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Synthesis and Characterization of La-Sr-Fe-Mn-O System and Pr-K-Fe-Mo-O System

Author: YangQing
Tutor: HuoGuoYan
School: Hebei University
Course: Materials Physics and Chemistry
Keywords: Giant magnetoresistance effect Structure Magnetic Electrical transport Doubly doped
CLC: O611.3
Type: Master's thesis
Year: 2007
Downloads: 7
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Abstract


The paper with a the perovskite type the La1 - xSrxFe1 - xMnxO3 traditional solid-phase synthesis was prepared from ( 0.3 ≤ x ≤ 0.7 ) and double perovskite PrKFexMo2 of - xO6 ( 0.8 lt ; x lt ; 1.1 ) series compounds samples . By powder X- ray diffraction, vibrating sample magnetometer (VSM) and four- probe method to measure the magnetic and electrical properties of the sample . The main research work and conclusions are as follows : 1 . Perovskite-type : the La1 - xSrxFe1 - xMnxO3 ( 0.3 ≤ x ≤ 0.7 ) series of samples of X-ray diffraction results show that the sample belongs to the orthorhombic system, space group Pnma . With Sr2 and Mn4 reduce the La3 , and Fe3 alternative increase in the amount of the first , with lattice parameters a increases , the unit cell parameters b, c slightly reduced . It has the magnetization slowly decreases as the temperature increases , the Curie temperature of 80.0 K or less . In the the paramagnetic temperature within the presence of the magnetic cluster , its size With the Mn4 and Sr2 doping amount increases and then decreases to 0.5 , and then with further doping significantly increase its size . La1-xSrxFe1-xMnxO3 (0.3 ≤ x ≤ 0.7) series of samples are presented in the measured temperature range of the insulator , and the resistivity of the sample is increased accordingly as the incorporation of Sr and Mn increased . In addition, the mechanism of the conductivity of the sample : The samples were all kinds of electric transport model fitting , found that at low temperatures , the conduction mechanism of some samples of variable range hopping model , while others are in line with the small polaron sub- step transport model ; at high temperatures , all samples are in line with bipolaron hopping model . The 2 double perovskite-type : sample PrKFexMo2 of - xO6 ( 0.8 ≤ x ≤ 1.1 ) XRD patterns of the sample belongs to monoclinic system , space group is P21 , as x increases , the unit cell parameters gradually decreases . The samples sintered samples sintered at 900 ℃ than 800 ° C cell parameters . Magnetization of PrKFexMo2 - xO6 series compound ( 0.8 ≤ x ≤ 1.1 ) as the temperature rises slowly decreases , and no apparent turning point in the measured temperature range , the Curie temperature of the sample to less than 80K ; their magnetization increases with increasing magnetic field , and gradually saturated , all samples showed an antiferromagnetic .

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Chemical elements and inorganic compounds > Nature
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