Magnetic structures and excitations in a multiferroic Y-type hexaferrite BaSrCo2Fe11AlO22

Multiferroic hexaferrites have been extensively investigated because they exhibit ferroelectricity associated with noncollinear magnetic orders in relatively low magnetic field and high temperature regions. To understand the static and dynamical spin-polarization coupling in such systems, it is necessary to determine the magnetic structures and spin-wave modes. This is impossible for polycrystalline samples. Here, the authors have successfully grown single crystals of BaSrCo${}_{2}$Fe${}_{12}$AlO${}_{22}$ by means of a laser floating zone technique. They perform magnetization, electric polarization, and neutron diffraction measurements to establish the magnetic phase diagram. Several interesting features are seen and the new understanding should provide a useful guide for developing multiferroic-based functional devices working at room temperature.