Quaternary Gd4Ni2Sb1±xSi2±x and Gd4Ni2Bi1±xSi2±x: Crystal structure, homogeneity regions and magnetic behavior

A new quaternary Gd 4 Ni 2 Sb 1.07(1) Si 1.93(1) phase was synthesized by arc-melting and its structure was determined through single crystal X-ray diffraction techniques. It crystallizes in an orthorhombic unit cell (the Pnma space group) with a = 11.1735(9), b = 4.2054(2) and c = 16.711(1) A and represents a new structure type. The isostructural Gd 4 Ni 2 BiSi 2 phase was obtained and characterized using the powder X-ray diffraction techniques: Pnma space group, a = 11.2715(2), b = 4.2046(1) and c = 16.7421(3) A. By the means of electron microprobe analysis, Sb/Si and Bi/Si solid solutions were proven to exist for corresponding phases, and their general formulas can be given as Gd 4 Ni 2 Sb 1± x Si 2± x and Gd 4 Ni 2 Bi 1± x Si 2± x . Gd 4 Ni 2 Sb 1.07 Si 1.93 and Gd 4 Ni 2 BiSi 2 order ferromagnetically at 93 K and 46 K, respectively.