Frustrated Magnetism in Mott Insulating (V$_{1-x}$Cr$_x$)$_2$O$_3$

TL;DR

This study uses neutron spectroscopy and DFT calculations to explore magnetic frustration in (V$_{1-x}$Cr$_x$)$_2$O$_3$, revealing its role in the Mott transition and magnetic phase behavior.

Contribution

It provides the first detailed mapping of magnetic excitations in (V$_{1-x}$Cr$_x$)$_2$O$_3$ and highlights the intrinsic magnetic frustration in its paramagnetic phase.

Findings

Magnetic frustration is inherent in the paramagnetic phase.

Magneto-elastic coupling relieves frustration at $T_N=185$ K.

Frustration suppresses magnetic ordering and broadens the Mott transition phase space.

Abstract

V2O3 famously features all four combinations of paramagnetic vs antiferromagnetic, and metallic vs insulating states of matter in response to %-level doping, pressure in the GPa range, and temperature below 300 K. Using time-of-flight neutron spectroscopy combined with density functional theory calculations of magnetic interactions, we have mapped and analyzed the inelastic magnetic neutron scattering cross section over a wide range of energy and momentum transfer in the chromium stabilized antiferromagnetic and paramagnetic insulating phases (AFI & PI). Our results reveal an important magnetic frustration and degeneracy of the PI phase which is relieved by the rhombohedral to monoclinic transition at $T_N=185$ K due to a significant magneto-elastic coupling. This leads to the recognition that magnetic frustration is an inherent property of the paramagnetic phase in $\rm (V_{1-x}Cr_x)_2O_3$ and plays a key role in suppressing the magnetic long range ordering temperature and exposing a large phase space for the paramagnetic Mott metal-insulator transition to occur.