A Colossal Electroresistance response, accompanied by metal-insulator transition, in a mixed-valent vanadate

TL;DR

This study investigates a Fe-doped hollandite lead vanadate that exhibits a colossal electroresistance and a temperature-dependent metal-insulator transition, revealing complex interactions between orbital order, MIT, and double exchange.

Contribution

It demonstrates for the first time a colossal electroresistance effect in a mixed-valent vanadate with a coupled spin and orbital degree of freedom.

Findings

Giant resistivity drop indicating CER under electric current

Shift of MIT to higher temperatures with increased current

Evidence of interplay between orbital order, MIT, and double exchange

Abstract

Colossal electroresistance (CER) in manganites, i.e., a large change in electrical resistance under the influence of either an applied electric field or an applied electric current, has often been described as complimentary to the colossal magnetoresistance (CMR) effect. Mixed valent vanadates with active t2g and empty eg orbitals, unlike manganites, have not naturally been discussed in this context, as double exchange based CMR is not realizable in them. However, presence of coupled spin and orbital degrees of freedom, metal-insulator transition (MIT) accompanied by orbital order-disorder transition, etc., anyway make the vanadates an exciting group of materials. Here we probe a Fe-doped hollandite lead vanadate PbFe1.75V4.25O11 (PFVO), which exhibits a clear MIT as a function of temperature. Most importantly, a giant fall in the resistivity, indicative of a CER, as well as a systematic shift in the MIT towards higher temperature are observed as a function of applied electric current. Detailed structural, magnetic, thermodynamic and transport studies point towards a complex interplay between orbital order/disorder effect, MIT and double exchange in this system.