Mossbauer effect and electrical properties studies of SmFexMn1-xO3 (x=0.7, 0.8 and 0.9)

The cation distributions in the B-site of the orthoferrites SmFexMn1-xO3 (x = 0.7, 0.8, 0.9) were studied by Fe-57 Mossbauer spectroscopy at room temperature. The spectra showed several nonequivalent sites of the iron ions. Five sextets were used in the fitting of the experimentally observed spectra and each one corresponds to different number of the Fe ions in the next nearest neighboring. A nonrandom cation distribution model in such compounds was proposed to interpret the multi-sextets spectra. According to the electric properties measurements, it was noted that the conductivity increases two times with increasing the Mn content but the activation energy decreases from 0.34 eV down to 0.22 eV The sample with x = 0.7 is an electron semiconductor while the other samples display hole conduction. The magnetoresistance MR of the studied samples value is of 10% and has a negative sign at room temperature while a positive sign is obtained with temperature raising. (C) 2004 Elsevier B.V. All rights reserved.