Change in lattice modulation upon gigantic magnetoelectric transition in GdMnO3 and TbMnO3

TL;DR

This study investigates how magnetic fields induce ferroelectric phases in GdMnO3 and TbMnO3, revealing changes in lattice modulation linked to spin structure alterations during magnetoelectric transitions.

Contribution

It provides direct experimental evidence of lattice modulation changes associated with magnetic-field-induced ferroelectric phases in GdMnO3 and TbMnO3.

Findings

Lattice modulation becomes commensurate with q=1/2 and 1/4 along the b axis.

Spin structure change correlates with electric phase transition.

Magnetic field induces specific lattice and spin modulations.

Abstract

Single-crystal synchrotron x-ray diffraction measurements in strong magnetic fields have been performed for magnetoelectric compounds GdMnO3 and TbMnO3. It has been found that the P || a ferroelectric phase induced by the application of a magnetic field at low temperatures is characterized by commensurate lattice modulation along the orthorhombic b axis with q = 1/2 and q = 1/4. The lattice modulation is ascribed to antiferromagnetic spin alignment with a modulation vector of (0 1/4 1). The change of the spin structure is directly correlated with the magnetic-field-induced electric phase transition, because any commensurate spin modulation with (0 1/4 1) should break glide planes normal to the a axis of the distorted perovskite with the Pbnm space group.