Magnetic and electronic transport properties of electron-doped La0.9−xBixTe0.1MnO3 (0.00≤ x≤0.2)Manganites

Abstract

The effect of Bi substitution at La site on magnetic and transport properties of electron-doped La0.9−xBixTe0.1MnO3 was investigated. The samples were prepared through the standard solid-state method. Analysis of X-ray diffraction data using Rietveld refinement confirmed single-phase samples crystallized in rhombohedral structure. The undoped sample (x = 0) exhibited paramagnetic (PM) to ferromagnetic (FM) transition behaviour with Curie temperature, TC = 242 K and metal–insulator (MI) transition behaviour at MI transition temperature, Tp1 = 240 K. Partial substitution of Bi3+ at the La site for x = 0.05–0.15 decreased transition temperatures, TC and Tp1 to 150 and 115 K, respectively. By contrast, for x = 0.2, the sample showed fully insulating behaviour and PM–FM transition at TC = 140 K. A secondary resistivity peak observed for x = 0 sample at temperature, Tp2 = 194 K below Tp1 in ρ versus T curve was strongly suppressed by low Bi substitution of x = 0.05. In addition, enhanced magnetoresistance effect reaching 50% observed for the x = 0.2 sample was suggested due to spin-dependent interfacial tunnelling which enhanced under low magnetic field of 0.8 T. The observed rapid decrease in TC and Tp1 may be due to the role of 6s2 lone pair Bi3+ which produced a type of blocking effect due to strong hybridization between Bi (6s2) and O (2p) orbitals. This caused a reduction on the rate of eg electron-hopping process and elongation of Mn-O bond length, thereby weakening the double exchange mechanism.