TEMPERATURE DEPENDENCE OF CURRENT POLARIZATION IN Ni80Fe20 BY SPIN WAVE DOPPLER MEASUREMENTS
Meng Zhu1,2, Cindi. L. Dennis3,
R. D. McMichael1
1 Center for Nanoscale Science and Technology, NIST, Gaithersburg, MD 20899
2 Maryland NanoCenter, University of Maryland, College Park, MD 20742
3 Metallurgy Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
The current polarization P in ferromagnetic metals describes the difference between currents carried by spin-up and spin-down electrons. P is an important quantity for development of spin-torque switched memories and devices based on the control of current-induced domain wall motion. The temperature dependence of P will be important for successful application of these technologies in a wide temperature range. Here, we use the spin wave Doppler technique  to measure the temperature dependence of both the magnetization drift velocity v(T) and the current polarization P(T) in current-carrying Ni80Fe20 wires. We obtain these values from current-dependent shifts of the spin wave transmission resonance frequency for fixed-wavelength spin waves in current-carrying wires. For current densities of 1011A/m2, we obtain v(T) decreasing from 4.8 ± 0.3 m/s to 4.1 ± 0.1 m/s and P(T) dropping from 0.75 ± 0.05 to 0.58 ± 0.02 over a temperature range from 80 K to 340 K. This work has been supported in part by the NIST-CNST/UMD-NanoCenter Cooperative Agreement.
 V. Vlaminck et al. Science 322, 410 (2008);