BaFe4O7 and K0.22Ba0.89Fe4O7: Canted Antiferromagnetic Diferrites with Exceptionally High Magnetic Ordering Temperatures

Abstract

Complex iron containing oxides, typically referred to as ferrites, have been extensively studied for their electronic and magnetic properties, including magnetotransport,(1) ferromagnetism,(2) ferroelectricity,(3) and a combination of the latter two, known as multiferroism.(4, 5) The search for materials possessing simultaneous ferromagnetic and ferroelectric behavior is of significant interest both for the advancement of fundamental science(6-10) and for applications in random access memory (RAM).(11, 12) Despite the great technological potential of multiferroics, one or both of the ferroic ordering temperatures tend to fall below room temperature, such as in the compositions TbMnO3(8) and Ni3V2O8,(13) thus eliminating their practical utility for RAM applications. The scarcity of multiferroics possessing room temperature ferroic orderings continues to drive exploratory research in this field. For this reason, ferrites have garnered significant interest due to their often high ferroic ordering temperatures, for example in BiFeO3.(3) Among all ferrites, hexaferrites are the most studied prototypical examples and constitute a specific subclass of ferrites that follows the stoichiometry BaO–nFe2O3, in which the n value dictates the nomenclature, i.e., (n = 6) is a hexaferrite or (n = 1) is a monoferrite. This versatile class of materials encompasses a wide range of related structures best described by Pullar,(14) serving as the motivation for this work.