Recording potential of anti-ferromagnetically coupled longitudinal media

A rigorous calculation of the switching fields and the energy barriers of anti-ferromagnetically coupled (AFC) grains is reported. It is found that the field dependence of the energy barrier for an AFC grain differs slightly from that of a grain reversing by coherent rotation, which implies that the dynamic coercivity curves also differ slightly. It is estimated that AFC media can gain 0.5 to 1 dB SNR by virtue of the flattening of the dynamic coercivity curve, and an additional 0.5 dB due to reduced demagnetizing fields. It is also found that dynamic effects can facilitate switching of AFC media at high speeds.