Structural and magnetic phase transitions in EuTi1-xNbxO3

TL;DR

This study explores how Nb-doping affects the structural and magnetic phase transitions in EuTiO3, revealing shifts in transition temperatures, changes in magnetic order, and elastic properties modeled by Landau theory.

Contribution

It provides new insights into the effects of Nb substitution on the structural and magnetic properties of EuTiO3, including the stabilization of ferromagnetism and detailed elastic behavior modeling.

Findings

Nb-doping shifts structural transition to higher temperatures

Long-range ferromagnetic order appears with >10% Nb

Elastic moduli soften near the structural transition

Abstract

We investigate the structural and magnetic phase transitions in EuTi1-xNbxO3 with synchrotron powder X-ray diffraction (XRD), resonant ultrasound spectroscopy (RUS), and magnetization measurements. Upon Nb-doping, the Pm-3m to I4/mcm structural transition shifts to higher temperatures and the room temperature lattice parameter increases while the magnitude of the octahedral tilting decreases. In addition, Nb substitution for Ti destabilizes the antiferromagnetic ground state of the parent compound and long range ferromagnetic order is observed in the samples containing more than 10% Nb. The structural transition in pure and doped compounds is marked by a step-like softening of the elastic moduli in a narrow temperature interval near TS, which resembles that of SrTiO3 and can be adequately modeled using the Landau free energy model employing the same coupling between strain and octahedral tilting order parameter as previously used to model SrTiO3.