Synthesis and characterization of K2NiF4-type phases Ln_(0.5)Sr_(1.5)Mn_(0.5)Fe_(0.5_O4 (Ln=La, Nd, Gd, and Dy)

摘要

A systematic investigation of layered perovskite oxides with general formula Ln_(0.5)Sr_(1.5)Mn_(0.5)Fe_(0.5_O4 (Ln=La, Nd, Gd, and Dy) has been undertaken mainly to understand their structural, magnetic, as well as electrical behavior. The materials were prepared by the ceramic method. X-ray data have been analyzed by using program Checkcell and the variations of various parameters are explained. It has been concluded that not only A-site cation radius, , but also the size variance factor (σ~2) influence electrical and magnetic properties. A systematic study of electrical resistivity of all the four materials was undertaken as a function of temperature to understand the conduction mechanism. On analyzing the electrical resistivity data, it has been concluded that variable range hopping model is found to fit well. The magnetic studies suggest that the phases are antiferromagnetic and this behavior could arise from Mn~(4+)-O-Mn~(4+), and Fe~(3+)-O-Fe~(3+) superex-change interaction.