期刊
JOURNAL OF APPLIED PHYSICS
卷 104, 期 10, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.3028264
关键词
antiferromagnetic materials; calcium compounds; charge-ordered states; electric impedance; equivalent circuits; ferromagnetic materials; ferromagnetic-antiferromagnetic transitions; ferromagnetic-paramagnetic transitions; grain boundaries; Jahn-Teller effect; lanthanum compounds; metal-insulator transition
Impedance spectroscopy has been employed to investigate the microscopic nature of the charge/orbital ordering (COO) in polycrystalline La0.50Ca0.50MnO3+delta sample at different temperatures. The modulations of relaxation time with temperatures show different behaviors of Z(') and Z('). An equivalent circuit model (R1C)(R(2)Q) has been employed to investigate the electrical parameters of La0.50Ca0.50MnO3+delta at different temperatures. The resistance of grain and grain boundaries shows maxima at metal-insulator (MI) transition temperature (approximate to 153 K). Three temperature zones have been identified. In the first temperature zone which has been from 85 to 140 K, below MI transition temperature, melting of COO with strong Jahn-Teller (JT) distortions has been reported. In the second zone, around MI transition temperature, melting and collapse of COO with weak JT distortion result in colossal drop in Z('). In the third temperature zone, above MI transition temperature, charge ordering (CO) around 203 K and onset of short range CO at 253 K have been determined.
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