Fe sublattice

This formalism has been applied to quasi-ternary oxides (glasses) [A. R. Cooper (1974)]. Often, the transport problem can be simplified by structural restrictions. For example, in the system Fe-Si-C, carbon is found in the interstitial sublattice only. Therefore, in the Fe sublattice, one has yFc + jSi = 0. Details of simplified evaluations can be found in [H. Schmalzried (1981) J.S. Kirkaldy, D. J. Young (1987)]. 

According to a two-sublattice mean field model, the EMD of inter-metallic compounds is determined by the competition between the EMDs of the rare earth sublattice and the transition metal sublattice. In the Th2Zn]7-type crystal lattice, the Sm sublattice prefers c-axis anisotropy to others because of the positive Stevens factor (aj) of Sm, and the Fe sublattice contributes to the c-plane anisotropy. Both Co and carbon in Sm2(Fe1 xCox)17C>. help to enhance the contribution of the Sm sublattice dominant to the EMD, but the effect of carbon is larger than that of Co. 

The obvious merit of Eq. (9) is the explicit dependence of the Curie temperature on the de Gennes factor and the possibility to estimate the exchange field h2 from the Fe sublattice acting on the rare-earth ions. 

The spin-reorientation transition in Er2Fei4B compound can be attributed to the competing of the uniaxial Fe sublattice and the planar rare-earth sublattice anisotropy, with the former being dominant at higher temperatures and the latter being dominant at lower ones. 

R2Fe14B is their magnetocrystalline anisotropy. It was shown by several authors that the Fe sublattice magnetization has its preferred direction parallel to the c-axis while the Co sublattice magnetization prefers a direction perpendicular to the c-axis... 

The SPD technique proved useful in particular for studying the temperature dependence of HA over an extended temperature range below Tc. Results of Grossinger et al. (1986a) are shown in fig. 17. It follows from their data and also from those published by Hirosawa et al. (1986) that the temperature dependences of Ha for the rare earth and Fe sublattices behave in opposite directions. Whereas HA decreases with T in the former, it increases in the latter. By contrast, Hirosawa et al. (1987) found that in compounds of the type R2Co14B the anisotropy in both the 4f and the 3d sublattice decreases with increasing temperature. 

Crystallographic and magnetic data of some selected ternary R-Fe-B compounds. Top part stable compounds. Bottom part metastable compounds. For more details, see main text. The lattice constant c of R1+EFe4B4 refers to the R-sublattice, the corresponding value of the Fe sublattice is given between parentheses, the quantity e for each compound can be obtained by using the relation e = cFe/cR — 1. 

Fig. 52. Schematic representation of the temperature dependence of the magnetization (M) and coercive force in amorphous alloys of the approximate composition Gd02Fe08. The orientations and relative magnitudes of the Gd and Fe sublattice magnetizations are indicated by arrows.

The experimental value of the saturation magnetisation at room temperature for practically the whole family of compounds R2Fci4B (R = rare earth) can be explained on the basis of a ferromagnetic coupling between both Fe sublattices and the rare-earth sublattice. Some corn-... 

Coehoorn (1991) used a similar method to calculate electronic structures of rare-earth-transition-metal compounds. Figure 4b shows schematic representations of his calculation of the dependence of the average magnetic moment on cell volume in bcc-Fe and Y2Fei7. In the case of yttrium-iron compounds, we can estimate the volume dependence of the magnetic properties of the Fe sublattice because of the lack of 4f electrons at rare-earth sites. The cross denotes the moment at the equihbrium volume. 

The discussion in this subsection will be based on the band structure of the lanthanide-transition-metal compounds as shown schematically in figs. la,b. If we think about the effect of the anisotropy of the inner 4f electrons of flie lanthanides (Sm or Nd) on the Fe sublattices, the 4f electrons should initially transfer their characteristics to 5d, 6s and 6p band electrons of the lanthanide atom, which in turn will transfer the information to 4s, 4p and 3d electrons of the Fe atoms, finally affecting the magnetic properties, for example the crystalline anisotropy, of the entire crystal. 

The variation in the spectra from different lanthanide elements corresponds to the difference in the polarization of the 4p-conduction bands of Fe in the structures. The authors treated the spectra by subtracting the spectrum of the Y2Fei4B compound [which should correspond to the direct contribution from only the Fe sublattice] from the observed... 

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