The importance of depth varying fields for MAMR switching-field reduction

Micromagnetic modeling of MAMR (microwave-assisted magnetic recording) switching-field reduction due to AC fields at GHz frequencies is presented in this study. A 4-layer media model based on current exchange-coupled media with the top layer describing a large lateral exchange “cap” with three low lateral exchange “oxide” layers below is employed. The hysteresis loops are examined in two scenarios: depth invariant applied fields (external and AC), and depth invariant external field with depth varying AC field. A DC-band write study is performed with realistic writer field and macrospin-based STO field to gauge switching-field reduction in a scenario more similar to actual recording.