Spectroscopic and first principle DFT+eDMFT study of complex structural, electronic, and vibrational properties of M2Mo3 O8 (M=Fe, Mn) polar magnets

Optical spectroscopy, X-ray diffraction measurements, density functional theory (DFT), density functional theory + embedded dynamical mean-field theory (DFT+eDMFT), and crystal-field calculations have been used to characterize structural and electronic properties of hexagonal M2Mo3O8 (M=Fe,Mn) polar magnets. Our experimental data are consistent with the room-temperature structure belonging to the space group P63mc for both compounds. The experimental structural and electronic properties at room temperature are well reproduced within DFT+eDMFT method, thus establishing its predictive power in the paramagnetic phase. With decreasing temperature, both compounds undergo a magnetic phase transition, and we argue that this transition is concurrent with a structural phase transition (symmetry change from P63mc to P63) in the Fe compound and an isostructural transition (no symmetry change from P63mc) in the Mn compound.