NEUTRON-DIFFRACTION AND MAGNETIC STUDY OF THE HONIGE AND ERNIGE COMPOUNDS

HoNiGe and ErNiGe crystallize in an orthorhombic TiNiSi-type structure with the space group Pnma. Neutron diffraction measurements at low te mperatures indicate magnetic structures with the wavevectors k1 = [1/2 , 0, 1/2] for HoNiGe and k2 = [0, 1/2, 0] for ErNiGe. With an increase in temperature, a change in the magnetic structure to a modulated one with the wavevector k1' = [0.469, 0.221, 0.426] at T = 2.55 K for HoN iGe and k2' = [0, 0.5, 0.084] at T = 2.36 K for ErNiGe is observed. Th e magnetic structures determined are verified by symmetry analysis.