Suppression of charge ordering and thermal hysteresis of electronic transport and magnetisation in La0.5Ca0.5Mn1-xNixO3

摘要

A series of polycrystalline La0.5Ca0.5Mn1-xNixO3 (x = 0.00, 0.025, 0.050, 0.075, 0.100 and 0.125) was synthesised using solid state reaction. Measurements in a cooling and warming cycle between 300 and 80 K were carried out to study the Ni-doping effects on the electrical resistivity, thermopower and magnetisation of single-phase La0.5Ca0.5Mn1-xNixO3. Partial substitution of Ni for Mn leads to the suppression of charge ordering state, the evidence of which is shown by the dramatic decrease in electrical resistivity and thermal hysteresis width in electrical resistivity, thermopower and magnetisation. However, the magnitude of both electrical resistivity and thermopower increases with increasing Ni content. This can be attributed to an increase in the Mn4+ concentration, which favours the antiferromagnetic state and leads to a gradual disappearance of ferromagnetic double exchange interaction. Besides, the metal-nonmetal transition temperature decreases with increasing Ni content until x = 0.075, which might arise from increased electron-phonon coupling due to less ordered spins at temperatures above ferromagnetic transition. For samples with x greater than 0.075, no metal-nonmetal transition is observed due to the suppression of double exchange mechanism.