Temperature dependence of Eu 4f and Eu 5d spin magnetizations in the filled skutterudite EuFe4Sb12

The element specific and shell specific magnetism of Eu in the filled skutterudite ferrimagnet Eu0.95Fe4Sb12 has been investigated using Eu M4,5 and Eu L2,3 edge x-ray magnetic circular dichroism (XMCD) spectroscopy as a function of temperature. Eu L3 edge and Eu M5 edge x-ray absorption spectroscopy clearly show that Eu is in a mixed valence state. Sum rule analysis of the Eu M4,5 edge XMCD spectrum measured at 4.9K yielded the 4f spin moment of 7.15+/-0.3uB per Eu2+ ion. By comparing the Eu L2,3 edge XMCD spectrum in the ferrimagnetic state of Eu0.95Fe4Sb12 and the divalent Eu reference compound, the clathrate Eu8Ga16Ge30, we show that the 5d magnetic moment of Eu in the skutterudite is strongly enhanced by the exchange coupling with the 3d band electrons of Fe, which were shown to have an ordered moment of -0.21uB/Fe in our earlier Fe L2,3 XMCD measurements. The temperature dependence of the ferromagnetic order parameter, determined from the Eu L3 edge XMCD intensity, yields a mean field like exponent (~0.52) in the skutterudite and a 3D Heisenberg like (~0.36) exponent in the clathrate.