1. Laboratory of Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
2. Neutron Spectroscopy Department, Wigner Research Centre for Physics, Konkoly Th. M. 29-33, 1122 Budapest, Hungary
3. Laboratory for Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
4. Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
5. Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston PR1 2HE, United Kingdom
6. Department of Physics, Technical University of Denmark, Kongens Lyngby 2800, Denmark