Researchers at NIST have developed a new method to measure current spin polarization in Permalloy (Ni80Fe20) over a wide temperature range. The technique uses spin-wave Doppler effect measurements to determine the polarization of electrical currents in ferromagnetic metals, which is crucial for understanding spin-transfer torque effects.
The spin-wave Doppler technique involves exciting spin waves in Permalloy wires using nanoscale microwave antennas and measuring the frequency shift caused by the current-driven magnetization drift. This method is advantageous because it is not affected by interfacial effects and allows temperature variations.
The researchers found that current spin polarization in Permalloy increases with decreasing temperature. This temperature-dependent behavior is important for the successful implementation of magnetic memory and oscillators technologies. The study was published in the April 2010 issue of Physical Review B.
Keywords: spin polarization, Permalloy, spin-wave Doppler technique
