Magnetic properties and crystal structure of Sr3CoIrO6and Sr3NiIrO6

We have studied the magnetic properties and crystal structure of Sr 3 CoIrO 6 and Sr 3 NiIrO 6 as a function of temperature. Two characteristic temperatures, T 1 = 90 K and T 2 = 25 K for Sr 3 CoIrO 6 , and T 1 = 85 K and T 2 = 15 K for Sr 3 NiIrO 6 , were observed. Below T 1 a significant increase of magnetization and below T 2 a weak temperature dependence of magnetization in the field-cooled and practically zero magnetization values in the zero-field-cooled mode were detected for both compounds. The existence of Ir 4 + in Sr 3 CoIrO 6 was confirmed by an Ir- L III x-ray absorption measurement. Magnetoelastic effects have been observed in the temperature dependence of the lattice parameters of Sr 3 CoIrO 6 and Sr 3 NiIrO 6 . The magnetic structure of Sr 3 CoIrO 6 in zero fields can be described as a commensurate modulated antiferromagnet with a propagation vector k = ( 0 , 0 , 1 ) . Neutron powder diffraction with polarized neutrons gave evidence of short-range magnetic order, above and below the magnetic ordering temperature.