We measure electron tunneling via discrete energy levels in ferromagnetic cobalt particles less than 4 nm in diameter, using non-magnetic electrodes. Due to magnetic anisotropy, the energy of each tunneling resonance shifts as an applied magnetic field rotates the particle's magnetic moment. We see both spin-increasing and decreasing tunneling transitions, but we do not observe the spin degeneracy at small magnetic fields seen previously in non-magnetic materials. The tunneling spectrum is denser than predicted for independent electrons, possibly due to spin-wave excitations.
@article{arxiv.cond-mat/9904248,
title = {Tunneling Via Individual Electronic States in Ferromagnetic Nanoparticles},
author = {S. Gueron and Mandar M. Deshmukh and E. B. Myers and D. C. Ralph},
journal= {arXiv preprint arXiv:cond-mat/9904248},
year = {2009}
}
Comments
4 pages, 4 figures. Improved by comments from referees, to appear in Phys. Rev. Lett