Exchange coupling and edge pinning in vertical head sensors

Calculations which were done for an idealized geometry, showed that exchange coupling around the edge of a sandwich structure formed by folding the top magnetic layer around the edge and connecting to the bottom magnetic layer, 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, the coupling material is likely to be less uniform and somewhat irregular providing 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.