JP4051451B2 - Magnetic materials for magnetic recording media - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は，高密度記録に適した磁気記録媒体用磁性材料に関する。
【０００２】
【従来の技術】
オーディオ用，ビデオ用，コンピュータ用などの磁気テープや磁気ディスク等の磁気記録媒体は，記録容量の高密度化による小型化，高性能化が一段と進み，それに伴って磁気記録媒体用の磁性粉も微粒子化が進んでいる。
【０００３】
記録密度の上昇のためには記録単位のサイズ低下が必要であるが，従来型の磁性粉を用いた媒体では高記録密度化の限界に近づいている。このようなことから，近年では，高密度磁気記録媒体として，高い結晶磁気異方性を有し且つ大きな保磁力を示す磁性金属ナノ粒子が注目されている。
【０００４】
遷移金属と白金族金属の一部の合金は高温熱処理による規則格子化により高い磁気異方性を発現することが知られており、特にＦｅＰｔ規則格子化合金はＫｕ＝７×１０7ｅｒｇ／ｃｃと大きな結晶磁気異方性エネルギーを有し、熱揺らぎの問題を解決する有力な磁性材料として注目を集めている。ＦｅＰｔナノ粒子の合成に関する技術として、例えば以下のものが報告された。
【０００５】
（１）ショウヘン・スンらにより，化学的手法を用いたＦｅＰｔナノ粒子の合成法がScience, 2000, Vol.287, p.1989に報告された。この方法によると，非親水性溶媒であるジオクチルエーテル中において, Pt(acac)2をアルコールにより還元し，Fe(CO)5を熱分解することにより，ＦｅＰｔナノ粒子が合成される。作製されたＦｅＰｔナノ粒子は組成制御が可能で，そのサイズも３〜１０ｎｍの間で制御できるとされている。
【０００６】
（２）城後らは，２００１年度第２５回応用磁気学会学術講演会において，逆ミセル法を用いたＦｅＰｔナノ粒子の合成法を発表した（該講演概要集2001, 26aC-6, P.155)。この方法によると，非親水性溶媒であるイソオクタンを溶媒に使用し，界面活性剤にビス（2-エチルヘキシル）スルホコハク酸ナトリウムを使用してミセル場を形成し，このミセル内の水溶液中においてＦｅおよびＰｔの塩化物をＮａＢＨ4により還元することによりＦｅＰｔナノ粒子を合成している。この方法では，反応場に逆ミセルを使用することにより分散性の良いナノ粒子が得られる。
【０００７】
（３）黒部らは，同じく２００１年度第２５回応用磁気学会学術講演会において，アルコール還元法によるＦｅＰｔナノ粒子の合成法を発表した（該講演概要集2001, 26aC-5, P.154)。この方法によると，Ｆｅ供給源にFe(acac)3を，Ｐｔ供給源にPt(acac)2を使用し，粒子表面を保護する保護高分子としてポリ（N-ビニル-2-ピロリドン）を使用し，溶媒と還元剤の作用を併せ持つエチレングリコールによるアルコール還元法によりＦｅＰｔナノ粒子を合成している。
【０００８】
このようにして得られるナノ粒子（ＦｅＰｔ）を基盤上に自己配列させた記録媒体では，Ｔbit/in2オーダーまで記録密度を上げられるポテンシャルを有することが知られている (前掲のScience, 2000, Vol.287, p.1989，およびJournal of the Magnetics Society of Japan, 2001, V.25, No.8, p.1434)。
【０００９】
【発明が解決しようとする課題】
前記のようなナノ粒子からなる強磁性合金で記録媒体を作成する場合には，ナノ粒子を規則格子化させるための熱処理が必要である。そのさい，規則格子化を基盤上で行う場合には，その熱処理温度に耐える基盤が必要となる。従来のハードディスクの基盤は主にガラス基盤やＡｌ基盤が用いられているが，これらを用いたのでは，該熱処理温度で変形するおそれがある。
【００１０】
他方，基盤を用いずに熱処理すると，すなわち，基盤上に塗布することなく分離・乾燥した粒子の状態で熱処理する場合には，前述の基盤変形の問題はないものの，粒子同士の焼結（ランダムに粒子が融着し合う現象）が起こり，ナノスケールサイズが保持できなくなって，高密度記録媒体用の磁性粉としては不適当なものになりかねない。
【００１１】
したがって，本発明の課題は，このようなナノ粒子を粉状のままで熱処理しても粒子同士の焼結が起きがたいものに変性することにある。
【００１２】
【課題を解決するための手段】
本発明によれば、ＦｅＰｔ規則格子化合金に、元素Ａが、Ａ／（Ｆｅ＋Ｐｔ）の原子百分率で１〜１００（ａｔ．％）の範囲で含まれ、４５０℃以上で熱処理されてなる磁気記録媒体用強磁性粒子を提供する。ただし、元素Ａは、Ｓｉ、ＡｌおよびＲ（ＲはＹを含む希土類元素の１種または２種以上を表す）からなる群から選ばれた少なくとも１種の元素、を表す。前記ＦｅＰｔ規則格子化合金の粒子は表面部に元素Ａが偏在している粒子であるのが好ましい。
【００１３】
【発明の実施の形態】
成分組成がＦxＭ100-xで表される合金のナノ粒子それ自身（ただし，ＦはＦｅまたはＣｏの１種以上，ＭはＰｔまたはＰｄの１種以上で，３０≦ｘ≦７０）は，前述(1) 〜(3) の製法やその他の製法によって得ることができるが，このものをＣｕＡｕ型構造の規則格子をもつ強磁性合金とするには前記のように熱処理するのが好ましい。適正な熱処理温度は，ナノ粒子の粒径，形状，成分組成等によって異なるが少なくとも４５０℃以上を必要とする。そのさい，ＦxＭ100-x合金ナノ粒子の表面部に適正な元素Ａが適量存在していると，粒子同士が融着（焼結）する現象を抑制することができ，ナノスケールサイズを保持したまま規則格子化を達成しやすくなる。
【００１４】
元素Ａとしては，Ｓｉ，ＡｌおよびＲ（ＲはＹを含む希土類元素の１種または２種以上を表す）からなる群から選ばれた少なくとも１種であるのがよい。Ｒのうちで，好ましいのはＹまたはＮｄである。
【００１５】
本発明に従う磁性材料を得るには，まずＦxＭ100-x合金ナノ粒子を製造してから，このナノ粒子に元素Ａを含有させる処理を施すのがよい。ＦxＭ100-x合金ナノ粒子の製造には，非親水性溶媒中で有機金属を熱分解・還元する方法（前記(1) の方法），非親水性溶媒中で界面活性剤を用いてミセルを成形して還元する逆ミセル法（前記(2) の方法），親水性のアルコール溶媒中で還元を行うアルコール還元法（前記(3) の方法），親水性溶媒中でＦの塩化物，硫酸塩等とＭの塩化物とを溶存させて還元剤で還元する方法（同一出願人に係る特願２００１−４００２１６号に記載の方法），そのほかの湿式還元法，気相法などあらゆる製法が適用できるが，非親水性溶媒を用いてＦxＭ100-x合金ナノ粒子を製造した場合には，その合金ナノ粒子が生成している非親水性溶媒に，元素Ａのアルコシド類，例えばテトラエチルオルトシリケート，アルミニウムトリイソプロポキシドなど添加して，該合金ナノ粒子表面部に元素Ａを含有させるのがよい。他方，親水性溶媒を用いてＦxＭ100-x合金ナノ粒子を製造した場合には，その合金ナノ粒子が生成している親水性溶媒に，元素Ａの硫酸塩や，ケイ酸塩，アルミン酸塩などの金属塩を添加して，該合金ナノ粒子表面部に元素Ａを含有させるのがよい。
【００１６】
ＦxＭ100-x合金ナノ粒子に元素Ａを含有させる量としては，Ａ／（Ｆ＋Ｍ）の原子百分率が１〜２００（at.%），好ましくは１〜１５０（at.%），さらに好ましくは１〜１００（at.%）となる量とするのがよい。この原子百分率が１未満では焼結を抑制する効果が現れず，２００を超える場合には，ナノ粒子の分散性が低下するようになる。
【００１７】
【実施例】
〔実施例１〕
４０ミリＬ（Ｌはリットルを表す）のジオクチルエーテル中に１ミリモルのＰｔ(acac)2を混合し，エチレングリコールを３ミリモル添加した。次いで，この混合液を１００℃で３０分間保持した後，オレイン酸を１ミリモル，オレイルアミンを１ミリモルおよびＦｅ(ＣＯ)5を１.６ミリモル添加し，２５０℃に昇温して３０分保持することにより，ＦｅＰｔ微粒子を合成した。
【００１８】
このＦｅＰｔ微粒子を含有したままの液をヘキサンで１０倍に希釈し，この希釈液に対し，アルミニウムトリイソプロポシキドを２−プロパノールに溶解した含アルミニウム溶液を，Ａｌ／（Ｆｅ＋Ｐｔ）の原子百分率が４６.５at.%に相当する割合で添加し，３０℃で６０分攪拌した。次いで，液から粒子を分離し，２−プロパノールで洗浄し，窒素ガス中で乾燥して微粉を得た。得られた微粉の平均粒径はほぼ４ｎｍであった。
【００１９】
この微粉をＮ2雰囲気中で５５０℃に３０分間保持する熱処理を施し，焼結が殆んど起きていない平均粒径がほぼ４ｎｍのＦｅＰｔ強磁性粒子を得た。この粒子の電子顕微鏡写真を図１に示した。また，このＦｅＰｔ強磁性粒子から，保磁力（Ｈｃ）＝２９２７（Ｏe ），飽和磁化（σｓ）＝３０.９（emu/g ）の磁気特性が得られた。
【００２０】
〔実施例２〕
４０ミリＬのジオクチルエーテル中に１ミリモルのＰｔ(acac)2を混合し，エチレングリコールを３ミリモル添加した。次いで，この混合液を１００℃で３０分間保持した後，オレイン酸を１ミリモル，オレイルアミンを１ミリモルおよびＦｅ(ＣＯ)5を１.６ミリモル添加し，２５０℃に昇温して３０分保持することにより，ＦｅＰｔ微粒子を合成した。
【００２１】
このＦｅＰｔ微粒子を含有したままの液をヘキサンで１０倍に希釈し，この希釈液に対し，テトラエチルオルトシリケートをエタノールに溶解した含Ｓｉ溶液を，Ｓｉ／（Ｆｅ＋Ｐｔ）の原子百分率が１００at.%に相当する割合で添加した。次いで，この混合液にナトリウムエチラートをｐＨ１２となるまで添加した後，水蒸気を含む Airでバブリングしながら３０℃で１８０分攪拌した。次いで，液から粒子を分離し，エタノールで洗浄し，窒素ガス中で乾燥して微粉を得た。得られた微粉の平均粒径はほぼ４ｎｍであった。
【００２２】
この微粉をＮ2雰囲気中で５５０℃に３０分間保持する熱処理を施し，焼結が殆んど起きていない平均粒径がほぼ４ｎｍのＦｅＰｔ強磁性粒子を得た。このＦｅＰｔ強磁性粒子から，保磁力（Ｈｃ）＝２５６６（Ｏe ），飽和磁化（σｓ）＝２３.０（emu/g ）の磁気特性が得られた。
【００２３】
〔実施例３〕
４０ミリＬのジオクチルエーテル中に１ミリモルのＰｔ(acac)2を混合し，エチレングリコールを３ミリモル添加した。次いで，この混合液を１００℃で３０分間保持した後，オレイン酸を１ミリモル，オレイルアミンを１ミリモルおよびＦｅ(ＣＯ)5を１.６ミリモル添加し，２５０℃に昇温して３０分保持することにより，ＦｅＰｔ微粒子を合成した。
【００２４】
このＦｅＰｔ微粒子を含有したままの液をヘキサンで１０倍に希釈し，この希釈液に対し，イットリウムイソプロポキシドをトルエンに溶解した含Ｙ溶液を，Ｙ／（Ｆｅ＋Ｐｔ）の原子百分率が２０at.%に相当する割合で添加し，３０℃で６０分攪拌した。次いで，液から粒子を分離し，トルエンで洗浄し，窒素ガス中で乾燥して微粉を得た。得られた微粉の平均粒径はほぼ４ｎｍであった。
【００２５】
この微粉をＮ2雰囲気中で５５０℃に３０分間保持する熱処理を施し，焼結が殆んど起きていない平均粒径がほぼ４ｎｍのＦｅＰｔ強磁性粒子を得た。このＦｅＰｔ強磁性粒子から，保磁力（Ｈｃ）＝２７３２（Ｏe ），飽和磁化（σｓ）＝２７.３（emu/g ）の磁気特性が得られた。
【００２６】
〔比較例〕
４０ミリＬのジオクチルエーテル中に１ミリモルのＰｔ(acac)2を混合し，エチレングリコールを３ミリモル添加した。次いで，この混合液を１００℃で３０分間保持した後，オレイン酸を１ミリモル，オレイルアミンを１ミリモルおよびＦｅ(ＣＯ)5を１.６ミリモル添加し，２５０℃に昇温して３０分保持することにより，ＦｅＰｔ微粒子を合成した。
【００２７】
このＦｅＰｔ微粒子を含有する液にエタノールを添加してＦｅＰｔ微粒子を凝集させたあと，遠心分離によって液から粒子を分離し，窒素ガス中で乾燥して微粉を得た。得られた微粉の平均粒径はほぼ４ｎｍであった。
【００２８】
この微粉をＮ2雰囲気中で５５０℃に３０分間保持する熱処理を施したところ，１０〜２５０ｎｍの大きさに焼結したＦｅＰｔ強磁性粒子を得た。このＦｅＰｔ強磁性粒子から，保磁力（Ｈｃ）＝３４０９（Ｏe ），飽和磁化（σｓ）＝３６.５（emu/g ）の磁気特性が得られた。
【００２９】
【発明の効果】
以上説明したように，本発明によると，ＦxＭ100-x合金ナノ粒子を規則格子化して強磁性材料とする場合の熱処理において，ナノ粒子同士のランダムな焼結の進行を抑制することができる。したがって，ＦxＭ100-x合金ナノ粒子を用いた磁気記録媒体用の強磁性材料を歩留りよく製造することができる。
【図面の簡単な説明】
【図１】本発明に従うＦｅＰｔ合金強磁性ナノ粒子の透過電子顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic material for a magnetic recording medium suitable for high density recording.
[0002]
[Prior art]
Magnetic recording media such as magnetic tapes and magnetic disks for audio, video, and computers are becoming smaller and higher performance due to higher recording capacities. The fine particles are progressing.
[0003]
In order to increase the recording density, it is necessary to reduce the size of the recording unit, but the medium using the conventional magnetic powder is approaching the limit of increasing the recording density. For these reasons, in recent years, magnetic metal nanoparticles having high crystal magnetic anisotropy and a large coercive force have attracted attention as high-density magnetic recording media.
[0004]
Some alloys of transition metals and platinum group metals are known to exhibit high magnetic anisotropy due to regular lattice formation by high-temperature heat treatment. In particular, FePt ordered lattice alloys are Ku = 7 × 10 7 erg / cc. As a powerful magnetic material that solves the problem of thermal fluctuation, it has attracted attention. For example, the following has been reported as a technique related to the synthesis of FePt nanoparticles.
[0005]
(1) A method of synthesizing FePt nanoparticles using chemical techniques was reported by Science, 2000, Vol.287, p.1989. According to this method, FePt nanoparticles are synthesized by reducing Pt (acac) 2 with alcohol and thermally decomposing Fe (CO) 5 in dioctyl ether, which is a non-hydrophilic solvent. The produced FePt nanoparticles can be controlled in composition and the size can be controlled between 3 and 10 nm.
[0006]
(2) Jogo et al. Presented a synthesis method of FePt nanoparticles using the reverse micelle method at the 2001 Annual Conference of the 25th Society of Applied Magnetics (2001, 26aC-6, P.155). ). According to this method, a non-hydrophilic solvent, isooctane, is used as a solvent, and sodium bis (2-ethylhexyl) sulfosuccinate is used as a surfactant to form a micellar field. In this aqueous solution in the micelle, Fe and FePt nanoparticles are synthesized by reducing Pt chloride with NaBH 4 . In this method, nanoparticles with good dispersibility can be obtained by using reverse micelles in the reaction field.
[0007]
(3) Kurobe et al. Also published a method for synthesizing FePt nanoparticles by the alcohol reduction method at the 25th Annual Conference of the Magnetic Society of Japan (2001), 2001 (26aC-5, P.154). According to this method, Fe (acac) 3 is used for the Fe source, Pt (acac) 2 is used for the Pt source, and poly (N-vinyl-2-pyrrolidone) is used as a protective polymer to protect the particle surface. However, FePt nanoparticles are synthesized by an alcohol reduction method using ethylene glycol, which has both a solvent and a reducing agent.
[0008]
It is known that a recording medium in which nanoparticles (FePt) thus obtained are self-arranged on a substrate has a potential to increase the recording density to the order of Tbit / in 2 (Science, 2000, supra). Vol.287, p.1989, and Journal of the Magnetics Society of Japan, 2001, V.25, No.8, p.1434).
[0009]
[Problems to be solved by the invention]
When a recording medium is made of a ferromagnetic alloy composed of nanoparticles as described above, heat treatment is required for making the nanoparticles into a regular lattice. At that time, when regular lattice formation is performed on the substrate, a substrate that can withstand the heat treatment temperature is required. Conventional hard disk bases are mainly glass bases or Al bases, but if these bases are used, they may be deformed at the heat treatment temperature.
[0010]
On the other hand, when the heat treatment is performed without using the base, that is, when the heat treatment is performed in the form of separated and dried particles without being coated on the base, there is no problem of the base deformation described above, but the particles are sintered (randomly). (A phenomenon in which particles fuse together), and the nanoscale size cannot be maintained, which may be inappropriate as a magnetic powder for high-density recording media.
[0011]
Therefore, an object of the present invention is to modify such nanoparticles so that the particles do not easily sinter even if they are heat-treated while still in powder form.
[0012]
[Means for Solving the Problems]
According to the present invention, the element A is contained in the FePt ordered latticed alloy in an atomic percentage of A / (Fe + Pt) in the range of 1 to 100 (at.%) And is heat-treated at 450 ° C. or higher. Ferromagnetic particles for a medium are provided. However, the element A represents at least one element selected from the group consisting of Si, Al, and R (R represents one or more rare earth elements including Y). The FePt ordered latticed alloy particles are preferably particles in which the element A is unevenly distributed on the surface portion.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The alloy nanoparticles represented by the component composition F x M 100-x itself (where F is one or more of Fe or Co, M is one or more of Pt or Pd, and 30 ≦ x ≦ 70) These can be obtained by the above-mentioned production methods (1) to (3) and other production methods, but it is preferable to heat-treat them as described above in order to obtain a ferromagnetic alloy having a regular lattice of CuAu type structure. An appropriate heat treatment temperature varies depending on the particle size, shape, component composition, etc. of the nanoparticles, but requires at least 450 ° C. or more. At that time, if an appropriate amount of the proper element A is present on the surface of the F x M 100-x alloy nanoparticles, the phenomenon that the particles are fused (sintered) can be suppressed, and the nanoscale size can be reduced. It becomes easy to achieve regular lattice formation while maintaining it.
[0014]
The element A is preferably at least one selected from the group consisting of Si, Al, and R (R represents one or more rare earth elements including Y). Of R, Y or Nd is preferred.
[0015]
In order to obtain a magnetic material according to the present invention, it is preferable to first produce F x M 100-x alloy nanoparticles and then perform a treatment of containing the element A in the nanoparticles. For the production of F x M 100-x alloy nanoparticles, a method of thermally decomposing and reducing an organic metal in a non-hydrophilic solvent (method (1) above), using a surfactant in a non-hydrophilic solvent Reverse micelle method in which micelles are formed and reduced (method (2) above), alcohol reduction method in which reduction is carried out in a hydrophilic alcohol solvent (method (3) above), F chloride in a hydrophilic solvent , A method of dissolving sulfate, etc. and M chloride and reducing with a reducing agent (method described in Japanese Patent Application No. 2001-400216 pertaining to the same applicant), other wet reduction methods, gas phase methods, and other various production methods However, when F x M 100-x alloy nanoparticles are produced using a non-hydrophilic solvent, the non-hydrophilic solvent in which the alloy nanoparticles are formed contains an alkoxide of element A, for example, Add tetraethylorthosilicate, aluminum triisopropoxide, etc. , It is preferable to contain an element A to alloy nanoparticle surface portion. On the other hand, when F x M 100-x alloy nanoparticles are produced using a hydrophilic solvent, the element A sulfate, silicate, or aluminine is added to the hydrophilic solvent in which the alloy nanoparticles are formed. It is preferable to add a metal salt such as an acid salt to contain the element A on the surface of the alloy nanoparticles.
[0016]
The amount of the element A contained in the F x M 100-x alloy nanoparticles is such that the atomic percentage of A / (F + M) is 1 to 200 (at.%), Preferably 1 to 150 (at.%), More preferably Is preferably 1 to 100 (at.%). If this atomic percentage is less than 1, the effect of suppressing sintering does not appear, and if it exceeds 200, the dispersibility of the nanoparticles decreases.
[0017]
【Example】
[Example 1]
1 millimole of Pt (acac) 2 was mixed in 40 milliliters (L represents liters) of dioctyl ether, and 3 millimole of ethylene glycol was added. The mixture is then held at 100 ° C. for 30 minutes, then 1 mmol of oleic acid, 1 mmol of oleylamine and 1.6 mmol of Fe (CO) 5 are added, heated to 250 ° C. and held for 30 minutes. Thus, FePt fine particles were synthesized.
[0018]
The solution containing the FePt fine particles was diluted 10-fold with hexane, and an aluminum-containing solution obtained by dissolving aluminum triisopropoxide in 2-propanol was used as an atomic percentage of Al / (Fe + Pt). Was added at a rate corresponding to 46.5 at.% And stirred at 30 ° C. for 60 minutes. Next, the particles were separated from the liquid, washed with 2-propanol, and dried in nitrogen gas to obtain a fine powder. The average particle size of the fine powder obtained was approximately 4 nm.
[0019]
The fine powder was heat-treated in an N 2 atmosphere at 550 ° C. for 30 minutes to obtain FePt ferromagnetic particles having an average particle diameter of approximately 4 nm with almost no sintering. An electron micrograph of the particles is shown in FIG. Further, magnetic characteristics of coercive force (Hc) = 2927 (Oe) and saturation magnetization (σs) = 30.9 (emu / g) were obtained from the FePt ferromagnetic particles.
[0020]
[Example 2]
1 mmol of Pt (acac) 2 was mixed in 40 mL of dioctyl ether, and 3 mmol of ethylene glycol was added. The mixture is then held at 100 ° C. for 30 minutes, then 1 mmol of oleic acid, 1 mmol of oleylamine and 1.6 mmol of Fe (CO) 5 are added, heated to 250 ° C. and held for 30 minutes. Thus, FePt fine particles were synthesized.
[0021]
The liquid containing the FePt fine particles was diluted 10-fold with hexane, and a Si-containing solution in which tetraethylorthosilicate was dissolved in ethanol was diluted to 100 at.% Of the atomic percentage of Si / (Fe + Pt). Added in corresponding proportions. Next, sodium ethylate was added to this mixed solution until pH 12 was reached, and then stirred at 30 ° C. for 180 minutes while bubbling with air containing water vapor. Next, the particles were separated from the liquid, washed with ethanol, and dried in nitrogen gas to obtain a fine powder. The average particle size of the fine powder obtained was approximately 4 nm.
[0022]
The fine powder was heat-treated in an N 2 atmosphere at 550 ° C. for 30 minutes to obtain FePt ferromagnetic particles having an average particle diameter of approximately 4 nm with almost no sintering. From the FePt ferromagnetic particles, magnetic properties of coercive force (Hc) = 2565 (Oe) and saturation magnetization (σs) = 23.0 (emu / g) were obtained.
[0023]
Example 3
1 mmol of Pt (acac) 2 was mixed in 40 mL of dioctyl ether, and 3 mmol of ethylene glycol was added. The mixture is then held at 100 ° C. for 30 minutes, then 1 mmol of oleic acid, 1 mmol of oleylamine and 1.6 mmol of Fe (CO) 5 are added, heated to 250 ° C. and held for 30 minutes. Thus, FePt fine particles were synthesized.
[0024]
The liquid containing the FePt fine particles was diluted 10-fold with hexane, and a Y-containing solution in which yttrium isopropoxide was dissolved in toluene was added to the diluted liquid. The atomic percentage of Y / (Fe + Pt) was 20 at.%. The mixture was added at a rate corresponding to and stirred at 30 ° C. for 60 minutes. Next, the particles were separated from the liquid, washed with toluene, and dried in nitrogen gas to obtain a fine powder. The average particle size of the fine powder obtained was approximately 4 nm.
[0025]
The fine powder was heat-treated in an N 2 atmosphere at 550 ° C. for 30 minutes to obtain FePt ferromagnetic particles having an average particle diameter of approximately 4 nm with almost no sintering. From the FePt ferromagnetic particles, magnetic properties of coercive force (Hc) = 2732 (Oe) and saturation magnetization (σs) = 27.3 (emu / g) were obtained.
[0026]
[Comparative Example]
1 mmol of Pt (acac) 2 was mixed in 40 mL of dioctyl ether, and 3 mmol of ethylene glycol was added. The mixture is then held at 100 ° C. for 30 minutes, then 1 mmol of oleic acid, 1 mmol of oleylamine and 1.6 mmol of Fe (CO) 5 are added, heated to 250 ° C. and held for 30 minutes. Thus, FePt fine particles were synthesized.
[0027]
Ethanol was added to the liquid containing the FePt fine particles to aggregate the FePt fine particles, and then the particles were separated from the liquid by centrifugation and dried in nitrogen gas to obtain fine powder. The average particle size of the fine powder obtained was approximately 4 nm.
[0028]
When this fine powder was heat-treated at 550 ° C. for 30 minutes in an N 2 atmosphere, FePt ferromagnetic particles sintered to a size of 10 to 250 nm were obtained. From this FePt ferromagnetic particle, magnetic properties of coercive force (Hc) = 3409 (Oe) and saturation magnetization (σs) = 36.5 (emu / g) were obtained.
[0029]
【The invention's effect】
As described above, according to the present invention, it is possible to suppress the progress of random sintering between nanoparticles in the heat treatment when the F x M 100-x alloy nanoparticles are made into a regular lattice to form a ferromagnetic material. it can. Therefore, a ferromagnetic material for a magnetic recording medium using F x M 100-x alloy nanoparticles can be manufactured with high yield.
[Brief description of the drawings]
FIG. 1 is a transmission electron micrograph of FePt alloy ferromagnetic nanoparticles according to the present invention.
Claims (2)
ただし、元素Ａは、Ｓｉ、ＡｌおよびＲ（ＲはＹを含む希土類元素の１種または２種以上を表す）からなる群から選ばれた少なくとも１種の元素、を表す。A ferromagnetic particle for a magnetic recording medium, wherein the FePt ordered lattice alloy contains element A in an atomic percentage of A / (Fe + Pt) in the range of 1 to 100 (at.%) And is heat-treated at 450 ° C. or higher.
However, the element A represents at least one element selected from the group consisting of Si, Al, and R (R represents one or more rare earth elements including Y).
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108060391A (en) * | 2017-12-15 | 2018-05-22 | 桂林电子科技大学 | A kind of method for accelerating FePd film phase transition |
| CN110560704A (en) * | 2019-10-11 | 2019-12-13 | 东北大学 | Method for inductively synthesizing fct-FePt nano particles by doping low-melting-point elements |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7592042B1 (en) | 2005-12-19 | 2009-09-22 | Fujifilm Corporation | Reverse micelle method of producing core/shell particles |
| JP5062754B2 (en) * | 2008-04-09 | 2012-10-31 | 独立行政法人物質・材料研究機構 | FePtP ternary alloy |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108060391A (en) * | 2017-12-15 | 2018-05-22 | 桂林电子科技大学 | A kind of method for accelerating FePd film phase transition |
| CN108060391B (en) * | 2017-12-15 | 2019-12-27 | 桂林电子科技大学 | Method for accelerating phase transition of FePd thin film |
| CN110560704A (en) * | 2019-10-11 | 2019-12-13 | 东北大学 | Method for inductively synthesizing fct-FePt nano particles by doping low-melting-point elements |
| CN110560704B (en) * | 2019-10-11 | 2021-10-22 | 东北大学 | Method for inductively synthesizing fct-FePt nano particles by doping low-melting-point elements |
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