GIANT MAGNETORESISTANCE AND MAGNETIC-ANISOTROPY OF CO9FE/CU/CO9FE MULTILAYER THIN-FILMS ON AN MGO(110) SUBSTRATE

Magnetoresistive effects have been investigated using Co9Fe/Cu/Co9Fe that were deposited on an MgO(110) substrate by ion beam sputtering with a 21-A-thick CU layer and with various thicknesses of the Co9Fe films. The influence of a 50-A-thick Fe buffer layer has also been investigated. In addition to a cubic symmetry anisotropy (K-l), an in-plane uniaxial magnetic anisotropy (K-u) was induced, which easy axis is parallel to the (110) plane of the MgO substrate and the (001) plane with and without the 50-A-thick Fe buffer layer, respectively. The magnetoresistance (MR) ratio decreased monotonically with increasing thickness of the Co9Fe films from 25 A to 70 A. A maximum MR ratio of 11.5 percent was obtained at room temperature. With increasing magnetic field, the MR ratio reached a plateau gradually after a steep drop at small magnetic fields without the Fe buffer layer. It reached a plateau rapidly at small magnetic fields with the Fe buffer layer. By considering both K-u and K-l, these behaviors can be accounted for by the magnetization processes involved.