57Fe Mössbauer effect studies were performed for the cubic C15, Fd3m, MgCu2-type Dy(Co0.4-xNixFe0.6)2 intermetallics. Hyperfine interaction parameters : isomer shift, magnetic hyperfine field and quadrupole interaction parameter were obtained from the fitting procedure of the collected 57Fe Mössbauer effect spectra. As a result of Co/Ni substitution, a Slater-Pauling type curve for the average magnetic hyperfine field vs. Ni content in the Dy(Co0.4-xNixFe0.6)2 series is observed.
Synthesis of Ho(Fe1–xCox)2 intermetallic compounds, studies of their crystal structure and 57Fe Mössbauer effect analysis were carried out at 295 K. X-ray measurements evidence a pure cubic Fd3m, C15, MgCu2-type Laves phase. The unit cell parameter decreases non-linearly with composition parameter x. Mössbauer effect spectra for the Ho(Fe1–xCox)2 series were composed of a number of locally originated subspectra due to random Fe/Co nearest neighbourhoods. Hyperfine interaction parameters, i.e. isomer shift, the magnetic hyperfine field and a quadrupole interaction parameter were determined from the fitting procedure of the spectra, for both the individual nearest neighbourhoods, and for the sample as bulk. As a consequence of Fe/Co substitution a Slater-Pauling type curve for the average magnetic hyperfine field vs. x is observed. The correlation between the local magnetic hyperfine fields and the average magnetic hyperfine fields is related to weak and strong ferromagnetism of the transition metal sublattice.
The synthesis of materials, crystal structure and 57Fe Mössbauer effect studies at 77 K were performed for intermetallics Tb0.27Dy0.73(Fe1–xCox)2. The starting compound Tb0.27Dy0.73Fe2 of this Fe/Co substituted series is known as Terfenol-D. XRD measurements evidence a pure cubic Laves phase C15, MgCu2-type. The determined unit cell parameter decreases across the series. Co substitution introduces a local area, in the subnanoscale, with random Fe/Co neighbourhoods of the 57Fe atoms. Mössbauer effect spectra for the Tb0.27Dy0.73(Fe1–xCox)2 series collected at 77 K consist of a number of locally originated subspectra due to random composition of Fe and Co atoms in the nearest neighbourhood. Hyperfine interaction parameters: isomer shift, 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 in the Tb0.27Dy0.73(Fe1–xCox)2 series 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 the Slater-Pauling type curve.
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