Structure and magnetism in the oxygen-deficient perovskites Ce1−xSrxCoO3−δ (x ≥ 0.90)

We have examined the structure and phase behaviour of strontium-doped Ce1−xSrxCoO3−δ and found that the perovskite form is stabilised over a relatively narrow solid solution range (x > 0.85). A combination of electron, powder X-ray and neutron diffraction has revealed tetragonal superstructures of the basic perovskite unit; (I4/mmm) 2ap × 2ap × 4ap (x = 0.90) and (P4/mmm) ap × ap × 2ap (x = 0.95). Magnetisation measurements show ferromagnetic behaviour under applied magnetic fields. Low temperature neutron diffraction of Ce0.10Sr0.90CoO2.80 in zero field reveals a magnetic cell of dimension 2ap × 2ap × 4ap with an ordered cobalt moment of 1.7 B.M. at 25 K.