Ohmic spin injection from a half-metal at finite temperatures: Is the conductivity mismatch problem relevant?

ORAL

Abstract

Spin injection from a normal ferromagnet into a semiconductor requires a highly-resistive tunnel or Schottky barrier at the interface to overcome the conductivity mismatch problem. This barrier limits the current that can be achieved in a device. A half-metallic ferromagnet used as a spin injector obviously overcomes this problem at zero temperature, but the situation at finite temperatures is nontrivial. We argue that the two-current model is inapplicable to half-metals, and that Ohmic (barrierless) spin injection from a half-metal is possible even at finite temperatures. This conclusion is reached using an intuitive model which sums up multiple scatterings at the interface. To complement this model, we calculate the spin injection efficiency for a half-metallic electrode using a single-band tight-binding model with explicit statistical averaging over thermal spin fluctuations. The results are contrasted with the case of a normal ferromagnet. We also consider a practically interesting case of a CrAs electrode within the tight-binding LMTO method.

–

Authors

  • James Glasbrenner

    University of Nebraska - Lincoln, University of Nebraska-Lincoln

  • Aleksander Wysocki

    Department of Physics and Astronomy, University of Nebraska-Lincoln, University of Nebraska - Lincoln, Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln

  • Kirill Belashchenko

    University of Nebraska, Lincoln, University of Nebraska-Lincoln, Department of Physics and Astronomy, University of Nebraska-Lincoln, University of Nebraska - Lincoln, Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, University of Nebraska