Field dependence of magnetization reversal by spin transfer
  We analyse the effect of the applied field (Happl) on the current-driven magnetization reversal in pillar-shaped Co/Cu/Co trilayers, where we observe two different types of transition between the parallel (P) and antiparallel (AP) magnetic configurations of the Co layers. If Happl is weaker than a rather small threshold value, the transitions between P and AP are irreversible and relatively sharp. For Happl exceding the threshold value, the same transitions are progressive and reversible. We show that the criteria for the stability of the P and AP states and the experimentally observed behavior can be precisely accounted for by introducing the current-induced torque of the spin transfer models in a Landau-Lifschitz-Gilbert equation. This approach also provides a good description for the field dependence of the critical currents. 
J. Grollier (1), V. Cros (1), H. Jaffres (1), A. Hamzic (1), J.M.   George (1), G. Faini (2), J. Ben Youssef (3), H. Legall ...