A structural, magnetic, and Mössbauer spectral study of the DyCo4−xFexB compounds, with x=–3

Abstract

The DyCo4−xFexB compounds, with x=0, 1, 1.5, 2, 2.5, and 3, have been investigated by x-ray diffraction, magnetic measurements, and iron-57 Mössbauer spectroscopy. The substitution of cobalt by iron induces both an anisotropic increase in the unit-cell volume and a large increase in the Curie temperature. The 4.2K magnetization decreases with increasing iron content. The Mössbauer spectra of the DyCo4−xFexB compounds with x=1, 1.5, and 2 reveal rather small iron hyperfine fields of approximately 16T and large quadrupole interactions of +1.0 and −1.0mm∕s, for the 6i and 2c sites, respectively. The relative areas of the 6i and 2c spectral components indicate a strong preferential substitution of iron on the 2c site. In DyCo3FeB approximately 70% of the iron occupies the 2c site; a strong increase in the a lattice parameter and in the Curie temperature is observed between DyCo4B and DyCo3FeB and smaller increases are observed for x>1. The compensation temperature of the DyCo4−xFexB compounds decreases from 350to270K between x=0 and 3, respectively, as a result of the iron induced increase in the transition metal magnetization.