Pas de deux of electricity and magnetism: an interview with Sang-Wook Cheong

Materials can be ferroelectric, having a spontaneous electric polarization that can be reversed by an external electric field, or they can be ferromagnetic, exhibiting spontaneous magnetization that is switchable by an applied magnetic field. However, until the 1960s, scientists did not expect that these two ferroic properties could co-exist in a single material. Today, materials exhibiting more than one of the primary ferroic properties are called multiferroics. Here, the primary ferroic properties can be ferroelectricity, ferromagnetism, antiferromagnetism, ferroelasticity, ferrotoroidicity or others. Basically, the multiferroic effect originates from the simultaneous breaking of space inversion and time-reversal symmetries. Multiferroics can be imagined as a pas de deux of electricity and magnetism. Recently, National Science Review interviewed Professor Sang-Wook Cheong from Rutgers University, who is one of the pioneering scientists in this field. Cheong talked about the multiferroics field, which has been fast developing since the early 2000s. His introductions and opinions on diverse multiferroic materials and potential multiferroic devices, as well as future research directions, may provide a useful resource for researchers both inside and outside the multiferroic research field.

A synthesis concept for a nanostructured CoFe2O4/BaTiO3 composite: Towards multiferroics

The synthesis of a periodically ordered, nanostructured composite consisting of CoFe2O4 and BaTiO3 is presented. In a first step, mesoporous CoFe2O4 is prepared by the structure replication method (nanocasting) using mesoporous KIT-6 silica as a structural mold.Subsequently, BaTiO3 is created inside the pores of CoFe2O4 by the citrate route, resulting ina well-ordered composite material of both phases. The two components are known for their distinct ferroic properties, namely ferrimagnetism (CoFe2O4) and ferroelectricity (BaTiO3), respectively. Therefore, this proof of synthesis concept offers new perspectives in the fabrication of composite materials with multiferroic properties.