We report results of electron spin resonance (ESR) measurements in single crystals of EuSn2As2. In the temperature range of antiferromagnetic (AFM) ordering of Eu atoms, T≤TN≈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 TN. 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 (∼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 EuSn2As2 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<TN→0.
@article{arxiv.2512.13571,
title = {Ferromagnetic resonance in an antiferromagnetic crystal EuSn$_2$As$_2$},
author = {I. I. Gimazov and D. E. Zhelezniakova and R. B. Zaripov and Yu. I. Talanov and A. Yu. Levakhova and A. V. Sadakov and K. S. Pervakov and V. A. Vlasenko and A. L. Vasiliev and V. M. Pudalov},
journal= {arXiv preprint arXiv:2512.13571},
year = {2025}
}