A structural, magnetic, and Mossbauer spectral study of the DyCo_(4-x)Fe_xB compounds, with x=0-3

摘要

The DyCo_(4-x)Fe_xB compounds, with x=0, 1, 1.5, 2, 2.5, and 3, have been investigated by x-ray diffraction, magnetic measurements, and iron-57 Mossbauer 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 4.2 K magnetization decreases with increasing iron content. The Mossbauer spectra of the DyCo_(4-x)Fe_xB compounds with x=1, 1.5, and 2 reveal rather small iron hyperfine fields of approximately 16 T and large quadrupole interactions of +1.0 and -1.0 mm/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 DyCo_3FeB 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 DyCo_4B and DyCo_3FeB and smaller increases are observed for x > 1. The compensation temperature of the DyCo_(4-x)Fe_xB compounds decreases from 350 to 270 K between x=0 and 3, respectively, as a result of the iron induced increase in the transition metal magnetization.