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arXiv · 2609.03274

Resolving the Magnetic Ground-State Controversy in RuO2 through A Flat Magnetic Energy Landscape

Tianxiao Liang·Fanhan Kong·Jijun Zhao·Xue Jiang
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Abstract

Rutile RuO2 is a prominent candidate for altermagnetism, yet its magnetic ground state remains highly controversial, with experiments reporting either a nonmagnetic state or altermagnetic order. Here, we develop a generalized environment-dependent spin-lattice framework that unifies localized Heisenberg exchange, itinerant Stoner magnetism via Landau spin fluctuations, and spin-orbit-coupling-mediated spin-lattice interactions. Parameterized from a high-throughput first-principles database using machine-learning and solved by large-scale Monte Carlo simulations, the framework reveals an exceptionally flat magnetic energy landscape in RuO2, where the nonmagnetic state lies nearly degenerate with multiple altermagnetic configurations. We find that material perturbations, exemplified by intrinsic defects, select distinct magnetic ground states primarily by modifying the localized Heisenberg exchange, with perturbation-induced itinerant Stoner polarization provides an essential secondary contribution. Spin-orbit coupling controls the orientation and stability of the N\'eel vector, but does not determine the emergence of long-range magnetic order. These results provide a unified explanation for the conflicting experimental observations and establish a general microscopic framework for understanding how material perturbations select competing magnetic ground states in systems with nearly flat magnetic energy landscapes.

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Tianxiao Liang, Fanhan Kong, Jijun Zhao, Xue Jiang. 2026-09-03. Resolving the Magnetic Ground-State Controversy in RuO2 through A Flat Magnetic Energy Landscape. https://arxiv.org/abs/2609.03274

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