Magnetoelectric multiferroic, y-type hexaferrites – A review

Magnetoelectric (ME) multiferroics are materials in which electric and magnetic dipoles are coupled. The possibility to control electrical properties in the material using magnetic field (and vice versa) in case of ME multiferroics make these materials highly versatile and useful. Over the years many magnetically induced ferroelectrics have been discovered but they show ME effect at low temperature and require high external magnetic field. Recently many Y-type hexaferrites (Ba_xSr_(2-x)Me₂Fe₁₂O₂₂), where Me is a divalent cation, have shown ME effect at room temperature and low applied magnetic field, that too in a single phase. Studies suggest that there are several factors that influence the ME properties of Y-type hexaferrites, such as annealing process, the sintering temperature, and ion substitution. It was reported that the lower critical magnetic field was required for inducing electrical polarization when Mg replaces Zn to form Ba₂Mg₂Fe₁₂O₂₂. Also, it was reported that Strontium doping at Barium site changes the magnetic transition temperature and enhances the ME effects. And it was found that increasing Co content favours high electrical resistivity. Further research and development require careful analysis and compilation of the work on hexaferrites. Y-Type hexaferrite is the focus of this review. Its structure, reason behind ME effect and salient research works has been discussed.