Comparative Study of the Layered Perovskites Pr1−x A1+x CoO4 , (A = Sr, Ca)

We present structural, magnetic, and electric properties of Pr1−xCa1+xCoO4 layered perovskites and compare them with the results of recently studied Pr1−xSr1+xCoO4. The Rietveld refinements of X-ray powder diffraction (XRD) patterns indicate that all samples crystallize in the K2NiF4-type structure with space group symmetry I4/mmm. The parent compounds Pr(Ca, Sr)CoO4 are paramagnetic insulators. Upon increasing x, a variety of different magnetic transitions can be identified. The complex magnetic behavior results from the interplay of competing interactions. The temperature-dependent electrical resistivity of the samples shows 2D variable range hopping (2D-VRH). The results are discussed with respect to structure−property relationships.