Magnetic properties and colossal magnetoresistance of La0.67Ca0.33Mn0.99Fe0.01O3 materials

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Polycrystalline perovskite with composition La0.67Ca0.33Mn0.99Fe0.01O3 has been produced by a metal- salt routed sol-gel processing method. Colossal magnetoresistance of La0.67Ca0.33Mn0.99Fe0.01O3 has been studied with x-ray diffraction, Rutherford back-scattering spectroscopy, Möossbauer spectroscopy and vibrating sample magnetometer. Crystalline La0.67Ca0.33Mn0.99Fe0.01O3 was perovskite cubic structure with a lattice parameter a0=3.868 Å. Mössbauer spectra of La0.67Ca0.33Mn0.99Fe0.01O3 have been at various temperature ranging from 4.2 K to room temperature. Analysis of 57Fe Mössbauer data in terms of the local configurations of Mn atoms has permitted the influence of the magnetic hyperfine interactions to be monitored. The values of the isomer shifts show that all iron ions are in the Fe3+ state. For magnetic fields > 8 kOe and T < 100 K the magnetic moment is saturated at the value is 85 emu/g. The Curie temperature, Tc, is determined to be 270 K. The doping of 57Fe reduces Curie temperature and saturation magnetization. The temperature dependence of the resistance for La0.67Ca0.33Mn0.99Fe0.01O3 under zero and 10kOe applied field is shown that a semiconductor-metal transition, TSC-M, occurs at 250 K. The relative magnetoresistance, MR, defined as : [R(0) -R(H)]/ R(H), is about 33 %.
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