Soft ferromagnet GdFe7.7Si1.3 with a CaCu5-to-Th2(Ni/Zn)17 transitional structure

GdFe7.7Si1.3 was synthesized by arc-melting with subsequent annealing at 1000 °C for 4 weeks. The basic structure of GdFe7.7Si1.3 is similar to that of CaCu5 but features random substitution of Gd atoms by Fe2 dumbbells along the z-axis. This random Gd/Fe2 distribution makes the GdFe7.7Si1.3 structure an intermediate between the CaCu5 (no dumbbells) and Th2(Ni/Zn)17 (full ordering of dumbbells) structures. Single crystal X-ray diffraction also points at the formation of a superstructure of a lower symmetry and diffuse scattering between the superstructure spots. GdFe7.7Si1.3 orders ferromagnetically at 640 K and exhibits a soft magnetic behavior.