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

We prepared bilayer systems composed of the ferromagnetic (FM) layer Ni
_0.8
Fe
_0.2
and the anti-FM (AFM) layer Co
_x
Ni
_1-x
O (x = 0.3, 0.4, 0.5, and 0.6) using the dc/RF magnetron sputtering methods. Coercive field H
_C
and exchange bias field H
_E
, the shift field in hysteresis loop, were observed in all the Ni
_0.8
Fe
_0.2
/Co
_x
Ni
_1-x
O bilayer systems after field cooling. The changes of H
_C
and H
_E
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 H
_C
and H
_E
, since the peaks (maximum or minimum) in AMR do not appear exactly at the coercive field H
_C
of the magnetic hysteresis measurement. We propose a new approach for the analysis of AMR to determine H
_C
and H
_EB
along the field angle θ with respect to the field-cooling direction. The results were compared with the variations of H
_EB
and H
_C
reported earlier.