Exchange Bias Effect Determined by Anisotropic Magnetoresistance in CoxNi1-xO/Ni0.8Fe0.2 Bilayer System

Abstract

We prepared bilayer systems composed of the ferromagnetic (FM) layer Ni0.8Fe0.2 and the anti-FM (AFM) layer CoxNi1-xO (x = 0.3, 0.4, 0.5, and 0.6) using the dc/RF magnetron sputtering methods. Coercive field HC and exchange bias field HE , the shift field in hysteresis loop, were observed in all the Ni0.8Fe0.2/CoxNi1-xO bilayer systems after field cooling. The changes of HC and HE were explicitly studied for various parameters, such as the composition of AFM material x, the measured temperature T, and the direction of applied magnetic field. Measured anisotropic magnetoresistance (AMR) was analyzed to extract the HC and HE , since the peaks (maximum or minimum) in AMR do not appear exactly at the coercive field HC of the magnetic hysteresis measurement. We propose a new approach for the analysis of AMR to determine HC and HEB along the field angle θ with respect to the field-cooling direction. The results were compared with the variations of HEB and HC reported earlier. © 2015 IEEE.