Antiferromagnetic order and evolution of magnetic entropy in RE4Zn5Ge6 (RE=Y, Gd–Lu)

We investigated the physical properties of eight new polar intermetallic phases RE4Zn5Ge6 (RE=Y, Gd, Tb, Dy, Ho, Er, Tm, Lu). The compounds are isostructural and crystallize in a novel orthorhombic structure type, space group Cmc21 (No. 36), Pearson's symbol oC60oC60. With the exception of the Y- and Lu-variants, all compounds show the onset of antiferromagnetic order below T=20K. Although the observed Weiss temperatures correspond fairly well to the respective Néel-temperatures, the magnetic entropy associated with the antiferromagnetic transitions is not recovered until temperatures one order of magnitude higher, due to the influence of crystal field effects.