The Structure and Magnetic Properties of New Iridium (IV) Perovskites Sr2LnIrO6 (Ln=Ce, Tb)

New compounds with the formula Sr2LnIrO6 (Ln=Ce, Sm~Lu) were characterized from X-ray diffraction measurements and magnetic susceptibility measurements in the temperatures between 5 and 300 K. They were determined to have ordered monoclinic perovskite structures with space group P21/n. The oxidation state of iridium is considered to be pentavalent for Sr2LnIrO6 (Ln=Sm~Gd, Dy~Lu), whereas it is tetravalent for Sr2LnIrO6 (Ln=Ce, Tb). The compounds in which the iridium is in the tetravalent state show an antiferromagnetic transition. Sr2CeIrO6 has a transition temperature at 21 K, and Sr2TbIrO6 has two transition temperatures at 25 and 51 K.