Bandwidth control effects in electron doped manganite La_0.7-xY_xCe_0.3MnO₃ thin films

Abstract

We report the effect of average A-site cation radius on the structural, magnetic and electrical properties of electron doped manganite La_0.7Ce_0.3MnO₃ thin films. A site cation radius 〈r_A〉 is varied systematically by partially replacing La⁺³ ions by smaller Y⁺³ ions in the parent compound. The carrier doping, i.e. the fraction of tetravalent Ce atoms at the A-site was kept at 30%. A series of La_0.7-xY_xCe_0.3MnO₃ (x=0, 0.05, 0.1, 0.15 and 0.25) thin films were prepared under identical conditions by using pulsed laser deposition technique. Metal–insulator transition temperature (T_p) and the ferromagnetic Curie temperature (T_c) are found to be decreasing significantly with increasing yttrium concentration, i.e. decreasing 〈r_A〉. The resistivity (ρ) at T_p increases by one order of magnitude when the yttrium concentration is increased from x=0 to 0.25, while magnetization decreases with decreasing 〈r_A〉. Magnetoresistance as measured under field of 1 T is significant near T_c. Structural analysis reveals the films are having single phase and c-axis lattice parameter decreasing linearly as 〈r_A〉 decreases. There is no marked difference in surface morphology of samples with different yttrium concentration. From EDX the Y:Ce:Mn ratio were consistent within 5% of the nominal composition.