Altermagnetism at finite temperature: Thermally induced spin fluctuations in CrSb and MnTe described fully from first principles
Date:
Contributed poster at the 2025 Institute of Physics Theory of Condensed Matter (TCM) Group Annual Meeting.
Abstract
So called ‘altermagnets’ are an intriguing class of magnetically ordered material in which there is a net zero magnetisation, but in which electronic bands are not spin-degenerate on account of the intrinsic symmetries of the underlying crystal structure. In the zero-temperature limit, the magnetic moments (or ‘spins’) will arranged in a perfectly ordered, collinear structure. However, at any finite temperature, thermal noise will cause the spins to deviate from this pristine arrangement. Above some critical temperature (the Néel temperature), long-range magnetic order disappears entirely, and the material transitions to a paramagnetic state. Here, we will present results of ab initio electronic structure calculations performed on two prototypical altermagnets: CrSb, which is metallic; and MnTe, which is semiconducting. We demonstrate that the magnetic phase transition in both materials is well-described by disordered local moment (DLM) theory [1-3] and describe in detail how site-diagonal spin disorder induces changes to calculated electronic band structures. We provide preliminary estimates for the Néel temperature of both materials, and also discuss implications for temperature-dependent transport properties.
References
[1] B. L. Gyorffy et al., J. Phys. F: Met. Phys. 15, 1337 (1985).
[2] J. Staunton et al., J. Phys. F: Met. Phys. 15, 1387 (1985).
[3] I. D. Hughes et al., New J. Phys. 10, 063010 (2008).