Strong competition between orbital-ordering and itinerancy in a frustrated spinel vanadate

TL;DR

This study explores how orbital order and electron itinerancy compete in a frustrated spinel vanadate, revealing how doping influences magnetic and structural phases through neutron scattering and theoretical modeling.

Contribution

It demonstrates the interplay between orbital order and electron itinerancy in Mn$_{1-x}$Co$_x$V$_2$O$_4$, showing how doping tunes magnetic frustration and structural transitions.

Findings

Orbital order suppresses magnetic frustration at low Co doping.

Electronic itinerancy melts orbital order and suppresses structural phase transition.

High Co doping leads to non-collinear magnetic states due to weakened anisotropy and enhanced Co-V interactions.

Abstract

The crossover from localized- to itinerant-electron behavior is associated with many intriguing phenomena in condensed-matter physics. In this paper, we investigate the crossover from localized to itinerant regimes in the spinel system Mn$_{1-x}$Co$_x$V$_2$O$_4$. At low Co doping, orbital order (OO) of the localized electrons on the V3+ ions suppresses magnetic frustration by triggering a tetragonal distortion. With Co doping, electronic itinerancy melts the OO and suppresses the structural phase transition while the reduced spin-lattice coupling produces magnetic frustration. Neutron scattering measurements and first-principles-guided spin models reveal that the non-collinear state at high Co doping is produced by weakened local anisotropy and enhanced Co-V spin interactions.