Experimental Investigation of Phase Equilibria in the R-Fe-Ge Ternary Systems (R= Gd, Er) at 1073K and Magetic Properties of R117Fe52Ge112

The interaction between the components in the R-Fe-Ge (R= Gd, Er) systems at 1073K have been
investigated using X-ray powder diraction and scanning electron microscopy energy dispersive X-ray
spectroscopy (SEM/EDS). The isothermals sections of the (Gd, Er) -Fe-Ge ternary phase diagram
contains; 19 single phase-regions, 37 two phase-regions, 20 three phase-regions and 19 single-phase
regions, 42 two-phases regions and 27 three-phases regions, respectively.
The diagram Gd-Fe-Ge contains three intermediate solid solutions have been identified or confirmed:
one lacunaire GdFexGe2 (CeNiSi2-type of structure space group P6/mmm) and two by substitition
GdFe4-xGex (AlB4-type of structure space group I4/mmm) and GdFe12-xGex (YCo6Ge6-type of structure
space group P6/mmm) and one ternary compound Gd117Fe52Ge112 (Tb117Fe52Ge112-type of structure
space group Fm-3m). Three ternary compounds were finally confirmed in Er-Fe-Ge isothermal section
at 800°C:, ErFe4Ge2, Er117Fe52Ge112 and Er0.05Fe0.95Ge and two solid solutions: one lacunaire
ErFexGe2 (CeNiSi2-type of structure space group P6/mmm) and ErFe12-xGex (YCo6Ge6-type of
structure space group P6/mmm).
The temperature dependence of the magnetic susceptibility indicates a magnetic phase transition
below, 89 K for the compound Gd117Fe52Ge112 and 25K for the compound Er117Fe52Ge112. At lower
temperatures, a deviation from the curie weiss law was observed and suggested onset of a ferromagnetic
magnetic ordering.