Flux Growth and Magnetic Properties of Helimagnetic Hexagonal Ferrite Ba(Fe_1- Sc )₁₂O₁₉ Single Crystals

Fabricating large, high-crystalline-quality single-crystal samples of hexagonal ferrite Ba(Fe_1- Sc )₁₂O₁₉ is the first important step to elucidating its helimagnetic structure and developing it for further applications. In this study, single crystals of Ba(Fe_1- Sc )₁₂O₁₉ of various Sc concentrations x were successfully grown by the spontaneous crystallization method using Na₂O-Fe₂O₃ flux. We determined the optimal starting composition of reagents for Ba(Fe_1- Sc )₁₂O₁₉ growth as a function of x. In situ monitoring of the crystal nucleus generation accelerated the success of crystal growth. The obtained crystals comprised black and lamellate structures with a size of 13 mm × 8 mm × 2 mm and a surface of {001} orientation. X-ray diffraction and elemental analysis revealed that the obtained crystals were composed of single-phase Ba(Fe_1- Sc )₁₂O₁₉ of high crystalline quality. The lattice constants a and c increased linearly with increasing x, thereby following Vegard's law. The temperature dependence of magnetization and the magnetization curves at 77 K of the x = 0.128 crystal exhibited behavior characteristics of helimagnetism. Neutron diffraction measurements of the x = 0.128 crystal exhibited magnetic satellite reflection peaks below 211 K, providing evidence that Ba(Fe_1- Sc )₁₂O₁₉ behaves as a helimagnetic material.