Exchange coupling between antiferromagnetic NiO and ferromagnetic films

We investigated the exchange field (H-ex) and the coercive field (H-e) for Ni81Fe19 films deposited on antiferromagnetic NiO films as Functions of the NiFe and the NiO thicknesses, the applied deposition field, and the annealing temperature. The H-ex and H-c in the NiFe(50 Angstrom)/NiO(300 Angstrom) bilayer were about 95 Oe and 44 Oe, respectively. Both H-ex and H-c varied approximately inversely with the thickness of the NiFe layer and saturated above a NiO film thickness of 300 Ht. The H-ex of the NiFe(200 Angstrom)/NiO(300 Angstrom) bilayer increased with the applied deposition field up to 360 Oe. The H-ex disappeared rapidly after annealing at 230 degrees C. We also studied the dependence of the exchange field and the magnetoresistance ratio on the thickness(t is 20, 70, and 100 Angstrom) of the pinned NiFe layer in Ta(50 Angstrom)/NiFe(50 Angstrom)/Cu(40 Angstrom)/NiFe(t)/NiO(300 Angstrom) spin valve films.