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Coherent transport of electron spin in a ferromagnetically contacted carbon nanotube

Nature volume 401, pages 572–574 (1999)Cite this article

Abstract

Conventional electronic devices generally utilize only the charge of conduction electrons; however, interest is growing in ‘spin-electronic’ devices1, whose operation depends additionally on the electronic spin. Spin-polarized electrons (which occur naturally in ferromagnetic materials) can be injected from a ferromagnet into non-ferromagnetic materials2,3,4, or through oxide tunnel barriers3,5,6,7,8,9,10. The electron-scattering rate at any subsequent ferromagnetic/non-ferromagnetic interface depends on the spin polarity, a property that is exploited in spin-electronic devices. The unusual conducting properties11,12,13,14,15,16,17,18 of carbon nanotubes offer intriguing possibilities for such devices; their elastic- and phase-scattering lengths are extremely long16,17, and carbon nanotubes can behave as one-dimensional conductors18. Here we report the injection of spin-polarized electrons from ferromagnetic contacts into multi-walled carbon nanotubes, finding direct evidence for coherent transport of electron spins. We observe a hysteretic magnetoresistance in several nanotubes with a maximum resistance change of 9%, from which we estimate the spin-flip scattering length to be at least 130 nm—an encouraging result for the development of practical nanotube spin-electronic devices.

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Figure 1: Structure of our devices, consisting of a single multi-walled carbon nanotube (MWNT) electrically contacted by ferromagnetic Co.
Figure 2: Two-terminal differential resistance as a function of magnetic field for three different MWNT devices.
Figure 3: Detailed characterization of a single nanotube device.

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Acknowledgements

We thank H. Mizuta, T. Nakanishi, M. D. R. Thomas, D. G. Hasko and H. O. Müller for discussions.

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Authors and Affiliations

  1. The Institute of Physical and Chemical Research (RIKEN), Wako, 351-0198, Saitama, Japan

    Kazuhito Tsukagoshi

  2. Hitachi Cambridge Laboratory, Madingley Road, Cambridge, CB3 0HE, UK

    Bruce W. Alphenaar

  3. Cavendish Laboratory, Madingley Road, Cambridge, CB3 0HE, UK

    Hiroki Ago

Authors
  1. Kazuhito Tsukagoshi
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  2. Bruce W. Alphenaar
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  3. Hiroki Ago
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Correspondence to Bruce W. Alphenaar.

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Tsukagoshi, K., Alphenaar, B. & Ago, H. Coherent transport of electron spin in a ferromagnetically contacted carbon nanotube. Nature 401, 572–574 (1999). https://doi.org/10.1038/44108

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