Micromagnetics of single and double point contact spin torque oscillators

Abstract

In micromagnetic simulations of spin waves in thin film geometries special boundary conditions have to be applied at the boundary of the computational domain in order to avoid the reflection of spin waves. In this paper we proposed to use an artificially rough surface that will suppress spin wave reflections in order to treat spin torque oscillators with point contact geometry numerically. It is shown that the surface roughness model disperses the reflected spin waves and improves the signal to background noise ratio. The model is tested in comparison to conventional approaches such as extended layer systems, variable damping constant, and focal point methods for double point contacts. The surface roughness model gives solutions that are stable in time, in qualitative agreement with experiments and capable to reproduce phenomena such as phase locking in double point contacts.