STRESS EFFECTS ON EXCHANGE COUPLING FIELD, COERCIVITY, AND UNIAXIAL ANISOTROPY-FIELD OF NIO NIFE BILAYER THIN-FILM FOR SPIN VALVES/

The effects of uniaxial stress on the exchange coupling field, H-ex, c oercivity, H-c, and uniaxial anisotropy field, H-K, in NiO/NiFe bilaye rs were experimentally studied. The NiO/NiFe bilayers were deposited o nto a Si(100) wafer using radio frequency reactive sputtering. Samples of the bilayers were externally and constantly uniaxial stressed (eit her tensile or compressed) using a specially designed sample holder wi th a fixed radius of curvature. The hysteresis loops of the stressed N iO/NiFe bilayer samples were measured in situ along the easy and hard axes of the NiFe films using a vibrating sample magnetometer. The comp osition of the NiFe film in the NiO/NiFe bilayer was characterized as Ni80.2Fe19.8 using x-ray photoelectron spectroscopy. The H-c and H-K o f the bilayers were significantly affected by the stress, while the H- ex was apparently not changed by the same stress. The large changes in the coercivity in the stressed NiO/NiFe bilayer were produced by the change of the effective uniaxial anisotropy field of the bilayer. We c onclude that the control and reduction of both intrinsic and external stress are very important in the fabrication of spin-valve giant magne toresonance heads and sensors. (C) 1997 American Institute of Physics.