Role of the rare-earth doping on the multiferroic properties of BaTiO$_3$: First-principles calculation

TL;DR

This study uses first-principles calculations to explore how rare-earth Eu doping affects the electronic, magnetic, and ferroelectric properties of BaTiO3, revealing increased polarization and ferromagnetism with higher Eu content.

Contribution

It provides a detailed first-principles analysis of Eu-doped BaTiO3, highlighting the effects of Eu concentration on multiferroic properties and magnetic behavior.

Findings

Band-gap decreases with Eu doping

Spontaneous polarization increases with Eu content

Eu doping induces ferromagnetism without external magnetic field

Abstract

Ab-initio spin-polarized Density Functional Theory plus U is used to study the electronic and magnetic properties of tetragonal doped barium titanate (Ba$_{1-x}$Eu$_x$O$_3$) system for different europium (Eu$^{3+}$) concentrations. For this study, the Projector Augmented Wave (PAW) method and a Perdew-Zunger (LSDA) approximation, which has been used for the exchange correlation energy, have been considered taking into account a supercell model. In this model, the spin polarization as well as the Hubbard's potential have been used for the correction of the electron-electron Coulomb interactions in the rare-earth ions partially filled f-orbitals. The electronic bands-structure reveals that the band-gap energy as well as the dielectric properties decreases with the increase of the doping concentration. On the other hand, the modern theory of polarization also shows that the spontaneous electric polarization increases with the increase of the europium content, whereas the states-density reveals ferromagnetic characteristics (with non-zero total magnetization), without an applied magnetic field, for the Ba$_{1-x}$Eu$_x$O$_3$ system. The magnetic properties also reveal to be strongly dependent on the exchange interaction of the strong localized Eu 4f-states in the crystal lattice.