Dual current-perpendicular-to-the-plane (CPP) magnetoresistive (MR) sensor with antiparallel-free (APF) structure and integrated reference layers/shields

摘要

A dual current-perpendicular-to-the-plane magnetoresistive (CPP-MR) sensor has an antiparallel-free (APF) structure as the free layer and uses the top and bottom shields as reference layers. The free layer is an APF structure that has the two free layers (FL1 and FL2) biased into a “spin-flop” state. In this state, the magnetic bias field from side biasing layers is great enough to stabilize the magnetizations of FL1 and FL2 to have a relative orientation preferably about 90 degrees and symmetrically positioned on either side of the magnetic bias field. The side biasing layers may be formed of soft magnetic material to also function as side shields and the top shield may be ferromagnetically coupled to the side shields, with the magnetization of the top shield being opposite that of the magnetization of the bottom shield.

主权项

1. A current-perpendicular-to-the-plane (CPP) magnetoresistive sensor comprising:
a substrate; a first shield layer of magnetically permeable material on the substrate, the first shield layer having an in-plane magnetization direction fixed in the presence of the external magnetic field to be sensed; a first nonmagnetic spacer layer on the first shield layer; an antiparallel free (APF) structure on the first spacer layer comprising first and second ferromagnetic free layers and an antiparallel coupling (APC) layer between said first and second ferromagnetic free layers, the APF structure having two spaced-apart side edges; a second nonmagnetic spacer layer on the APF structure; a second shield layer of magnetically permeable material on the second nonmagnetic spacer layer, the second shield layer having an in-plane magnetization direction fixed in the presence of the external magnetic field to be sensed; and a ferromagnetic side biasing layer at each side edge of the APF structure and having a magnetization direction substantially parallel to the magnetization direction of at least one of the first and second shield layers; wherein in the absence of a magnetic field to be sensed the magnetization directions of the first and second free layers are oriented relative to one another at a non-zero angle less than 180 degrees and are biased toward the direction of magnetization of the side biasing layers.