EXAFS study of Mn1.28Fe0.67P0.46Si0.54 compound with first-order phase transition

The Fe2P-type MnFe(P,Si) compounds are investigated by means of magnetic measurements and X-ray absorption fine structure spectroscopy. Magnetic measurements show that the Mn1.28Fe0.67P0.46Si0.54 compound undergoes a first-order phase transition at the Curie temperature of 254 K. The Fe K-edge and Mn K-edge X-ray absorption fine structure spectra show that Mn atom mainly located at the 3g sites, while the 3f sites are occupied by Fe atoms and Mn atom randomly. The distances between the Fe atom and its nearest neighbor atoms in a triangle Fe-Mn-Fe change from 2.80 Å at 25 K to 2.74 Å at 300 K. On the other hand, the distances between Fe atom and its second neighbor atoms change from 4.06 Å at 25 K to 4.02 Å at 300 K.