Mössbauer and structural studies of Fe_0.7-xV _xSi_0.3 alloy system

X-ray diffraction patterns for Fe_0.7-xV_xSi _0.3, (x = 0, 0.05, 0.1, 0.15, 0.2, and 0.3) yield a single BCC-type phase for small values of x and a minor non-cubic phase starts to develop for large values of x. The lattice parameter is found increase with increasing vanadium concentration. Mössbauer experiments were made at room temperature and 20 K. Room temperature spectra show magnetic order for x = 0, 0.05, and 0.1, a central paramagnetic line of high intensity superimposed to the magnetically ordered component for x = 0.15, and a almost completely paramagnetic state for x = 0.2 and 0.3. A similar behavior prevails at 20 K, except that hyperfine splittings are larger and the magnetic ordering starts to show up for x = 0.2 and 0.3. In data analysis, each room-temperature and 20-K spectrum is fitted with a distribution of hyperfine sextets. The results clearly indicate the expected atomic disorder in the materials. The average magnetic hyperfine field is found to decrease with increasing x, reflecting the replacement of magnetic iron by non-magnetic vanadium. The average isomer shift shows the same vanadium-concentration dependence.