GD-155 MOSSBAUER-EFFECT AND MAGNETIC-PROPERTIES OF GDMN6-XCRXGE6

The compounds GdMn6-xCrxGe6 crystallize in the hexagonal HfFe6Ge6 stru cture. The magnetic properties of these compounds were determined. The magnetic ordering temperature (T(c) = 490 K for x = 0) and the 3d sub lattice magnetization in GdMn6-xCrxGe6 strongly decrease with x. In Gd Cr6Ge6 the magnetic ordering temperature dropped to T(c) = 15 K but fr om the magnetic isotherms studied at lower temperatures it is derived that magnetic ordering is more complex than simple ferromagnetism. The re is also appreciable short range ordering above T(c), as was shown b y Gd-155 Mossbauer spectroscopy. From the Gd-155 Mossbauer spectra of GdCr6Ge6 at 4.2 K it was derived that the electric field gradient pres ent at the nuclear site of Gd is almost the same as that found in GdMn 6Ge6 although the hyperfine field in the former is much larger than in the latter.