Spin-Orbital Driven Ferroelectricity

TL;DR

This paper introduces a general formalism to evaluate electric polarization in transition metal chains influenced by ligand octahedral tilting, revealing how orbital and spin orderings jointly determine polarization features.

Contribution

It presents a novel formalism based on local coordinates to analyze polarization in systems with ligand octahedral rotations, highlighting new polarization behaviors in collinear and cycloidal spin orders.

Findings

Nonvanishing polarization occurs in collinear spin order.

Polarization direction is unrestricted in the plane of spin rotation.

Orbital ordering and ligand rotation jointly influence polarization.

Abstract

Proposing a general formulism in terms of local coordinates representing the tilting of the ligands' octahedra, we evaluate the electric polarization in a chain of transition metal ions with unpolar octahedron rotation. We find the orbital ordering produced by the ligands's rotation and the spin order, together, determine the polarization features, manifesting that nonvannishing polarization appears in collinear spin order and the direction of polarization is no more restricted in the plane of spin rotation in cycloidal ordering.