Site Preference of Metal Atoms in Gd5–xMxTt4 (M = Zr, Hf; Tt = Si, Ge)

AbstractZirconium and hafnium were incorporated into the Gd5Ge4 and Gd5Si4 parent compounds in order to study the metal‐site occupation in the M5X4 magnetocaloric phases (M = metals; X = p elements) family. The Gd5–xZrxGe4 phases adopt the orthorhombic Sm5Ge4‐type (space group Pnma) structure for x ≤ 1.49 and the tetragonal Zr5Si4‐type (P41212) structure for x ≥ 1.77. The Gd5–xHfxSi4 compounds crystallize in the orthorhombic Gd5Si4‐type (Pnma) structure forx ≤ 0.41 and the Zr5Si4‐type structure for x ≥ 0.7. In both systems, single‐crystal X‐ray diffraction reveals that the Zr/Hf atoms preferentially occupy the slab‐surface M2 and slab‐center M3 sites, both of which have a significantly larger Zr/Hf population than the slab‐surface M1 site. The metal‐site preference, i.e. the coloring problem on the three metal sites, is discussed considering geometric and electronic effects of the local coordination environments. The analysis of the metal‐site occupation in Gd5–xZrxGe4 and Gd5–xHfxSi4 as well as other metal‐substituted M5X4 systems suggests that both geometric and electronic effects can be used to explain the metal‐site occupation.

Site Preference of Metal Atoms in Gd_5–xMxTt₄ (M = Zr, Hf; Tt = Si, Ge) Journal Articles