Eur. Phys. J. B 19, 475-490 (2001)
https://doi.org/10.1007/s100510170293

Antiferromagnetic order and phase transitions in GdS as studied with X-ray resonance-exchange scattering

¹ Forschungszentrum Jülich, Institut für Festkörperforschung, 52425 Jülich, Germany
² Advanced Photon Source at Argonne National Laboratory, LOM 433 - D 008, 9700 South Cass Avenue, Argonne, IL 60439, USA
³ Eidgenössische Technische Hochschule Zürich Hönggerberg (ETH), Labor für Festkörperphysik, 8093, Zürich, Switzerland
⁴ European Synchrotron Radiation Facility (ESRF), BP 2 20, 38043 Grenoble Cedex 9, France
⁵ CEA Grenoble, DRFMC, 38054 Grenoble, France
⁶ Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France

Corresponding author: ^a T.Brueckel@fz-juelich.de

Received: 19 November 1999
Revised: 12 December 2000
Published online: 15 February 2001

Abstract

We report on X-ray resonance exchange and neutron scattering of metallic GdS. At the L_II and L_III absorption edges of Gd, resonance enhancements of more than two orders of magnitude over the non-resonant magnetic scattering are observed. Polarisation analysis proves that these enhancements are due to dipolar transitions from the 2p to the 5d states. The branching ratio between the L_II and L_III edges of 2.5 suggests a polarisation of the 5d electrons in the ground state. The antiferromagnetic order is of type II in the fcc lattice. Single crystal diffraction of hot neutrons suggests that the spin direction lies within the (111) planes with a value for the sublattice magnetisation of 6.51(3) . The critical exponent for the sublattice magnetisation has a value of in agreement with a pure Heisenberg model. Above T_N, a sharp component persists in the critical diffuse scattering. Lattice distortions give indications for two additional low-temperature phase transitions at about 49 K and 32 K. We argue that these transitions are not connected to spin reorientations and discuss the possible influence of fourth-order exchange interactions.