Landau-Lifshitz magnetization dynamics driven by a random jump-noise process (invited)

In the paper, a jump-noise process is introduced in magnetization dynamics equations in order to account for random thermal effects. It is demonstrated that in the case of small noise, Landau–Lifshitz and Gilbert damping terms emerge as average effects caused by the jump-noise process. This approach leads to simple formulas for the damping constant in terms of the scattering rate of the jump-noise process. These formulas also reveal the dependence of the damping constant on magnetization. The analysis of random switching of magnetization caused by the jump-noise process is presented. It is shown that the switching rate at very low temperatures may appreciably deviate from the predictions of thermal activation theory, which is consistent with experimental observations of low temperature switchings and is usually attributed to the phenomenon of “macroscopic tunneling” of magnetization.