Spin structure and magnetic frustration in multiferroic RMn2O5 (R = Tb, Ho, Dy)

TL;DR

This study investigates the magnetic and crystal structures of RMn2O5 multiferroics, revealing temperature-dependent magnetic ordering, the role of R ion size, and how lattice distortions relieve magnetic frustration, leading to complex magnetic phases.

Contribution

It provides detailed neutron diffraction analysis of magnetic structures and elucidates the influence of R ion size and lattice distortions on magnetic frustration and multiferroic behavior.

Findings

All three materials show incommensurate antiferromagnetic order below 40 K.

A commensurate-incommensurate transition occurs at low temperatures.

Lattice distortions involving Mn3+ shifts lift magnetic frustration, resulting in canted antiferroelectric phases.

Abstract

We have studied the crystal and magnetic structures of the magnetoelectric materials RMn2O5 (R = Tb, Ho, Dy) using neutron diffraction as a function of temperature. All three materials display incommensurate antiferromagnetic ordering below 40 K, becoming commensurate on further cooling. For R = Tb, Ho, a commensurate-incommensurate transition takes place at low temperatures. The commensurate magnetic structures have been solved and are discussed in terms of competing exchange interactions. The spin configuration within the ab plane is essentially the same for each system, and the radius of R determines the sign of the magnetic exchange between adjacent planes. The inherent magnetic frustration in these materials is lifted by a small lattice distortion, primarily involving shifts of the Mn3+ cations and giving rise to a canted antiferroelectric phase.