Letters to Nature

Nature 401, 572-574 (7 October 1999) | doi:10.1038/44108; Received 6 May 1999; Accepted 2 August 1999

Coherent transport of electron spin in a ferromagnetically contacted carbon nanotube

Kazuhito Tsukagoshi1, Bruce W. Alphenaar2 & Hiroki Ago3

  1. The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan
  2. Hitachi Cambridge Laboratory, Madingley Road, Cambridge CB3 0HE, UK
  3. Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK

Correspondence to: Bruce W. Alphenaar2 Correspondence and requests for materials should be addressed to B.W.A. (Email: alphenaar@phy.cam.ac.uk).

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.