Engineering room-temperature multiferroicity in Bi and Fe codoped BaTiO3

TL;DR

This paper demonstrates the engineering of room-temperature multiferroic properties in Bi and Fe codoped BaTiO3, achieving enhanced ferroelectricity, ferromagnetism, and dielectric properties suitable for high-k dielectric applications.

Contribution

It introduces a novel Bi-Fe codoping strategy in BaTiO3 to enhance room-temperature multiferroic responses and dielectric properties, which was not previously achieved.

Findings

Bi-Fe codoped BaTiO3 shows significantly increased ferroelectric and ferromagnetic strength.

The x=0.08 Bi-Fe codoped sample exhibits high dielectric constant and low loss tangent at room temperature.

Evidence of enhanced magnetoelectric coupling and larger bandgap in the codoped samples.

Abstract

Fe doping into BaTiO3, stabilizes the paraelectric hexagonal phase in place of the ferroelectric tetragonal one [P. Pal et al. Phys. Rev. B, 101, 064409 (2020)]. We show that simultaneous doping of Bi along with Fe into BaTiO3 effectively enhances the magnetoelectric (ME) multiferroic response (both ferromagnetism and ferroelectricity) at room-temperature, through careful tuning of Fe valency along with the controlled-recovery of ferroelectric-tetragonal phase. We also report systematic increase in large dielectric constant values as well as reduction in loss tangent values with relatively moderate temperature variation of dielectric constant around room-temperature with increasing Bi doping content in Ba1-xBixTi0.9Fe0.1O3 (0<x<0.1), which makes the higher Bi-Fe codoped sample (x=0.08) promising for the use as room-temperature high-k dielectric material. Interestingly, x=0.08 (Bi-Fe codoped) sample is not only found to be ferroelectrically (~20 times) and ferromagnetically (~6 times) stronger than x=0 (only Fe-doped) at room temperature, but also observed to be better insulating (larger bandgap) with indirect signatures of larger ME coupling as indicated from anomalous reduction of magnetic coercive field with decreasing temperature. Thus, room-temperature ME multiferroicity has been engineered in Bi and Fe codoped BTO (BaTiO3) compounds.