CeSb compounds

In addition to the OP formalism, several alternative schemes have been suggested in the past to account, within a relativistic band-structure calculation, for correlation effects not incorporated within the local approximation to SDFT (LSDA). For example, the LDA+U scheme has been applied to the compound CeSb (Antropov et al. 1995), a system that has a maximum Kerr-rotation angle of 90° (Pittini et al. 

In conjunction with the reflectivity data obtained by Reim et al. for the compounds CeSb and CeTe these authors were able to derive the following picture of the electronic structure of these compounds in CeSb the 4f1- 5d transition... 

The Fermi surface of CeSb was thus calculated on the basis of p-f mixing theory, although it was not easy. This is because the Ce pnictides are semimetals and their energy band structures and Fermi surfaces are simple. In the usual Ce compounds where the 4f electrons are believed to be localized, it is difficult to carry out such calculations. Therefore, simplified calculations were carried out for such Ce compounds as CeAl2... 

As for an appropriate band theory for the localized 4f-electron system, an attractive approach based on the p-f mixing model was proposed, and was plied to CeSb. A future problem is to refine the approach so as to carry out quantitative calculations in a self-consistent way. The anomalously large enhancement factors for the cyclotron effective masses and the y values observed in the Ce compounds cannot be explained by band structure alone. Quantitative analysis of the mass enhancement factor is a problem challenging to many-body theory. There is still much room for improvement for a complete understanding of the electronic structures of lanthanide compoimds. 

Note the superficial similarities between the excitation spectra of CeSb, CeBi (fig. 16) and PuSb (fig. 25). On closer examination, however, it must be remembered that the Ce compounds are antiferromagnets so that a minimum at the X point ( =1) is anticipated. Furthermore, it is the mode that is transverse to the moment direction that has the minimum at X. a is smaller by a factor of 6 for the Ce compounds compared with PuSb, but the dispersion is similar, despite a factor of 4 in the ordering temperatures. Clearly, more experiments and theory are required before the complex polarization dependence of the excitations in such systems as UTe and PuSb are understood. 

Electrical resistivity measurements on CeSb and CeBi single crystals are displayed in fig. 123 (Suzuki et al. 1981). For CeSb a sharp decrease of p versus T is observed at Tn (16.5 K), indicating a first-order magnetic transition. A shallow minimum follows around 80 K. Subtracting Pph(T), determined from the isostructural LaSb compound, reveals that p g is proportional to — In T, which is typical for a Kondo lattice (Kasuya et al. 1982). The magnetic-field dependence of the electrical resistivity of CeSb at various temperatures is given in fig. 124. 

Unfortunately, in many compounds of interest the form factor exhibits considerably less anisotropy than the examples shown in figs. 6-8. The difficulty then is to be certain that the ground-state wavefunction can properly be represented in the jSLJ) basis. An early example is US, measured by Wedgwood (1972). No doubt to his disappointment, he measured a form factor that showed an almost steadily smooth decrease as a function of Q. A similar situation was found by Busch et al. (1979) in studies of the ferromagnets UTe and USbo,8Teo,2> and is also evident in the measurements on CeSb (Boucherle and Schweizer 1985) and CeTe (Boucherle et al. 1982a). In all these materials, particularly the uranium compounds, there is remarkably... 

Solid solutions can be found also for the cerium compounds, and Rossat-Mignod et al. (1985) have discussed the system CeSbi Te. A small amount off Te doping has a pronounced effect on the magnetism of CeSb. By 4% doping the complex ordering found in CeSb gives way to simple type I order and at higher concentra-... 

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