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Double perovskite LaAFeMoO_6 Preparation and Characterization of compounds (A = alkali metal )

Author: ZuoMeiXiu
Tutor: HuoGuoYan
School: Hebei University
Course: Materials Physics and Chemistry
Keywords: GMR Double perovskite structure Crystal structure Magnetic Properties Electrical transport properties
CLC: O614.331
Type: Master's thesis
Year: 2008
Downloads: 14
Quote: 0
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Abstract


In this paper , using a conventional solid-state reaction method a series of compounds La1 xNa1-xFe1 xMo1-xO6 (x = 0,0.1,0.2,0.3,0.4,0.5), LaNaFe1 xMo1-xO6 (x = 0.1,0.2, 0.3 ) and La1 xKxFe1-yCoyMoO6 (x = 0, y = 0.1; x = 0, y = 0.2; x = 0.05, y = 0.1; x = 0.1, y = 0.2) were determined by powder X-ray diffraction of the compound crystal structure, using a vibrating sample magnetometer and a four -probe method were used to measure the magnetic properties of the samples and electrical properties to obtain the main results are as follows : La1 xNa1-xFe1 xMo1-xO6 and LaNaFe1 xMo1-xO6 series of samples belong to monoclinic , P21 / c space group . Samples in the temperature range 80-300K no Curie temperature , and magnetic properties change with temperature decreases slowly . In the measured temperature range , La1 xNa1-xFe1 xMo1-xO6 series presents positive magnetoresistance effect, and LaNaFe1 xMo1-xO6 series of samples negative magnetoresistance . Two series of samples belong to the semiconductor properties . Also conduction mechanism of the samples were studied , respectively, of samples of various electrical transport model fit and found that the sample belongs to a small polaron variable range hopping conduction mechanism . La1 xKxFe1-yCoyMoO6 series of samples X-ray diffraction results showed that the single-phase unit cell parameters a, b as the amount of Co increases , and the lattice parameter c showing the opposite trend . For x = 0 of the sample measured in the temperature range increases with the Co content gradually increases the magnetization of the sample ; samples for x ≠ 0 , showing a magnetization opposite trend . All samples showed semiconducting properties , and further analysis : La1.1K0.9Fe0.8Co0.2MoO6 and La1.05K0.95Fe0.9Co0.1MoO6 samples meet the non-adiabatic small polaron conduction mechanism , while LaKFe0.8Co0.2MoO6 and LaKFe0. 9Co0.1MoO6 meet variable range of small polaron conduction mechanism .

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > Section III group metal elements and their compounds > Lanthanides ( rare earth elements ) > Lanthanum La
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