Preparation And Characterization Of Double Perovskite Sr-k-fe-mo-o System

In this paper, double perovskite SrKFeMoO6, Sr2-xKxFeMoO6(x=0.3,0.5,0.7,0.9), Sr2-xKxFeMoO6(x=0.2,0.4,0.6,0.8) and Sr2-xKxFeMoO6(x=1.2,1.4,1.6) samples have been successfully synthesized by conventional reaction processing. By means of X-ray diffraction meter, vibrating sample magnetometer and four probes method, the crystal structure, magnetic and electric properties have been investigated. The main results of the dissertation are as follows:The structure of the double perovskite SrKFeMoO6 sample belongs to monoclinic system with space group P21/n. X-ray diffraction pattern suggests that the lattice parameters are a=5.489A, b=5.468A, c=7.846A andβ=89.182°, and some of Fe and Mo orderly occupy on B sites. Thermal magnetization shows that the magnetization decreases slowly with temperature, and the transition temperature was not observed in the studied temperature range which indicated that the transition temperature is over 300K. The magnetic moment increases with the increase of magnetic field from 0T to 1T gradually, and the saturation magnetic moment (Ms) of 2.55μBper formula unit (f.u.). The sample exhibits metallic behavior (dp/dT >0) under zero,0.5T and 1.0T magnetic fields over the temperature range, from 80K to 300K. The sample shows distinct magnetoresistance effects in 0.5T and 1.0T applied magnetic fields, respectively. The electrical transportation of SrKFeMoO6 can be described by double exchange interaction model.The structures of the series of double perovskite Sr2-xKxFeMoO6(x=0.3,0.5,0.7,0.9) samples belong to monoclinic system with space group P21/n. The lattice volumes increase with the content of K increasing. Thermal magnetization shows that the magnetization decreases slowly with temperature, and the transition temperature was not observed in the studied temperature range which indicated that the transition temperature is over 300K. The magnetic moment increases with the increase of magnetic field from 0T to 1T gradually, and the magnetic moments increase with the content of K increasing. The Sr1-xKxFeMoO6(x=0.9) sample exhibits metallic behavior (dp/dT>0) under zero,0.5T and 1.0T magnetic fields over the temperature range, from 80K to 300K. The Sr2-xKxFeMoO6(x=0.9) sample shows distinct magnetoresistance effects in 0.5T and 1.0T applied magnetic fields, respectively. The electrical transportation of Sr2-xKxFeMoO6(x=0.9) can be described by single magnon dispersion model.The structures of the series of double perovskite Sr2-xKxFeMoO6(x=0.2,0.4,0.6,0.8) samples belong to monoclinic system with space group P21/n. The lattice volumes first increase and then decrease with the content of K increasing. Thermal magnetization shows that the magnetization decreases slowly with temperature, and the transition temperature was not observed in the studied temperature range which indicated that the transition temperature is over 300K. The magnetic moment increases with the increase of magnetic field from 0T to 1T gradually, The Sr2-xKxFeMoO6(x=0.2,0.6,0.8) sample exhibits metallic behavior (dp/dT >0) under zero,0.5T and 1.0T magnetic fields over the temperature range, from 80K to 300K. The Sr2-xKxFeMoO6(x=0.8) sample shows giant magnetoresistance effects in 1.0T applied magnetic fields. The electrical transportation of Sr2-xKxFeMoO6(x=0.2,0.8) can be described by double exchange interaction model, while that of Sr2-xKxFeMoO6(x=0.6) can be described by single magnon dispersion model.The structures of the series of double perovskite Sr2-xKxFeMoO6(x=1.2,1.4,1.6,) samples belong to monoclinic system with space group P21/n. The lattice volumes increase with the content of K increasing. Thermal magnetization shows that the magnetization decreases slowly with temperature, and the transition temperature was not observed in the studied temperature range which indicated that the transition temperature is over 300K. The magnetic moment increases with the increase of magnetic field from 0T to 1T gradually.