Quaternary Gd4Ni2Sb1±x Si2±x and Gd4Ni2Bi1±x Si2±x : Crystal structure, homogeneity regions and magnetic behavior

A new quaternary Gd4Ni2Sb1.07(1)Si1.93(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)Å and represents a new structure type. The isostructural Gd4Ni2BiSi2 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)Å. 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 Gd4Ni2Sb1±x Si2±x and Gd4Ni2Bi1±x Si2±x . Gd4Ni2Sb1.07Si1.93 and Gd4Ni2BiSi2 order ferromagnetically at 93K and 46K, respectively.