Micromagnetic Simulations of the Quasi-static Properties of Dissimilar Bilayers

Abstract

Achieving a strong perpendicular magnetic anisotropy is of great importance for materials intended for use in spintronics devices. Perpendicular anisotropy in magnetic multilayers arises from the broken symmetry at the interfaces due to the enhanced orbital and spin moments relative to the bulk system1. In order to accurately describe the quasi-static properties of these materials using a macrospin approach, the inclusion of both second-order (K2) fourth-order (K4) uniaxial anisotropies is essential. Beik Mohammadi et al2 have shown that lateral inhomogeneities of the second-order uniaxial anisotropy in thin films with perpendicular uniaxial anisotropy can give rise to higher-order anisotropy contributions. Here, we report on the study of the layer to layer variation of the second-order perpendicular anisotropy in magnetic bilayers and its influence on the quasi-static properties. We analyze the results of micromagnetic simulations3 in magnetic bilayers using a macrospin model. We show that in order to describe the micromagnetic simulation data using macrospin model, one requires a fourth-order uniaxial anisotropy contribution although the underlaying micromagnetic model does not include such term. Quasi-static calculations show that the fourth-order uniaxial anisotropy is caused by the deviation of the magnetization from the applied field direction.