MAGNETISM AND CRYSTAL-STRUCTURE IN ORTHORHOMBIC FE2P - A THEORETICAL AND EXPERIMENTAL-STUDY

A theoretical and experimental study of the electronic and magnetic structure of Fe2P1-xSix is performed. A hexagonal-orthorhombic crystal structure transition occurs with increasing Si substitution. The latter crystal structure is extremely complex with six inequivalent Fe sites. The magnetic moments, as obtained by our electronic structure calculations, vary substantially between the different sites, from 0.71 mu(B) to 2.6 mu(B). The latter value is one of the largest Fe moments ever found. The estimated hyperfine fields are in fair agreement with Mossbauer data. For this compound it is found that the hyperfine field cannot be assumed to be proportional to the spin magnetic moment when the majority spin band is saturated. This is explained in terms of a hybridization mechanism between the Fe 3d and 4s states, which results in a 4s valence electron contribution that may be large and of either sign.