US Patent 9472216 Differential dual free layer magnetic reader

A magnetic read apparatus has an air-bearing surface (ABS) and includes a differential read sensor, side bias structure(s) and rear magnetic bias structure(s). The differential read sensor includes first and second free layers and a nonmagnetic spacer layer between the first and second free layers in a down-track direction. The side bias structure(s) are adjacent to the first and second free layers in a cross-track direction perpendicular to the down-track direction. The side bias structure(s) magnetically bias the first and second free layers in the cross-track direction. The differential read sensor is between the ABS and the rear magnetic bias structure(s). The rear magnetic bias structure(s) provide a first magnetic bias for the first free layer in a first direction along a stripe height direction perpendicular to the ABS and provide a second magnetic bias for the second free layer in a second direction opposite to the first direction.