Design Concept of MAS Effect Dominant MAMR Head and Numerical Study

We summarize several key factors in microwave-assisted magnetic recording (MAMR) design, particularly interactions between spin-torque oscillators (STOs) and write poles, frequency matching, the negative flux-control (FC) effect, and the STO vertical field effect. To satisfy these key factors, we study several configurations with longer gap lengths of 30 nm using a simulation based on the Landau-Lifshitz-Gilbert equation with a spin torque (ST) term including both the write head and STO. This simulation compared a dual spin-injection layer (SIL) structure, a dual flux-generation layer (FGL) structure, and two types of all-in-plane STO. While the dual SIL and dual FGL structures indicate sufficient oscillation behavior to satisfy the examined key factors, the dual SIL structure demonstrates poorer signal-to-noise ratio (SNR) performance than even conventional magnetic recording (CMR). We conclude that this poor performance is due to the STO vertical field effect. We newly propose a dual FGL structure with no vertical field in the in-plane field peak, leading to much better performance than that of the dual SIL structure. While this structure requires a much longer write gap than does a CMR writer, it retains an erase width comparable with CMR writers. These results indicate that MAMR with the proposed dual FGL structure will be usable at over 2800 kFCI without TPI loss.