Spin transfer and current-induced switching in antiferromagnets

Recent experiments show that spin-polarized current may influence the state of generally accessory element of spin valves, an antiferromagnetic (AFM) layer, which is used for ``pinning.'' Here we study the dynamics of AFM component of the ``pinned'' ferromagnetic (FM) layer induced by simultaneous application of the spin-polarized current and external magnetic field. We find stability range of such a configuration of FM/AFM system in which orientation of FM magnetization is parallel to AFM vector. We calculate the field dependence of the critical current for different orientations of the external magnetic field with respect to the crystal axes of FM/AFM bilayer. We show the possibility of stable current-induced precession of AFM vector around FM magnetization with the frequency that linearly depends on the bias current. Furthermore, we estimate an optimal duration of the current pulse required for switching between different states of FM/AFM system and calculate the current and field dependencies of switching time. The results obtained reveal the difference between dynamics of ferromagnets and antiferromagnets subjected to spin transfer torques.