Cation size mismatch effect in (La1-yREy)1.4Ca1.6Mn2O7 perovskite manganites

The size variance (sigma(2)) that indicates random disorder of cations distributed over the A or B-site, has significant influence on the basic quantities on perovskite manganites. In this study, we investigate the effect of A-site variance (sigma(2)(A)) in double layered perovskite manganites. In order to understand how the magneto-electrical properties of layered perovskite type RE2-2xCa1+2xMn2O7 change with sigma(2)(A), we have prepared a series of four samples with optimal doping (x = 0.3) and fixed mean A-cation radius ( = 1.3353 angstrom). A-site disorder is varied by use of different rare earth combinations by co-doping of La with Gd, Sm, Nd and Pr. Based on structural analysis by Rietveld profile fitting, all the samples crystallize in Sr3Ti2O7-type tetragonal phase (space group I4/mmm). As sigma(2)(A) increases, paramagnetic (PM) to ferromagnetic (FM) transition temperature shows a linear decrease. However, metal-insulator transition temperature shows a linear correlation with sigma(2). (C) 2019 Elsevier B.V. All rights reserved.