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Coherent transport of electron spin in a ferromagnetically contacted carbon nanotube

K. Tsukagoshi
Present address - The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan

B. W. Alphenaar
Hitachi Cambridge Laboratory, Madingley Road, Cambridge CB3 0HE, UK

H. Ago
Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK

Abstract

            Conventional electronic devices generally utilize only the charge of conduction electrons; however, interest is growing in ‘spin-electronic’ devices, 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 materials, or through oxide tunnel barriers. 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 properties of carbon nanotubes offer intriguing possibilities for such devices; their elastic- and phase-scattering lengths are extremely long, and carbon nanotubes can behave as one-dimensional conductors. 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 resis-tance change of 9%, from which we estimate the spin-flip scatter-ing length to be at least 130 nm--an encouraging result for the development of practical nanotube spin-electronic devices.

K. Tsukagoshi, B. W. Alphenaar and H. Ago, "Coherent transport of electron spin in a ferromagnetically contacted carbon nanotube," NATURE 401, 572-572 (October 1999)

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