Spin fluctuations, effect resistivity

UIr2 is paramagnetic down to 4.2 K. The susceptibility is nearly temperature-independent and has a slight maximum at 60 K (x3ook = L48 X 10 8 m3/mol). The T2 dependence of the resistivity at low temperatures together with the relatively high y value [62 mJ/mol K2 (Brodsky et al. 1976)] are indicative of spin-fluctuation effects. 

Although such an anomalous magnetic low-temperature behaviour, as observed in URuAl and URuGa, is frequently associated with spin-fluctuation effects, other possible explanation cannot be omitted. Possible explanation in terms of band effects may be considered since no anomaly was found in the temperature dependence of the specific heat (no T3 In T term) and the y-values are 45 and 52 mJ/mol K2, respectively. By contrast the resistivity behaviour supports the first interpretation (Havela et al. 1985a, Sechovsky et al. 1986b). 

However, the overall thermal variation up to room temperature must have another origin since a-Pu is a spin-fluctuation system, in which magnetic scattering is important. As has been shown by Lapierre et al. (1987), in spin-fluctuation systems asymmetric scattering is certainly present, giving rise to an extraordinary Hall effect (see sect. 2.4.2), and its thermal variation reflects that of the magnetic resistivity. This is even more obvious in the case of /3-Pu (see fig. 20), where the Hall resistivity closely follows the thermal variation of the electrical resistivity. 

An alternative explanation of the anomalous resistivity, specific heat and susceptibility of UAlj has been suggested by De Groot et al. (1985). Their explanation of the resistivity behaviour is based on band-structure effects. From a band-structure calculation these authors conclude that the structure of the density of states near the Fermi energy can explain the resistivity variation without the necessity of the introduction of spin fluctuations or any other many-body effect. 

We shall consider two refractory compounds in which electron scattering due to magnetic effects may appear TiB2, which shows a resistivity minimum at low temperatures that has been attributed to the Kondo effects, and VN, in which spin fluctuations have been suggested to affect... 

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