Characterization of the Magnetic Properties of HAMR Media Using the Temperature Dependence of the AC Susceptibility

The ac susceptibility of heat-assisted magnetic recording media was measured from room temperature to 750 K for the frequencies ranging from 500 Hz to 50 kHz. Using an analytical model for the ac susceptibility of weakly interacting uniaxial superparamagnetic particles, we were able to characterize the temperature dependence of the anisotropy energy (K) distribution and the saturation magnetization (M
_s
) near the Curie temperature (T
_c
). In addition, we were able to extract information about the dependence of Tc on the grain diameter.