Transport Property of La0.67-xSmxSr0.33MnO3 at Heavy Samarium Doping (0.40 ≤x ≤0.60)

The influence of heavy samarion (Sm) doping (0.40 ≤ x ≤ 0.60) on magnetic and electric properties of La0.67-xSmxSr0.33MnO3 was investigated by measuring the magnetization-temperature (M ∼ T) curves, magnetization-magnetic density (M ∼ H) curves, resistivity-temperature(ρ-T) curves and magnetoresistivity-temperature(MR ∼ T) curves of the samples under different temperatures. It is found that, with the increase of Sm doping amount, the samples transform from long-range ferromagnetic order to spin-cluster glass state and anti-ferromagnetic state; and when x = 0.60, the transport property becomes abnormal under magnetic background; and the magnetic structure changes and extra magnetic coupling induced by doping leads to colossal magnetoresistance effect. The transport mechanism of metallic conduction at low temperature is mainly electron-magneton interaction and can be fitted by the formula ρ = ρ0 + AT4.5, and the insulator-like transport mechanism on high temperature range is mainly the function of variable-range hopping and can be fitted by the formula ρ = ρ0exp(T0/T)1/4. In the formulas above, ρ is resistivity, T is temperature, and A, ρ0, T0 are constants.