinum and chromium.

前記酸化物が、マグネシウムと珪素の酸化物、ニオブと珪素の酸化物、アルミニウムとマグネシウムと珪素の酸化物のうちのいずれかであることを特徴とする請求項１記載の垂直磁気記録媒体。 2. The perpendicular magnetic recording medium according to claim 1, wherein the oxide is any one of an oxide of magnesium and silicon, an oxide of niobium and silicon, and an oxide of aluminum, magnesium and silicon.

前記非磁性下地層と記録層の間に、該記録層の結晶粒の空間的な分離を促進するための非磁性中間層を有することを特徴とする請求項１記載の垂直磁気記録媒体。 2. The perpendicular magnetic recording medium according to claim 1, further comprising a nonmagnetic intermediate layer for promoting spatial separation of crystal grains of the recording layer between the nonmagnetic underlayer and the recording layer.

前記非磁性下地層と非磁性中間層の間に、軟磁性下地層を有することを特徴とする請求項５記載の垂直磁気記録媒体。 6. The perpendicular magnetic recording medium according to claim 5, further comprising a soft magnetic underlayer between the nonmagnetic underlayer and the nonmagnetic intermediate layer.

基板面に平行な方向の記録層の結晶粒像を透過電子顕微鏡により撮影し、得られた写真をスキャナで取り込み、画像のコントラストが観察されるコア部分を結晶粒と定義し、各結晶粒に存在するピクセル数を計算し、ピクセル数とスケールとの換算から各結晶の面積を求め、得られた各結晶粒の面積と同じ面積の真円の直径として結晶粒径を定義し、個々の結晶粒の粒径Ｄｉを求め、この計算を３００個程度の結晶粒について行ない、得られた粒子径の算術平均値を平均結晶粒径＜Ｄ＞とし、個々の結晶粒の粒径Ｄｉと平均結晶粒径＜Ｄ＞の差分の二乗和を測定した結晶の個数Ｎで割り、その平方根から標準偏差σを求め、この標準偏差σを平均結晶粒径＜Ｄ＞で除した量σ／＜Ｄ＞を粒径分散とした場合、σ／＜Ｄ＞が１８．２％以下であることを特徴とする請求項１記載の垂直磁気記録媒体。 Take a crystal grain image of the recording layer in the direction parallel to the substrate surface with a transmission electron microscope, capture the obtained photograph with a scanner, define the core part where the contrast of the image is observed as a crystal grain, Calculate the number of existing pixels, calculate the area of each crystal from the conversion of the number of pixels and the scale, define the crystal grain size as the diameter of a perfect circle of the same area as the area of each obtained crystal grain, individual crystal The grain size Di is obtained, and this calculation is performed for about 300 crystal grains. The arithmetic average value of the obtained grain sizes is defined as the average crystal grain size <D>. The sum of squares of the difference of the grain size <D> is divided by the number N of the measured crystals, the standard deviation σ is obtained from the square root, and the quantity σ / <D> obtained by dividing the standard deviation σ by the average crystal grain size <D> Is a particle size dispersion, σ / <D> is 18.2% or less The perpendicular magnetic recording medium according to claim 1, wherein the door.

基板上に、少なくとも非磁性下地層と記録層と保護層とを有する垂直磁気記録媒体であって、前記記録層は、強磁性のコバルトを主成分とする結晶粒と、前記結晶粒内に比べコバルトの濃度が低い結晶粒界とを有し、該結晶粒界がアルミニウムと珪素とマグネシウムの酸化物を含み、該酸化物の融点が１５００°Ｃ以下であることを特徴とする垂直磁気記録媒体。 A perpendicular magnetic recording medium having at least a non-magnetic underlayer, a recording layer, and a protective layer on a substrate, wherein the recording layer has a crystal grain mainly composed of ferromagnetic cobalt compared to the inside of the crystal grain. A perpendicular magnetic recording medium having a crystal grain boundary having a low cobalt concentration, the crystal grain boundary containing an oxide of aluminum, silicon, and magnesium, and a melting point of the oxide of 1500 ° C. or lower. .

前記酸化物の濃度範囲が、
５ｗｔ．％Ａｌ_２Ｏ_３−３０ｗｔ．％ＭｇＯ−６５ｗｔ．％ＳｉＯ_２と、
１２ｗｔ．％Ａｌ_２Ｏ_３−２０ｗｔ．％ＭｇＯ−６８ｗｔ．％ＳｉＯ_２と、
１７ｗｔ．％Ａｌ_２Ｏ_３−１０ｗｔ．％ＭｇＯ−８３ｗｔ．％ＳｉＯ_２と、
１５ｗｔ．％Ａｌ_２Ｏ_３−５ｗｔ．％ＭｇＯ−８０ｗｔ．％ＳｉＯ_２と、
３９ｗｔ．％Ａｌ_２Ｏ_３−１４ｗｔ．％ＭｇＯ−４７ｗｔ．％ＳｉＯ_２と、
２３ｗｔ．％Ａｌ_２Ｏ_３−３０ｗｔ．％ＭｇＯ−４７ｗｔ．％ＳｉＯ_２と、
により囲まれる範囲であることを特徴とする請求項８記載の垂直磁気記録媒体。 The concentration range of the oxide is
5 wt. % _Al 2 _O 3 -30wt. % MgO-65 wt. And% SiO _2,
12 wt. % _Al 2 _O 3 -20wt. % MgO-68 wt. And% SiO _2,
17 wt. % _Al 2 _O 3 -10wt. % MgO-83 wt. And% SiO _2,
15 wt. % _Al 2 _O 3 -5wt. % MgO-80 wt. And% SiO _2,
39 wt. % _Al 2 _O 3 -14wt. % MgO-47 wt. And% SiO _2,
23 wt. % _Al 2 _O 3 -30wt. % MgO-47 wt. And% SiO _2,
The perpendicular magnetic recording medium according to claim 8, wherein the perpendicular magnetic recording medium is surrounded by a magnetic field.

前記非磁性下地層と記録層の間に、該記録層の結晶粒の空間的な分離を促進するための非磁性中間層を有することを特徴とする請求項８記載の垂直磁気記録媒体。 9. The perpendicular magnetic recording medium according to claim 8, further comprising a nonmagnetic intermediate layer for promoting spatial separation of crystal grains of the recording layer between the nonmagnetic underlayer and the recording layer.