Magnetic structures of RCuGe (R = rare earth) compounds

Abstract

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 AlB 2-type crystal structure, while other compounds represent hexagonal LiGeGa-type. All compounds are antiferromagnetic at low temperatures. The Néel temperatures change from 1.8 K for R = Pr to 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 lanthanide 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.