Effect of Oxygen Content on Magnetic Properties of Layered Cobaltites   PrBaCo2O5+\delta
  The effect of oxygen content on the magnetic properties of the layered perovskites has been investigated. The samples, PrBaCo$_{2}$O$_{5+\delta}$ (0.35 $\leq \delta \leq$ 0.80) were prepared by sol-gel method and characterized by X-ray diffraction and DC magnetization. A detailed magnetic phase diagram for PrBaCo$_{2}$O$_{5+\delta}$ is presented. It is found that unlike in the case of heavier rare-earths, ferromagnetic interactions are present at all temperatures below Tc and even in the antiferromagnetically ordered phase. Moreover, in compounds with lower oxygen content, short range ferromagnetic interactions are present even above Tc. This dependence of magnetic properties on oxygen content in these layered perovskites has been linked to the changes in polyhedra around the Co ions. 
Shraddha Ganorkar, K. R. Priolkar, P. R. Sarode and A. Banerjee
cond-mat.str-el