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arXiv · 2607.20298

Competing ferromagnetic and antiferromagnetic interactions in non-altermagnetic Ru$_{1-x}$Cr$_{x}$O$_{2}$

David T. Plouff·Nawsher J. Parvez·Subhash Bhatt·Xixiang Zhang·Adam A. Aczel·Jonathan Gaudet·John Q. Xiao
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Abstract

We investigate the proposal of hole doping RuO$_{2}$ via alloying with Cr ions to induce altermagnetism. Thin film samples of Ru$_{1-x}$Cr$_{x}$O$_{2}$ ($0 \leq x \leq 0.28$) were prepared by reactive magnetron co-sputtering on TiO$_{2}$ 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 $x \geq 0.16$ show a gradual downturn below $T\approx20~$K, suggestive of antiferromagnetic interactions, although this coexists with ferromagnetic hysteresis and remnant magnetization at $4~$K for samples with $x \geq 0.23$. Together, our magnetometry and neutron scattering measurements suggest the coexistence of antiferromagnetically coupled ferromagnetic CrO\textsubscript{2} 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.

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David T. Plouff, Nawsher J. Parvez, Subhash Bhatt, Xixiang Zhang, Adam A. Aczel, Jonathan Gaudet, John Q. Xiao. 2026-07-22. Competing ferromagnetic and antiferromagnetic interactions in non-altermagnetic Ru$_{1-x}$Cr$_{x}$O$_{2}$. https://arxiv.org/abs/2607.20298

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