New As-based filled skutterudite compounds EuT 4 As 12 (T ¼ Fe, Ru, and Os) have been synthesized under high pressure; these compounds have lattice constants of 8.3374, 8.5120, and 8.5504 Å , respectively, which are larger than those expected from the lanthanide contraction in trivalent ions. The large lattice constants and effective magnetic moments (6.9 -8.3 B /Eu) of the compounds suggest that Eu ions in the compounds are in a divalent or mixed-valent state. Magnetic measurements reveal that EuFe 4 As 12 and EuOs 4 As 12 exhibit ferromagnetic-like phase transitions at 152 and 25 K, respectively. By contrast, EuRu 4 As 12 shows no anomaly down to 2 K. The reciprocal susceptibility À1 of EuFe 4 As 12 has a nonlinear temperature dependence, which implies that the compound has a canted ferromagnetic or ferrimagnetic structure below 152 K. Furthermore, magnetization measurements of EuFe 4 As 12 show that its magnetic moment is about 4.5 B /Eu at 2 K, which is much less than the magnetic moment (7 B /Eu) expected for Eu 2þ . The unexpectedly high transition temperature of 152 K in EuFe 4 As 12 could be related to the interaction of Eu 4f moments with the ferromagnetic [Fe 4 As 12 ] host lattice.

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