Polar Antiferromagnets Produced with Orbital-Order

TL;DR

This study demonstrates how orbital-order-induced Jahn-Teller distortions in polar manganite thin films on high-index substrates create broken-inversion symmetry and off-centering of Mn sites, linking orbital order with magnetic properties.

Contribution

It reveals a new mechanism where orbital order and Jahn-Teller distortions induce polar states in manganite thin films, distinct from bulk materials.

Findings

Large optical second harmonic generation signals indicate broken inversion symmetry.

First-principles calculations show Jahn-Teller mode drives Mn-site off-centering.

Orbital order correlates with emergent polar and magnetic states.

Abstract

Polar magnetic states are realized in pseudocubic manganite thin films fabricated on high-index substrates, in which a Jahn-Teller (JT) distortion remains an active variable. Several types of orbital-orders were found to develop large optical second harmonic generation, signaling broken-inversion-symmetry distinct from their bulk forms and films on (100) substrates. The observed symmetry-lifting and first-principles calculation both indicate that the modified JT q2 mode drives Mn-site off-centering upon orbital order, leading to the possible cooperation of "Mn-site polarization" and magnetism.