Steep magnetoresistance change with low saturation fields in Co/Ni multilayer thin films

Co/Ni multilayer thin films with a constant Co thickness of 2.2 nm, Ni thickness ranging from 0.5 to 5.0 nm, and a total of 20 bilayers were fabricated using de magnetron sputtering. These multilayers show a steep magnetoresistance (MR) change with low saturation magnetic field in-plane uniaxial anisotropic properties, and an especially large magnetoresistance change between magnetic field H applied parallel and perpendicular to the in-plane easy axis. For H parallel to the multilayer easy axis and H at 45 degrees to the current I, a MR ratio of 15% with a FWHM of 13 Oe was obtained. While for H perpendicular to the easy axis and at 45 degrees to I, a MR ratio of 19.1% with a FWHM of 34 Oe was obtained. The former implies a MR sensitivity of 1.15%/Oe, while the sensitivity of the latter is 0.56%/Oe. All the peaks of the MR curve appeared at the coercive held H, of the multilayers. The most important characteristics of the MR change were a sharp increase in resistance followed by a very steep decrease with increasing H. These Co/Ni multilayers are promising candidates for magnetic storage and sensor technology. (C) 1996 American Institute of Physics.