Structure and magnetic properties on A0.33Sr0.67CoO3-δ(A=Y,Gd)

We have studied the structure and magnetic properties of the A0.33Sr0.67CoO3-δ(A=Y,Gd). X-ray diffraction and Rietveld refinement show that the structure is the perovskite-type structure with layered alternate ion of CoO6 octahedron and CoO4 tetrahedral polyhedron. In the Y-doped sample, a magnetization jump was observed around 180K below the Curie temperature TC=304K during the magnetic field cooling. The magnetization jump may be associated with the onset of antiferromagnetism appeared as the Co3+ ion orbital ordering state in the intermediate spin state. The Gd-doped sample exhibits higher magnetization and lower Curie temperature than Y-doped sample. The field magnetization vs temperature curve reveals a paramagnetic behavior below 100K, which suggests there is a possible spin state transition of Co3+ ions from the intermediate to low spin state at 100K in addition to the Gd3+ ion paramagnetic contribution