SITE OCCUPANCIES OF SI ATOMS AND CURIE TEMPERATURES FOR SM2FE17-XSIX

The system Sm2Fe17-xSix (x=0, 0.5, 1, 2, and 3) has been studied by Fe57 Mössbauer spectroscopy. The distributions of Fe and Si atoms over the four sites have been deduced by convolution of the Mössbauer spectra. The results show that Si atoms are excluded from the 9d site and prefer the 18f sites at all concentrations; Fe atoms preferentially occupy the 6c and 18h sites at low Si concentrations, but at x=3 the occupancy of the Si atoms increases rapidly. The Curie temperatures increase at first, then decrease with Si substitution; a maximum occurs at a Si concentration of x=2. The Curie temperature results are interpreted by a model that considers the competition between the positive and negative exchange interactions. © 1995 The American Physical Society.