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Studies on the Colossal Magnetoresistance in Perovskite-manganese Oxides and Phase Relations Related with Manganese Oxides

Author: GuZhiJun
Tutor: HuoGuoYan
School: Hebei University
Course: Inorganic Chemistry
Keywords: colossal magnetoresistance perovskite structure manganese oxides double exchange phase relations
CLC: O614.7
Type: Master's thesis
Year: 2005
Downloads: 176
Quote: 1
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Abstract


In this paper, a series of bulk polycrystalline La1-xKxMnO3（0<x<1） samples were made by conventional reaction processing in air. By means of X-ray diffraction, scanning electric microscope, vibrating sample magnetometer and four probe method, we investigated the magnetic and electric properties, phase relations related with manganese oxide at room temperature. The main works and results of the dissertation are as follow:1 The samples La1-xKxMnO3 contained a single perovskite when x≤0.65, and were composed of two phases （a magnetic perovskite phase and a nonmagnetic KMnO2 phase） for x>0.65. For x≥0.65 ,the lattice parameter irregularly changed with substituting K+ for La3+.2 Below the curie temperature the samples were ferromagnet, and a transition from ferromagnetic state to paramagnetic state was observed.3 At low temperature the samples were metallic state and with the temperature increasing a transition from metal to semiconductor was observed. The resistivity data fit equally well with three conducting mechanisms.4 The phase relations in the Bi2O3-Fe2O3-MnOy ternary system were investigated by means of X-ray powder diffraction at room temperature .The compounds Bi25FeO40, Bi12MnO20, BiFeO3, BiMn2O5, Bi2Fe4O9 and FeMnO3 were identified in this system. In this ternary system, there were seven three-phase regions and no ternary compounds were observed.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > The Ⅶ group metal elements and their compounds
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