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 |Jc|=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 |Jc|.