Modulating spin transfer torque switching dynamics with two orthogonal   spin-polarizers by varying the cell aspect ratio
  We study in-plane magnetic tunnel junctions with additional perpendicular polarizer for subnanosecond-current-induced switching memories. The spin-transfer-torque switching dynamics was studied as a function of the cell aspect ratio both experimentally and by numerical simulations using the macrospin model. We show that the anisotropy field plays a significant role in the dynamics, along with the relative amplitude of the two spin-torque contributions. This was confirmed by micromagnetic simulations. Real-time measurements of the reversal were performed with samples of low and high aspect ratio. For low aspect ratios, a precessional motion of the magnetization was observed and the effect of temperature on the precession coherence was studied. For high aspect ratios, we observed magnetization reversals in less than 1 ns for high enough current densities, the final state being controlled by the current direction in the magnetic tunnel junction cell. 
B. Lacoste, M. Marins de Castro, T. Devolder, R. C. Sousa, L. D.   Buda-Prejbeanu, S. Auffret, U. Ebels, C. Ducruet, I. L. P...
cond-mat.mes-hall