Spin Hall magnetoresistance across a paramagnetic Pt/NdGaO₃ interface

In recent years, spin Hall magnetoresistance (SMR) has emerged as an efficient way to probe the spontaneous magnetization state in ordered magnetic systems by electrical current. Less known is its versatility as a probe of materials that do not possess spontaneous magnetization, such as in paramagnets. In this work, SMR is used to probe paramagnetic NdGaO3 (NGO), a rare earth oxide, possessing a sizable spin-orbit interaction (L = 6). NGO has not been investigated earlier for its efficiency in propagating spins. We have performed extensive temperature and angle dependent-magnetoresistance (ADMR) studies along different crystallographic axes in NGO, using platinum (Pt) as a spin injector and a detector and utilizing (inverse) spin Hall effect. We find a close correlation between the temperature dependence of the ADMR response with magnetization in NGO and a linear current bias dependence of the ADMR amplitudes. These are characteristics of the SMR effect in Pt/NGO, arising from the torque acting on localized moments in NGO and considering crystal field induced intermultiplet transitions with temperature. Control experiments on Pt/SrTiO3 and Pt/SiO2 devices were also carried out in order to validate the observed SMR response in the Pt/NGO bilayer and to rule out magnetoresistive contributions from Pt.