Spin current leakage and Onsager reciprocity in interfacial spin-charge interconversion

Spintronics involves converting spin currents to charge currents and vice versa, a process that has wide-ranging applications. However, in magnetic heterostructures, the efficiency of converting spins into charges is not always equivalent to converting charges into spins. This study intends to explain this discrepancy by accounting for both interfacial and bulk spin-orbit coupling. It shows that the charge-to-spin conversion is highly sensitive to spin current leakage, whereas spin-to-charge conversion is less affected by it. As a result, spin pumping appears as a more robust process than spin-orbit torque to quantify spin-charge interconversion efficiencies.