Mössbauer effect studies of Tb0.27Dy0.73(Fe1−x Co x )2 intermetallics at 295 K

Abstract

The synthesis of materials and the studies of crystal structure and 57 Fe Mössbauer effect were performed for Tb0.27Dy0.73(Fe1−xCox)2 intermetallics. Terfenol-D (Tb 0.27Dy0.73Fe2) is the starting compound of this Fe/Co-substituted series. X-ray measurements showed evidence of a pure cubic Laves phase C15, MgCu2-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 57 Fe atoms.Mössbauer effect spectra for the Tb 0.27Dy0.73(Fe1−xCox)2 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.

Optimization on magnetic transitions and magnetostriction in TbxDyyNdz(Fe0.9Co0.1)1.93 compounds

“…We speculate the types of lattice distortion on the basis of the EMD obtained in the present work and previous M€ osbauer spectra results. 12,[22][23][24] With the increase of temperature, a peak is observed in the curve for x ¼ 0:00, corresponding to a spin reorientation taking place from h100i to h111i, which was confirmed by previous M€ osbauer spectra investigations. [22][23][24] The peak is slightly shifted to higher temperature with increasing x, and exceeds 300 K when x !…”

“…The compounds, lattice parameter a, Curie temperature T C , the absolute value of anisotropy constant jK 1 j (10 6 erg/cm 3 ), the saturation magnetization M s (emu/g), the magnetostriction at the field of 1 kOe k 1k (ppm), and the saturation magnetostriction k s (ppm) for (Tb 0.27 Dy 0.73 ) 1Àx (Tb 0.1 Nd 0.9 ) x (Fe 0.9 Co 0.1 ) 1.93 system along with the performance of Tb 0.20 Dy 0. 22 XRD pattern, small magnetostriction, even in the case of EMD along h111i, would lead to a tiny rhombohedral-type structure distortion and, consequently, resulting in the double split f440g lines overlap like a single peak in XRD patterns, which might be mistaken as EMD along h100i. Therefore, to further confirm the types of lattice distortion, the temperature dependence of ac initial susceptibility v ac (T) of the Laves phase Tb x Dy y Nd z (Fe 0.9 Co 0.1 ) 1.93 system between 50 K and 300 K was carried out, as is shown in Fig.…”

Hyperfine interactions in Ho(Fe1−xCox)2compounds at 77 K

“…The experimental data (figure 8) are covered with a fitted surface (small open points), described by the following numerical formula: The formula µ 0 H hf (x, S) can be useful for predicting the magnetic hyperfine field for new rare earth-transition metal compounds or even for new series of materials. [42] and Gd [43]. Small open circles, the numerical fitted surface.…”

“…Figure 8. Magnetic hyperfine fields µ 0 H hf as a function of the composition parameter x and as a function of rare earth ion spin S, for R(Fe 1−x Co x ) 2 compounds, where R = Ho, Tb 0.27 Dy 0.73[42] and Gd[43]. Small open circles, the numerical fitted surface.…”