High field Moessbauer investigations on REFe4Sb12 (RE = Yb, Nd, Pr) skutterudites

Full text: Ternary skutterudites RExTM4X12 are of large interest because of their high thermoelectric potential. To get more information about magnetic ground state we have investigated samples with RE = Yb, Nd, Pr and TM = Fe by magnetic and high field Moessbauer investigations. From x-ray investigation the Fe and Sb sublattice is found to be fully occupied, whereas a considerable amount of voids is present in the RE - sublattice (e.g. for Pr x = 0.73). Theoretical investigations predict zero moment at the Fe-site. In contrast to this magnetic measurements point to a considerable large Fe-moment. Although there exists only one crystallographic site for Fe, from analysis of the 57Fe Moessbauer spectra in fields up to 13.5 T two different hyperfine fields are verified. One which can be assigned to Fe with a very small moment and a larger one which shows sauration in higher fields. According to the obtained intensity ratio the second one can be attributed to Fe with a RE-void in the first neighbor shell, whereas the first one is attributed to those Fe which have no voids in their neighborhood. (author)