Mössbauer Studies of Perovskite La<sub>0.67</sub>Ca<sub>0.33</sub>Mn<sub>1-x</sub>Fe<sub>x</sub>O<sub>3</sub>

The perovskite of (La0.67Ca0.33Mn1-xFexO3)-Fe-57 (x = 0, 0.01, 0.03, and 0.05) compounds have been studied with Mossbauer spectroscopy, vibrating sample magnetometer (VSM), and x-ray diffractometer. The (La0.67Ca0.33Mn1-xFexO3)-Fe-57 powders have been prepared by sol-gel processing method. Mossbauer spectra of (La0.67Ca0.33Mn1-xFexO3)-Fe-57 powders have been taken at various temperatures ranging from 4.2 K to room temperature. The line width of each Lorentzian 6-line at 4.2 K was broaden in proportion as doped Fe-57 increased. 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 values of the isomer shifts show that all the iron ions are in the ferric (Fe3+) state. The temperature dependence of the resistance under zero and 10 kOe applied magnetic field shown that a semiconductor-metal transition temperature, TSC-M, decreased from 274 to 155 K in proportion as doped Fe-57 increased. The relative magnetoresistance (MR) of the (La0.67Ca0.33Mn0.97Fe0.03O3)-Fe-57 is about 45 % at the TSC-M = 210 K.