Very weak itinerant ferromagnetism

There are a few exceptions, such as very weak itinerant ferromagnets (for example ZrZn2) and low-spin high-spin transition in fee iron. 

Very weak itinerant ferromagnets, defined as materials for which the splitting in energy between the + and - bands is very small, are predicted to have a number of distinctive properties. In particular, the value of the ratio qc/q% should be much greater than unity and roughly inversely proportional to the Curie temperature (Rhodes and Wohlfarth 1963). Here qc is obtained from the observed paramagnetic susceptibility using the relationship... 

For the LU3C07 778714 compound measurements of flie bulk magnetization and susceptibility were carried out over the temperature range 4-300 K (Skolozdra et al. 1996a). It turns out that it is a very weak itinerant ferromagnet with Tc=63 K and the Co moment of 0.19jttB at 4 K. Above 63 K x(T) follows the Curie-Weiss law (fig. 26), and the elfective... 

NMR nuclear magnetic resonance VWIF very weak itinerant ferromagnetism... 

Three types of characteristic behaviours are mainly observed for R concentrations near or larger than the critical ones, namely collective electron metamagnetism (CEM), very weak itinerant ferromagnetism (VWIF) and Co antiferromagnetism. 

UNi2 behaves as a weak itinerant ferromagnet. The value Tc — 20-21 K was determined on polycrystals (Sechovsky et al. 1980a, Havela et al. 1980) while Tc = 27 K (Frings et al. 1986) was found on a single crystal. The most appropriate value, however, would be Tc = 24 K which corresponds to a peak in the C(T) data (Frings et al. 1986). A very low spontaneous moment jus = 0.08jaB/f.u. locked in the... 

The reduced orbital overlap between the radicals reduces the bandwidth and the electronic structures could be better considered as those of a localised rather than itinerant electron system. This poor overlap results in very small antiferromagnetic interactions being observed, and the compounds behave as nearly perfect Curie-Weiss paramagnets. In the cases when improved lateral interactions between the stacks are achieved by change of the substituents85 the compounds behave as weak ID ferromagnets due to the effective orthogonality of the S C interactions. 

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