Effects of magnetocrystalline anisotropy and magnetization saturation on the mechanically induced switching in nanomagnets

摘要

The effects of magnetocrystalline anisotropy (K_u) and magnetization saturation (M_s) on the mechanically induced switching in nanomagnets are studied using a constraint-free phase field model, which allows explicit magneto-mechanical coupling and strictly constant magnetization magnitude. The effects of K_u and M_s on the transition boundary between the coherent and incoherent switching modes are presented in terms of the nanomagnet geometry. It is found that M_s rather than K_u can affect the transition boundary between the two switching modes. In the coherent mode, there exists a critical strain (ε_c) to induce a deterministic 90° switching. By using the dynamic nature and overrun behavior of the magnetization, a deterministic 180° switching can occur if the mechanical strain is removed once the magnetization rotates to the largest achievable angle (v_1~m). For 90° switching, increasing K_u can enhance both ε_c and v_1~m, whereas M_s incurs no noticeable changes. For 180° switching, the switching time (t_s) increases with M_s linearly, but initially decreases with increasing K_u and then saturates. The results for t_s suggest that moderate K_u and M_s are advisable to simultaneously obtain relatively low ε_c, quick switching, high storage density, and high magnetization-state stability in nanomagnets. This work provides insight on tuning mechanically assisted nanomagnet-based logic and memory devices through M_s and K_u.