Response to 'Comment on 'Metastable state in a shape-anisotropic single-domain nanomagnet subjected to spin-transfer-torque'' [Appl. Phys. Lett. 105,116101 (2014)]

摘要

In a preceding Comment, Bazaliy argued that the metastable states discussed in our Letter are always unstable and thus irrelevant. This is not correct. In a shape-anisotropic single-domain nanomagnet, there are two degenerate stable states (potential minima) separated by an energy barrier. In the absence of switching current (i.e., no spin-transfer-torque), magnetization is stable only at these two energy minima. Thus, magnetization will relax to either of these two states from any other position (whether that is potential energy maxima or not). In our Letter, we have demonstrated by solving stochastic Landau-Lifshitz-Gilbert (LLG) equation considering thermal fluctuations that magnetization may get stuck at some metastable states corresponding to certain switching currents, and if it gets stuck, it cannot be unstuck by room-temperature thermal perturbations. Different initial values (both for polar angle θ and azimuthal angle (φ) are chosen and it is shown that still the metastable states do appear, but in different current ranges (supplementary Figs. S5-S7 in Ref. 2). Simulation for a long time (500 ns) at higher temperature (400 K) could not also make these metastable states disappear (supplementary Fig. S8 in Ref. 2). Also, the choice of substantially different aspect ratio of the elliptical cross-section of the nanomagnet could not eradicate the metastable states (supplementary Fig. S10 in Ref. 2). Hence, these metastable states are stable against thermal fluctuations.