Impact of in-plane currents on magnetoresistance properties of an exchange-biased spin-valve with insulating antiferromagnetic layer

摘要

The impact of in-plane alternating currents on the exchange bias, resistance,and magnetoresistance of a CoFe/NiCoO/CoFe/Cu/CoFe spin-valve is studied. Withincreasing current, the resistance is increased while the maximummagnetoresistance ratio decreases. Noticeably, the reversal of the pinned layeris systematically suppressed in both field sweeping directions. Since the NiCoOoxide is a good insulator, it is expected that the ac current flows only in theCoFe/Cu/CoFe top layers, thus ruling out any presence of spin-transfer torqueacting on the spins in the antiferromagnetic layer. Instead, our measurementsshow clear evidences for the influence of Joule heating caused by the current.Moreover, results from temperature-dependent measurements very much resemblethose of the current dependence, indicating that the effect of Joule heatingplays a major role in the current-in-plane spin-valve configurations. Theresults also suggest that spin-transfer torques between ferromagnetic layersmight still exist and compete with the exchange bias at sufficiently highcurrents.