Anomalous Anisotropies in Rare-Earth Magnetic Compounds and Their Behavior under High Magnetic Field
Recently, the valence fluctuating state in the rare earth compounds is attracting much attention. Among various different characters of valence fluctuation, the dense Kondo-like behavior, which is observed most typically in Ce compounds such as CeAl2, CeAl3 and CeB6, and the strongly correlated narrow band Fermi liquid like behavior, which is observed typically in Sm compounds such as SmB6 and SmS under pressure, are most typical and have been studied in detail . Both of them are common in the sense that the Fermi level is in the conduction bands which are made in most cases by the 5d character on the rare earth atom, and the d-f mixing is particularly important in the former case. In most cases, however, the anions are situated in the nearest neighbour sites of the cation and thus the p-f mixing is much larger than the d-f mixing, where valence bands are formed mostly by the p-character on the anion atom. In this sense, the valence fluctuating states in the materials in which the Fermi levels are in the valence bands or near them are very interesting. Cemonopnictides and Eu-hexaboride, EuB6 are typical examples for such a category and are attracting considerable attention in the recent years. In this paper, we present some experimental results of these two materials focusing on the high field experiment performed recently by our group and draw several new physical pictures by analyzing the data.
KeywordsValence Band Ferromagnetic State Rare Earth Atom Quartet State Paramagnetic Region
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