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Enhanced spin accumulation and novel magnetotransport in nanoparticles

Nature Materials volume 4, pages 57–61 (2005)Cite this article

Abstract

Spin injection and accumulation are key phenomena supporting a variety of concepts for spin-electronic devices. These phenomena are expected to be enhanced in nanoparticles over bulk structures due to their discrete energy levels and large charging energies. In this article, precise magnetotransport measurements in the single-electron tunnelling regime are performed by preparing appropriate microfabricated devices containing cobalt nanoparticles. Here we provide experimental evidence for characteristic features of spin accumulation in magnetic nanoparticles, such as oscillations of the magnetoresistance with a periodical sign change as a function of bias voltage. Theoretical analysis of the magnetoresistance behaviour clearly shows that the spin-relaxation time in nanoparticles is highly enhanced in comparison with that in the bulk.

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Figure 1: Schematic illustration of a sample with pillared structure, which was prepared for the current-perpendicular-to-plane measurement.
Figure 2: Magnetotransport properties measured at 4.2 K in a Al/Al-O/Co-Al-O/Co sample with sub-micrometre-sized area.
Figure 3: Theoretical model to study the spin-accumulation effect on TMR, and the results assuming an infinite spin-relaxation time in a ferromagnetic island.
Figure 4: Bias voltage (V) dependence of the tunnel magnetoresistance (TMR) behaviour for various values of the spin-relaxation time τSF.

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Acknowledgements

We thank G. G. Khalliulin and J. Martinek for useful discussions. Some of the experiments were performed at LAM, IMR, Tohoku University. K. T. and S. Mitani were supported by the Asahi glass foundation. S. Mitani was supported by the Sumitomo Foundation. F.E. was supported by the 21st century COE program for young researchers. F.E. is grateful to the Post-doctoral fellowship program of JSPS. H.I. is supported by MEXT. Kakenhi (No. 14076204 and 16710061). H.I., S.T. and S.Maekawa were supported by the NAREGI Nanoscience Project.

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Authors and Affiliations

  1. Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, 980-8577, Sendai, Japan

    Kay Yakushiji, Franck Ernult, Kazutaka Yamane, Seiji Mitani, Koki Takanashi, Saburo Takahashi & Sadamichi Maekawa

  2. CREST, Japan Science and Technology Agency, 4-1-8 Honcho,, Kawaguchi, 332-0012, Japan

    Kay Yakushiji, Hiroshi Imamura, Seiji Mitani, Koki Takanashi, Saburo Takahashi, Sadamichi Maekawa & Hiroyasu Fujimori

  3. Graduate School of Information Sciences, Tohoku University, Aramaki,, Aoba-ku, 980-8579, Sendai, Japan

    Hiroshi Imamura

  4. The Research Institute for Electric and Magnetic Materials, 2-1-1 Yagiyama-minami, Taihaku-ku, 982-0807, Sendai, Japan

    Hiroyasu Fujimori

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  1. Kay Yakushiji
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Correspondence to Kay Yakushiji.

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Yakushiji, K., Ernult, F., Imamura, H. et al. Enhanced spin accumulation and novel magnetotransport in nanoparticles. Nature Mater 4, 57–61 (2005). https://doi.org/10.1038/nmat1278

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