On the Crystal Structure, Metal Atom Site Preferences and Magnetic Properties of Nd 5– x Er x Tt 4 ( Tt = Si or Ge)

A crystallographic study of the Nd/Er site preferences in the Nd 5– x Er x Tt 4 ( Tt = Si, Ge) series prepared by high‐temperature methods is presented. For Nd 5– x Er x Si 4 , phases with x ≤ 1.0 adopt the tetragonal Zr 5 Si 4 ‐type structure. On the other hand, phases in the composition range of 2.0 ≤ x ≤ 5.0 exhibits the Gd 5 Si 4 ‐type structure. For all silicides, all silicon atoms belong to Si–Si dimers. In the Nd 5– x Er x Ge 4 system, phases with x < 3.2 and x = 4.0 adopt the orthorhombic Sm 5 Ge 4 ‐type structure. For the composition range of 3.2 ≤ x ≤ 4.0, a monoclinic U 2 Mo 3 Si 4 ‐type structure (space group P 2 1 / c ) occurs as the majority phase. This monoclinic structure, until recently, was not reported for similar RE 5 T 4 systems, and differs from the known monoclinic Gd 5 Si 2 Ge 2 ‐type (space group P 2 1 / a ) because all Ge···Ge contacts between slabs are equivalent. The structural relationships between the Zr 5 Si 4 ‐type, Gd 5 Si 4 ‐type, Sm 5 Ge 4 ‐type, and U 2 Mo 3 Si 4 ‐type structures are discussed. Single crystal refinements of the metal atom occupancies for the three different metal sites in the asymmetric unit of all structure types reveal a partially ordered nonstatistical arrangement of neodymium and erbium atoms. The magnetic properties of some Nd 5– x Er x Ge 4 phases are also reported. Nd 4 ErGe 4 shows an antiferromagnetic‐type transition similar to Gd 5 Ge 4 . As the erbium concentration increases (2 ≤ x ≤ 4), these phases exhibit, at least, ferrimagnetic‐type ordering.