JP4069205B2 - Method for manufacturing magnetic recording medium - Google Patents
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- JP4069205B2 JP4069205B2 JP2004096591A JP2004096591A JP4069205B2 JP 4069205 B2 JP4069205 B2 JP 4069205B2 JP 2004096591 A JP2004096591 A JP 2004096591A JP 2004096591 A JP2004096591 A JP 2004096591A JP 4069205 B2 JP4069205 B2 JP 4069205B2
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- 230000005291 magnetic effect Effects 0.000 title claims description 134
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 238000000034 method Methods 0.000 title claims description 15
- 229910005335 FePt Inorganic materials 0.000 claims description 68
- 239000010409 thin film Substances 0.000 claims description 60
- 239000000758 substrate Substances 0.000 claims description 46
- 238000004544 sputter deposition Methods 0.000 claims description 9
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 5
- 229910052697 platinum Inorganic materials 0.000 claims description 5
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 3
- RZJQYRCNDBMIAG-UHFFFAOYSA-N [Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Zn].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn] Chemical class [Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Cu].[Zn].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Ag].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn].[Sn] RZJQYRCNDBMIAG-UHFFFAOYSA-N 0.000 claims description 3
- 239000011521 glass Substances 0.000 claims description 3
- 239000011780 sodium chloride Substances 0.000 claims description 3
- 230000005415 magnetization Effects 0.000 description 19
- 239000010408 film Substances 0.000 description 17
- 239000013078 crystal Substances 0.000 description 15
- 239000010419 fine particle Substances 0.000 description 11
- 239000002245 particle Substances 0.000 description 9
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 238000001000 micrograph Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 229910000684 Cobalt-chrome Inorganic materials 0.000 description 2
- 239000010952 cobalt-chrome Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 241000238366 Cephalopoda Species 0.000 description 1
- 229910000905 alloy phase Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000002003 electron diffraction Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 230000005381 magnetic domain Effects 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000007847 structural defect Effects 0.000 description 1
- 239000011882 ultra-fine particle Substances 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
Description
この出願の発明は、磁場を印加した箇所に所定の保磁力にて磁気的に情報を記録する磁気記録媒体の製造方法に関するものである。さらに詳しくは、この出願の発明は、書き込みが容易で、一旦書き込めば外部磁場による擾乱により容易に消去されない高い保磁力を有する磁気記録媒体の製造方法に関するものである。
The invention of this application relates to a method of manufacturing a magnetic recording medium in which information is magnetically recorded at a location where a magnetic field is applied with a predetermined coercive force. More specifically, the invention of this application relates to a method of manufacturing a magnetic recording medium having a high coercive force that is easy to write and is not easily erased by disturbance due to an external magnetic field once written.
情報化社会の発展にともない大量の情報を処理・記憶することのできる超高密度磁気記録媒体の開発が切望されている。記録媒体の高密度化には１０ｎｍ以下の強磁性微粒子を非磁性マトリックス中に均一に分散させる必要がある。しかし、現行のＣｏＣｒ基媒体では、微粒子のサイズが１０ｎｍ以下になると熱擾乱により磁化反転が起こる。一方、Ｌ１0構造を有するＦｅＰｔ規則相はＣｏＣｒ基合金よりも１桁大きい７×１０7ｅｒｇ／ｃｃもの大きな異方性を有するため、ナノサイズの超微細粒子であっても熱擾乱により磁化反転を起こさない。このため次世代の超高密度磁気記録媒体として期待されている。本発明者らは、この材料で結晶配向させた孤立単磁区粒子を分散させることにより、簡便なプロセスで４０ｋＯｅ以上の高い保磁力を持つ高配向磁性薄膜の製造方法（特許文献１）を提案している。また、この材料で単磁区粒子を作製することによって、保磁力が１２０ｋＯｅにも達すると理論的に考えられており、実験的には約７０ｋＯｅの大きな保磁力が実現されている。
しかしながら、高保磁力を有する上記のような単磁区微粒子の媒体を記録媒体に応用した場合、情報の書き込み（磁化の反転）に対して５０ｋＯｅ以上の大きな磁場が必要となる。現在のところ、このような大きな磁場を発生させることのできる書き込み用磁気ヘッドの開発はされていない。また、別の記録方式として、記録媒体をレーザー光などで局所的に加熱することにより、キュリー温度付近まで磁性体の温度を上昇させ、保磁力が小さくなったところで書き込みを行う熱アシスト型磁気記録などの光磁気記録の技術が提案されている。しかし、この技術は現在開発中であり、未だ実用化には至っていない。 However, when a single-domain fine particle medium having a high coercive force as described above is applied to a recording medium, a large magnetic field of 50 kOe or more is required for information writing (magnetization reversal). At present, no writing magnetic head capable of generating such a large magnetic field has been developed. As another recording method, heat-assisted magnetic recording is performed when the temperature of the magnetic material is increased to near the Curie temperature by locally heating the recording medium with laser light, etc., and writing is performed when the coercive force is reduced. The magneto-optical recording technology has been proposed. However, this technology is currently under development and has not yet been put into practical use.
そこで、この出願の発明は、以上の通りの背景から、新たな記録ヘッドや記録方式を必要とすることなく、現行の記録ヘッドで書き込みができる、書き込み容易な、外部磁場による擾乱に極めて安定な高保磁力を有するＦｅＰｔ磁性薄膜を備えた磁気記録媒体の製造方法を提供することを課題としている。
In view of the above, the invention of this application is capable of writing with the current recording head without requiring a new recording head or recording method, and is extremely stable against disturbance due to an external magnetic field. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium including a FePt magnetic thin film having a high coercive force.
第１には、基板上に不連続な島状となって位置する厚さ２０〜４０ｎｍのＦｅＰｔ磁性薄膜がＬ１０構造を有すると共に、４ＫＯｅ〜１０ＫＯｅの磁場を印加することにより４０ＫＯｅ以上の保磁力を有することを特徴とする磁気記録媒体の製造方法を提供する。
First, a 20-40 nm thick FePt magnetic thin film located in a discontinuous island shape on the substrate has an L10 structure, and a coercive force of 40 KOe or more is applied by applying a magnetic field of 4 KOe to 10 KOe. A method for manufacturing a magnetic recording medium is provided.
第２には、基板上に成膜されるＦｅＰｔ磁性薄膜の膜厚が、２５ｎｍ〜４０ｎｍであることを特徴とする磁気記録媒体の製造方法を提供する。
Second, the present invention provides a method for producing a magnetic recording medium , wherein the film thickness of the FePt magnetic thin film formed on the substrate is 25 nm to 40 nm.
第３には、ＦｅＰｔ磁性薄膜におけるＦｅＰｔ相の合金組成がＦｅ１−ｘＰｔｘ（０．４＜ｘ＜０．６）であることを特徴とする磁気記録媒体の製造方法を提供する。
Thirdly, the present invention provides a method for producing a magnetic recording medium , wherein the FePt phase alloy composition in the FePt magnetic thin film is Fe1-xPtx (0.4 <x <0.6).
第４には、ＦｅＰｔ磁性薄膜を成膜する基板が、ＭｇＯ（００１）、ＮａＣｌ（００１）、ＧａＡｓ（００１）、およびＳｉ（００１）のうちのいずれから選択されることを特徴とする磁気記録媒体の製造方法を提供する。
Fourth, the magnetic recording is characterized in that the substrate on which the FePt magnetic thin film is formed is selected from any of MgO (001), NaCl (001), GaAs (001), and Si (001). A method for manufacturing a medium is provided.
第５には、ＦｅＰｔ磁性薄膜を成膜する基板がガラス製であり、ＦｅＰｔ磁性薄膜の下地層としてＭｇＯ、ＺｎＯ、Ｃｒ、Ｐｔのうちのいずれから選択されることを特徴とする磁気記録媒体の製造方法を提供する。 Fifth, the substrate on which the FePt magnetic thin film is formed is made of glass, and the underlayer of the FePt magnetic thin film is selected from MgO, ZnO, Cr, and Pt . A manufacturing method is provided.
この出願の第１の発明によれば、新たな記録ヘッドや記録方式を必要とすることなく、現行の記録ヘッドで書き込みができる、書き込み容易な、外部磁場による擾乱に極めて安定な高保磁力を有するＦｅＰｔ磁性薄膜を備えた磁気記録媒体を得ることができる。 According to the first invention of this application, it is possible to write with the current recording head without requiring a new recording head or recording system, and it has a high coercive force that is easy to write and extremely stable against disturbance by an external magnetic field. A magnetic recording medium provided with an FePt magnetic thin film can be obtained.
第２の発明によれば、上記第１の発明の効果とともに、磁気的に孤立した微粒子構造のＦｅＰｔ磁性薄膜とすることができ、微粒子内に磁壁を導入することができる。 According to the second invention, in addition to the effects of the first invention, a magnetically isolated fine particle structure FePt magnetic thin film can be obtained, and a domain wall can be introduced into the fine particles.
第３の発明によれば、上記第２の発明の効果とともに、磁気記録媒体用の合金として重要な、ＦｅＰｔ相が安定に存在できる特定の構成のものが実現される。 According to the third aspect of the invention, in addition to the effects of the second aspect of the invention, a specific configuration that is important as an alloy for a magnetic recording medium and in which the FePt phase can exist stably is realized.
第４、第５の発明によれば、上記第３の発明の効果とともに、格子のミスフィットが小さい基板上にエピタキシャル成長させることにより、より高い規則度およびより大きい膜面垂直方向に一軸磁気異方性を有するＬ１0構造のＦｅＰｔ磁性薄膜を備えた磁気記録媒
体とすることができる。
According to the fourth and fifth inventions, in addition to the effects of the third invention, by epitaxial growth on a substrate having a small lattice misfit, a higher degree of order and a larger uniaxial magnetic anisotropy in the direction perpendicular to the film surface are achieved. It may be a magnetic recording medium having a FePt magnetic thin film of L1 0 structure having sex.
この出願の発明は、上記のとおりの特徴をもつものであるが、以下、さらに詳しく発明の実施の形態について説明する。 The invention of this application has the characteristics as described above, and the embodiments of the invention will be described in more detail below.
この出願の発明は、表面温度が６５０℃〜８５０℃である基板上に、スパッタ法によりＦｅＰｔ磁性薄膜を成膜し、前記ＦｅＰｔ磁性薄膜に４ＫＯｅ〜１０ＫＯｅの磁場を印加して４０ＫＯｅ以上の保磁力を有するＦｅＰｔ磁性薄膜を備えた磁気記録媒体の製造方法である。 In the invention of this application, a FePt magnetic thin film is formed on a substrate having a surface temperature of 650 ° C. to 850 ° C. by a sputtering method, and a magnetic field of 4 KOe to 10 KOe is applied to the FePt magnetic thin film so as to have a coercive force of 40 KOe or more. This is a method for manufacturing a magnetic recording medium comprising a FePt magnetic thin film having the following.
この出願の発明では、薄膜が（１）核生成→（２）島状→（３）連続状という初期成長過程を経て成長することに着目し、基板温度を上昇させて原子拡散の活発な温度領域において、基板上にＦｅＰｔ磁性薄膜をスパッタ成膜するものである。工業的に広く用いられているスパッタ法や蒸着法などの気相急冷法などによりＦｅＰｔ磁性薄膜を成膜すると、磁気異方性の小さい不規則相であるｆｃｃ合金相のＦｅＰｔ磁性薄膜が形成されることになる。完全に規則化したＦｅＰｔ微粒子を島状に成長させるためには、スパッタ成膜時の基板の表面温度を６５０℃〜８５０℃にする必要がある。これによって、Ｌ１0構造を有
するＦｅＰｔ磁性薄膜とすることができ、ＦｅＰｔ微粒子は島状となって形成される。
In the invention of this application, focusing on the fact that the thin film grows through an initial growth process of (1) nucleation → (2) island shape → (3) continuous state, the substrate temperature is raised to increase the temperature of active atomic diffusion. In the region, an FePt magnetic thin film is formed on the substrate by sputtering. When an FePt magnetic thin film is formed by a vapor phase quenching method such as sputtering or vapor deposition widely used in industry, an FePt magnetic thin film of fcc alloy phase, which is an irregular phase with small magnetic anisotropy, is formed. Will be. In order to grow perfectly ordered FePt fine particles in an island shape, the surface temperature of the substrate at the time of sputtering film formation needs to be 650 ° C. to 850 ° C. Thus, an FePt magnetic thin film having an L1 0 structure can be obtained, and FePt fine particles are formed in an island shape.
また、基板とエピタキシャル成長させることにより、膜面に垂直方向に一軸磁気異方性を有するＬ１0構造を持つＦｅＰｔ磁性薄膜が得られる。 Further, by the substrate and the epitaxial growth, FePt magnetic thin film is obtained having the L1 0 structure having uniaxial magnetic anisotropy in the direction perpendicular to the film plane.
このＦｅＰｔ磁性薄膜を、４ＫＯｅ〜１０ＫＯｅの低磁場で印加すると、ＦｅＰｔ微粒子の磁壁移動により容易に磁化反転がおこる。一旦磁化反転が起こると、４０ＫＯｅ以上の保磁力を備えることになり、印加磁場の方向を逆向きにしても磁化反転が起こりにくく
なる。このため、このＦｅＰｔ磁性薄膜を磁気記録層とした磁気記録媒体は、書き込みが容易で、外部磁場による擾乱に極めて安定な、高保磁力を有するＦｅＰｔ磁性薄膜を備えた磁気記録媒体を得ることになる。
When this FePt magnetic thin film is applied in a low magnetic field of 4 KOe to 10 KOe, magnetization reversal easily occurs due to the domain wall movement of FePt fine particles. Once magnetization reversal occurs, a coercive force of 40 KOe or more is provided, and magnetization reversal hardly occurs even when the direction of the applied magnetic field is reversed. For this reason, a magnetic recording medium using the FePt magnetic thin film as a magnetic recording layer is easy to write and is extremely stable against disturbance caused by an external magnetic field, and a magnetic recording medium having a FePt magnetic thin film having a high coercive force is obtained. .
低磁場印加で高保磁力を示すＦｅＰｔ磁性薄膜を得るには、島状のＦｅＰｔ微粒子中に磁壁を導入する必要があるため、ＦｅＰｔ磁性薄膜の膜厚を２５ｎｍ〜４０ｎｍとなるようにスパッタ成膜されることが好ましい。 In order to obtain a FePt magnetic thin film exhibiting a high coercive force when a low magnetic field is applied, it is necessary to introduce a domain wall into the island-shaped FePt fine particles. Therefore, the FePt magnetic thin film is formed by sputtering so that the film thickness is 25 nm to 40 nm. It is preferable.
スパッタリングそのもののプロセスについては公知のものをはじめとして各種の装置や条件を適宜に採用することができる。ターゲットとしても、たとえば合金を構成する各々の純金属を用いた同時スパッタリングでもよく、組成が予備的に調整された合金ターゲットを用いてもよい。 As for the process of sputtering itself, various apparatuses and conditions including known ones can be appropriately employed. As the target, for example, simultaneous sputtering using pure metals constituting the alloy may be used, or an alloy target whose composition is preliminarily adjusted may be used.
基板上に成膜されるＦｅＰｔ磁性薄膜のＦｅＰｔ相の合金組成は、Ｆｅ1-xＰｔx（０．４＜ｘ＜０．６）となるように成膜を行うことが好ましい。合金組成比をこの範囲に設定したとき、成膜されるＦｅＰｔ磁性薄膜は、高い一軸磁気異方性定数を示し、極めて高い保磁力が得られる。 It is preferable to form the film so that the FePt phase alloy composition of the FePt magnetic thin film formed on the substrate is Fe 1−x Pt x (0.4 <x <0.6). When the alloy composition ratio is set within this range, the formed FePt magnetic thin film exhibits a high uniaxial magnetic anisotropy constant and an extremely high coercive force is obtained.
さらに、この出願の発明は、基板の結晶配向の制御を行うことで、基板上に成膜される合金薄膜に磁気異方性を付与する。すなわち、エピタキシャル成長可能な、格子のミスフィットが小さい基板として、ＮａＣｌ（００１）、ＧａＡｓ（００１）、および、Ｓｉ（００１）のうちのいずれかから選択することで、磁化容易軸をより高い規則度で垂直方向に配向させることが可能となる。また、基板がガラス製の場合には、ＦｅＰｔ磁性薄膜の下地層としてＭｇＯ、ＺｎＯ、Ｃｒ、Ｐｔのうちのいずれから選択することで、磁化容易軸を垂直方向に配向させることも可能となる。 Furthermore, the invention of this application gives magnetic anisotropy to the alloy thin film formed on the substrate by controlling the crystal orientation of the substrate. That is, by selecting one of NaCl (001), GaAs (001), and Si (001) as a substrate that can be epitaxially grown and has a small lattice misfit, the easy magnetization axis has a higher degree of order. It becomes possible to orient in the vertical direction. Further, when the substrate is made of glass, the easy axis can be oriented in the vertical direction by selecting any of MgO, ZnO, Cr, and Pt as the underlayer of the FePt magnetic thin film.
以上より、この出願の発明は、低磁場で一旦磁化反転すると容易に磁化反転が起こりにくくなり、外部磁場による擾乱に極めて安定な高保磁力を有するＦｅＰｔ磁性薄膜を備えた磁気記録媒体を製造することができる。この磁気記録媒体は、新たな記録ヘッドや記録方式を必要とすることなく、現行の記録ヘッドで書き込みができ、一旦書き込めば外部磁場による擾乱により容易に消去されることはない。 As described above, the invention of this application is to manufacture a magnetic recording medium including a FePt magnetic thin film having a high coercive force which is difficult to cause magnetization reversal once it is easily reversed by a low magnetic field and is extremely stable against disturbance due to an external magnetic field. Can do. This magnetic recording medium can be written with an existing recording head without requiring a new recording head or recording method, and once written, it is not easily erased by disturbance due to an external magnetic field.
この出願の発明は、以上の特徴を持つものであるが、以下に実施例を示し、さらに具体的に説明する。 The invention of this application has the above-described features, and will be described more specifically with reference to examples.
＜実施例１＞
ＭｇＯ（００１）単結晶基板上に、高純度（９９．９９％）のＦｅとＰｔの共ターゲットを用いて、マルチＤＣスパッタ装置において、ＦｅＰｔ磁性薄膜を成膜し、磁気記録媒体を得た。基板温度は７８０℃とし、ＦｅＰｔ磁性薄膜の膜厚を２５ｎｍとした。真空圧は〜６．０×１０-7Ｐａに排気し、０．１ＰａのＡｒガスを導入した。
<Example 1>
On a MgO (001) single crystal substrate, a FePt magnetic thin film was formed in a multi-DC sputtering apparatus using a high purity (99.99%) Fe and Pt co-target to obtain a magnetic recording medium. The substrate temperature was 780 ° C., and the film thickness of the FePt magnetic thin film was 25 nm. The vacuum pressure was evacuated to ˜6.0 × 10 −7 Pa, and 0.1 Pa Ar gas was introduced.
図１には、ＦｅＰｔ磁性薄膜の面内の電子顕微鏡像（ＴＥＭ）を示す。ＦｅＰｔの微粒子の形状が島状になっていることが確認され、個々の島はお互いに孤立していることから、これらは磁気的にも孤立した粒子であると考えられる。平均粒子サイズは約２００ｎｍ程度であることが観察された。制限視野電子回折像からは、ＦｅＰｔはＭｇＯ単結晶基板上にエピタキシャル成長をしており、なおかつｃ軸が面直に向いていることがわかる。 FIG. 1 shows an in-plane electron microscope image (TEM) of the FePt magnetic thin film. Since the shape of the FePt fine particles is confirmed to be island-like, and the individual islands are isolated from each other, these are considered to be magnetically isolated particles. The average particle size was observed to be around 200 nm. From the limited-field electron diffraction image, it can be seen that FePt is epitaxially grown on the MgO single crystal substrate and that the c-axis is in a plane.
図２には、ＦｅＰｔ磁性薄膜の断面の電子顕微鏡像（ＴＥＭ）を示す。この図から、ほとんどのＦｅＰｔの微粒子は約２５ｎｍと同じ高さを示し、粒子の形状はテーブル状、す
なわちメサ形状を示していることがわかる。
FIG. 2 shows an electron microscope image (TEM) of a cross section of the FePt magnetic thin film. From this figure, it can be seen that most of the FePt fine particles have the same height as about 25 nm, and the shape of the particles shows a table shape, that is, a mesa shape.
図３には、ＦｅＰｔ磁性薄膜の断面の高分解能電子顕微鏡像（ＨＲＥＭ）を示す。Ｌ１0構造の[００１]方向、すなわち膜面垂直方向にＦｅおよびＰｔが交互に積層したコント
ラストが観察される。また、双晶や結晶粒界などの構造欠陥はみられず、粒子の表面は原子オーダーで平坦であることがわかる。
FIG. 3 shows a high-resolution electron microscope image (HREM) of the cross section of the FePt magnetic thin film. A contrast is observed in which Fe and Pt are alternately stacked in the [001] direction of the L1 0 structure, that is, in the direction perpendicular to the film surface. In addition, structural defects such as twins and grain boundaries are not observed, and it can be seen that the surface of the particles is flat on the atomic order.
図４（ａ）（ｂ）から図８（ａ）（ｂ）には、ＦｅＰｔ磁性薄膜の磁化曲線を示す。ＦｅＰｔ磁性薄膜に最初に印加する磁場を＋２ｋＯｅ（図４（ａ）（ｂ））、＋３ｋＯｅ（図５（ａ）（ｂ））、＋４ｋＯｅ（図６（ａ）（ｂ））、＋５ｋＯｅ（図７（ａ）（ｂ））、＋６ｋＯｅ（図８（ａ）（ｂ））と徐々に増加させ、その後、逆方向に磁場を印加したものである。各図（ａ）は全体図であり、（ｂ）は、（ａ）の低磁場部分の拡大図である。最初に印加する磁場が＋２ｋＯｅ（図４（ａ）（ｂ））、＋３ｋＯｅ（図５（ａ）（ｂ））のときは、−数ｋＯｅの磁場において磁場が容易に反転することがわかる。＋４ｋＯｅ（図６（ａ）（ｂ））の印加磁場では、プラスに方向に磁化されたＦｅＰｔ粒子が容易に反転しなくなり、保磁力が５０ｋＯｅを示すようになる。さらに印加磁場を、＋５ｋＯｅ（図７（ａ）（ｂ））、＋６ｋＯｅ（図８（ａ）（ｂ））と増加させると、ほとんどのＦｅＰｔ粒子が磁化されるようになることがわかる。ここで、一度磁化したＦｅＰｔ粒子はＳＱＵＩＤの印加磁場である５５ｋＯｅでは反転せず、結果として非対称な磁化曲線を示す（図８（ａ）（ｂ））。 4A and 4B to FIG. 8A and FIG. 8B show the magnetization curves of the FePt magnetic thin film. The magnetic field first applied to the FePt magnetic thin film is +2 kOe (FIGS. 4A and 4B), +3 kOe (FIGS. 5A and 5B), +4 kOe (FIGS. 6A and 6B), and +5 kOe (FIG. 7). (A) (b)) and +6 kOe (FIGS. 8A and 8B) are gradually increased, and then a magnetic field is applied in the opposite direction. Each figure (a) is a general view, and (b) is an enlarged view of the low magnetic field part of (a). It can be seen that when the magnetic field applied first is +2 kOe (FIGS. 4A and 4B) and +3 kOe (FIGS. 5A and 5B), the magnetic field is easily reversed in a magnetic field of −several kOe. With the applied magnetic field of +4 kOe (FIGS. 6A and 6B), the FePt particles magnetized in the positive direction are not easily reversed, and the coercive force becomes 50 kOe. Furthermore, it can be seen that when the applied magnetic field is increased to +5 kOe (FIGS. 7A and 7B) and +6 kOe (FIGS. 8A and 8B), most of the FePt particles become magnetized. Here, the once magnetized FePt particles are not reversed at 55 kOe, which is the applied magnetic field of SQUID, and as a result, show asymmetric magnetization curves (FIGS. 8A and 8B).
図９には、ＦｅＰｔ磁性薄膜の最初に印加した磁場に対して得られる保磁力を示す。試料は同一のものである。この図から、＋３ｋＯｅまでの印加磁場では、保磁力は数ｋＯｅ程度しか得られないが、＋４ｋＯｅ以上の印加磁場では、ほぼ５０ｋＯｅに達しており、磁気記録媒体に一旦書き込みすると容易に消去されないことを示している。 FIG. 9 shows the coercivity obtained with respect to the first applied magnetic field of the FePt magnetic thin film. The sample is the same. It can be seen from this figure that a coercive force of only about several kOe can be obtained with an applied magnetic field up to +3 kOe. Show.
＜実施例２＞
実施例１と同様にして、７８０℃のＭｇＯ（００１）単結晶基板上に膜厚１０ｎｍ〜４０ｎｍのＦｅＰｔ磁性薄膜を成膜し、磁気記録媒体を得た。
<Example 2>
In the same manner as in Example 1, an FePt magnetic thin film having a film thickness of 10 nm to 40 nm was formed on a 780 ° C. MgO (001) single crystal substrate to obtain a magnetic recording medium.
図１０は、膜厚１０ｎｍ，２０ｎｍ，３０ｎｍ，４０ｎｍのＦｅＰｔ磁性薄膜の磁化曲線を示す。この図から、各膜厚でのＦｅＰｔ磁性薄膜の保磁力は５０ｋＯｅ程度と非常に大きく、磁気記録媒体に一旦書き込みすると容易に消去されないことを示している。 FIG. 10 shows magnetization curves of FePt magnetic thin films having thicknesses of 10 nm, 20 nm, 30 nm, and 40 nm. From this figure, it is shown that the coercive force of the FePt magnetic thin film at each film thickness is as large as about 50 kOe and is not easily erased once written on the magnetic recording medium.
図１１は、膜厚２５ｎｍ，３０ｎｍ，４０ｎｍのＦｅＰｔ磁性薄膜の初磁化曲線を示す。この図から、低い磁場で書き込みができることがわかる。 FIG. 11 shows initial magnetization curves of FePt magnetic thin films having film thicknesses of 25 nm, 30 nm, and 40 nm. From this figure, it can be seen that writing can be performed with a low magnetic field.
この出願の発明は以上の例に限定されるものではなく、細部については様々な態様が可能であることは言うまでもない。 The invention of this application is not limited to the above examples, and it goes without saying that various aspects are possible in detail.
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| JP4810360B2 (en) | 2006-08-31 | 2011-11-09 | 石福金属興業株式会社 | Magnetic thin film |
| JP2008197089A (en) * | 2007-01-17 | 2008-08-28 | Fujikura Ltd | Magnetic sensor element and method for manufacturing the same |
| US8147994B2 (en) | 2009-02-26 | 2012-04-03 | Tdk Corporation | Layered structure having FePt system magnetic layer and magnetoresistive effect element using the same |
| US9207292B2 (en) | 2011-02-02 | 2015-12-08 | Infineon Technologies Ag | Magnetoresistive device and method for manufacturing the same |
| WO2015111384A1 (en) | 2014-01-23 | 2015-07-30 | 富士電機株式会社 | Perpendicular magnetic recording medium |
| CN105874536B (en) | 2014-08-12 | 2018-08-31 | 富士电机株式会社 | Magnetic recording media |
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| US9672854B2 (en) | 2013-09-30 | 2017-06-06 | Seagate Technology Llc | Magnetic stack including MgO-Ti(ON) interlayer |
| US10453487B2 (en) | 2013-09-30 | 2019-10-22 | Seagate Technology Llc | Magnetic stack including MgO—Ti(ON) interlayer |
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