Mössbauer Spectroscopic Study of R ₃ Fe _29–x Cr _x and R ₃ Fe _29—x Cr _x H _y (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

Magnetic and Mössbauer spectral studies of R3Fe29−Mo compounds (R = Y, Nd, Sm, Gd, Tb, and Dy)

“…A positive correlation between the transferred hyperfine field and the effective spin can be clearly seen, indicating that there exists a significant spin polarization induced by neighboring rare earths. The anomalously high value of the transferred hyperfine field for Sm 3 Fe 28.0 Mo 1.0 may be due to admixture with the Sm 3+ ion J = 7/2 excited state [18].…”

“…The large number of fitting parameters can be drastically reduced by finding a minimum number of magnetic sextets, needed to reproduce the most obvious features of the spectra. This simplified procedure used by Nagamine et al [16,18] proved to be appropriate to obtain reliable values for the average hyperfine fields in R 3 (Fe,V) 29 and R 3 (Fe,Cr) 29 (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) compounds. The authors found that for the R 3 Fe 29−x V x compounds, with small V content (from 0.6 up to 2.3 atoms/f.u.)…”

“…In contrast, for the R 3 Fe 29−x Cr x compounds, with a high content of Cr (from 1.0 up to 5.0 atoms/f.u.) [18] five sextets have been used to fit the Mössbauer spectra. In the present work the smallest number of magnetic sextets, capable of yielding a satisfactory least-squares fit of the Mössbauer spectra, proved to be four in all studied R 3 Fe 29−x Mo x compounds, with a very low content of Mo (from 0.5 up to 1.2 atoms/f.u.).…”

“…As an empirical guide-line, it is often assumed that larger Fe magnetic moments, hence larger hyperfine fields, correspond to larger numbers of nearestneighbor (NN) Fe atoms and/or to larger average Fe Fe bond lengths. A very useful tool in establishing the number [23] and Nagamine et al [16,18]. The relevant quantities for these four groups of Fe sites, including the calculated fractional Fe occupancy are given in Table 4.…”

“…It has also been found that introduction of the interstitial N, H, or C atoms leads to remarkable improvements of the magnetic properties including Curie temperature, the saturation magnetization, and the magnetic anisotropy [7,8]. The hyperfine interactions at R and Fe atoms in R 3 (Fe,Ti) 29 , R 3 (Fe,V) 29 , and R 3 (Fe,Cr) 29 were investigated [8][9][10][11][12][13][14][15][16][17][18] at various temperatures. The only 57 Fe Mössbauer study on magnetically aligned powder samples of Nd 3 (Fe,Mo) 29 [19] have been intended to confirm that a spin reorietation takes place between 250 and 300 K. In order to understand the magnetic structure and intrinsic magnetic properties of these compounds, a systematic study on the role of the different rare earth elements in a series of similar compounds is definitely necessary.…”