Unidirectional anisotropy magnetoresistance and exchange coupling in 81NiFe/Cr multilayer

There is unidirectional anisotropy in 81 NiFe/Cr multilayers prepared by electronic beam evaporation. The samples exhibit asymmetrical hysteresis loop, which is equivalent to the existence of an exchange bias of the order of 1 Oe. The results show that (1) two branches of the magnetoresistance loop measured with increasing and decreasing magnetic field respectively are different, especially in transverse field condition; (2) the difference in the maximum transverse magnetoresistance of some samples even reaches 0.78% and its (R_max-R_min)/R reaches 4.72%, which is much larger than the value 3% of 82 NiFe alloy of high quality. It was inferred that the magnetoresistance effect of these multilayers is caused by both the spin-orbit coupling mechanism and the mechanism of electron spin dependent scattering.