Magnetic order in RAgGe (R=Gd-Er) intermetallic compounds

Polycrystalline samples of the ternary intermetallics RAgGe (R=Tb-Er) were investigated by means of magnetization and neutron diffraction measurements. For GdAgGe compounds only magnetic measurements were performed. They crystallize in the hexagonal ZrNiAl-type structure. Magnetic measurements show antiferromagnetic ordering at Neel temperatures between 15.6 K for R-Gd and 3.6 K for R=Er. For TbAgGe the neutron diffraction data reveal a complicated sine modulated magnetic structure which is affected by temperature changes. For DyAgGe and HoAgGe the square modulated magnetic ordering is described by the wave vector k=(1/3 1/3 0) while for ErAgGe by k=(1/2 1/2 0). With increasing number of 4f-electrons one observes a change of the direction of magnetic moment from parallel to the c-axis for R = Tb via one which forms an angle phi with the c-axis for R = Dy, to one which lies in the basal plane for R = Ho and Er. (C) 1998 Elsevier Science S.A. All rights reserved.