CPP and MTJ reader design with continuous exchange-coupled free layer

摘要

As track widths of magnetic read heads grow very small, conventional longitudinal bias stabilization has been found to no longer be suitable since the strong magnetostatic coupling at the track edges also pins the magnetization of the free layer. This problem has been overcome by extending the free layer so that it is no longer confined to the area immediately below the spacer or tunneling layer. A longitudinal bias layer immediately below the free layer is given a relatively weak magnetic exchange coupling field of about 200 Oe. Although there is strong exchange coupling between this and the free layer, the degree of pinning of the free layer is low so that the device's output signal is reduced by less than about 10%. A process for manufacturing both the CPP SV and a MTJ versions of the invention is described.