Optimization of the 3-D-MAMR Media Stack

Microwave-assisted magnetic recording (MAMR) is an advanced magnetic recording scheme that is expected to extend the areal density beyond that achieved by conventional perpendicular magnetic recording (PMR). This is done by introducing a high-frequency (HF) oscillating magnetic field during the writing, reducing the write field from the head needed to switch the grains. Grains with larger anisotropy, greater thermal stability, and reduced grain size can thereby be used in the media. 3-D-MAMR uses this same principle not only to assist the writing but also to select a particular layer in a multi-layer medium stack for writing, thereby realizing 3-D magnetic recording. Optimization of a 3-D-MAMR system is complicated by the large number of variables involved and interactions between the recording layers. It is generally difficult to write on a target layer without some degree of unwanted writing on a different layer in a multi-layer stack. In this paper, we perform an optimization of a 3-D-MAMR media stack using the response-surface methodology (RSM), a method used in the design of experiments (DoEs). This results in a media design in which the signal-to-noise ratio (SNR) performance in the target layer and the number of written errors in the other layer are jointly optimized.