Compounds band magnetism

The problem could be stated from another point of view. In an isostructural series the uranium and neptunium compounds tend to be itinerant electron magnets or band magnets (like iron) and their orbital contribution is at least partially quenched. For much heavier actinides we know that the compounds will make local moment magnets with orbital contributions. It is quite possible that in between these two clear cut forms of magnetism that the intermediate case could be dominated by fluctuations, and no recognizable form of magnetism would occur. To state that the... 

Compound Band gap (eV) Ref. Magnetic susceptibility ref Curie point (°C) Ref... 

The Stoner product of UN (see Chaps. A and D) is greater than one, in agreement with the antiferromagnetic behaviour of this solid. The antiferromagnetism was attributed to itinerant band magnetism (as in some d-metals and compounds but unlike light actinide metals). In fact, cohesive properties of this solid have been well explained in a pure spin-polarised picture and Fournier et al. have shown that the magnetic uranium sublattice moment and the Neel temperature have a similar pressure dependence. Discrepancies existed, however, between calculations and experiments ... 

The effects of an external pressure on the magnetic moment at 4.2 K and on Tc were found to be large and negative (Franse 1983) and to become larger with decreasing Fe content (table 2.2). The results are in accordance with the predictions of the SEW theory (Wohlfarth 1968,1981) which suggests that these compounds can be treated within the framework of band magnetism. 

A more complex magnetic behaviour is expected for RI compounds in which the second component is a 3d transition metal such as Mn, Fe, or Co. The magnetic behaviour of the transition metal component is now based on the magnetic polarization of the electronic d-bands. Consequently, in this section we summarize the theory of itinerant or band magnetism and its application to transport properties. We begin with the Stoner-Wohlfarth model and include a summary of recent works. 

The R-M systems, where M is a 3d transition metal, form an outstanding tool for the study of 3d band magnetism and in particular the interactions, instabilities and anisotropies of such magnetism. In the majority of cases, for a given M element, a series of compounds with different rare earths crystallize in the same crystallographic structure and thus have practically the same band structure. It is then possible to study the 3d magnetism under... 

Other physical methods were also applied to the elucidation of the isomerism of diazocyanides, e. g., determination of diamagnetic susceptibility, the Faraday effect (optical rotation in a magnetic field), and electronic and infrared spectra. Hantzsch and Schulze measured ultraviolet spectra at a remarkably early date (1895 a). Unfortunately, their results and later work (Le Fevre and Wilson, 1949 Freeman and Le Fevre, 1950) did not allow unambiguous conclusions, except perhaps the observation that the molar extinction coefficients of the band at lowest frequency are consistently larger in all types of (i -compounds Ar — N2 - X than in the corresponding (Z)-iso-mers (Zollinger, 1961, p. 62). 

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