Current-Driven Magnetic Excitations in Permalloy-Based Multilayer Nanopillars

Authors:
  • SUS. Urazhdin
    S. Urazhdin
  • NBNorman O. Birge
    Norman O. Birge
  • WJW. P. Pratt Jr
    W. P. Pratt Jr
  • JBJ. Bass
    J. Bass
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Abstract
We study current-driven magnetization switching in nanofabricated Ni84Fe16/Cu/Ni84Fe16 trilayers at 295 K and 4.2 K. We find a direct correspondence between the magnetization switching current and the threshold for magnetic excitations. The excitations appear as a linear background or a series of peaks in the differential resistance. In high field, the magnetization switching is characterized by telegraph noise, with average period decreasing exponentially with current. We describe these behaviors in terms of a minimum energy for magnetic excitations and a current-dependent effective magnetic temperature.