Valence-electron transfer and a metal-insulator transition in a strongly correlated perovskite oxide

TL;DR

This study investigates a metal-insulator transition in a perovskite oxide linked to valence-electron transfer from Ru to Cu, revealing how electron filling influences magnetic and transport properties in strongly correlated materials.

Contribution

It demonstrates the correlation between Ru-induced electron transfer and the metal-insulator transition in quadruple-perovskites, highlighting the role of Cu 3d shell filling.

Findings

MIT occurs at Ru concentration x~0.75

Cu magnetic entropy is suppressed by Ru doping

Electron transfer from Ru to Cu drives the transition

Abstract

We present transport and thermal data for the quadruple-perovskites MCu3(Ti1-xRux)4O12 where 0 < x < 1. A metal-insulator transition (MIT) occurs for Ru concentrations x~0.75. At the same time, the Cu2+ antiferromagnetic state is destroyed and it's magnetic entropy suppressed by Ru on a 1:1 basis. This implies that each Ru transfers an electron to a Cu ion and thus the MIT correlates with filling the Cu 3d shell. The Cu spin entropy in this strongly correlated electron material provides a unique probe among MIT systems.