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

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 50 atm 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 4–5 mm and with lengths up to 50 mm. 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 50 atm, is approximately 0.3 wt%. In the system of hexaferrite–aluminates the macroscopic magnetic moment of the material disappears at x=3.

► To grow single crystals of hexaferrites–aluminates we used the floating zone method with optical heating.
► For limiting of FeO content in crystals the high oxygen pressure up to 50 atm in crystallization chamber was used.
► It has been established that obtaining perfect crystal is possible if not more than half of iron is substituted by aluminum.
► The magnetic and electronic properties of hexaferrites–aluminates single crystals were investigated.