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arXiv · 2605.25564

Magnetoelastic effects in the metallic frustrated antiferromagnet CrB$_2$

Tadataka Watanabe·Mai Watanabe·Sakurako Suganuma·Andreas Bauer·Christian Pfleiderer
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Abstract

Hexagonal chromium diboride CrB$_2$ is a metallic frustrated antiferromagnet with a N\'{e}el temperature $T_N \sim$ 88 K. In CrB$_2$, Cr 3$d$ electrons not only give rise to localized magnetic moments but also contribute to metallic conduction. We perform ultrasound velocity measurements on a single crystal of hexagonal CrB$_2$ to determine its elastic properties. The temperature dependence of the $ab$-plane shear elastic modulus exhibits Curie-type softening upon cooling from $\sim$120 K down to $T_N$. This behavior is interpreted as a precursor to a symmetry-lowering lattice distortion at $T_N$, indicating that magnetic frustration is relieved via transverse magnetoelastic coupling. In addition, the $a$-axis and $c$-axis compressive elastic moduli show unusual softness and their suppression upon cooling, which are naturally explained by Fermi-surface nesting and its suppression upon cooling. The present results suggest that, in CrB$_2$, longitudinal magnetoelastic coupling suppresses Fermi-surface nesting and enhances frustrated exchange interactions, while transverse magnetoelastic coupling plays a key role in relieving the frustration.

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Tadataka Watanabe, Mai Watanabe, Sakurako Suganuma, Andreas Bauer, Christian Pfleiderer. 2026-05-25. Magnetoelastic effects in the metallic frustrated antiferromagnet CrB$_2$. https://doi.org/10.1103/b4zd-yhkl

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