Crystal-field splittings criticized

A prediction of crystal field theory as outlined in the preceding subsections is that the crystal field splitting parameter, A, should be rather critically dependent upon the details of the crystal lattice in which the transition metal ion is found, and that the splittings of the /-orbital energies should become larger and quite complicated in lattices of symmetry lower than cubic. The theory could not be expected to apply, for example, to the spectra of transition metal ions in solution. 

It is the dialuminides for which there is the most direct Fermi surface data amongst the Laves phase materials dHvA measurements exist for CeAlj (Lonzarich 1988, Springford and Reinders 1988, Reinders and Springford 1989). The primary reason for interest in the dialuminides is that one may expect that there will be no direct f-f interaction and that the hybridization interactions will also be very weak lattice separations are well beyond the critical separation of the Hill plots and Al has no d orbitals to hybridize with the lanthanide or actinide f states. Consequently, heavy-lanthanide dialuminides have been studied as classic systems of crystal-field-split f states interacting through RKKY interactions. 

Critical temperature the temperature above which vapor cannot be liquefied, no matter what pressure is applied. (16.11) Crosslinking the existence of bonds between adjacent chains in a polymer, thus adding strength to the material. (22.5) Crystal field model a model used to explain the magnetism and colors of coordination complexes through the splitting of the d orbital energies. (20.6)... 

In an NMR investigation of the spectrum in TmV04, Bleaney and Wells (1980) found that the frequency of oscillation of the RF circuit containing the crystal was a sensitive monitor of variations in the RF (adiabatic) magnetic susceptibility Zs-Below To, where the ground doublet is split by the distortion, is independent of a field applied along the c-axis, until this reaches the critical field B at which the Jahn-Teller distortion is reduced to zero. At this field Zs falls sharply, and the effect can be used to give a precise measurement of B. The results were fitted accurately to the relation b = B /Bo = tanh(b/f), where t - T/T ) = T/2.156 is the reduced temperature. This is the result expected from mean-field theory. In the distorted state below T, the presence of domains with principal axes [110] and [110] was confirmed by observation of two sets of anisotropic resonance curves (see fig. 13c), one set for (/ —i) and the other for the enhanced NMR of Tm (/ = i). 

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