Colossal magnetoresistance in La_(0.7)Ca_(0.3-x)Hg_xMnO_3 (0≤x≤0.2) system over wide temperature range

摘要

The divalent substitutions in rare-earth manganites create quenched disorders; those are responsible for the modification of magnetoelectronic properties through competition of two phases. In this regards, the substitution of divalent Hg is rarely studied. Here, we present the results on effect of Hg~(2+) substitution in LCMO manganites. We have synthesized polycrystalline samples with nominal compositions La_(0.7)Ca_(0.3-x)Hg_xMnO_3 (0≤x≤0.2) by the standard solid-state reaction method. The X-ray diffraction data revealed monophasic nature without a signature of Hg related or any other impurity phase. The ac susceptibility measurement showed variation in the magnetic transition temperature as well as the transition width. The electrical resistivity measurement showed variation in metal-insulator transition temperature. The magnetoresistance (MR) measurements were carried out at 5T magnetic field. The samples show varying magnitude of magnetoresistance as high as 74.48%. The distinct feature seen with Hg substitution is the increase in the magnitude of MR and temperature range over which MR value is sustained. It also improves the microstructure of the samples.