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Sakai, Seiji; Yakushiji, Kei*; Mitani, Seiji*; Sugai, Isamu; Takanashi, Koki*; Naramoto, Hiroshi*; Avramov, P.; Lavrentiev, V.*; Narumi, Kazumasa; Maeda, Yoshihito
Materials Transactions, 48(4), p.754 - 758, 2007/04
Times Cited Count:9 Percentile:51.38(Materials Science, Multidisciplinary)Magnetic properties were investigated for the alternately deposited film of C and Co which has found to exhibit tunnel magnetoresistance (MR) of 10-80 %. Magnetic field and temperature dependences of magnetization showed typical superparamagnetic behaviors with the blocking temperature of 40 K. The magnetization curve at 300 K was well fitted by the Langevin function with the size distribution of Co particles, and the mean diameter and size distribution were evaluated to be 3.1 nm and 1 nm, respectively. Based on the magnetic properties, the detailed structure and magnetotransport properties are discussed.
Sakai, Seiji; Yakushiji, Kei*; Mitani, Seiji*; Takanashi, Koki*; Naramoto, Hiroshi; Avramov, P.; Narumi, Kazumasa; Lavrentiev, V.; Maeda, Yoshihito
Applied Physics Letters, 89(11), p.113118_1 - 113118_3, 2006/09
Times Cited Count:58 Percentile:86.26(Physics, Applied)In this study, the first results are described on the spin-dependent transport in the Co-C hybrid film in which Co nanoparticles are dispersed in a matrix of the Co-C compound. It is found that the hybrid film shows significant tunnel magnetoresistance (MR) of a few 10 %, which is comparable to granular metal-insulator systems, under the small applied bias voltage. Additionally, it is found that the electrical conductivity and MR ratio are strongly influenced by the bias voltage and the MR ratio under the higher bias voltage reaches 80%, which is anomalously high in granular systems. The bias-dependent magnetotransport behaviours are surmised to be related to the electronic structure of the Co-C compound.
Sakai, Seiji; Yakushiji, Kei*; Naramoto, Hiroshi; Narumi, Kazumasa; Mitani, Seiji*; Takanashi, Koki*
no journal, ,
no abstracts in English
Sakai, Seiji; Sugai, Isamu; Yakushiji, Kei*; Mitani, Seiji*; Takanashi, Koki*; Naramoto, Hiroshi; Avramov, P.; Narumi, Kazumasa; Maeda, Yoshihito
no journal, ,
no abstracts in English
Sakai, Seiji; Sugai, Isamu; Yakushiji, Kei*; Mitani, Seiji*; Takanashi, Koki*; Naramoto, Hiroshi; Avramov, P.; Narumi, Kazumasa; Maeda, Yoshihito
no journal, ,
We have revealed that the Co/Co-C films prepared by alt-deposition show the tunnel MR of a few 10% under low bias voltage and the further enhancement to above 80% by the voltage increase at lower temperature than 10 K. In the present study, the magnetotransport properties in the co-deposited Co/Co-C films are reported. The co-deposited film shows the remarkable tunnel MR effect (10-50%) whose ratio is significantly influenced by the applied voltage. Such a significant MR enhancement by the bias-voltage is found to take place commonly in the Co/Co-C films irrespective of the deposition method, and that is in contrast to the small extent of changes in the conventional metal/insulator systems. In the presentation, the comparative results for the co-deposited and alt-deposited Co/Co-C films are also reported in comparison with the analyzed structures by Raman spectroscopy et al..