Optimum Multilayer Anisotropy Distribution for Microwave-Assisted Magnetic Recording [CoX/Pt] n Media

The optimum multilayered anisotropy distribution in [CoX/Pt] 4 media is studied for microwave-assisted magnetic recording by micromagnetic simulations. The model of the magnetic CoX layer was built upon a regular mesh, including a Voronoi-tessellation polycrystalline structure. If each CoX layer has the same anisotropy, it is found that the moments of grains at the same in-plane position but in different layers may be in the opposite directions, which damages the signal-to-noise ratio (SNR) performance and the thermal stability of recording media. In the optimum media design, the anisotropy field constant $K_{n}$ decreases from the top layer to the bottom layer, where the magnetic moments of grains in each bits are switched nearly uniformly. A medium SNR gain of $1.5\sim 6.8$ dB assisted by spin-transfer oscillator field is confirmed for media with average $\bar H_{k}$ in a range of 2–2.4 T. A best SNR performance of 15.8 dB is found in media with an average $\bar H_{k} =2$ T, with ( $K_{1}-K_{4})$ of $2\times 10^{6}$ erg/cc and an interlayer exchange field constant of 2 kOe.