Band-Mott mixing hybridizes the gap in Fe2Mo3O8

Abstract

We combined optical spectroscopy and first-principles electronic structure calculations to reveal the charge gap in the polar magnet Fe 2 Mo 3 O 8 . Iron occupation on the octahedral site draws the gap strongly downward compared to the Zn parent compound, and subsequent occupation of the tetrahedral site creates a narrow resonance near the Fermi energy that draws the gap downward even further. This resonance is a many-body effect that emanates from the flat valence band in a Mott-like state due to screening of the local moment-similar to expectations for a Zhang-Rice singlet, except that here it appears in a semiconductor. We discuss the unusual hybridization in terms of orbital occupation and character as well as the structure-property relationships that can be unveiled in various metal-substituted systems (Ni, Mn, Co, Zn).

Electronic structure of the frustrated diamond lattice magnet NiRh$_2$O$_4$

“…Such an explicit demonstration of the failure of a single ion model and requirement for metal-metal charge transfer in NiRh 2 O 4 highlights the importance of metal-metal hybridization in mixed 3d-4d/5d compounds in general. This hybridization can affect both the magnetic degrees of freedom and exchange interactions so should be an essential consideration in the design of novel magnetic states in materials such as spinels, double perovskites [70,71], or A 2 Mo 3 O 8 compounds [28,72].…”

Phase Transitions and Physical Properties of the Mixed Valence Iron Phosphate Fe3(PO3OH)4(H2O)4

“…The pattern of the structural distortions at LT, together with the mixed valence character of Fe ions, points to some unusual electronic states in the Fe 3 (PO 3 OH) 4 (H 2 O) 4 compound. We see similarities with other systems such as AgNiO 2 , where a pattern of structural distortions exists at LT and is associated with a charge-disproportionation inside a metallic state [63,64], BiMnO 3 and LaMnO 3 , where a pattern of structural distortions exists at LT and is associated with an orbital order that can be interpreted as site and orbital selectivity [65][66][67][68][69], RNiO 3 , where a pattern of structural distortions exists at LT and is associated with a metal to insulator transition [70][71][72][73], TM 2 Mo 3 O 8 (TM = Mn, Fe, Co, Ni, Zn), where tiny structural distortions exist together with band and Mott gaps within the same electronic state [74,75], etc. Thus, our work shows that further theoretical and experimental studies are necessary to obtain deeper insights into the electronic-structural interplay responsible for the structural phase transition discovered in the Fe 3 (PO 3 OH) 4 (H 2 O) 4 compound.…”

Antiferromagnetic to Ferrimagnetic Phase Transition and Possible Phase Coexistence in Polar Magnets (Fe1–xMnx)2Mo3O8 (0 ≤ x ≤ 1)

“…Importantly, all these properties are found to closely relate to the magnetic structure. The band gap of Fe 2 Mo 3 O 8 exhibits a notable narrowing at the AFM transition T N ∼ 60 K, implying intimate coupling between the charge and spin degrees of freedom . The optical ME depends on the relative arrangement between magnetization ( M ) and electric polarization P , e.g., the diagonal term M · P leads to the gyrotropic birefringence and the off-diagonal term M × P determines the nonreciprocal directional dichroism. , For the thermal Hall effect, the transverse thermal conductivity jumps to a unprecedentedly large value driven by the AFM to FRM transition .…”