2003 Fiscal Year Annual Research Report

ナノ磁性ドット規則配列格子の磁気的挙動の解明と超高密度メモリーへの応用

Research Project

Project/Area Number	13555087
Research Institution	TOHOKU UNIVERSITY
Principal Investigator	北上修東北大学, 多元物質科学研究所, 助教授 (70250834)
Co-Investigator(Kenkyū-buntansha)	深道和明東北大学, 大学院・工学研究科, 教授 (00005969) 島田寛東北大学, 多元物質科学研究所, 教授 (00006157) 岡本聡東北大学, 多元物質科学研究所, 助手 (10292278) 萩野谷千積株式会社日立製作所, 研究員
Keywords	磁性メモリ / ナノ磁性粒子 / 熱揺らぎ / 磁気異方性 / 高密度記録 / FePt規則合金 / 微細加工 / パターン媒体
Research Abstract	超高密度磁性メモリーの最小構成単位は既にナノメートルサイズ領域に入ろうとしている.こうしたメモリーの性能やデータの長期保存性を予想し,更に性能向上を図っていくためには,最小構成単位であるナノ粒子一個一個の性質を定量的に把握しておくことが必要である.しかし,従来の測定技術の感度ではその測定は到底不可能であった.こうした状況の中,我々は昨年度までに,異常ホール効果を利用した高感度磁化測定技術を確立し,単一ナノ粒子の磁化検出に初めて成功した.本年度は,この計測技術を基に,将来の超高密度メモリー材料として有望視されるL1_0構造FePtなどのナノ粒子1個1個の磁化反転様式及び熱安定性を詳細に調べた.その結果,磁性材料の特性長(交換結合長)を凡その境にして,ナノ粒子の磁化反転様式は一斉⇔非一斉モードに変化することが明らかになった.この実験結果はマイクロマグネティクス理論の予測と一致し,粒子サイズを交換結合長以内に抑えれば,粒子の全スピンが平行性を保ちつつ一斉に振舞うことを示している.この一斉モード領域では,高密度メモリーに求められる特性(例えば高速スイッチングやデータの長期保存性など)を引き出しやすく,またシステムに適合した材料設計も容易という特徴がある.今回の実験と理論計算によれば,代表的メモリー材料であるCo基合金やFePtなどの場合,交換結合長は20〜40nm程度であるので,磁性ナノ粒子の集合体や規則配列格子で超高密度メモリーを構成する際には,最小単位をこのサイズよりも小さくすれば一斉モードの磁化挙動を実現できる. 以上,本研究を通して得られた知見に基づいて,0.4テラ及び1テラビット/平方インチという超高密度メモリーを実現できる磁性材料とディメンションを明確にした.

Research Products

(20 results)

All Other

All Publications (20 results)

[Publications] S.Okamoto et al.: "Size dependence of magnetic properties and switching behavior in FePt L1_0 nanoparticles"Physical Review B. 67. 094422-1-094422-7 (2003)
[Publications] A.Yoshihara et al.: "Brillouin light scattering from spin waves in epitaxial hcp Co films"Physical Review B. 67. 134435-1-134435-7 (2003)
[Publications] N.Kikuchi et al.: "Sensitive detection of irreversible switching in a single FePt nanosized dot"Applied Physics Letters. 82. 4313-4315 (2003)
[Publications] O.Kitakami et al.: "Energy barrier enhanced by higher-order magnetic anisotropy terms"Japanese Journal of Applied Physics. 42. L455-L457 (2003)
[Publications] K.Oikawa et al.: "Magnetically induced phase separation and magnetic properties of Co-Mo HCP structure thin films"Applied Physics Letters. 83. 966-968 (2003)
[Publications] H.Yamaguchi et al.: "Magnetic anisotropy energy of L1_0 CoPt-B thin films elongated c-axis"Material Transactions. 44. 1514-1519 (2003)
[Publications] Y.Endo et al.: "Study of the low temperature ordering of L1_0 Fe-Pt in Fe/Pt multilayers"Journal of Applied Physics. 94. 7222-7226 (2003)
[Publications] T.Miyazaki et al.: "Fabrication of two-dimensional assembly of L1_0 FePt nanoparticles"Journal of Applied Physics. 93. 7759-7761 (2003)
[Publications] Y.Shimada et al.: "Fabrication of two-dimensional assembly of L1_0 FePt particles"Journal of Magnetism and Magnetic Materials. 262. 329-338 (2003)
[Publications] T.Shimatsu, O.Kitakami: "Development of ultra-high density perpendicular recording media [Invited]"Proceedings of International Symposium on Ultra-High Density Spinic Storage Systems. 22-27 (2003)
[Publications] T.Shimatsu et al.: "Large perpendicular magnetic anisotropy of CoPtCr/Ru films for granular-type perpendicular media"Proceedings of International Symposium on Ultra-High Density Spinic Storage Systems. 68-69 (2003)
[Publications] 岡本聡他: "磁性体の熱揺らぎの評価(解説)"日本金属学会報まてりあ. 42. 1047-1053 (2003)
[Publications] S.Okamoto et al.: "Anisotropy field of FePt L1_0 nanoparticles controlled by insertion of very thin Pt layer"Journal of Physics : Condensed Matter. 16. 2109-2114 (2004)
[Publications] O.Kitakami et al.: "Sharrock relation for perpendicular recording media with higher-order magnetic anisotropy terms"Japanese Journal of Applied Physics. 43. L115-L117 (2004)
[Publications] T.Imazono et al.: "Interdiffused layers in antiferromagnetically-coupled Fe/Si multilayers studied by soft-X-ray fluorescence spectroscopy"Japanese Journal of Applied Physics. (in press). (2004)
[Publications] T.Shimatsu et al.: "High perpendicular magnetic Anisotropy of CoPtCr/Ru films for granular-type perpendicular recording media"IEEE Transactions on Magnetics. (in press). (2004)
[Publications] T.Hino et al.: "Observation of magnetic domain structure in FePt(001) films by electron holography and Lorentz microscopy"Material Transactions. (in press). (2004)
[Publications] 桜井伴明他: "ZnO下地上におけるL1_0FePt(001)優先成長"日本応用磁気学会誌. (印刷中). (2004)
[Publications] 藤慶彦他: "L1_0FePt(001)c軸配向の熱処理条件依存性"日本応用磁気学会誌. (印刷中). (2004)
[Publications] 佐藤公宣他: "Co-Mo, W合金薄膜における磁気相分離"日本応用磁気学会誌. (印刷中). (2004)

2003 Fiscal Year Annual Research Report

ナノ磁性ドット規則配列格子の磁気的挙動の解明と超高密度メモリーへの応用

Principal Investigator

北上 修 東北大学, 多元物質科学研究所, 助教授 (70250834)

Research Products

[Publications] S.Okamoto et al.: "Size dependence of magnetic properties and switching behavior in FePt L1_0 nanoparticles"Physical Review B. 67. 094422-1-094422-7 (2003)

[Publications] A.Yoshihara et al.: "Brillouin light scattering from spin waves in epitaxial hcp Co films"Physical Review B. 67. 134435-1-134435-7 (2003)

[Publications] N.Kikuchi et al.: "Sensitive detection of irreversible switching in a single FePt nanosized dot"Applied Physics Letters. 82. 4313-4315 (2003)

[Publications] O.Kitakami et al.: "Energy barrier enhanced by higher-order magnetic anisotropy terms"Japanese Journal of Applied Physics. 42. L455-L457 (2003)

[Publications] K.Oikawa et al.: "Magnetically induced phase separation and magnetic properties of Co-Mo HCP structure thin films"Applied Physics Letters. 83. 966-968 (2003)

[Publications] H.Yamaguchi et al.: "Magnetic anisotropy energy of L1_0 CoPt-B thin films elongated c-axis"Material Transactions. 44. 1514-1519 (2003)

[Publications] Y.Endo et al.: "Study of the low temperature ordering of L1_0 Fe-Pt in Fe/Pt multilayers"Journal of Applied Physics. 94. 7222-7226 (2003)

[Publications] T.Miyazaki et al.: "Fabrication of two-dimensional assembly of L1_0 FePt nanoparticles"Journal of Applied Physics. 93. 7759-7761 (2003)

[Publications] Y.Shimada et al.: "Fabrication of two-dimensional assembly of L1_0 FePt particles"Journal of Magnetism and Magnetic Materials. 262. 329-338 (2003)

[Publications] T.Shimatsu, O.Kitakami: "Development of ultra-high density perpendicular recording media [Invited]"Proceedings of International Symposium on Ultra-High Density Spinic Storage Systems. 22-27 (2003)

[Publications] T.Shimatsu et al.: "Large perpendicular magnetic anisotropy of CoPtCr/Ru films for granular-type perpendicular media"Proceedings of International Symposium on Ultra-High Density Spinic Storage Systems. 68-69 (2003)

[Publications] 岡本聡 他: "磁性体の熱揺らぎの評価(解説)"日本金属学会報 まてりあ. 42. 1047-1053 (2003)

[Publications] S.Okamoto et al.: "Anisotropy field of FePt L1_0 nanoparticles controlled by insertion of very thin Pt layer"Journal of Physics : Condensed Matter. 16. 2109-2114 (2004)

[Publications] O.Kitakami et al.: "Sharrock relation for perpendicular recording media with higher-order magnetic anisotropy terms"Japanese Journal of Applied Physics. 43. L115-L117 (2004)

[Publications] T.Imazono et al.: "Interdiffused layers in antiferromagnetically-coupled Fe/Si multilayers studied by soft-X-ray fluorescence spectroscopy"Japanese Journal of Applied Physics. (in press). (2004)

[Publications] T.Shimatsu et al.: "High perpendicular magnetic Anisotropy of CoPtCr/Ru films for granular-type perpendicular recording media"IEEE Transactions on Magnetics. (in press). (2004)

[Publications] T.Hino et al.: "Observation of magnetic domain structure in FePt(001) films by electron holography and Lorentz microscopy"Material Transactions. (in press). (2004)

[Publications] 桜井伴明他: "ZnO下地上におけるL1_0FePt(001)優先成長"日本応用磁気学会誌. (印刷中). (2004)

[Publications] 藤慶彦他: "L1_0FePt(001)c軸配向の熱処理条件依存性"日本応用磁気学会誌. (印刷中). (2004)

[Publications] 佐藤公宣他: "Co-Mo, W合金薄膜における磁気相分離"日本応用磁気学会誌. (印刷中). (2004)

北上修東北大学, 多元物質科学研究所, 助教授 (70250834)

[Publications] 岡本聡他: "磁性体の熱揺らぎの評価(解説)"日本金属学会報まてりあ. 42. 1047-1053 (2003)