- 著者
- Yanagihara H. Uwabo K. Minagawa M. Kita Eiji Hirota Noriyuki
- 出版者
- American Institute of Physics
- 雑誌
- Journal of applied physics (ISSN:00218979)
- 巻号頁・発行日
- vol.109, no.7, pp.07C122, 2011-04
- 被引用文献数
- 57 16
We report on the magnetic properties of epitaxial cobalt-ferrite films with orientations parallel to [001] and [111] grown by a reactive molecular beam epitaxy method using pure ozone gas as an oxidation agent. Both Mössbauer spectroscopy and magnetization measurement of the CoFe2O4(001) film grown on MgO(001) indicate that the film has perpendicular magnetic anisotropy (PMA) with high coercivity, whereas the film of CoFe2O4(111) grown on α-Al2O3(0001) appears to be paramagnetic. The maximum uniaxial anisotropy energy for CoFe2O4(001) estimated from the magnetization and coercivity at room temperature is ≈ 3×106 erg/cm3.
- 著者
- Kita Eiji Tsukuhara Naoki Sato Hidenori Ota Keishin Yangaihara Hideto Tanimoto Hisanori Ikeda Naoshi
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.88, pp.152501, 2006-04
- 被引用文献数
- 22 19
We prepared high-purity oxygen-free and single-phase Ni nanocrystals using the gas condensation and deposition method in order to examine the random anisotropy model (RAM). The grain size of an as-prepared sample was estimated to be 8–10 nm. Thermal annealing increased grain sizes (D) up to 22 nm. Clear D6 dependence of the coercive force on a grain size smaller than 13 nm was obtained for samples prepared on both plastic and KBr single-crystal substrates. For larger grain sizes, Hc decreased with D–1 and these results clearly conform to the RAM in single-element nanocrystal systems. A local anisotropy constant was estimated from the slope of the D6 relation and the peak of Hc at D=13 nm.
- 著者
- Suzuki Kazuya Z. Yanagihara Hideto Niizeki Tomohiko Kojio Ken Kita Eiji
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.101, no.22, pp.222401, 2012-11
- 被引用文献数
- 5 4
Magnetic and magnetotransport properties of pyromellitic dianhydride-4,4′-oxydianiline polyimide-Co granular thin films prepared by vapor deposition polymerization are investigated. The prepared sample is composed of Co particles with diameters of 2–3 nm homogeneously dispersed in a denatured polyimide matrix. The temperature dependence of the resistivity closely follows the T−1/2 law, suggesting that the dominant conduction mechanism is tunneling between metallic granules embedded in the insulating polyimide matrix. The magnetoresistances at 300 and 90 K are 2.6% and 3.0%, respectively. The results indicate that polyimide is a promising material for organic spintronics.