The magnetic structures of DyNi2Ge2

In this paper we report the results of neutron diffraction measurements of the magnetic structures of a single crystal of DyNi2Ge2 in zero applied magnetic field. There are two distinct magnetic transitions in this material; one is from the paramagnetic phase to an amplitude modulated (AM) antiferromagnetic phase at the Neel temperature, T-N = 8.3+/-0.1 K, and the other is at a lower temperature, T-t = 3.1+/-0.2 K, from this phase to an equal moment (EM) antiferromagnetic structure. The EM structure is described by a set of three wave vectors, namely, tau(1) = (0 0 3/4), tau(2) = (1/2 1/2 0) and tau(3) = (1/2 1/2 1/2). A weak third harmonic, tau(1) = (0 0 1/4), related to tau(1), also appears indicating that the magnetic structure is not purely sinusoidal. In this phase Dy moments have their full saturation value of mu(s) = 10 mu(B). The AM phase is described by a single propagation vector tau(1). In both the phases there is an ordered component of the Dy moments in the basal plane. The angle between the ordered Dy moments and the the (c) over bar axis is estimated to be 17 degrees+/-6 degrees at 1.5 K. These results are consistent with the de susceptibility as a function of temperature data which shows weak anisotropy and two transitions. (C) 1998 Elsevier Science Ltd. All rights reserved.