Enhanced Damping-Like Torque through Strain Modulation in RuO2.

RuO2, recognized for its predicted strong nonrelativistic spin splitting, holds considerable potential for spin-orbit torque (SOT) applications. However, the mechanism by which lattice strain modulates its spin transport remains elusive. Here, we combine strain engineering with multiscale characterization to correlate strain, orbital hybridization, and spin Hall conductivity in RuO2. Using RuO2 (100)/Py heterostructures, we quantify the strain-dependent SOT response via harmonic Hall measurements and probe orbital hybridization through oxygen K-edge X-ray absorption spectroscopy. Results demonstrate that strain relaxation induces a systematic shift in the Ru t2g peak, indicating a reconstruction of the orbital density of states. Concomitantly, the spin Hall conductivity of RuO2 increases by approximately 200%, reaching 3.09 × 104 (Ω·m)-1, which aligns well with theoretical calculation result. Our findings highlight the lattice strain as a crucial factor for tailoring spin transport in altermagnetic RuO2, offering a promising avenue for the design and optimization of altermagnetic spintronic devices.