Magnetic and Mössbauer spectral studies of R 3Fe 29− x Mo x compounds (R = Y, Nd, Sm, Gd, Tb, and Dy (original) (raw)
The investigation of the structure, magnetic and Mössbauer properties for the series of R 3 (Fe,Mo) 29 compounds has been performed, where R = Y, Nd, Sm, Gd, Tb, and Dy. The crystallographic structure of the ternary phase compounds has been investigated by Rietveld refinement of the X-ray diffraction patterns obtained at room temperature. The quality of the single-phase compounds was also checked by thermomagnetic measurements, from room temperature to above the Curie temperatures. From the magnetic isotherms for the free powder samples, measured at 4.2 K, the saturation magnetizations and the iron average magnetic moments have been derived. 57 Fe Mössbauer spectra of the R 3 (Fe,Mo) 29 compounds have been measured at 15 K. The analysis of spectra, in a model which takes into account both the Fe atom nearest neighbor numbers and the Fe Fe nearest neighbor bond lengths, indicates that the transferred contribution to the hyperfine field at the iron sites, due to rare earth moments, can be correlated with the rare earth effective spin.
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Magnetic and Mössbauer spectral studies of R3Fe29−Mo compounds (R = Y, Nd, Sm, Gd, Tb, and Dy)
Journal of Alloys and Compounds, 2005
The investigation of the structure, magnetic and Mössbauer properties for the series of R 3 (Fe,Mo) 29 compounds has been performed, where R = Y, Nd, Sm, Gd, Tb, and Dy. The crystallographic structure of the ternary phase compounds has been investigated by Rietveld refinement of the X-ray diffraction patterns obtained at room temperature. The quality of the single-phase compounds was also checked by thermomagnetic measurements, from room temperature to above the Curie temperatures. From the magnetic isotherms for the free powder samples, measured at 4.2 K, the saturation magnetizations and the iron average magnetic moments have been derived. 57 Fe Mössbauer spectra of the R 3 (Fe,Mo) 29 compounds have been measured at 15 K. The analysis of spectra, in a model which takes into account both the Fe atom nearest neighbor numbers and the Fe Fe nearest neighbor bond lengths, indicates that the transferred contribution to the hyperfine field at the iron sites, due to rare earth moments, can be correlated with the rare earth effective spin.
Journal of Alloys and Compounds, 2006
The study of the effect of Co substitution on the structural and magnetic properties of R 3 (Fe 1−x Co x) 29−y M y (R = Y, Nd, Tb, Dy; M = Ti, V, Cr, Mn; 0 ≤ x ≤ 1; y = 0.9-7.0) is presented. For the compounds with low Co content (0 ≤ x ≤ 0.4) the unit cell volume is decreasing as the Co content increases. 57 Fe Mössbauer spectroscopy has shown that the Co atoms avoid the dumb-bell sites. The Curie temperature values, T C , increase monotonically with x. For the compounds with high Co and low M content (0.6 ≤ x ≤ 1 and y = 1.6) the situation is rather different. Starting with the 3:29 stoichiometry a disordered variant of the hexagonal Th 2 Ni 17-type structure is formed. In Y 3 (Fe 1−x Co x) 29−y Cr y the monoclinic 3:29 structure is retained if the amount of the stabilizing element is increased. The T C values of the compounds are reduced; this should be attributed to the larger Cr content. The same behavior is observed in the case of Nd based products with 0.6 ≤ x ≤ 1 stabilized by Cr or Mn.
A Mössbauer study of R6Fe13X (R=Pr, Nd; X=In, Sn, Tl, Pb, Cu, Ag, Au)
Hyperfine Interactions, 1994
Compounds with the composition R6Fet3X (R = Pr, Nd; X = In, Sn, TI, Pb, Cu, Ag, Au) were studied by 57Fe MOssbauer spectroscopy. Attention was focused on the influence of the easy axis of the magnetization on the shape of the hyperfine patterns. The spectra are composed of at least four subpatterns, originating from the different Fe lattice sites. Contrary to the magnetization, a significant dependence of the hyperfine parameters on the specific elements R and X could not be detected. Predominantly, the easy axis of the magnetization was found to lie within the basal plane; only for R = Nd and X = In, Sn, T1, Pb is an easy c-axis present. Since the low temperature magnetization data obtained for the different compounds show a wide spread, while the 57Fe hyperfine fields remain almost constant over the whole series, some kind of antiferromagnetic ordering within the Fe sublattice is anticipated.
Magnetic properties, Mössbauer, and specific-heat studies ofRBa2Fe3O8(R=Y,Eu) compounds
Physical Review B, 1993
Complete replacement of Cu by Fe in RBa2Cu307 leads to R Ba2Fe308 (R = Y and Eu). We investigated YBa&Fe308 and EuBa2Fe308 by several complementary experimental techniques. These compounds crystallize in a tetragonal structure with the configuration of the atoms in the unit cell very similar to that in the superconductor YBa2Cu307. Magnetic-susceptibility and Mossbauer-spectroscopy measurements of ' Fe and "'Eu in R Ba2Fe308 (R = Y and Eu) at temperatures from 4.2 to 800 K have been performed. In both compounds the iron moments order antiferromagnetically at the same Neel temperature T&-700 K. In YBa2Fe30, the Mossbauer spectra reveal two inequivalent iron sites, probably corresponding to iron in the Fe(2) site (fivefold oxygen coordination) and in the Fe(1) site (distorted octahedral oxygen coordination). The quadrupole splitting of Fe(2) is zero. Specific-heat (C~) measurements at different magnetic fields have been carried out between 1.5 and 30 K. The C~(T, H) curves can be resolved into a contribution of the form C, (T) =y*T with finite y* and a lattice contribution that consists of Debye terms. The pronounced high @*=10. 5 mJ/mol K for YBa&Fe30, is discussed.
physica status solidi (a), 2002
R 2 Fe 17 (R ¼ rare earth) intermetallic compounds constitute one of the most important classes of materials identified as high-energy permanent magnet materials. They crystallize either in the rhombohedral Th 2 Zn 17 structure (for light R) or in the hexagonal Th 2 Ni 17 structure (for heavy R). In this article, we discuss the variations in the lattice parameters (unit cell volume), site occupancies and Curie temperature when non-transition and transition metals are substituted for Fe in R 2 Fe 17 compounds.
Nukleonika
Two isostructural series of polycrystalline compounds: Er 2−x Y x Fe 14 B and Er 2−x Ce x Fe 14 B have been studied by 57 Fe Mössbauer spectroscopy in the temperature range 80−370 K. The spin reorientation phenomenon (a transition from basal plane to axial easy magnetisation direction) has been studied extensively by a narrow step temperature scanning in the vicinity of the transition. Using the procedure of subtracting the Mössbauer spectra taken for the same compound at different temperatures, it was possible to follow the influence of transition on the shape of spectra. From this procedure it was concluded that in the region of transition each subspectrum splits into two Zeeman sextets, which are characterised by different hyperfine magnetic fields and quadrupole splittings. The consistent way of describing the Mössbauer spectra was proposed. The spin reorientation temperatures have been established for all compositions and compared with the values obtained from theoretical calculations of spin orientation angle based on phenomenological model. The spin arrangement diagrams have been constructed.
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