Simplified analysis of two-layer antiferromagnetically coupled media

Analytic expressions for the energy barrier at zero applied field and the switching field for a field applied along the easy axis are derived for a pair of antiferromagnetically coupled (AFC) single-domain particles at zero temperature. The energy barriers of the two single-domain particles add in zero field if the antiferromagnetic coupling exceeds a critical value \J(c)\=2(KV)(1)(KV)(2)/[S((KV)(1)+(KV)(2))]. The antiferromagnetic coupling increases both the effective energy barrier as well as the switching field, so that optimized AFC media for recording applications require less than critical coupling \J(c)\. (C) 2002 American Institute of Physics.