Strain-induced insulator state in La_0.7Sr_0.3CoO_3

TL;DR

This paper demonstrates that applying strain to La_0.7Sr_0.3CoO_3 films induces a reversible insulator state, significantly altering their electrical resistivity through strain-mediated modifications of electronic structure.

Contribution

It reveals a strain-induced insulator transition in La_0.7Sr_0.3CoO_3, highlighting the role of strain in tuning electronic and magnetic properties in cobaltite thin films.

Findings

Resistivity increases by orders of magnitude under tensile strain.

Reversible strain causes a factor of 10 change in resistance at room temperature.

Weak strain dependence observed in magnetization below ferromagnetic transition.

Abstract

We report on the observation of a strain-induced insulator state in ferromagnetic La_0.7Sr_0.3CoO_3 films. Tensile strain above 1% is found to enhance the resistivity by several orders of magnitude. Reversible strain of 0.15% applied using a piezoelectric substrate triggers huge resistance modulations, including a change by a factor of 10 in the paramagnetic regime at 300 K. However, below the ferromagnetic ordering temperature, the magnetization data indicate weak dependence on strain for the spin state of the Co ions. We interpret the changes observed in the transport properties in terms of a strain-induced splitting of the Co e_g levels and reduced double exchange, combined with a percolation-type conduction in an electronic cluster state.