Symmetry-breaking induced surface magnetization in non-magnetic RuO2

Published

February 6, 2025

Author(s)

Garnett Bryant, Quoc Dai Ho, Quang To, Ruiqi Hu, Anderson Janotti

Abstract

Altermagnetism is a newly identified phase of magnetism distinct from ferromagnetism and antiferromagnetism. RuO2 has been considered a prototypical metallic altermagnet with a critical temperature higher than room temperature. Previous interpretations of unusual magnetic properties of RuO2 relied on the theoretical prediction that local moments on two Ru sublattices, which are connected by four-fold rotational symmetry, are quite significant (∼ 1 μB), leading to long-range antiferromagnetic order. However, accumulated experimental data suggest that local moments on Ru in RuO2 are vanishingly small, indicating the bulk material is likely non-magnetic. This observation is consistent with the delocalized nature of the 4d electron of Ru and the strong screening effect in the metallic state. In this work, we show that despite the non-magnetic bulk, RuO2 surface (110) exhibits spontaneous magnetization, which we attribute to the breaking of local symmetry, resulting in electronic redistribution and magnetic moment enhancement. The emergence of surface magnetism gives rise to interesting spectroscopic phenomena, including spin-polarized surface states, spin-polarized scanning probe microscopy images and potentially spin-dependent transport effects. These highlight the important role of surface magnetic structures in the otherwise non-magnetic bulk RuO2.

Citation

Physical Review Materials

Pub Type

Journals

Keywords

altermagnetism, surface magnetization, symmetry-breaking

Citation

Bryant, G. , Ho, Q. , To, Q. , Hu, R. and Janotti, A. (2025), Symmetry-breaking induced surface magnetization in non-magnetic RuO2, Physical Review Materials (Accessed February 23, 2025)