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 1.5~6.8 H̅
_k
2-2.4 of dB assisted by spin-transfer oscillator field is confirmed for media with average in a range of T. A best SNR performance of 15.8 dB is found in media with an average H̅
_k
= 2 T, with (K
₁
- K
₄
) of 2 × 10
⁶
erg/cc and an interlayer exchange field constant of 2 kOe.