The solid solution Gd _{1– x} Y _x

Abstract

The Heusler phases GdAg ₂ Mg and YAg ₂ Mg form a continuous solid solution Gd _{1– x} Y _x Ag ₂ Mg. Samples were prepared in steps of x = 0.1 and characterized by powder X-ray diffraction and temperature dependent magnetic susceptibility measurements. The a lattice parameter decreases in a Vegard-type manner from GdAg ₂ Mg to YAg ₂ Mg. The crystal structure of Gd _0.577(7) Y _0.423 Ag ₂ Mg was refined from single-crystal X-ray diffractometer data:

, a = 697.33(7) pm, w R = 0.0386, 69 F ² values and six variables. The rare earth atoms are coordinated by a cube of silver atoms ( bcc superstructure) with (Gd/Y)–Ag distances of 302 pm. The continuous substitution of gadolinium ( T _C = 98.3(5) K) by yttrium keeps (i) the stable trivalent ground state of gadolinium and (ii) the long-range ferromagnetic ordering, however, with a continuous decrease of the Curie temperature with increasing yttrium content. The ferromagnetic ordering in the sample with the lowest gadolinium content, Gd _0.1 Y _0.9 Ag ₂ Mg, sets in below 2.6 K. The magnetization isotherms classify the Gd _{1– x} Y _x Ag ₂ Mg samples as soft ferromagnets.