Leveraging Symmetry for an Accurate Spin-Orbit Torques Characterization in Ferrimagnetic Insulators

Spin-orbit torques (SOTs) have emerged as an efficient means to electrically control the magnetization in ferromagnetic heterostructures. Lately, increasing attention has been devoted to SOTs in heavy metal (HM)/magnetic insulator (MI) bilayers owing to their tunable magnetic properties and insulating nature. Quantitative characterization of SOTs in HM/MI heterostructures is, thus, vital for the fundamental understanding of charge-spin interrelations and designing novel devices. However, the accurate determination of SOTs in MIs is limited due to low electrical signals and dominant spurious thermoelectric effects caused by Joule heating. Here, a simple method based on harmonic Hall voltage detection and macrospin simulations is reported that accurately quantifies the damping-like and field-like SOTs, and thermoelectric contributions separately in MI-based systems. Experiments on the archetypical Bi-doped YIG/Pt heterostructure using the developed method yield precise values for the field-like and damping-like SOTs, reaching -0.14 and -0.15 mT per 1.7 x 10(11) A m(-2), respectively. It is further revealed that current-induced Joule heating changes the spin transparency at the interface, reducing the spin Hall magnetoresistance and damping-like SOT, simultaneously. These results and the devised methodology can be beneficial for the fundamental understanding of SOTs in MI-based heterostructures and device designs where accurate SOTs knowledge is necessary.

Automated summary

Spin-orbit torques (SOTs) in heavy metal (HM)/magnetic insulator (MI) bilayers attract increasing attention due to their tunable magnetic properties and insulating nature. However, accurate determination of SOTs in MIs is limited by low electrical signals and dominant spurious thermoelectric effects. A simple method based on harmonic Hall voltage detection and macrospin simulations is reported, accurately quantifying the damping-like and field-like SOTs, and thermoelectric contributions separately in MI-based systems. This method yields precise values for SOTs in the Bi-doped YIG/Pt heterostructure and reveals the influence of current-induced Joule heating on spin transparency and SOTs.