Magnetic and neutron diffraction study on iridium(IV) perovskites Sr2LnIrO6 (Ln = Ce, Tb)

Powder neutron diffraction measurements have been performed for two tetravalent iridium perovskites, Sr2CeIrO6 (T-N = 21 K) and Sr2TbIrO6 (T-N = 51 K). It is found that moments of Tb4+ in these ordered perovskites are stacked antiferromagnetically along the c-axis, and the magnetic structure is of type I. The ordered magnetic moment of Tb4+ is 4.96 mu(B) at 28 K and 6.60 mu(B) at 2 K. From magnetic susceptibility measurements on Sr2CexTb1-xIrO6, the antiferromagnetic transition temperatures decrease greatly with decreasing Tb4+ ion, which indicates that the pathway of such interactions must involve the Tb4+ ions.