Optimization of spin Hall magnetoresistance in heavy-metal/ferromagnetic-metal bilayers

Abstract

AbstractWe present experimental data and their theoretical description on spin Hall magnetoresistance (SMR) in bilayers consisting of a heavy metal (H) coupled to in-plane magnetized ferromagnetic metal (F), and determine contributions to the magnetoresistance due to SMR and anisotropic magnetoresistance (AMR) in five different bilayer systems: $$\hbox {W}/\text {Co}_{20}\text {Fe}_{60}\text {B}_{20}$$W/Co20Fe60B20, $$\text {Co}_{20}\text {Fe}_{60}\text {B}_{20}/\hbox {Pt}$$Co20Fe60B20/Pt, $$\hbox {Au}/\text {Co}_{20}\text {Fe}_{60}\text {B}_{20}$$Au/Co20Fe60B20, W/Co, and Co/Pt. The devices used for experiments have different interfacial properties due to either amorphous or crystalline structures of constitutent layers. To determine magnetoresistance contributions and to allow for optimization, the AMR is explicitly included in the diffusion transport equations in the ferromagnets. The results allow determination of different contributions to the magnetoresistance, which can play an important role in optimizing prospective magnetic stray field sensors. They also may be useful in the determination of spin transport properties of metallic magnetic heterostructures in other experiments based on magnetoresistance measurements.