Preparation, structure and properties of new ternary chalcogenides and germanides of the metals from the first transition series, Cr, Mn, Fe and Ni

This thesis deals with the synthesis, structure determination and investigation of the properties of Cr 2 Ge 2 Se 6 , Mn 2 GeSe 4 , Fe 3 GeTe 2 and Ni 3 GeTe 2 . Mn 2 GeSe 4 crystallizes in the orthorhombic space group Pnma (a=1335,0(3) pm, b = 776,5(2) pm, c = 630,7(1) pm) is one of the rare ternary transition metal selenides representatives of the olivine ((Fe, Mg) 2 SiO 4 ) structure - type. Fe 3 GeTe 2 and Ni 3 GeTe 2 are the first ternary members of the filled NiAs - structures. Both crystallize in the hexagonal group P6 3 /mmc (a = b = 399,1(1) pm, c=1633,6(3) pm for Fe 3 GeTe 2 and a = b = 319,1(1) pm, c=1602,2(3) pm for Ni 3 GeTe 2 , respectively). Their structures are characterized by alternating layer packages, each one built of five layers. Cr 2 Ge 2 Se 6 is a new compound belonging to the the M 2 X 2 Y 6 (M = transition metal, X = Si, Ge, Y = chalcogen) structure family. X - ray powder diffraction investigations find a hexagonal symmetry. The lattice constants are a = b = 629,3(3) pm, c = 1942,1(6) pm, γ = 120°. Magnetic properties studies show antiferromagnetic interactions in Mn 2 GeSe 4 and ferromagnetic spin ordering in Fe 3 GeTe 2 . Ni 3 GeTe 2 exhibits weak paramagnetism.