A Model Study of an Error-Free Magnetization Reversal Through Dipolar Coupling in a Two-Magnet System

A systematic study on the feasibility of an error-free switching of two nanomagnets coupled via their dipolar fields by applying a spin current to one of them is presented. It is demonstrated that the dynamic nature of dipolar interaction between the nanomagnets may cause the magnetization of the second magnet to precess back to its original state despite having crossed the free-axis equatorial plane during the transient phase. This non-reversal is very different than the purely successful or unsuccessful switchings noted in other reversal analyses presented in the literature and, in this paper, is referred to as a dipolar switching glitch. The dynamic dipolar coupling between nanomagnets creates temporary titled precessional trajectories pushing the magnetization of the nanomagnet into high-energy states. Relaxation from these high-energy positions leads to fast, but quasi-random switching behavior. The maximum separation between the magnets for perfect coupling has been quantified as a function of the magnet planar dimensions. It is also shown that the simpler models that do not consider the mutual coupling between the two magnets underestimate the maximum allowed separation between the two magnets and, as such, are too conservative.