Linearity and hysteresis in the magnetoresistive response of (NiFe,NiFeCo)/Cu and Co/Cu/NiFe multilayers in patterned stripes

The linearity and hysteresis in the magnetoresistive (MR) response of NiFe/Cu and NiFeCo/Cu multilayers prepared by ion beam sputtering, and Cu/Co/Cu/NiFe multilayers prepared by MBE are investigated. These characteristics in the linear regions for the second peak of antiferromagnetically coupled NiFe/Cu multilayers are almost the same as those of NiFeCo/Cu ones at 50-Hz ac applied fields. The MR amplitude at the first peak is inferior to that at the second one, whereas, the linearity and hysteresis are superior. In weakly coupled Cu/Co/Cu/NiFe multilayers, a nonhysteretic MR response is obtained at a NiFe layer thickness of 10 Å. The linearity and symmetry around the zero magnetic field of the MR curve depend on the Cu layer thickness. When the thicknesses of the NiFe and Cu layers are 10 and 45 Å, respectively, good linearity and no hysteresis are observed without biasing techniques. The output levels in the linear regions of three different multilayers are 1.5-2.5 times as large as that of the conventional Permalloy film. These multilayers are promising materials for the fabrication of MR head for ultrahigh density recording.