Magnetic properties and Mössbauer effect in R5Fe18B18 (R1+ϵFe4B4) (original) (raw)
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57Fe Mössbauer and magnetic studies of RFe4B (R = Tm, Er) alloys
Journal of Magnetism and Magnetic Materials, 1988
Magnetic and Mossbauer measurements have been carried out in the borides (RF%B (R = Er, Tm), which have the hexagonal CeCo,B-type structure with an interchange of sites between Fe and B. Powder X-ray diffraction diagrams were indexed with the space group P6/mmm. Magnetization studies in the temperature range from 4.2 to 700 K reveal the presence of compensation temperatures arising from the antiferromagnetic coupling between the Fe and R sublattices. There was no indication of spin reorientation for both Mossbauer and magnetic measurements. Miissbauer spectra were analysed with a program which assumes binomial distributions of the B atoms. Independent occupancy probabilities for the i and (c, d)-sites of the CeCo,B-type structure were determined by this analysis.
57Fe and 166Er Mössbauer and magnetic studies of RFe4B (R= Er, Tm, Lu) compounds* 1
Journal of magnetism …, 1985
Magnetic and MOssbauer studies have been carried out on a series of ternary borides RFe4B (R = Er, Tm, Lu) which have the hexagonal C¢Co4B type structure. These compounds are found to be magnetically ordered at room temperature. Magnetization studies in the temperature range from 5 to 300 K reveal the presence of compensation temperatures in Er and Tm compounds and indicate antiferromagnetic coupling between the rare earth and Fe moments. Room temperature S7Fe M~Ssshaner studies yield values of hyperfine fields at the two Fe sites as 246 and 185 kOe in ErFe4B and TmFe4B, and 204 and 145 kOe in LuFe4B. The 16~Er MOssbauer studies give nearly free-ion hyperfine field at the Er sites which indicates that the exchange interaction in ErFe4B is much stronger than crystal field interaction.
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.
Mössbauer spectroscopy in modern permanent magnet alloys
Hyperfine Interactions, 1989
Intermetallic compounds involving the rare earths and a transition metal, especially iron, arousedgreat interest in the past twenty five years with particular attention been paid to their magnetic properties, due to the fact that these compounds have been used as a permanent rhagnet materials. Their study using different techniques has given new information about the mechanisms of the magnetic interactions, which are present in these compounds. Among them M'Xossbauer Spectroscopy (MS) has been proven to be an indispensable tool, due to the fact that information can be obtained either from the spectra of the iron sublattice or from the spectra of the rare earth sublattice. Thus information on local moments, crystal field effects, single ion anisotropy and exchange interactions can be extracted from such spectra and compared with results from other techniques. Among the best alloys for permanent magnet applications are the ones based on the Nd2Fe14B type structure. Very interesting magnetic properties are also present in the recently discovered series of RFe12_xM x, where M = V, Ti, Mo, Si. We will review their intrinsic and extrinsic magnetic properties, as they have been measured using (MS) and correlate them with the findings from other techniques.
Physica B+C, 1985
Commercially procured rare earth metals frequently contain 2-5 atomic per cent oxygen. Rare earth intermetallic compounds prepared from these materials with compositions estimated by synthesis can significantly deviate from the intended composition. Several R2Fe,aB systems have been synthesized using rare earth metals obtained from the Ames Laboratory which typically contain < 25 ppm oxygen (by weight) and their fundamental magnetic properties determined. Curie temperatures range from 565 (for Y2Fet4B) to 669 K (for Gd2Fe,4B). Anisotropy fields (2(1 C) range from 27 to 71 kOe. Results for Y~Fe,4B and Gd2Fe,4B suggest that about 40% of the anisotropy in Nd2Fe,4B originates with the Fe sublattice. The Fe moment in these systems exceeds by a small margin that of elemental Fe. suggesting that B is acting as an electron donor. The Nd moment in Nd2Fe~4B is estimated as 3.0 p.,, which is 92% of the free ion moment. The Nd-Fe and Gd-Fe couplings are ferromagnetic and antiferromagnetic, respectively. Coupling for these systems conforms to the systematics observed earlier for simpler rare earth intermetallics.
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.