Unconventional critical behaviors at the magnetic phase transition of Co3Sn2S2kagome ferromagnet

Co(3)Sn(2)S(2)has generated a growing interest as a rare example of the highly uniaxial anisotropic kagome ferromagnet showing a combination of frustrated-lattice magnetism and topology. Recently, via precise measurements of the magnetization and AC susceptibility we have found a low-field anomalous magnetic phase (A-phase) with very slow spin dynamics that appears just below the Curie temperature (T-C). The A-phase hosts high-density domain bubbles after cooling throughT(C)as revealed in a previousin-situLorentz-TEM study. Here, we present further signatures of the anomalous magnetic transition (MT) atT(C)revealed by a study of the critical behaviors of the magnetization and magnetocaloric effect using a high-quality single crystal. Analyses of numerous magnetization isotherms aroundT(C)(similar or equal to 177 K) using different approaches (the modified Arrot plot, Kouvel-Fisher method and magnetocaloric effect) result in consistent critical exponents that do not satisfy the theoretical predictions of standard second-order-MT models. Scaling analyses for the magnetization, magnetic entropy change and field-exponent of the magnetic entropy change, all consistently show low-field deviations belowT(C)from the universal curves. Our results reveal that the MT of Co(3)Sn(2)S(2)can not be explained as a conventional second-order type and suggest an anomalous magnetic state belowT(C).

Automated summary

Co(3)Sn(2)S(2) is a rare example of highly uniaxial anisotropic kagome ferromagnet with frustrated-lattice magnetism and topology. The study of critical behaviors of magnetic transition reveals an anomalous magnetic state below the Curie temperature, suggesting deviations from standard theoretical predictions.