Spin-orbit torque efficiency is conventionally fixed by bulk materials. D-wave altermagnets introduce an additional nonrelativistic spin-charge conversion channel beyond inverse spin-Hall effect. Using prototypical candidate RuO2 as an example, we show that the adjacent ferromagnet alone can dictate both the magnitude and sign of spin-charge conversion. Spin-pumping measurements on RuO2/Y3Fe5O12 (YIG) and RuO2/Ni80Fe20 (Py) bilayers yield opposite effective spin-Hall angles that persist across crystalline and polycrystalline RuO2. Inserting an ultrathin Au spacer at the RuO2/YIG interface reverses the signal, envidencing a dominant interfacial inverse Rashba-Edelstein effect, whereas RuO2/Py is governed by bulk inverse spin-Hall effect. First-principles calculations trace this dichotomy to interface-selective band hybridization: Rashba surface states survive at the insulating YIG contact yet are quenched by metallic Py. Our findings establish ferromagnetic interfacing as a deterministic knob for tailoring spin-charge conversion in altermagnetic oxides, paving the way to field-free, low-dissipation spintronic memory devices.
@article{arxiv.2512.21100,
title = {Ferromagnetic interface engineering of spin-charge conversion in RuO$_2$},
author = {Dongchao Yang and Zhaoqing Li and Yu Dai and Lili Lang and Zhong Shi and Zhe Yuan and Shi-Ming Zhou},
journal= {arXiv preprint arXiv:2512.21100},
year = {2026}
}