| The perovskite structure manganese oxide R1-xAxMnO3 (R:3 valence rare earth, A:2 valence alkaline earth) are paid attention since the discovery of colossal magnetoresistive effect. The complex interaction and interplay among the charge, orbital, spin and lattice give rise to the abundant physics properties the magnetic transition, metal-insulator transformation, charge-order and phase separation. Manganese Lai1-xCaxMnO3 that origins from the matrix of LaMnO3 by replacing the La with the Ca change the matrix structure and bring about the different valence of Mn. The change of micro role and the intrinsic inhomogeneity on micro-nanometer scale give rise to the change of the macroscopic physical properties. The change of structure and interaction enrich the physical sense and the application in life of this kind of strong-correlation manganese material.The series of power and bulk sample of La1-xCaxMnO3 (x=0.5,0.67,0.75) are prepared by sol-gel and solid-state method respectively. The electronic, magnetic and infrared properties of high-doped manganese La1-xCaxMnO3 (x=0.5,0.67,0.75) are studied systematically.The X-ray diffraction is applied to analyze structure of La1-xCaxMnO3 (x=0.5,0.67, 0.75). And the lattice structure parameter of La1-xCaxMnO3=0.5,0.67,0.75)is fitted by means of the Rietica refinement software. The studies of influence of sintering temperature on the structural characteristic signify that the higher sintering temperature will generate the better crystallinity and the bigger grain. Moreover, the more density doping of Ca require the higher sintering temperature. For bulk material, along with the increase of doping density of Ca, the volume of cell and the size of grain magnify.The SQUID and VSM are employed for the magnetic properties of these manganese La1-xCaxMnO3 (x=0.5,0.67,0.75)underμ0H= 0.1 and 1T. As the doping density of Ca increase, the transformations from paramagnetic to the anti-ferromagnetic occur for every sample with different transformation temperature.The standard four probe method is used for the electrical properties under zero magnetic fields and the curve of resistivity with the changing temperature at the range of 75K-300K. These samples are insulator on the basis of careful analysis about the results. The curve of differential coefficient of logarithm of resistivity about temperature displays the different charge-order phase transition for different doping density of Ca. For infrared properties of these samples, Fourierf transformation infrared spectrometer is applied to measure the infrared absorption spectrum of power samples obtained in different sintering temperature. We found the distortion of octahedral structure and the frequency decrease with the increasing sintering temperature. For bulk sample, synchrotron radiation infrared spectrograph is used for intermediate infrared (4500～370cm-1) and far infrared (700～20cm-1) at the interval of 10K from room temperature to the temperature of liquid nitrogen. The whole refraction curve at the range of intermediate and far infrared is fitted by appropriated software. Conductivity and permittivity can be obtained from the refraction spectrum data by means of Kramers-Kroning analysis. All these analysis about infrared spectrum show that the manganese La1-xCaxMnO3 (x=0.5,0.67,0.75) samples have phase transformation temperature, and the change of micro structures, electrical and magnetic properties according to the magnetic and electrical transport mechanism. |
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