SNR Impact of Noise by Different Origins in FePt- HAMR Media

In this paper, we present a micromagnetic analysis on two key noise mechanisms for current FePt-L10-based heat-assisted magnetic recording (HAMR) media: grain-to-grain variations of anisotropy field and Curie temperature. We found that the signal-to-noise ratio (SNR) versus heating power measurement could be used to distinguish the noise arising from these two different origins. We also found that in today´s HAMR media, the dominate noise origin is likely to be the combination of Curie temperature distribution and heating, or temperature, variation from grain to grain. As one of the possible mechanisms for grain-to-grain heating variation, the effect of grain boundary thickness distribution is studied in terms of its impact to recording SNR. It is concluded that reducing the combined heating and Curie temperature distribution is critical for the realization of the area density capability gain promised by the technology.