Magnetic inversion symmetry breaking and ferroelectricity in TbMnO3

TL;DR

This paper investigates the magnetic structures of TbMnO3 across its ferroelectric transition, revealing a spiral magnetic order that breaks inversion symmetry and explains its magnetoelectric properties.

Contribution

It provides detailed neutron diffraction analysis of magnetic structures in TbMnO3, linking spiral magnetic order to ferroelectricity and symmetry breaking.

Findings

Incommensurate longitudinal spin order above T_N

Transverse spiral magnetic order below T_C

Spiral magnetic order breaks inversion symmetry

Abstract

TbMnO3 is an orthorhombic insulator where incommensurate spin order for temperature T_N < 41K is accompanied by ferroelectric order for T < 28K. To understand this, we establish the magnetic structure above and below the ferroelectric transition using neutron diffraction. In the paraelectric phase, the spin structure is incommensurate and longitudinally-modulated. In the ferroelectric phase, however, there is a transverse incommensurate spiral. We show that the spiral breaks spatial inversion symmetry and can account for magnetoelectricity in TbMnO3.