Abnormal Spin Hall Magnetoresistance Effect in Pt/Ni Bilayer System
For spintronics,the non-magnetic/ferromagnetic bilayer structure is a fundimental device configuration,serving as a traditional framework for exploring various spin-related mechanisms,especially the charge-spin conversion.This work systematically investigates magnetoresistance in a series of Pt/Ni bilayer devices.An abnormal negative spin-hall magnetoresistance(SMR)is reported within this system.It is found that the SMR ratio sign is tied to the thickness of the Ni layer,transitioning from positive to negative as the Ni layer thickness increases.After analyzing together with reference samples,several common mechanisms are distinguished and evaluated.To suppress the bulk contribution of Pt layer to the SMR and limit the potential mechanism to interface and Ni layer-related effects,the Pt layer thickness is initially set to 1 nm.By comparing with Ni monolayer devices,the negative SMR and its sign change feature are ascribed to the competition between the interfacial spin-orbit coupling effect and the geometrical size effect,offering positive and negative contributions to SMR ratio,respectively.This investigation into the origins and evolution of spin Hall magnetoresistance in bilayer structures not only deepens the understanding of magnetoresistance phenomena in similar structures but also broadens the scope for further development and application of spin-based devices.
spintronicsspin hall magnetoresistancegeometric size effectsinterfacial spin orbit-coupling effect
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