Metal-insulator-metal transition in NdNiO3 films capped by CoFe2O4

TL;DR

This study reveals two consecutive metal-insulator-metal transitions in NdNiO3 films capped with CoFe2O4, driven by charge transfer and magnetic interactions, with implications for tuning electronic phases in oxide heterostructures.

Contribution

It uncovers a novel insulator-metal transition below 40 K in NdNiO3 films with CoFe2O4 capping, and elucidates the role of charge transfer and magnetic interactions in these transitions.

Findings

Two consecutive transitions at 85 K and below 40 K.

Charge transfer from Co to Ni influences magnetic and electronic states.

Phase diagram illustrating the metal-insulator-metal transitions.

Abstract

Metal-insulator transition features as a transformation, from a highly charge conductive state to another state where charge conductivity is greatly suppressed when decreasing the temperature. Here we demonstrate two consecutive transitions in NdNiO3 films with CoFe2O4 capping, in which the metal-insulator transition occurs at 85 K, followed by an unprecedented insulator-metal transition below 40 K. The emerging insulator-metal transition associated with a weak antiferromagnetic behavior is observed in 20 unit cell-thick NdNiO3 with more than 5 unit cell CoFe2O4 capping. Differently, the NdNiO3 films with thinner CoFe2O4 capping only exhibit metal-insulator transition at 85 K, accompanied by a strong antiferromagnetic state below 40 K. Charge transfer from Co to Ni, instead of from Fe to Ni, formulates the ferromagnetic interaction between Ni-Ni and Ni-Co atoms, thus suppressing the antiferromagnetic feature and producing metallic conductive behavior. Furthermore, a phase diagram for the metal-insulator-metal transition in this system is drawn.