Influence of Ru composition deviation from stoichiometry on intrinsic spin-to-charge conversion in SrRuO3

TL;DR

This study investigates how deviations from stoichiometry in SrRuO3 affect its intrinsic spin-to-charge conversion efficiency, revealing that Ru deficiency reduces spin Hall conductivity and emphasizing defect control for spintronic applications.

Contribution

It provides experimental and theoretical evidence that Ru composition deviations diminish spin Berry curvature and spin Hall conductivity in SrRuO3, highlighting the importance of defect management.

Findings

Stoichiometric SrRuO3 exhibits higher spin Hall angle than Ru-deficient SrRu0.7O3.

Ru deficiency decreases spin Hall conductivity as shown by first-principles calculations.

Controlling point defects is crucial for maximizing spin-charge conversion in SrRuO3.

Abstract

Interconversion between charge and spin currents is a key phenomenon in realizing next-generation spintronic devices. Highly efficient spin-charge interconversion is expected to occur at band crossing points in materials with large spin-orbit interactions due to enhanced spin Berry curvature. On the other hand, if defects and/or impurities are present, they affect the electronic band structure, which in turn reduces the spin Berry curvature. Although defects and impurities are generally numerous in materials, their influence on the spin Berry curvature and, consequently, spin-charge interconversion has often been overlooked. In this paper, we perform spin-pumping experiments for stoichiometric SrRuO3 and non-stoichiometric SrRu0.7O3 films at 300 K, where the films are in paramagnetic states, to examine how Ru composition deviation from the stoichiometric condition influences the spin-to-charge conversion, showing that SrRuO3 has a larger spin Hall angle than SrRu0.7O3. We derive the band structures of paramagnetic SrRuO3 and SrRu0.75O3 using first-principles calculations, indicating that the spin Hall conductivity originating from the spin Berry curvature decreases when the Ru deficiency is incorporated, which agrees with the experimental results. Our results suggest that point-defect- and impurity control is essential to fully exploit the intrinsic spin Berry curvature and large spin-charge interconversion function of materials. These insights help us with material designs for efficient spin-charge interconversions.