A Mössbauer spectral study of theYCo4−xFexB compounds

Abstract

The Mössbauer spectra of the YCo4−xFexB compounds, where x is 1, 2 and 3, have been measured at 78 and 295 K and reveal relatively small ironhyperfine fields of about 15 T, relatively large quadrupole interactions of about+1.0 and−1.0 mm s−1 and very differentspectra for YCo3FeB and YCo2Fe2B ascompared with YCoFe3B. As a consequence, the spectra have been fitted with a full Hamiltonianby adjusting the hyperfine parameters of the iron 2c and 6i sites foundin these compounds. The fits have used an asymmetry parameter,η, and Eulerangles, θ and ϕ, that relate the hyperfine field to the iron electric field gradient axes of each iron site in anorientation that is consistent with the structural and magnetic properties of the site. Thefits indicate that the relative areas of the spectral components assigned to the two iron 2cand 6i sites are in agreement with the iron occupancy of the sites as determined by neutrondiffraction. The results of the fits also indicate both that the full Hamiltonian approach isrequired for physically reasonable spectral fits and that the small observed fieldsresult from the presence of large orbital contributions which subtract from theFermi contact contributions to the magnetic hyperfine fields of the two sites.