Single crystal growth from the melt and magnetic properties of hexaferrites–aluminates

Abstract

Single crystals of aluminum substituted barium hexaferrite were grown by the floating zone method with optical heating. Single crystals were produced from a melt of stoichiometric composition. The process was carried out under a pressure of 50atm of oxygen. In the system BaO–(x)Al2O3–(6−x)Fe2O3 the region of single phase crystal growth from the melt is limited by the value x=3. For higher substitutions single-phase crystallization is not observed. The grown single crystals are cylindrical boules with a diameter of 4–5mm and with lengths up to 50mm. To avert cracking the crystals have been annealed during the process of growth at 1100°C. The content of FeO in the composition of single crystals of barium hexaferrite, grown by zone melting under an oxygen pressure of 50atm, is approximately 0.3wt%. In the system of hexaferrite–aluminates the macroscopic magnetic moment of the material disappears at x=3.