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.
@article{arxiv.1107.2975,
title = {Antiferromagnetic transitions in `T-like' BiFeO3},
author = {G. J. MacDougall and H. M. Christen and W. Siemons and M. D. Biegalski and J. L. Zarestky and S. Liang and E. Dagotto and S. E. Nagler},
journal= {arXiv preprint arXiv:1107.2975},
year = {2012}
}
Comments
9 pages, 7 figures. Slight modifications to introductory text and presentation of data. Supplementary Material section added