2026/07/22 by David T. Plouff, Nawsher J. Parvez, Subhash Bhatt +4
#cond-mat.mtrl-sci
We investigate the proposal of hole doping RuO2 via alloying with Cr ions to induce altermagnetism. Thin film samples of Ru1-xCrxO2 (0 ≤ x ≤ 0.28) were prepared by reactive magnetron co-sputtering on TiO2 substrates, with epitaxial nature verified by X-ray diffraction and composition depth profiles determined by X-ray photoelectron spectroscopy combined with Ar etching. Neutron diffraction measurements of samples with x = 0 and x = 0.23 at low temperatures show no evidence of long-range altermagnetic order with spins oriented along the c-axis or within the ab-plane. In contrast, temperature dependent susceptibility measurements in samples with x ≥ 0.16 show a gradual downturn below T≈20~K, suggestive of antiferromagnetic interactions, although this coexists with ferromagnetic hysteresis and remnant magnetization at 4~K for samples with x ≥ 0.23. Together, our magnetometry and neutron scattering measurements suggest the coexistence of antiferromagnetically coupled ferromagnetic CrO\textsubscript2 clusters. This indicates that Cr ions do not hole dope Ru bands to induce an altermagnet state, but rather the holes remain localized to the Cr ions.