Structure and electronic properties of CaAl12−xFexO19 hibonites

Abstract

Dilution of iron in the AM12O19 has shown promising coupling of magnetic and electric properties in the hexaferrites. We have prepared samples of low iron content in the isostructural hibonite, CaAl12−xFexO19, to investigate the structural effects of larger iron substitution into the aluminum sites and the resultant properties. We found a solid solution exists for CaAl12−xFexO19 where x ≤ 5.5. Iron distributes into all sites with the tetrahedral M3 and octahedral M5 sites displaying nominally larger preference at higher Fe content. Paramagnetic behavior was observed for x ​= ​1–3, while x ​= ​4–5.5 displayed a broad ferromagnetic-like transition with increasing Curie temperature. Differences in field-cooled and zero-field-cooled magnetic susceptibility measurements and low magnetic moment indicate the presence of a frustrated antiferromagnetic structure as the source of the ferromagnetic-like behavior. Increasing Fe content also increases the dielectric constant up to 21 ​at room temperature with high dielectric loss.