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arXiv · 2512.13571

Ferromagnetic resonance in an antiferromagnetic crystal EuSn$_2$As$_2$

I. I. Gimazov·D. E. Zhelezniakova·R. B. Zaripov·Yu. I. Talanov·A. Yu. Levakhova·A. V. Sadakov·K. S. Pervakov·V. A. Vlasenko·A. L. Vasiliev·V. M. Pudalov
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Abstract

We report results of electron spin resonance (ESR) measurements in single crystals of EuSn$_2$As$_2$. In the temperature range of antiferromagnetic (AFM) ordering of Eu atoms, $T \leq T_N\approx 24$\,K, the ESR signal splits into two resonance lines, one of which, at high-field (or low-frequency), is the conventional acoustic AFM resonance mode that occurs at temperatures below $T_N$. The lower-field (high-frequency) line, as we have proven here, is the ferromagnetic resonance associated with the presence in the layered AFM crystal of a small amount ($\sim 3\%$) of planar nanodefects with a non-zero ferromagnetic (FM) moment. The existence of ferromagnetic nano-inclusions in the bulk of the antiferromagnetic compound makes EuSn$_2$As$_2$ a peculiar example of a natural magnetic metamaterial. We believe that the planar FM nanodefects are also inherent in other layered AFM compounds, which explains often observed increase in their magnetic susceptibility upon cooling at $T< T_N\rightarrow 0$.

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I. I. Gimazov, D. E. Zhelezniakova, R. B. Zaripov, Yu. I. Talanov, A. Yu. Levakhova, A. V. Sadakov, K. S. Pervakov, V. A. Vlasenko, A. L. Vasiliev, V. M. Pudalov. 2025-12-15. Ferromagnetic resonance in an antiferromagnetic crystal EuSn$_2$As$_2$. https://arxiv.org/abs/2512.13571

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