Antiferromagnetic transitions in 'tetragonal-like' BiFeO3

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. Though there is abundant evidence that structural and ferroelectric properties are different than in 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. A minority magnetic phase with C-type character is also reported with TN = 260 K. The co-existence of the two 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.