A Moessbauer investigation of equiatomic FeCo with vanadium and niobium additions

The structure and magnetic properties of equiatomic Fe-Co alloys with ternary additions of up to 1.92 at% Nb and 6 at% V are studied by means of Moessbauer spectroscopy, complemented with light and electron microscopy and the determination of magnetisation curves, as function of heat treatment. The main features of the Moessbauer spectra, namely a Zeeman hyperfine pattern and a paramagnetic peak are discussed in terms of the number and the position of the ternary solute atoms in the ferromagnetic matrix, and the volume fraction of second phase, respectively. It is shown that the solubility of niobium in the matrix is considerably less than that of vanadium, and that vanadium occupies the iron sublattice of the B2 ordered matrix. The saturation magnetisation of the alloys is correlated with the volume fraction of the second phase and the average hyperfine field. (author)