Paramagnetic behaviour

The experimental results will be considered first of all. Comparing the values for K, found in the Zintl phases with the ones in the pure metals one notices that the AB phases show a normal paramagnetic behaviour. For the AB compounds K, is distinctly smaller than in the case of pure metals. Kj is even negative for NaTl. 

This picture is confirmed by the paramagnetism behaviour. In the simplest case,the tight binding model,we can calculate from xp the integral transfer valued) t = 0.020 eV which is of the correct order of magnitu8e. 

In cases where the hybridization is stronger, it leads to the formation of a relatively broad 5f band. Such compounds display a weakly paramagnetic behaviour. In some cases the impact of the stronger hybridization can be followed step by step. For instance, when substituting Ni for Cu in UCu5, the disappearance of the antiferromagnetic ordering and the local-moment character of the susceptibility is accompanied by a drop in the y-values as soon as the 3d states start to influence the situation in the vicinity of the Fermi level. 

The compound UCo2Ge2 was studied by Chelmicki et al. (1985) and found to contain a second unidentified phase. The temperature dependence of x measured in the temperature range of 4.2-300 K displays paramagnetic behaviour. 

Low iron content Fe-ZSM-5 has been synthesised and shown to contain well-separated Fe(III) ions in a tetrahedral environment which display paramagnetic behaviour [36]. Partial extraction of the framework iron occurs on hydrothermal treatment to generate nanosize iron oxide or oxyhydroxide ferrimagnetic particles with size 3 nm. 

Most metals show paramagnetic behaviour. It is rather small and independent of temperature and is quite different from the Curie law behaviour of a normal paramagnetic ion. The cause of the weak paramagnetism was explained by Pauli in terms of the Fermi-Dirac statistics of electrons in solids. It is known as Pauli paramagnetism. 

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