Phase transitions and critical phenomena, which are dominated by fluctuations and correlations, are one of the fields replete with physical paradigms and unexpected discoveries. Especially for two-dimensional magnetism, the limitation of the Ginzburg criterion leads to enhanced fluctuations breaking down the mean-field theory near a critical point. Here, by means of magnetic resonance, we investigate the behavior of critical fluctuations in the two-dimensional ferromagnetic insulators CrXTe3(X=Si,Ge). After deriving the classical and quantum models of magnetic resonance, we deem the dramatic anisotropic shift of the measured g factor to originate from fluctuations with anisotropic interactions. The deduction of the g factor behind the fluctuations is consistent with the spin-only state (g≈ 2.050(10) for CrSiTe3 and 2.039(10) for CrGeTe3). Furthermore, the abnormal enhancement of g shift, supplemented by specific heat and magnetometry measurements, suggests that CrSiTe3 exhibits a more typical two-dimensional nature than CrGeTe3 and may be closer to the quantum critical point.
@article{arxiv.2101.02440,
title = {Abnormal Critical Fluctuations Revealed by Magnetic Resonance in the Two-Dimensional Ferromagnetic Insulators},
author = {Zefang Li and Dong-Hong Xu and Xue Li and Hai-Jun Liao and Xuekui Xi and Yi-Cong Yu and Wenhong Wang},
journal= {arXiv preprint arXiv:2101.02440},
year = {2021}
}