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The structural and physical properties of nickel-diluted Tb 0.27 Dy 0.73 ( Fe 0.7 − x Ni x Co 0.3 ) 2 intermetallics were studied by X-ray diffraction, four-probe dc electrical measurements and standard strain gauge method. X-ray analysis shows that all samples crystallize in a cubic Laves structure. The lattice parameter decreases linearly with the nickel content. Electrical resistivity was measured in a temperature range of 15–1100 K. The parameters involved in the dependence of resistivity on temperature and composition were determined. Residual, phonon and magnetic resistivity were separated from the electrical resistivity using both the Matthiessen and Bloch-Grüneisen formulas. The compounds’ Curie temperatures, which decrease nonlinearly with x , were obtained from the magnetic resistivity curves. The maximum values of magnetostriction attained for the Tb 0.27 Dy 0.73 ( Fe 0.6 Ni 0.1 Co 0.3 ) 2 compound exceed about 851 ppm. Electronic 3d-band structure and magnetic moment calculations were performed using the Full-Potential Linearized Augmented Plane Waves method. The distribution function for the densities of 3d-states was used to characterise the transition metal subbands. [ABSTRACT FROM AUTHOR]

The synthesis of materials and the studies of crystal structure and Fe Mössbauer effect were performed for TbDy(FeCo) intermetallics. Terfenol-D (TbDyFe) is the starting compound of this Fe/Co-substituted series. X-ray measurements showed evidence of a pure cubic Laves phase C15, MgCu-type, and unit cell parameters were determined across the series. A Co substitution introduced local area, at sub-nanoscale, with random Fe/Co neighbourhoods of the Fe atoms. Mössbauer effect spectra for the TbDy(FeCo) series at room temperature are composed of a number of locally originated subspectra due to the random distribution of Fe and Co atoms in the transition metal sublattice, and due to [1 1 1] an easy axis of magnetization. Isomer shift, magnetic hyperfine field and quadrupole interaction parameter were obtained from the spectra, both for the local area and for the bulk sample. As a result of Fe/Co substitution, a Slater-Pauling-type curve for the average magnetic hyperfine field vs. Co content was observed. It was found that the magnetic hyperfine fields corresponding to the local area also create a dependence of the Slater-Pauling-type vs. Co contribution in the Fe/Co neighbourhoods. [ABSTRACT FROM AUTHOR]

Abstract: The after-effects of Fe/Co substitution in the intermetallic series , with a starting compound known as Terfenol-D, were studied. Co substitution introduces a local area, at sub-nanoscale, with random Fe/Co neighbourhoods of the atoms. Mössbauer effect measurements for the intermetallic system carried out at 4.2K evidence an easy axis of magnetization. Hyperfine interaction parameters: isomer shift, a magnetic hyperfine field and a quadrupole interaction parameter were obtained from the fitting procedure of the spectra, both for the local area and for the sample as bulk. As a result of Fe/Co substitution, a Slater–Pauling type curve for the average magnetic hyperfine field vs. Co content is observed. It is found that the magnetic hyperfine fields corresponding to the local area sorted out against Co contribution in the Fe/Co neighbourhoods also create a dependence similar to a Slater–Pauling type curve. Band structure calculations using the Full-Potential Linearized Augmented Plane Waves (FLAPW) method were performed. The experimentally determined magnetic hyperfine field correlates linearly with the weighted magnetic moment calculated per transition metal atom. [Copyright &y& Elsevier]