A Mössbauer study of Fe 2P 1- xSi x ( x ≤ 0.35)

A crystallographic hexagonal/orthorhombic transformation is observed in partially Si-substituted Fe ₂P. The transformation temperature dependence is shown to increase linearly with increasing {P}/{Si} substitution. The paramagnetic/ferromagnetic transition temperature is also found to increase with increasing substitution, e.g., T_c = 216 K for x = 0 and T_c = 660 K for x = 0.35. In the hexagonal phase the {P}/{Si} substitution is shown to be close to random with respect to the two phosphorus sites. It has been possible from the ⁵⁷Fe Mössbauer spectra to distinguish between iron sites having zero or one silicon nearest neighbor at either of the phosphorus sites. In the orthorhombic phase, the Mössbauer spectra were very complex and since complete crystal data are not yet available, only limited information can be drawn from these spectra.