Recording performance evaluation of high-density patterned media

Continuous increment of magnetic recording density requires the realization of necessary signal-to-noise-ratio (SNR) with less number of grains per bit, a fundamental limit in this approach is that the thermal effect for continued scaling would cause spontaneous magnetization reversal of individual grains, which would result in loss of recorded data. Patterned media can significantly reduce the grain number per bit at the required SNR by its good pattern shape uniformity. This paper focused on the recording performance evaluation of bit patterned media. Using Karlqvist head and single pole head, the SNR of oriented continuous media (CM), patterned longitudinal media (PLM) and perpendicular patterned media (PPM) were investigated via finite element method. It is found that the SNR of PLM is approximately 20% higher than that of CM, with the same anisotropy orientation distribution. At each areal density, the SNR of PPM remains the highest before the areal density reaches 800Gbit/in2. By comparing the simulation results of SNR of patterned longitudinal media at different bit aspect ratio, it is indicated that with the dot size dispersion increase, the perfect media with the highest SNR was also the most susceptible to size variation. These dispersions significantly increase down-track noise and the effect was greatest at high linear densities where the signal was low. The effect of grain diameter on magnetization variance of both PLM and PPM were also investigated.