From heavy fermions to random-localized-site behaviour via Anderson localization

For sufficiently strong scattering by randomly-distributed imperfections th e integrated intensity of a wave initiated at some starting point becomes l ocalized within some finite distance. We discuss how this Anderson localiza tion can be self-induced. with possible enhancement by magnetic ordering, i n light actinide systems. This mechanism provides an nb initio based predic tion, in close agreement with experiment, of the variation of the magnetic ordering temperatures and low-temperature ordered moments in a number of ur anium compounds which are driven by alloying through a phase transition fro m non-magnetic behaviour to strong magnetic ordering. This mechanism also e xplains the phase transition to the delta face-centred-cubic (fcc) structur e at 592 K in elemental plutonium, which has a low-temperature alpha monocl inic structure, and the substantial depression of melting temperature of pl utonium and neptunium with respect to neighbouring elements. Both the stron gly magnetically-ordered uranium systems and elemental plutonium in the fee delta phase are described by the if electronic behaviour of a random-local ized-fluctuating-site (RLFS) solid-solution-like phase. The physical pictur e developed here shows that hybridization treated via the Coqblin-Schrieffe r resonant-scattering point of view (pertinent in the weak hybridization re gime) provides the physical connection (under certain conditions described herein, an actual phase transition) between localized (i.e. coupled magneti c ions) magnetism and strongly-correlated extremely-narrow band behaviour c haracterized as heavy fermion behaviour in solids. Furthermore, the overall physical picture thus provided for the intermediate delocalized regime of transition-shell electron behaviour (comprising the two subregimes of RLFS random solid-solution-like behaviour and extreme-narrow-band heavy fermion behaviour, respectively) provides the physical connection between localized (e.g. heavy rare earth) and itinerant (e.g. nickel) magnetism.