Role of Media Parameters in Switching Granular Perpendicular Media Using Microwave Assisted Magnetic Recording

This paper describes the role of media parameters in magnetization switching in the presence of a DC bias and an in-plane RF field using a micromagnetic model. In this study, two sets of media parameters are compared for reduction in switching field based on the Larmor precessional frequency of the medium. It is found that a significant reduction in equivalent Stoner Wohlfarth (SW) field (H_SW ^E) is observed only when a DC field is applied at a finite angle relative to the medium anisotropy direction (thetas_A) and we observe a shallow minimum between 20deg and 30deg. A small field magnitude H_SW ^E ( = 0.50 H_K) for thetas_A of 20deg for medium 1 using an RF field magnitude of 0.068 H_K and an even smaller magnitude H_SW ^E (=0.22 H_K) for thetas_A of 25degfor medium 2 using an RF field magnitude of 0.035 H_K is required to switch the media for the case of a uniform granular medium without any distributions at T = 0 K. With the inclusion of magnetic materials distributions and/or introducing finite temperature, the coherent precession is lost due to the demagnetization field of neighboring grains. We compare H_SW ^E required to switch the medium in the presence of RF assist to the SW field (H_SW) required to switch the medium when there is no assist field. It is found that medium 1 shows a reduction of 28% in SW field while medium 2 shows no reduction in presence of in-plane RF field compared to the case when no RF field is applied. This highlights the importance of medium properties in microwave-assisted magnetic recording. Selection of media parameters will depend on the potential application of microwave-assisted recording in a continuous granular or the bit patterned media.