Exchange coupled composite media for heat assisted magnetic recording

Micromagnetic simulation is used to calculate the temperature derivative of the switching field dH_sw/dT for a composite media with a superparamagnetic writing layer. The results show that dH_sw/dT is reduced for a defined probability of switching, and switching field line width remains almost unchanged. An analytical two-spin model is established to relate exchange coupling between the two layers J_ex to energy barrier and the switching probability distribution (SPD). Both the analytical model and micro-magnetic simulation show that the full-width half-maximum FWHM∝(J_ex)^−0.5 and writing temperature T_sw∝(J_ex)⁻¹. It is also found that the writing layer leads the storage layer during switching.