Magnetic properties of BiFeO$_3$-BaTiO$_3$ ceramics in the morphotropic phase boundary: a role of crystal structure and structural parameters

TL;DR

This study investigates how crystal structure variations in BiFeO$_3$-BaTiO$_3$ ceramics influence their magnetic properties, revealing the role of structural parameters and phase transitions in magnetic behavior across the morphotropic boundary.

Contribution

It provides new insights into the correlation between crystal structure, phase coexistence, and magnetic properties in BiFeO$_3$-BaTiO$_3$ ceramics, emphasizing the influence of oxygen octahedra tilting.

Findings

Magnetic structure transitions from modulated G-type to collinear antiferromagnetic.

Magnetic moment per iron ion decreases with increasing BaTiO$_3$ content.

Remanent magnetization reduces significantly as cubic phase dominates.

Abstract

A correlation between the crystal structure and magnetic properties of system (1-x)BiFeO$_3$-(x)BaTiO$_3$ with compounds across the morphotropic phase boundary was studied using X-ray and neutron diffraction, magnetometry, and Mossbauer spectroscopy measurements. Increase in the dopants content leads to the structural transition from the rhombohedral phase to the cubic phase via a formation of the two-phase region (0.2 < x < 0.33), wherein the magnetic structure changes from the modulated G-type antiferromagnetic to the collinear antiferromagnetic via a stabilization of the non-collinear antiferromagnetic phase with non-zero remanent magnetization. The value of magnetic moment calculated per iron ion based on the Mossbauer and neutron diffraction data decreases from m = 4.4 mB for the compound with x=0.25 to m=3.2 mB for the compound with x=0.35 testifying a dominance of 3+ oxidation state of the iron ions. Increase in the amount of the cubic phase leads to a reduction in the remanent magnetization from 0.02 emu.g for the compounds with the dominant rhombohedral phase (x < 0.27) down to about 0.001 emu/g for the compounds with dominant cubic structure (x >= 0.27). Rapid decrease in the remanent magnetization observed in the compounds across the phase coexistence region points at no direct correlation between the type of structural distortion and non-zero remanent magnetization, while the oxygen octahedra tilting is the key factor determining the presence of non-zero remanent magnetization.