Antiferromagnetic transitions in `T-like' BiFeO3

TL;DR

This study investigates the magnetic properties of epitaxially-stabilized T-like BiFeO3 thin films, revealing antiferromagnetic order with two distinct transition temperatures and co-existing magnetic phases, differing from R-like BiFeO3.

Contribution

It provides the first detailed neutron scattering analysis of T-like BiFeO3, identifying its antiferromagnetic phases and transition temperatures, and explains differences from R-like BiFeO3.

Findings

Confirmed antiferromagnetism with TN = 324 K in T-like BiFeO3.

Identified a possible second magnetic transition at 260 K.

Explained magnetic phase differences via Fe-O-Fe bond distances.

Abstract

Recent studies have reported the existence of an epitaxially-stabilized tetragonal-like ('T-like') monoclinic phase in BiFeO3 thin-films with high levels of compressive strain. While their structural and ferroelectric properties are different than those of rhombohedral-like ('R-like') films with lower levels of strain, little information exists on magnetic properties. Here, we report a detailed neutron scattering study of a nearly phase-pure film of T-like BiFeO3. By tracking the temperature dependence and relative intensity of several superstructure peaks in the reciprocal lattice cell, we confirm antiferromagnetism with largely G-type character and TN = 324 K, significantly below a structural phase transition at 375 K, contrary to previous reports. Evidence for a second transition, possibly a minority magnetic phase with C-type character is also reported with TN = 260 K. The co-existence of the two magnetic phases in T-like BiFeO3 and the difference in ordering temperatures between R-like and T-like systems is explained through simple Fe-O-Fe bond distance considerations.