Europium $L_{2,3}$ and iron $K$-edge x-ray magnetic circular dichroism investigation of ferromagnetic ordering in EuFe$_{4}$Sb$_{12}$

The magnetic behavior of Eu and Fe in the filled skutterudite ferromagnet EuFe$_{4}$Sb$_{12}$ has been investigated using Eu $L_{2,3}$ edge and Fe $K$ edge x-ray magnetic circular dichroism (XMCD) spectroscopy. Eu $L_3$ edge x-ray absorption spectra (XAS) in EuFe$_{4}$Sb$_{12}$ clearly show that Eu is in a mixed valence state with about 15$\%$ non-magnetic Eu$^{3+}$ states at 5 K. By comparing the XMCD spectra measured at the Eu $L_{2,3}$ edges in the ferromagnetic state at 5 K in EuFe$_{4}$Sb$_{12}$ and in the clathrate Eu$_8$Ga$_{16}$Ge$_{30}$, in which the {\it 4f} magnetic moment of Eu is known to be 7 $\mu_B$, and by accounting for the mixed valence of Eu in the XAS, we show that Eu$^{2+}$ has the free ion like magnetic moment of $\sim$7 $\mu_B$ in EuFe$_{4}$Sb$_{12}$. XMCD observed at the Fe $K$ edge in EuFe$_{4}$Sb$_{12}$ at 5 K indicates magnetic short range order and a small orbital magnetic moment for the {\it 4p} states of Fe. The relative signs of XMCD at Eu $L_3$ edge and Fe $K$ edge indicate that the $5d$ spin moment of Eu and the $4p$ spin moment of Fe are ferromagnetically coupled in EuFe$_{4}$Sb$_{12}$.