Strong magneto-elastic coupling and polar properties in orthorhombic Eu1-xYxMnO3 manganite

TL;DR

This study explores the magneto-elastic coupling and polarization properties of Eu1-xYxMnO3 manganites, revealing reentrant ferroelectric phases and significant spin-phonon interactions through comprehensive experimental techniques.

Contribution

It provides new experimental evidence of magneto-elastic and ferroelectric behaviors in Eu1-xYxMnO3, and constructs a revised (x,T) phase diagram differing from previous reports.

Findings

Reentrant improper ferroelectric phases for x=0.2 and 0.3.

Significant changes in Mn-O bond lengths and angles at magnetic transitions.

Lattice anomalies indicating strong spin-phonon coupling.

Abstract

This work reports an experimental investigation of the magneto-elastic coupling and polarization character of magnetic phases of the orthorhombic Eu1-xYxMnO3 system at low temperatures. The temperature dependence of the polarization reversal curves clearly reveals the existence of a reentrant improper ferroelectric phase for x = 0.2 and 0.3. Although a ferroelectric phase is also stable for x = 0.4, we have no experimental evidence that it vanishing at finite temperatures. From these results and those obtained from other experimental techniques, the corresponding (x,T) phase diagram was traced, yet yielding significant differences with regard to previous reports. An expressive magneto-elastic coupling is revealed by changes observed in both Mn-O bond lengths and Mn-O1-Mn bond angle at the magnetic phase transitions, obtained by temperature dependence of synchrotron x-ray diffraction experiments. Furthermore, signatures of the lattice deformations across the magnetic phase transitions were evidenced by anomalies in the temperature dependence of the lattice mode involving rotations of the MnO6 octahedra. These anomalies confirm the important role of the spin-phonon coupling in these materials.