Chiral magnetism and ordering of oxygen vacancies in SrTiO$_{2.5}$

TL;DR

This study reveals that oxygen vacancy ordering in SrTiO$_{2.5}$ induces chiral magnetic states with net moments, explaining experimental phenomena through advanced computational methods.

Contribution

It demonstrates that the orientation and ordering of TiO$_5$ pentahedra are crucial in forming chiral magnetic states in oxygen-deficient SrTiO$_3$.

Findings

Chiral ordering of TiO$_5$ pentahedra in SrTiO$_{2.5}$

Chiral magnetic state with net moment at room temperature

Correlation with experimental observations

Abstract

Oxygen vacancies in the perovskite insulator SrTiO$_3$ free electrons that couple with other physical degrees of freedom such as lattice, orbital, and spin. This leads to the emergence of exotic quantum states such as superconductivity and unusual ferromagnetism. We perform density-functional theory and dynamical mean-field theory calculations and demonstrate that the orientation and ordering of the TiO$_5$ pentahedra plays a crucial role. Specifically, for vacancy-rich SrTiO$_{3-\delta}$ ($\delta\sim$0.5), we find a chiral ordering of the TiO$_5$ pentahedra in a sixfold superlattice. This chiral structure is accompanied by a chiral magnetic state with a net moment in the (111) direction at room temperature, which can explain several experimental observations.