Mossbauer studies of CMR compound La0.67Ca0.33Mn0.9757Fe0.03O3

The perovskite (La0.67Ca0.33Mn0.97Fe0.03O3)-Fe-57 compound has been prepared by sol-gel method. Colossal magnetoresistance and magnetic properties of (La0.67Ca0.33Mn0.97Fe0.03O3)-Fe-57 has been studied using X-ray diffraction pattern, Rutherford back-scattering spectroscopy, Miissbauer spectroscopy and vibrating sample magnetometer. Crystalline (La0.67Ca0.33Mo0.97Fe0.03O3)-Fe-57 was a cubic perovskite structure with a lattice parameter a(0) = 3.859 Angstrom. Mossbauer spectra of (La0.67Ca0.33Mn0.97Fe0.03O3)-Fe-57 have been taken at various temperatures ranging from 4.2 K to room temperature. Analysis of Fe-57 Mossbauer spectrum data has considered nearest-neighbor interactions and anisotropic hyperfine field fluctuation. Analysis of Fe-57 Mossbauer data in terms of the local configurations of Mn atoms has permitted the influence of the magnetic hyperfine interaction to be monitored. The saturation magnetization of (La0.67Ca0.33Mn0.97Fe0.03O3)-Fe-57 is found to be 68 emu/g at 77 K. The Curie temperature, T-C, is determined to be 210 K. The temperature dependence of the resistance under zero and 10 kOe applied field shows that a semiconductor-metal transition, TSC-M, occurs at 200 K. The relative magnetoresistance, MR, is about 45%. (C) 2000 Elsevier Science B.V. All rights reserved.