A theoretical study of thermally activated magnetization switching under microwave assistance

Microwave-assisted magnetization switching (MAS) is attracting much attention because of its applications in future magnetic recording techniques such as microwave-assisted magnetic recording and three-dimensional magnetic recording. For the implementation of these applications, it is indispensable to elucidate large-amplitude magnetization excitation induced by a microwave magnetic field, which accounts for switching field reduction in MAS. In addition, for understanding thermally activated switching at finite temperature, it is necessary to estimate barrier height under microwave assistance. In this work, the paths and barrier height of magnetization switching under microwave assistance were theoretically investigated. A single domain magnet having a uniaxial easy axis along the z direction with an effective anisotropy field was considered. The switching in a static magnetic field in the -z direction H_z and a microwave field H_rf rotating counterclockwise in the x-y plane at a frequency of ω_rf were also studied.