Electrical detection of dynamic nuclear polarization and nuclear magnetic resonance in ferromagnet-semiconductor heterostructures

ORAL

Abstract

We report all-electrical measurements of dynamic nuclear polarization (DNP) and nuclear magnetic resonance (NMR) in ferromagnet-semiconductor heterostructures. Nuclei in GaAs are polarized by electron spins injected through an epitaxial Fe/GaAs Schottky tunnel barrier. In an oblique Hanle geometry, electron spin depolarization due to the hyperfine field is detected by measuring the change in spin-dependent electrochemical potential with a Fe contact.We also report electrical measurements of both magnetic and current driven NMR. A transverse magnetic field or the injection current is modulated at the NMR frequency to suppress DNP, resulting in changes of up to 80{\%} in the spin-dependent voltage. We measured resonant frequencies of different isotopes in the GaAs channel. Harmonics of the fundamental transitions are observed, reflecting the existence of either quadrupolar coupling or dipole-dipole interactions.

*This work was supported by the Office of Naval Research and NSF under DMR 08-04244.

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Authors

  • M. K. Chan

    • University of Minnesota, Twin Cities
    • University of Minnesota

  • J. Zhang

    • University of Minnesota, Twin Cities

  • Q. Hu

    • University of California, Santa Barbara

  • T. Kondo

    • University of Minnesota, Twin Cities

  • E. Garlid

    • University of Minnesota, Twin Cities

  • C.J. Palmstrom

    • University of California, Santa Barbara

  • P.A. Crowell

    • University of Minnesota, Twin Cities