Hydrothermal synthesis, magnetism and resistivity of orthorhombic perovskite manganates Y1?xCaxMnO3 (x = 0, 0.07, 0.55, 0.65)
文摘
Orthorhombic Y1?xCaxMnO3 (x = 0, 0.07, 0.55, 0.65) crystals were successfully prepared in one step via the mild hydrothermal synthesis, and the magnetic and electric properties were investigated in detail. The formation and composition of Y1?xCaxMnO3 crystals mainly depend on the molar ratios of starting materials, reaction temperature and alkalinity of the reaction system. The magnetic properties of Y1?xCaxMnO3 strongly depend on the doping content of Ca. Y1?xCaxMnO3 (x = 0, 0.07 and 0.55) demonstrate the spin-glass-like behaviors. Y1?xCaxMnO3 (x = 0.55 and 0.65) show charge ordering and antiferromagnetic transition, and the antiferromagnetic state is stabilized by charge ordering. The signal of charge ordering transition of Y1?xCaxMnO3 (x = 0.65) is very strong and its magnetization increases significantly below 46 K due to the Dzyaloshinsky-Moriya (DM) anisotropic super-exchange interaction. The charge transport of samples that have charge ordering takes on the behavior of semiconductors. They show a small magnetoresistance effect. Their electric conduction mechanism accords with the variable-range hopping mode of highly correlated electrons.