Crystal Structure and Ferromagnetic Component in Layered Perovskite Sr0.8Y0.2CoO2.65

The crystal structure and magnetic state of Sr 0.8 Y 0.2 CoO 2.65 layered perovskite have been studied using neutron diffraction and synchrotron radiation diffraction and measuring the magnetization. It is shown that the crystal structure in the temperature range of 90–375 K can be described within the framework of the monoclinic sp. gr. A 2/ m with a cell 4√2 a p × 2√2 a p × 4 a p . The unit-cell parameter a is doubled (sp. gr. A 2/ m ) below T N ≈ 375 K. The basic magnetic structure can be described as G -type antiferromagnetic ordering with cobalt ion magnetic moments of 2.7 µ B and 1.7 µ B in the anion-deficient CoO 4+γ and stoichiometric CoO 6 layers, respectively. Based on the magnetization measurements, the ferromagnetic component of cobalt ion magnetic moment amounts to 0.27 µ B at 8 K. In both layers, the Co 3+ ions are predominantly in the mixed low/high-spin state. The ferromagnetic component is assumed to be due to the orbital ordering in the CoO 5 pyramids at T N and the ferromagnetic exchange coupling between CoO 5 pyramids in anion-deficient layers.