Reduction of the spin-torque critical current by partially canceling the free layer demagnetization field

Liu, Luqiao; Moriyama, Takahiro; Ralph, D. C.; Buhrman, R. A.
March 2009
Applied Physics Letters;3/23/2009, Vol. 94 Issue 12, p122508
Academic Journal
We significantly reduce the critical current Ic0 for the onset of spin torque switching of the free layer in nanometer-scale in-plane magnetized spin valves by partially cancelling its intrinsic demagnetization field through the utilization of Co/Ni multilayer free layers. The out-of-plane magnetic anisotropy arising from the Co/Ni interfaces reduces the effective demagnetization field (Heff) while not significantly affecting the thermal stability of the free layer. A zero-thermal-fluctuation critical current density Jc0∼2×106 A/cm2 is determined through both current ramp rate and nanosecond pulse measurements, and comparisons with large Heff control samples confirm that this strategy is efficient in substantially decreasing Ic0.


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