Suppression of noise in magnetic layers by a periodic spin torque.

The simultaneous effect of thermal noise and time-periodic spin torques on magnetic multilayers are treated in this work. Using two commonly studied magnetic systems with multiple stable states at zero temperature as examples, we show that periodic spin torques can enhance the stability of the system and suppress the noise due to interwell transitions. In the case of weak periodic spin torques, stochastic resonance, which is usually associated with ac magnetic fields, is also manifested for nonconservative torques. In more complex systems with a relatively low energy barrier, it is shown that high-frequency spin torques can inhibit interwell transitions and in effect suppress the telegraph noise due to the switching between neighboring states.