JP2013143156A - Co-Fe ALLOY SOFT MAGNETIC BASE LAYER - Google Patents
Co-Fe ALLOY SOFT MAGNETIC BASE LAYER Download PDFInfo
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Abstract
Description
本発明は、垂直磁気記録媒体に用いられるＣｏ−Ｆｅ系合金軟磁性下地層に関するものである。 The present invention relates to a Co—Fe based soft magnetic underlayer used in a perpendicular magnetic recording medium.
近年、高度情報化社会により磁気記録の高密度化が強く望まれている。この高密度化を実現する技術として、従来の面内磁気記録方式に代わり、垂直磁気記録方式が実用化されている。
垂直磁気記録方式とは、垂直磁気記録媒体の磁性層を媒体面に対して磁化容易軸が垂直方向に配向するように形成されたものであり、記録密度を上げてもビット内の反磁界が小さく、記録再生特性の低下が少ない高記録密度に適した方法である。そして、垂直磁気記録方式においては、一般的に、ガラス等の基板上に密着層、軟磁性下地層、非磁性中間層、磁性層、保護層が順次成膜されている。
In recent years, high recording density has been strongly demanded by an advanced information society. As a technique for realizing this high density, a perpendicular magnetic recording system has been put into practical use instead of the conventional in-plane magnetic recording system.
Perpendicular magnetic recording is a method in which the magnetic layer of a perpendicular magnetic recording medium is formed so that the axis of easy magnetization is oriented perpendicularly to the medium surface. This method is suitable for high recording density, which is small and has little deterioration in recording / reproducing characteristics. In the perpendicular magnetic recording system, generally, an adhesion layer, a soft magnetic underlayer, a nonmagnetic intermediate layer, a magnetic layer, and a protective layer are sequentially formed on a substrate such as glass.
この軟磁性下地層には、磁気ヘッドからの記録磁界を還流させる役割があり、記録磁界を強力に引き込むために飽和磁束密度が０．２〜１．７Ｔの範囲であることが求められている（例えば、特許文献１参照）。また、軟磁性下地層としては、磁気記録媒体の記録再生効率を向上させるため高い透磁率を有すること、低ノイズ化を図るためアモルファス構造であることが求められている（例えば、特許文献２参照）。また、強い記録磁界を作用させる必要性から、磁気ヘッドと磁性層との近接化が図られてきており、保護層が薄膜化してきている。このため保護層による耐食性の付与は期待できなくなってきており、軟磁性下地層に対しても、高い耐食性が求められている（例えば、特許文献３参照）。 The soft magnetic underlayer has a role of circulating the recording magnetic field from the magnetic head, and is required to have a saturation magnetic flux density in the range of 0.2 to 1.7 T in order to draw the recording magnetic field strongly. (For example, refer to Patent Document 1). Further, the soft magnetic underlayer is required to have a high magnetic permeability in order to improve the recording / reproducing efficiency of the magnetic recording medium and to have an amorphous structure in order to reduce noise (for example, see Patent Document 2). ). Further, due to the necessity of applying a strong recording magnetic field, the magnetic head and the magnetic layer have been made closer to each other, and the protective layer has been made thinner. For this reason, it has become impossible to expect the provision of corrosion resistance by the protective layer, and high corrosion resistance is also required for the soft magnetic underlayer (see, for example, Patent Document 3).
軟磁性下地層としては、非磁性スペーサ層を用いて反強磁性結合させることにより、軟磁性下地層の磁壁から発生する漏れ磁束が再生ヘッドに流入するのを防ぐとともに、軟磁性下地層中に存在する磁壁が容易に動かないように固定し、ノイズを低減することが提案されている（例えば、特許文献４参照）。そして、このような軟磁性下地層においては、最大反強磁性結合力の３０〜７０％の範囲内となるようにスペーサ層のＲｕ膜厚を制御し、反強磁性結合力を下げることによって、高周波信号に対する透磁率の向上を図ることが提案されている（例えば、特許文献５参照）。
これまでの垂直磁気記録媒体の軟磁性下地層の材料としては、Ｆｅ−Ｃｏ−Ｎｂ系合金やＦｅ−Ｃｏ−Ｔａ系合金等が提案されている（例えば、特許文献６および特許文献７参照）。
As a soft magnetic underlayer, a nonmagnetic spacer layer is used for antiferromagnetic coupling to prevent leakage magnetic flux generated from the magnetic wall of the soft magnetic underlayer from flowing into the reproducing head and in the soft magnetic underlayer. It has been proposed to fix the existing domain wall so that it does not move easily and reduce noise (see, for example, Patent Document 4). In such a soft magnetic underlayer, the Ru film thickness of the spacer layer is controlled so as to be within a range of 30 to 70% of the maximum antiferromagnetic coupling force, and the antiferromagnetic coupling force is lowered, It has been proposed to improve the permeability for high-frequency signals (see, for example, Patent Document 5).
As materials for the soft magnetic underlayer of conventional perpendicular magnetic recording media, Fe—Co—Nb alloys, Fe—Co—Ta alloys, and the like have been proposed (see, for example, Patent Document 6 and Patent Document 7). .
上述した特許文献５に開示される軟磁性下地層では、反強磁性結合力の最大値の３０〜７０％の範囲内で反強磁性結合させる方法である。しかし、この手法では最大値を用いないため、反強磁性結合が不安定になる可能性がある。
また、特許文献６および特許文献７に開示される軟磁性下地層の材料として用いられるＮｂやＴａを２０原子％以下含有したＦｅ−Ｃｏ−Ｎｂ合金やＦｅ−Ｃｏ−Ｔａ合金は、高い耐食性を有する点では有利であるものの、反強磁性結合力の最大値が高く、高周波信号に対する透磁率が低下し、磁気記録媒体の書き込み特性が悪くなるという問題があった。
In the soft magnetic underlayer disclosed in Patent Document 5 described above, antiferromagnetic coupling is performed within a range of 30 to 70% of the maximum value of antiferromagnetic coupling force. However, since this method does not use the maximum value, the antiferromagnetic coupling may become unstable.
In addition, Fe—Co—Nb alloys and Fe—Co—Ta alloys containing 20 atomic% or less of Nb and Ta used as materials for the soft magnetic underlayer disclosed in Patent Document 6 and Patent Document 7 have high corrosion resistance. Although it is advantageous in that it has a problem, there is a problem that the maximum value of the antiferromagnetic coupling force is high, the magnetic permeability for high-frequency signals is lowered, and the writing characteristics of the magnetic recording medium are deteriorated.
本発明の目的は、高い耐食性を有し、且つ、低い反強磁性結合力が安定して得られる垂直磁気記録媒体用の軟磁性下地層を提供することである。 An object of the present invention is to provide a soft magnetic underlayer for perpendicular magnetic recording media that has high corrosion resistance and can stably obtain a low antiferromagnetic coupling force.
本発明者らは、ＣｏとＦｅの組成比とＣｏ−Ｆｅ合金への添加元素の適正化により、高い耐食性と、低い反強磁性結合力の安定化が達成できることを見出し、本発明に到達した。
すなわち本発明は、原子比における組成式が（Ｃｏ１００−Ｘ−ＦｅＸ）１００−Ｙ−ＭＹ、２０＜Ｘ＜７０、２０＜Ｙ＜３０、Ｍ元素（Ｎｂおよび／またはＴａ）で表され、残部不可避的不純物からなる厚さ１０〜１００ｎｍの軟磁性層が、厚さ０．３〜０．７ｎｍの非磁性のスペーサ層の両面に反強磁性結合された軟磁性下地層であって、反強磁性結合力の最大値が５００〜２３００Ａ／ｍのＣｏ−Ｆｅ系合金軟磁性下地層である。
前記スペーサ層は、Ｒｕでなることが好ましい。
The inventors of the present invention have found that high corrosion resistance and stabilization of low antiferromagnetic coupling force can be achieved by optimizing the composition ratio of Co and Fe and the elements added to the Co—Fe alloy, and have reached the present invention. .
That is, the present invention, the table by a composition formula in the atomic ratio (Co 100-X -Fe X) 100-Y -M Y, 20 <X <70,20 <Y <30, M element (Nb and / or Ta) A soft magnetic underlayer in which the soft magnetic layer having a thickness of 10 to 100 nm composed of the remaining inevitable impurities is antiferromagnetically coupled to both surfaces of a nonmagnetic spacer layer having a thickness of 0.3 to 0.7 nm. The Co—Fe alloy soft magnetic underlayer having a maximum antiferromagnetic coupling force of 500 to 2300 A / m.
The spacer layer is preferably made of Ru.
本発明により、高い耐食性を有し、且つ、低い反強磁性結合力が安定して得られる軟磁性下地層を提供でき、垂直磁気記録媒体を製造する上で有効な技術となる。 According to the present invention, it is possible to provide a soft magnetic underlayer having high corrosion resistance and stably obtaining a low antiferromagnetic coupling force, which is an effective technique for manufacturing a perpendicular magnetic recording medium.
本発明者らは、反強磁性結合を安定化できる反強磁性結合力の最大値を発現する構成を適用しても、その反強磁性結合力が低いレベルにできる組成を検討した。
そして、本発明のＣｏ−Ｆｅ系合金における反強磁性結合力の最大値の調整と耐食性の向上を両立できる添加元素を選択し、Ｃｏ−Ｆｅ系合金の最適な組成範囲を見出した。
以下、詳しく説明する。
The inventors of the present invention have studied a composition that can reduce the antiferromagnetic coupling force to a low level even when a configuration that exhibits the maximum antiferromagnetic coupling force that can stabilize the antiferromagnetic coupling is applied.
Then, an additive element capable of achieving both the adjustment of the maximum antiferromagnetic coupling force and the improvement of the corrosion resistance in the Co—Fe based alloy of the present invention was selected, and the optimum composition range of the Co—Fe based alloy was found.
This will be described in detail below.
まず、本発明の軟磁性層を形成するベースとなるＣｏ−Ｆｅ合金について説明する。
本組成の軟磁性層を形成するベースとなるＣｏ−Ｆｅ合金は、原子比における組成式をＣｏ１００−Ｘ−ＦｅＸ、２０＜Ｘ＜７０で表される組成とする。この組成範囲のＣｏ−Ｆｅ合金は、高い透磁率と高い飽和磁束密度を有し軟磁気特性に優れたものとなる。
具体的には、Ｃｏに対するＦｅの原子比が２０％以下であると飽和磁束密度の低下が大きくなり、Ｃｏに対するＦｅの原子比が７０％を以上であると、透磁率が低下するため、Ｃｏに対するＦｅの原子比を、２０％を超えて７０％未満の範囲にする。
First, a Co—Fe alloy serving as a base for forming the soft magnetic layer of the present invention will be described.
The Co—Fe alloy serving as a base for forming the soft magnetic layer of this composition has a compositional formula in terms of atomic ratio represented by Co 100-X— Fe X , 20 <X <70. The Co—Fe alloy having this composition range has a high magnetic permeability and a high saturation magnetic flux density, and is excellent in soft magnetic properties.
Specifically, when the atomic ratio of Fe to Co is 20% or less, the saturation magnetic flux density is greatly decreased. When the atomic ratio of Fe to Co is 70% or more, the magnetic permeability is decreased. The atomic ratio of Fe to is in the range of more than 20% and less than 70%.
本発明の軟磁性層におけるＭ元素は、アモルファスの形成、耐食性の向上、反強磁性結合力の最大値の低減を同時に実現させるための元素であり、Ｎｂおよび／またはＴａを選択する。
ＮｂとＴａは、ベース元素のＣｏやＦｅと共晶型の平衡状態図を示すことから、アモルファスを形成するために有効な元素である。また、ＮｂとＴａは、電位−ｐＨ図のｐＨの全領域において不動態化するものであり、耐食性を向上できる元素である。
本発明においては、あらかじめベースとなるＣｏ−Ｆｅ合金を高い飽和磁束密度が得られる組成範囲としているため、耐食性等に有効な量である２０原子％を超えて添加しても、軟磁性下地層として必要な軟磁気特性は確保できる。そして、ＮｂとＴａを、２０原子％を超えて３０原子％未満の範囲にすることで、軟磁気特性を確保しつつ、反強磁性結合力の最大値を低減することができる。より好ましくは、Ｍ元素を、２０原子％を超えて２５原子％以下の範囲とする。
なお、本発明の軟磁性層は、上述のＣｏ−Ｆｅ系合金にＮｂまたはＴａを単独で含有させた場合でも、安定したアモルファスを形成できる。薄膜のアモルファス性をより高めて表面平坦性の向上させるためには、ＮｂおよびＴａを複合で含有させることが好ましい。
The M element in the soft magnetic layer of the present invention is an element for simultaneously realizing the formation of amorphous, improvement of corrosion resistance, and reduction of the maximum value of antiferromagnetic coupling force, and Nb and / or Ta are selected.
Nb and Ta are effective elements for forming an amorphous state because they show an eutectic equilibrium diagram with the base elements Co and Fe. Nb and Ta passivate in the entire pH range of the potential-pH diagram, and are elements that can improve corrosion resistance.
In the present invention, the Co—Fe alloy serving as a base has a composition range in which a high saturation magnetic flux density can be obtained in advance, so even if it exceeds 20 atomic%, which is an effective amount for corrosion resistance, etc., the soft magnetic underlayer As a result, the necessary soft magnetic characteristics can be secured. And by making Nb and Ta into the range exceeding 20 atomic% and less than 30 atomic%, the maximum value of antiferromagnetic coupling force can be reduced while ensuring soft magnetic characteristics. More preferably, the element M is in the range of more than 20 atomic% and not more than 25 atomic%.
The soft magnetic layer of the present invention can form a stable amorphous even when Nb or Ta is contained alone in the above-described Co—Fe alloy. In order to enhance the amorphous property of the thin film and improve the surface flatness, it is preferable to contain Nb and Ta in a composite.
また、本発明の軟磁性下地層は、非磁性のスペーサ層の両面に配置する軟磁性層のそれぞれの膜厚を１０〜１００ｎｍとする。これは、軟磁性層の膜厚が１０ｎｍ未満であると、膜厚が薄いために、磁気記録における記録効率低下が顕著になり、記録ビットの磁化反転が確実に行えない問題が生じる場合がある。一方、膜厚が１００ｎｍを超えると、膜応力が大きくなり膜が剥れやすくなる上、膜を形成するのに時間がかかり、生産性が低下するためである。 In the soft magnetic underlayer of the present invention, the thickness of each soft magnetic layer disposed on both sides of the nonmagnetic spacer layer is 10 to 100 nm. This is because if the thickness of the soft magnetic layer is less than 10 nm, the film thickness is so thin that the recording efficiency declines significantly in magnetic recording, and there is a problem that the magnetization reversal of the recording bit cannot be performed reliably. . On the other hand, if the film thickness exceeds 100 nm, the film stress increases and the film is easily peeled off, and it takes time to form the film, resulting in a decrease in productivity.
また、本発明の軟磁性下地層は、上記で説明した表裏２層の軟磁性層を非磁性の厚さが０．３〜０．７ｎｍのスペーサ層により反強磁性結合させたものである。反強磁性結合させることによって、軟磁性下地層起因のノイズを低減することが可能である。本発明では、例えば、スペーサ層としては、Ｒｕ、Ｃｒ、Ｃｕ、Ｒｅ、およびＲｈ等を用いることができる。これらの中でも特に安定した反強磁性結合が得られるＲｕを用いることが好ましい。
また、反強磁性結合力の最大値が得られるスペーサ層の膜厚は、軟磁性層のＣｏとＦｅの比率に概ね比例し、Ｃｏに対するＦｅの原子比が大きい場合には、反強磁性結合力が得られるスペーサ層の膜厚は厚くなり、Ｃｏに対するＦｅの原子比が小さい場合には、反強磁性結合力が得られるスペーサ層の膜厚は薄くなる。そのため、本発明では、Ｃｏ−Ｆｅ系合金軟磁性層のＣｏに対するＦｅの原子比に合せてスペーサ層の膜厚を０．３〜０．７ｎｍの範囲に設定する。スペーサ層の膜厚が０．３ｎｍ未満であると、反強磁性結合が得られず、一方、スペーサ層の膜厚が０．７ｎｍを超えると、反強磁性結合力の最大値を低減することができないという問題がある。このため、本発明では、スペーサ層の膜厚を０．３〜０．７ｎｍの範囲とする。
The soft magnetic underlayer of the present invention is obtained by antiferromagnetically coupling the two front and back soft magnetic layers described above with a spacer layer having a nonmagnetic thickness of 0.3 to 0.7 nm. By antiferromagnetic coupling, it is possible to reduce noise caused by the soft magnetic underlayer. In the present invention, for example, Ru, Cr, Cu, Re, Rh, or the like can be used as the spacer layer. Among these, it is preferable to use Ru that can obtain a particularly stable antiferromagnetic coupling.
In addition, the thickness of the spacer layer at which the maximum antiferromagnetic coupling force is obtained is approximately proportional to the ratio of Co and Fe in the soft magnetic layer. When the atomic ratio of Fe to Co is large, antiferromagnetic coupling is achieved. The thickness of the spacer layer from which the force can be obtained is increased, and when the atomic ratio of Fe to Co is small, the thickness of the spacer layer from which the antiferromagnetic coupling force is obtained is reduced. Therefore, in the present invention, the thickness of the spacer layer is set in the range of 0.3 to 0.7 nm in accordance with the atomic ratio of Fe to Co in the Co—Fe alloy soft magnetic layer. If the spacer layer thickness is less than 0.3 nm, antiferromagnetic coupling cannot be obtained. On the other hand, if the spacer layer thickness exceeds 0.7 nm, the maximum antiferromagnetic coupling force is reduced. There is a problem that can not be. For this reason, in this invention, the film thickness of a spacer layer shall be the range of 0.3-0.7 nm.
また、本発明の軟磁性下地層においては、上記で説明したように、軟磁性層を構成するＣｏ−Ｆｅ合金を高い飽和磁束密度が得られる組成範囲としているため、耐食性等に有効なＭ元素を２０原子％超〜３０原子％未満の範囲で添加しても、軟磁性下地層として必要な軟磁気特性を確保できるとともに、反強磁性結合力の最大値を５００〜２３００Ａ／ｍにすることができる。
これにより本発明は、高周波信号に対する透磁率を向上させることが可能となり、磁気記録媒体の書き込み特性の向上に寄与できる。尚、本発明では、反強磁性結合力の最大値を２０００Ａ／ｍ以下にすることが好ましい。
In the soft magnetic underlayer of the present invention, as described above, the Co-Fe alloy constituting the soft magnetic layer has a composition range in which a high saturation magnetic flux density can be obtained. Even when adding more than 20 atomic% to less than 30 atomic%, it is possible to secure the necessary soft magnetic characteristics as the soft magnetic underlayer and to set the maximum antiferromagnetic coupling force to 500 to 2300 A / m. Can do.
As a result, the present invention can improve the magnetic permeability with respect to the high-frequency signal, and can contribute to the improvement of the write characteristics of the magnetic recording medium. In the present invention, it is preferable that the maximum value of the antiferromagnetic coupling force is 2000 A / m or less.
本発明の軟磁性下地層の形成方法としては、真空蒸着法、スパッタリング法および化学気相成長法を用いることができる。中でも、Ｃｏ−Ｆｅ系合金の軟磁性下地層およびスペーサ層とそれぞれ同一組成のスパッタリングターゲット材を用意して、スパッタリングして薄膜を形成するスパッタリング法が、高速に安定した膜を形成できるため、好ましい。 As a method for forming the soft magnetic underlayer of the present invention, a vacuum deposition method, a sputtering method, and a chemical vapor deposition method can be used. Among them, a sputtering method in which a sputtering target material having the same composition as that of the soft magnetic underlayer and spacer layer of a Co—Fe alloy is prepared and a thin film is formed by sputtering is preferable because a stable film can be formed at high speed. .
軟磁性層を形成するＣｏ−Ｆｅ系合金スパッタリングターゲット材の製造方法としては、溶解鋳造法や粉末焼結法が適用可能である。溶解鋳造法では、鋳造したインゴットのままでもよいし、鋳造したインゴットに塑性加工や加圧加工を加えたバルク体とすることで製造可能となる。
粉末焼結法では、ガスアトマイズ法でＣｏ−Ｆｅ系合金の最終組成の合金粉末を製造し原料粉末とすることや、複数の合金粉末や純金属粉末をＣｏ−Ｆｅ系合金の最終組成となるように混合した混合粉末を原料粉末とすることが可能である。原料粉末の焼結方法としては、熱間静水圧プレス、ホットプレス、放電プラズマ焼結、押し出しプレス焼結等の加圧焼結を用いることが可能である。
As a method for producing a Co—Fe based alloy sputtering target material for forming a soft magnetic layer, a melt casting method or a powder sintering method can be applied. In the melt casting method, the cast ingot may be used as it is, or it can be manufactured by forming a bulk body obtained by applying plastic processing or pressure processing to the cast ingot.
In the powder sintering method, an alloy powder having a final composition of a Co—Fe alloy is manufactured by a gas atomization method to be a raw material powder, or a plurality of alloy powders or pure metal powders are used as a final composition of a Co—Fe alloy. It is possible to use the mixed powder mixed in the raw material powder. As a method for sintering the raw material powder, it is possible to use pressure sintering such as hot isostatic pressing, hot pressing, discharge plasma sintering, and extrusion press sintering.
以下の実施例で本発明をさらに詳しく説明する。
（本発明例１）
軟磁性層形成用のＣｏ−Ｆｅ系合金スパッタリングターゲットを作製するために、それぞれ純度９９．９％以上のＣｏガスアトマイズ粉末と純度９９．９％以上のＦｅ粉末、Ｎｂ粉末を準備し、原子比で（Ｃｏ３５−Ｆｅ６５）７８−Ｎｂ２２合金組成となるように秤量し、Ｖ型混合機により混合して混合粉末を作製した。次に、得られた混合粉末を軟鋼製カプセルに充填し、脱気封止した後、温度１２５０℃、圧力１５０ＭＰａ、保持時間２時間の条件で熱間静水圧プレスによって焼結し、焼結体を作製した。得られた焼結体に機械加工を施し、直径１８０ｍｍ×厚さ４．０ｍｍのＣｏ−Ｆｅ系合金スパッタリングターゲットを作製した。
そして、スペーサ層形成用のＲｕスパッタリングターゲットを作製するために、純度９９．９％以上のＲｕ粉末を軟鋼製カプセルに充填し、脱気封止した後、温度１３００℃、圧力１５０ＭＰａ、保持時間３時間の条件で熱間静水圧プレスによって焼結し、焼結体を作製した。得られた焼結体に機械加工を施し、直径１８０ｍｍ×厚さ８．５ｍｍのＲｕスパッタリングターゲットを作製した。
また、Ｃ（カーボン）のスパッタリングターゲットは、日立化成工業株式会社製のものを用いた。
The following examples further illustrate the present invention.
(Invention Example 1)
In order to produce a Co—Fe based alloy sputtering target for forming a soft magnetic layer, a Co gas atomized powder having a purity of 99.9% or more, an Fe powder having a purity of 99.9% or more, and an Nb powder were prepared. (Co 35 -Fe 65) 78 -Nb 22 were weighed so as to alloy composition, to prepare a mixed powder were mixed by a V-type mixer. Next, after filling the obtained mixed powder into a mild steel capsule and deaeration-sealing, it was sintered by hot isostatic pressing under conditions of a temperature of 1250 ° C., a pressure of 150 MPa, and a holding time of 2 hours, and a sintered body Was made. The obtained sintered body was machined to produce a Co—Fe based alloy sputtering target having a diameter of 180 mm × a thickness of 4.0 mm.
Then, in order to produce a Ru sputtering target for forming a spacer layer, a Ru powder having a purity of 99.9% or more is filled in a mild steel capsule and degassed and sealed, and then temperature 1300 ° C., pressure 150 MPa, holding time 3 Sintering was performed by hot isostatic pressing under conditions of time to prepare a sintered body. The obtained sintered body was machined to produce a Ru sputtering target having a diameter of 180 mm and a thickness of 8.5 mm.
A C (carbon) sputtering target was manufactured by Hitachi Chemical Co., Ltd.
上記で作製したＣｏ−Ｆｅ系合金スパッタリングターゲットとＲｕスパッタリングターゲットとＣ（カーボン）スパッタリングターゲットをＤＣマグネトロンスパッタ装置（キャノンアネルバ株式会社製 型式番号：３０１０）のチャンバ１、チャンバ２、チャンバ３内にそれぞれ配置し、各チャンバ内を真空到達度２×１０−５Ｐａ以下となるまで排気を行った。
そして、相構造の評価用として、寸法７５×２５ｍｍのガラス基板上に膜厚４０ｎｍの軟磁性層を成膜した試料を作製した。
また、耐食性の評価用として、寸法５０×２５ｍｍのガラス基板上に膜厚２００ｎｍの軟磁性層、保護膜として膜厚５ｎｍのＣ（カーボン）を順に成膜した試料を作製した。
また、反強磁性結合力の評価用として、寸法φ１０ｍｍのガラス基板上に膜厚２０ｎｍの軟磁性層、膜厚０．０００〜０．４５０ｎｍ（０．０２５ｎｍ毎）スペーサ層、膜厚２０ｎｍの軟磁性層を順に成膜した試料を作製した。
なお、軟磁性層のスパッタリング条件は、Ａｒガス雰囲気、圧力０．６Ｐａ、投入電力１０００Ｗで成膜した。また、Ｒｕのスパッタリング条件は、Ａｒガス雰囲気、圧力０．６Ｐａ、投入電力５０Ｗで成膜した。また、Ｃ（カーボン）のスパッタリング条件は、Ａｒガス雰囲気、圧力０．６Ｐａ、投入電力１５００Ｗで成膜した。
The Co—Fe-based alloy sputtering target, the Ru sputtering target, and the C (carbon) sputtering target prepared above are respectively placed in chamber 1, chamber 2, and chamber 3 of a DC magnetron sputtering apparatus (model number: 3010 manufactured by Canon Anelva Co., Ltd.). Arranged and evacuated in each chamber until the vacuum reached 2 × 10 −5 Pa or less.
Then, a sample in which a soft magnetic layer having a thickness of 40 nm was formed on a glass substrate having a size of 75 × 25 mm was prepared for evaluation of the phase structure.
For evaluation of corrosion resistance, a sample in which a soft magnetic layer having a thickness of 200 nm and a C (carbon) film having a thickness of 5 nm as a protective film were sequentially formed on a glass substrate having a size of 50 × 25 mm was prepared.
For evaluation of antiferromagnetic coupling force, a soft magnetic layer with a thickness of 20 nm, a spacer layer with a thickness of 0.000 to 0.450 nm (every 0.025 nm), a soft layer with a thickness of 20 nm on a glass substrate having a size of φ10 mm. A sample in which a magnetic layer was sequentially formed was prepared.
The sputtering conditions for the soft magnetic layer were as follows: Ar gas atmosphere, pressure 0.6 Pa, input power 1000 W. Further, the sputtering conditions for Ru were as follows: an Ar gas atmosphere, a pressure of 0.6 Pa, and an input power of 50 W. C (carbon) sputtering was carried out under an Ar gas atmosphere, a pressure of 0.6 Pa, and an input power of 1500 W.
（比較例１）
合金組成を原子比で（Ｃｏ３５−Ｆｅ６５）８２−Ｎｂ１８とする以外は、本発明例１と同様の条件でＣｏ−Ｆｅ系合金スパッタリングターゲット材を作製した。
上記で作製したＣｏ−Ｆｅ系合金スパッタリングターゲットを用いて、本発明例１と同様の条件で軟磁性層と軟磁性下地層を形成し、評価用の各試料を得た。
(Comparative Example 1)
A Co—Fe based alloy sputtering target material was produced under the same conditions as Example 1 except that the alloy composition was changed to (Co 35 —Fe 65 ) 82 —Nb 18 in atomic ratio.
Using the Co—Fe-based alloy sputtering target produced above, a soft magnetic layer and a soft magnetic underlayer were formed under the same conditions as in Invention Example 1, and each sample for evaluation was obtained.
（比較例２）
合金組成を原子比で（Ｃｏ３５−Ｆｅ６５）８０−Ｎｂ２０とする以外は、本発明例１と同様の条件でＣｏ−Ｆｅ系合金スパッタリングターゲット材を作製した。
上記で作製したＣｏ−Ｆｅ系合金スパッタリングターゲットを用いて、本発明例１と同様の条件で軟磁性層と軟磁性下地層を形成し、評価用の各試料を得た。
(Comparative Example 2)
A Co—Fe based alloy sputtering target material was produced under the same conditions as Example 1 except that the alloy composition was changed to (Co 35 —Fe 65 ) 80 —Nb 20 in atomic ratio.
Using the Co—Fe-based alloy sputtering target produced above, a soft magnetic layer and a soft magnetic underlayer were formed under the same conditions as in Invention Example 1, and each sample for evaluation was obtained.
（相構造の評価）
上記でガラス基板（寸法７５×２５ｍｍ）上に形成した本発明例１、比較例１、比較例２の軟磁性層の各試料について、株式会社リガク製のＸ線回折装置（型式番号：ＲＩＮＴ２５００Ｖ）を使用し、線源にＣｏを用いてＸ線回折測定を行った。その結果、全ての試料において、得られたＸ線回折パターンはブロードなピークであり、軟磁性層がアモルファス構造であることを確認した。
(Evaluation of phase structure)
About each sample of the soft magnetic layer of the present invention example 1, comparative example 1 and comparative example 2 formed on the glass substrate (dimension 75 × 25 mm) as described above, an X-ray diffraction apparatus (model number: RINT2500V) manufactured by Rigaku Corporation. X-ray diffraction measurement was performed using Co as a radiation source. As a result, in all samples, the obtained X-ray diffraction patterns were broad peaks, and it was confirmed that the soft magnetic layer had an amorphous structure.
（耐食性の評価）
上記でガラス基板（寸法５０×２５ｍｍ）上に形成した本発明例１、比較例１、比較例２の軟磁性層の各試料について、純水で１０％に希釈した硝酸溶液５０ｍＬ中に２４時間浸漬させた後、硝酸１０％溶液中に溶出したＣｏ量を株式会社島津製作所製の型式番号：ＩＣＰＶ−１０１７のＩＣＰ（誘電プラズマ発光分析装置）により分析した。測定したＣｏ溶出量を表１に示す。
(Evaluation of corrosion resistance)
For each sample of the soft magnetic layers of Invention Example 1, Comparative Example 1, and Comparative Example 2 formed on the glass substrate (dimension 50 × 25 mm) in the above, 24 hours in 50 mL of nitric acid solution diluted to 10% with pure water. After the immersion, the amount of Co eluted in a 10% nitric acid solution was analyzed by an ICP (dielectric plasma emission analyzer) of model number: ICPV-1017 manufactured by Shimadzu Corporation. Table 1 shows the measured Co elution amount.
次に、上記でガラス基板（φ１０ｍｍ）上に形成した本発明例１、比較例１、比較例２のスペーサ層であるＲｕの膜厚を変化させた軟磁性下地層の各試料について、東英工業株式会社製の振動試料型磁力計（型式番号：ＶＳＭ−３）を使用し、面内磁化容易軸方向に最大磁場１００００Ａ／ｍを印加してＢ−Ｈカーブを測定した。図１に本発明例１の表裏２層の軟磁性層を０．４ｎｍのスペーサ層により反強磁性結合した軟磁性下地層のＢ−Ｈカーブを示す。
図１のＢ−Ｈカーブでは、零印加磁場近傍の残留磁束密度がほぼ零であり、表裏２層の軟磁性層が反強磁性結合をしていることが確認される。この安定な反強磁性結合の状態から磁化し始める印加磁界を反強磁性結合力として定義した。
図２に上記の各試料で測定したＢ−Ｈカーブから求めた反強磁性結合力とスペーサ層であるＲｕ膜厚の関係を示す。また、表１に反強磁性結合力の最大値と、そのときのスペーサ層であるＲｕ膜厚と、飽和磁束密度の結果を示す。
Next, with respect to each sample of the soft magnetic underlayer in which the film thickness of Ru, which is the spacer layer of the present invention example 1, comparative example 1, and comparative example 2, formed on the glass substrate (φ10 mm) is changed, Toei Using a vibrating sample magnetometer (model number: VSM-3) manufactured by Kogyo Co., Ltd., a maximum magnetic field of 10,000 A / m was applied in the in-plane magnetization easy axis direction, and a BH curve was measured. FIG. 1 shows a BH curve of a soft magnetic underlayer in which two soft magnetic layers of Example 1 of the present invention are antiferromagnetically coupled by a 0.4 nm spacer layer.
In the BH curve in FIG. 1, it is confirmed that the residual magnetic flux density in the vicinity of the zero applied magnetic field is almost zero, and the two soft magnetic layers on the front and back sides are antiferromagnetically coupled. The applied magnetic field that began to magnetize from this stable antiferromagnetic coupling state was defined as the antiferromagnetic coupling force.
FIG. 2 shows the relationship between the antiferromagnetic coupling force obtained from the BH curve measured for each sample and the Ru film thickness as the spacer layer. Table 1 shows the maximum value of the antiferromagnetic coupling force, the Ru film thickness as the spacer layer, and the saturation magnetic flux density.
表１に示すように、比較例１、比較例２のＣｏ−Ｆｅ系合金の軟磁性下地層は、硝酸液中へのＣｏ溶出量が多く、耐食性は十分といえず、また、反強磁性結合力の最大値が２３００Ａ／ｍより高いことがわかる。
一方、本発明例１の軟磁性下地層は、硝酸液中へのＣｏ溶出量がいずれの比較例よりも少ないことから、高い耐食性を有していることが確認できた。また、反強磁性結合力の最大値は、いずれの比較例よりも低いことがわかる。また、飽和磁束密度は、比較例よりも低いものの、上記で説明したように軟磁性下地層として最低限必要とされる０．２Ｔ以上を実現できていることから、磁気記録媒体の軟磁性下地層として機能できる範囲であることが確認できた。
As shown in Table 1, the soft magnetic underlayers of the Co—Fe alloys of Comparative Examples 1 and 2 have a large amount of Co elution into the nitric acid solution, and cannot be said to have sufficient corrosion resistance. It can be seen that the maximum value of the binding force is higher than 2300 A / m.
On the other hand, it was confirmed that the soft magnetic underlayer of Example 1 of the present invention had high corrosion resistance because the amount of Co elution into the nitric acid solution was smaller than that of any of the comparative examples. Moreover, it turns out that the maximum value of antiferromagnetic coupling force is lower than any comparative example. Although the saturation magnetic flux density is lower than that of the comparative example, as described above, 0.2 T or more required as a soft magnetic underlayer can be realized. It was confirmed that it was a range that could function as a stratum.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2015144033A (en) * | 2015-02-05 | 2015-08-06 | 山陽特殊製鋼株式会社 | Soft magnetic film layer alloy having low-saturation magnetic flux density used for magnetic recording medium, and sputtering target material |
| TWI823989B (en) * | 2018-08-20 | 2023-12-01 | 日商山陽特殊製鋼股份有限公司 | Sputtering targets for soft magnetic layers of magnetic recording media and magnetic recording media |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2015144033A (en) * | 2015-02-05 | 2015-08-06 | 山陽特殊製鋼株式会社 | Soft magnetic film layer alloy having low-saturation magnetic flux density used for magnetic recording medium, and sputtering target material |
| TWI823989B (en) * | 2018-08-20 | 2023-12-01 | 日商山陽特殊製鋼股份有限公司 | Sputtering targets for soft magnetic layers of magnetic recording media and magnetic recording media |
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