The reversible susceptibility tensor of synthetic antiferromagnets

In this work we propose to study the reversible susceptibility tensor (including the transverse susceptibility components) of a synthetic antiferromagnetic (SAF) structure. This study is motivated by the fact that knowing the magnetic anisotropy of SAF structure is essential for the device functioning and the transverse susceptibility is known as one of the best methods to determine magnetic anisotropy and switching properties of magnetic systems. The starting point of this work is the magnetization's equation of motion Landau-Lifshitz-Gilbert for the coupled two layers. By solving the inhomogeneous system of linear equations on the magnetization's spherical coordinate deviations, the susceptibility tensor of the SAF structure is obtained. Simplified equations for the very low frequency case are given. By comparing the plots of the susceptibility versus the applied field with the regular hysteresis loops one concludes that susceptibility experiments are more appropriate for switching investigations of the SAF systems.