R-Fe compounds

Figure 1 displays the plots of the TCATC/G quantity as a function of ATC derived from our experimental results for the R2Fei4B compounds and their hydrides. The data for the lutetium compounds (TCo = 535 K for Lu2Fei4B and Tco = 620 K for Lu2Fe14BH2 5) have been adopted as a TCo- It is known that the 4f electron shell of the Lu3+ (4f14) - ion has no magnetic moment. Therefore, in our case, the Lu compound models the iron sublattice magnetization for the whole series of R-Fe compounds under consideration. 

From the band model point of view one can expect an essential variation of Oq under pressure in ferromagnets where 3d subbands of opposite spin directions are not full (Buschow et al. 1977). Such a situation is realized in R-Fe compounds where large values of 9 In o /dP are observed experimentally for YgFe23, YFe3, YFe2 and CeFe2 with exclusion of Y2Fei7 (see table 8). On the contrary in R-Co compounds the 3d band of one spin direction is full and this should correspond to the small variation of Oq. Unfortunately, experimental data on 9 In Oo/9P in R-Co compounds are not available. 

The dimeric dialkoxy-bridged compounds [L2FeOR]2 (L = enolate of acac or dipivaloylmethane R = Me, Et, or Pr ) have been prepared by the oxidation of Fe compounds in alcoholic solutions containing the free ligand and base or directly from Fe compounds. The structure (57) is proposed. ... 

The purpose of the work is to study the effects associated with the influence of interstitial hydrogen on the exchange interactions (Fe-Fe, R-Fe, R-R) in ferrimagnetic R2Fei4B compounds (R = Gd, Tb, Dy, Ho and Er). 

On the other hand, the hydrogenation causes the weakening of R-Fe exchange interactions for Gd, Tb and Dy compounds the R-Fe exchange interactions are virtually unchanged for compounds with Ho and Er. 

Furthermore, the insertion of hydrogen atoms doesn t practically change the intersublattice exchange interactions in R2Fei4B compounds. To explain this result a number of factors should be taken into account (i) the volume effect under the hydrogen atoms incorporation, which increases the Fe-Fe and R-Fe interatomic distances, (ii) the enhancement of magnetism of the iron sublattice, (iii) the elastic... 

Thus, we established that incorporation of hydrogen atoms into the crystal lattice of R2Fe14B compounds leads to a substantial increase of the Curie temperature Tc, and to enhancement of the Fe-Fe exchange interactions. The R-Fe and R-R exchange interactions remain unchanged. Some of these phenomena can be explained as a result of the unit cell volume and an electronic structure of the compounds changes. 

From the microwave studies of different substituted ferrocene compounds, correlations between properties of the substituents and structural changes were established. It was noted that the carbon-iron bond distance in -qS CsHs-Fe is much more sensitive to substitution on the cyclopentadienyl ligand than the C-C bond distances of the C5H5 ring. This is summarized in Table 2. A linear correlation of the gas phase structural parameter r(Fe-Cp) and the electronegativity of the... 

A (T-allyl complex is formed from allylmagnesium halide and (> -Cp)Fe(COXPPh3)Br in 90% yield this compound liberates PPh3 when heated, affording the r/ -allyl compound in quantitative yield ... 

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