Exchange coupling and edge pinning in vertical head sensors

Calculations which were done for an idealized geometry, showed that exchang e coupling around the edge of a sandwich structure formed by folding the to p magnetic layer around the edge and connecting to the bottom magnetic laye r, increases the field necessary to nucleate the rotational reversal of the edge magnetization by a factor of more than 9. In a more realistic case, t he coupling material is likely to be less uniform and somewhat irregular pr oviding an additional contribution to the edge magnetization coercive force . Edge coupling is a major contributor to the high edge coercive force for "hard edge" sensors.