EFFECT OF STRESS ON EXCHANGE COUPLING FIELD, COERCIVITY, AND UNIAXIALANISOTROPY-FIELD OF NIFE NIO BILAYER THIN-FILMS/

The effects of stress on the exchange coupling field, H-ex, and coerci vity, H-c, in NiFe/NiO bilayers deposited onto a Si wafer using rf-rea ctive sputtering were experimentally studied. Samples of the bilayers were externally and constantly uniaxial strained (either tensile or co mpressive) using a specially designed sample holder. The hysteresis lo ops of the stressed NiFe/NiO bilayer samples were measured in situ alo ng the easy and hard axis of the NiFe films using a vibrating sample m agnetometer. The composition of the NiFe film was characterized to be Ni80.2Fe19.8 using x-ray photoelectron spectroscopy. The H-c of the bi layers were significantly affected by the stress, while the H-ex was n ot apparently changed by the same stress. The large changes in the coe rcivity in the stressed NiFe/NiO bilayer were produced by the large ch ange of the effective uniaxial anisotropy field, H-K, of the bilayer. The control and reduction of both intrinsic and external stresses are important in the fabrication of spin-valve giant magnetoresistance hea ds and sensors. (C) 1997 American Institute of Physics.