Asymmetric giant magnetoresistance effect in Py/Cu multilayers

The asymmetric GMR field dependencies at room temperature were observed in (Ni83Fe17 = Py)/Cu multilayers deposited by sputtering. The appearance of giant magnetoresistance (GMR(H)) asymmetry is related to the existence of superparamagnetic entities located at the vicinity of the Py/Cu interfaces. It is shown that the presence of an external magnetic field can reduce the scattering of the conduction electrons, by fluctuating superparamagnetic moments leading to the occurrence of an extra contribution to the GMR effect. The amount of asymmetry observed in the magnetic field dependencies of the GMR effect depends both on the value of the external magnetic field as well as on its sweeping rate. It reflects the importance of the interfacial magnetic states and their influence on the GMR effect observed in multilayered structures. (C) 2000 Elsevier Science B.V. All rights reserved.