Magnetic field induced flop of cycloidal spin order in multiferroic TbMnO3: The magnetic structure of the P||a phase

TL;DR

This study uses neutron diffraction to reveal that applying a magnetic field causes a flop in the cycloidal spin order of TbMnO3, which in turn reverses its ferroelectric polarization.

Contribution

The paper provides the first direct determination of the magnetic structure of TbMnO3 in the high field P||a phase, linking spin order to polarization flop.

Findings

Ferroelectric polarization arises from cycloidal Mn spins in the ab plane.

Magnetic field causes a flop of the Mn cycloidal plane.

Polarization reversal is directly linked to the flop of the spin cycloid.

Abstract

Using in-field single crystal neutron diffraction we have determined the magnetic structure of TbMnO3 in the high field P||a phase. We unambiguously establish that the ferroelectric polarization arises from a cycloidal Mn spins ordering, with spins rotating in the ab plane. Our results demonstrate directly that the flop of the ferroelectric polarization in TbMnO3 with applied magnetic field is caused from the flop of the Mn cycloidal plane.