A Structural, Magnetic, and Mössbauer Spectral Study of the TbCo₄₋ₓFeₓB Compounds with X=0, 1, and 2
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The TbCo4−xFexB compounds with x=0, 1, and 2 have been investigated by x-ray and neutron 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 of approximately 250 K in the Curie temperature; the 4.2 K magnetization decreases continuously with increasing iron content. The powder neutron diffraction patterns and the Mössbauer spectra of the TbCo4−xFexB compounds reveal a strong preferential substitution of iron for cobalt on the 2c site, small transition metal magnetic moments of approximately 1.7µB, and small iron hyperfine fields of approximately 16 T. The compensation temperature of the TbCo4−xFexB compounds decreases continuously from 400 to 350 K between x=0 and 2 as the result of an iron induced increase in the transition metal magnetization. The magnetic moment and hyperfine field are found to be larger on the 2c site than on the 6i site, a difference that reflects the strong hybridization of the 3d orbitals of the 6i site transition metal with the boron 2p orbitals.