Effect of MnO2 layers on transport properties of Lan−nxCa1+nxMnn−yCryO3n+1 (n=2, 3; x=0.3; y=0.075, 0.15, 0.3)

A series of bulk polycrystalline layered perovskite manganites Lan−nxCa1+nxMnn−yCryO3n+1 (n=2, 3; x=0.3; y=0.075, 0.15, 0.3) are prepared by conventional solid-state reaction technique and the effect of MnO2 layers on their transport properties are studied. Powder X-ray diffraction (XRD) patterns of the samples indicate their single-phase character. Metal–insulator (MI) transition is observed in both Cr-doped and undoped samples. There is a systematic change of MI transition temperature with the increase of Cr concentration. Results on the transport properties of these samples have indicated methodical variations in a number of features like electrical resistivity, MI transition, low-field magnetoresistance, etc. with the number of MnO2 layers. A regular variation of different features is also observed when Mn site is substituted by Cr.