Magnetic properties and magnetic structures of R2TGe6 (T = Ni, Cu; R = Tb, Ho and Er)

Abstract The magnetic properties and magnetic structures of the R 2 TGe 6 compounds (T = Ni and Cu, R = Tb, Ho and Er) were studied by magnetometric and neutron diffraction measurements. All compounds have an orthorhombic crystal structure of the Ce 2 CuGe 6 -type and are antiferromagnetic with the Neel temperatures ranging from 6 K for Er 2 CuGe 6 up to 42 K for Tb 2 NiGe 6 . Based on the neutron diffraction data the magnetic structures were determined for R 2 NiGe 6 (R = Tb, Er) and R 2 CuGe 6 (R = Ho, Er). In these compounds the magnetic moments localized on the rare earth element form a collinear commensurate magnetic structure. The magnetic unit cell is equal to the crystal one in R 2 NiGe 6 (R = Tb, Er) while it is doubled along the a-axis (propagation vector k  = (½, 0, 0)) in R 2 CuGe 6 (R = Ho and Er). The obtained magnetic structures are discussed on the basis of competition between the RKKY-type interactions and influence of Crystalline Electric Field (CEF).