Electronic structure and magnetism of actinide compounds: 6d versus 5f electrons (invited)

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Abstract
We have studied the electronic structure of cleaved (100) single crystals of UAsxSe1−x, UxTh1−xSb, UxY1−xSb, and USbxTe1−x with high resolution (ΔE<150 meV) photoemission using synchrotron radiation 10⩽hν⩽130 eV. In contrast to the general belief we find significant differences in the photoemission density of states near EF for these compounds. We conclude that these differences are mainly due to valence d electrons and that U has a quasi-localized 5f3 configuration in resonance with itinerant 6d states. This explains the quite similar magnetic behavior of UxTh1−xSb and USbxTe1−x, both of which change from highly anisotropic 〈100〉 antiferromagnets (x≳0.85) to 〈111〉 ferromagnets (x≲0.85), i.e., with an increasing number of 6d electrons. Namely, the smaller ordered moment in UTe and the gradually decreasing moment in UxTh1−xSb for 1.0⩾x⩾0.3 are attributed to the 6d moments which are polarized antiparallel to the 5f moments.