Quasi-Equilibrium Stoner-Wohlfarth Versus Strongly Out-of-Equilibrium Dynamics in HAMR

The heat-assisted magnetic recording (HAMR) technology is one of the most promising alternatives to replace conventional perpendicular magnetic recording (PMR). To better understand the writing processes involved in HAMR, a better description of the magnetization dynamics at elevated temperatures is needed. The Landau-Lifshitz-Bloch formalism represents a good choice for describing the out-of-equilibrium phenomena at temperatures as high as the Curie point. An approach using micromagnetics allows investigating the effects of writer rise time, disk velocity, and thermal gradient on the writing process on realistic HAMR media in order to identify some potential physical limitations of the HAMR paradigm. In principle, the temperature assist makes it possible to use recording layers with a very large room-temperature magnetic anisotropy and smaller grain size for an increased areal density, and it is commonly thought that the main parameter that needs to be improved on the writer side is the thermal gradient. However, the simulations indicate that there are many tradeoffs between several combinations of parameters that need to be taken into account.