The anomalous valence state of Eu and magnetic order in

According to x-ray absorption, M?ssbauer effect measurements, lattice constants and static susceptibility, Eu in the novel compound is non-integral valent with a valence of the order of 2.2. On the other hand, the compound orders antiferromagnetically below 50 K, the M?ssbauer isomer shift is rather independent of temperature, and the resistivity shows no anomalies in the paramagnetic region. Hence, according to existing theories the Eu 4f level cannot be strongly hybridized with the conduction band as in usual intermediate-valent compounds. We therefore propose a considerable participation of the 4f electrons in a covalent Eu - P bond. However, the absence of the ESR signal of as well as the small but finite temperature dependence of the valence clearly demonstrate that the hybridization of the 4f electrons with the conduction band is not negligible in this compound.

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