Structure and magnetic properties of the orthorhombic n=2 Ruddlesden–Popper phases Sr3Co2O5+δ (δ=0.91, 0.64 and 0.38)

The reduced Ruddlesden–Popper phases, Sr3Co2O5+δ with image, 0.64 and 0.38, have been prepared in a nitrogen atmosphere. The crystal structures were determined by powder neutron diffraction. Oxygen vacancies are found both in O(3) and O(4) sites but the majority are along one crystallographic axis in the CoO2 plane, inducing an orthorhombic distortion of the normally tetragonal image Ruddelsden–Popper structure. Superstructures due to oxygen ordering are observed by electron microscopy. The magnetic measurements reveal complex behavior with some ferromagnetic interactions present for Sr3Co2O5.91 and Sr3Co2O5.64.