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Long spin-relaxation time in a single metal nanoparticle

Nature Nanotechnology volume 5, pages 593–596 (2010)Cite this article

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Abstract

Spin-relaxation time is key to the performance of spin-based devices1,2. Although the spin-relaxation times of semiconductor materials are typically ∼100 ns (ref. 3), they are on the order of picoseconds in bulk metals due to the high density of scattering centres. In metallic nanoparticles, the spin-relaxation times can be strongly enhanced due to the quantum size effect4,5, reaching 150 ns in cobalt nanoparticles6. Here, we show that for extra electrons confined in a single ferromagnetic-metal MnAs nanoparticle embedded in a GaAs semiconductor matrix, the spin-relaxation time can reach 10 µs at 2 K, which is seven orders of magnitude longer than those of conventional metallic thin film or bulk systems, and the longest value ever reported for metallic nanoparticles. This long relaxation time is made possible by using epitaxially grown single-crystal devices with abrupt interfaces, and by avoiding surface contamination of the MnAs nanoparticle. Such a long spin-relaxation time can be very useful in nanoscale spintronic devices.

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Figure 1: Device structure.
Figure 2: Transport characteristics.
Figure 3: TMR oscillation.

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Acknowledgements

This work was partly supported by Grant-in-Aids for Scientific Research, the Special Coordination Programs for Promoting Science and Technology, R&D for Next-generation Information Technology by MEXT, PRESTO of JST. P.N.H. acknowledges support from the Global COE program (C04). The authors thank T. Fujii for his help in measurements at Cryogenic Research Centre, and members of the Nakano Laboratory at RCAST, University of Tokyo, for their help in the nanofabrication of our samples.

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  1. Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan

    Pham Nam Hai, Shinobu Ohya & Masaaki Tanaka

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  1. Pham Nam Hai
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  2. Shinobu Ohya
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  3. Masaaki Tanaka
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Contributions

P.N.H. designed the experiment, fabricated the samples, collected most of the data and carried out analysis of the data. S.O. provided experimental advice. M.T. planned and managed the research and supervised the experiment. All authors discussed the results and commented on the manuscript.

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Correspondence to Masaaki Tanaka.

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Hai, P., Ohya, S. & Tanaka, M. Long spin-relaxation time in a single metal nanoparticle. Nature Nanotech 5, 593–596 (2010). https://doi.org/10.1038/nnano.2010.130

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