1,243,021. Rare earth orthoferrites. WESTERN ELECTRIC CO. 15 Aug., 1968 [15 Aug., 1967], No. 39102/68. Heading C1A. [Also in Divisions H1 and H3] Crystals of RFeO 3 (where at least 80% of the R atoms comprise at least one of Y, Sm, Eu, Gd, Tb Dy, Ho, Er, Tm and Yb, and 0-20% of the R atoms comprise at least one of La, Ce, Pr, and Nb) are grown by placing a seed crystal and a nutrient mass in a closed vessel in a 10-25M aqueous solution of KOH, heating the solution to at least 300‹ C. while under a pressure exceeding the critical pressure, and maintaining a temperature difference between the seed and the mass of at least 5‹ C. The temperature is preferably 350-425‹ C., the pressure 8000-35,000 p.s.i., and the temperature difference 10-50‹ C. The seed crystal is orthorhombic and may be TbAlO 3 ; its orientation is preferably (110) or (001). The nutrient mass may be a mixture of oxides, which may be sintered, or crystals grown by flux methods. The vessel may be Pt lined and may be filled to 70-95% of its volume before heating. A baffle may be placed between the nutrient mass in the bottom of the vessel and the crystals suspended above, to maintain the temperature difference. The + 3 valence state of La and Eu may be maintained by the presence of H 2 and O 2 respectively. In the examples, R was Yb, Sm/Er, Y, Ho, and Tb. The product is antiferromagnetic.