MXene Fe2C as a promising candidate for the 2D XY ferromagnet

Monolayer Fe₂C is expected to possess strong electronic correlations, which can significantly contribute to electronic and magnetic properties. In this study we consider electronic and magnetic properties of MXene Fe₂C within the DFT+DMFT approach. We establish the existence of local magnetic moments $\mu_{\mathrm{loc}} = 3.3\,\mu_B$ in this compound, characterized by sufficiently long lifetime of $\tau\sim 350$ fs. We also calculate exchange interaction parameters accounting for electronic correlations using the recently developed approach for paramagnetic phase. At low temperatures, we obtain the strongest exchange interaction 11 meV between next nearest neighboring Fe atoms, located above (or below) the carbon plane, and the subleading interaction 6 meV between the next to next nearest neighboring atoms, located across the carbon plane. The resulting dependence of the Berzinskii-Kosterlitz-Thouless (BKT) and Curie temperatures on magnetic anisotropy is obtained. The BKT temperature for the pristine Fe₂C is $T_{\mathrm{BKT}}\simeq 300$ K, which makes this compound a good candidate for the two-dimensional ferromagnet with XY anisotropy.