Spin transfer torque devices utilizing the giant spin Hall effect of tungsten

We report a giant spin Hall effect in beta-W thin films. Using spin torque induced ferromagnetic resonance with a beta-W/CoFeB bilayer microstrip, we determine the spin Hall angle to be vertical bar theta(beta-W)(SH)vertical bar = 0.30 +/- 0.02, large enough for an in-plane current to efficiently reverse the orientation of an in-plane magnetized CoFeB free layer of a nanoscale magnetic tunnel junction adjacent to a thin beta-W layer. From switching data obtained with such 3-terminal devices, we independently determine vertical bar theta(beta-W)(SH)vertical bar = 0.33 +/- 0.06. We also report variation of the spin Hall switching efficiency with W layers of different resistivities and hence of variable (alpha and beta) phase composition. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4753947]