Magnetic structures of RCuGe (R equals rare earth) compounds

The crystal and magnetic structures of RCuGe (R = Pr, Nd, Tb, Dy, Ho and Er) compounds were determined by neutron diffraction on polycrystalline samples. Their magnetic data along with those for GdCuGe are reported. The compounds with R = Pr and Nd have the hexagonal AIB(2)-type crystal structure, while other compounds represent hexagonsal LiGeGa-type. All compounds are antiferromagnetic at low temperatures. The Neel temperatures changes from 1.8 K for R = 17 K for R = Gd. The magnetic structure of these compounds is sine modulated with the wave vector k = [1/3, 0, 0] (except NdCuGe in case of which k = [1/2, 0, 0]). For heavy lanthanided compounds, the change of direction of the magnetic moments from the one perpendicular to the c-axis (R = Tb and Dy) to the one parallel (R = Ho and Er) has been found. For ErCuGe, the change of magnetic structure is observed at low temperatures.