Induced ferroelectric phases in TbMn_2O_5

TL;DR

This paper theoretically analyzes the magnetostructural and magnetoelectric transitions in TbMn2O5, revealing two mechanisms of induced ferroelectricity and explaining its complex dielectric behavior.

Contribution

It provides a theoretical framework distinguishing two different mechanisms of ferroelectricity in TbMn2O5 and explains the material's dielectric response across temperature regimes.

Findings

Incommensurate and commensurate phases exhibit hybrid pseudoproper ferroelectricity.

Below 24 K, the phase shows improper ferroelectricity due to magnetic order coupling.

Dielectric properties are highly sensitive to magnetic field variations.

Abstract

The magnetostructural transitions and magnetoelectric effects reported in TbMn2O5 are described theoretically and shown to correspond to two essentially different mechanisms for the induced ferroelectricity. The incommensurate and commensurate phases observed between 38 and 24 K exhibit a hybrid pseudoproper ferroelectric nature resulting from an effective bilinear coupling of the polarization with the antiferromagnetic order parameter. This explains the high sensitivity of the dielectric properties of the material under applied magnetic field. Below 24 K the incommensurate phase shows a standard improper ferroelectric character induced by the coupling of two distinct magnetic order parameters. The complex dielectric behavior observed in the material reflects the crossover from one to the other transition regime. The temperature dependences of the pertinent physical quantities are worked out, and previous theoretical models are discussed.