Strain-induced magnetic phase transition in SrCoO$_{3-\delta}$ thin films

TL;DR

This study demonstrates a strain-induced transition from ferromagnetic to antiferromagnetic order in SrCoO$_{3-eta}$ thin films, confirming theoretical predictions and revealing a new magnetic phase under large tensile strain.

Contribution

It provides experimental evidence of a magnetic phase transition in SrCoO$_{3-eta}$ films caused by large epitaxial strain, a phenomenon previously predicted theoretically.

Findings

Observation of antiferromagnetic order under large tensile strain

Neutron diffraction confirms G-type antiferromagnetic structure

Neel temperatures range from 135 K to 325 K depending on oxygen content

Abstract

It has been well established that both in bulk at ambient pressure and for films under modest strains, cubic SrCoO$_{3-\delta}$ ($\delta < 0.2$) is a ferromagnetic metal. Recent theoretical work, however, indicates that a magnetic phase transition to an antiferromagnetic structure could occur under large strain accompanied by a metal-insulator transition. We have observed a strain-induced ferromagnetic to antiferromagnetic phase transition in SrCoO$_{3-\delta}$ films grown on DyScO$_3$ substrates, which provide a large tensile epitaxial strain, as compared to ferromagnetic films under lower tensile strain on SrTiO$_3$ substrates. Magnetometry results demonstrate the existence of antiferromagnetic spin correlations and neutron diffraction experiments provide a direct evidence for a G-type antiferromagnetic structure with Ne\'el temperatures between $T_N \sim 135\,\pm\,10\,K$ and $\sim 325\,\pm\,10\,K$ depending on the oxygen content of the samples. Therefore, our data experimentally confirm the predicted strain-induced magnetic phase transition to an antiferromagnetic state for SrCoO$_{3-\delta}$ thin films under large epitaxial strain.