[1
]Clarendon
Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford
OX1 3PU, United Kingdom
[2
]Physik Department, Technische Universität München, 85748 Garching, Germany
[3
]Diamond Light Source, Didcot OX11 0DE, United Kingdom
[4
]Institut für Angewandte Photophysik, TU Dresden, 01069 Dresden, Germany
[5
]Crystal
Growth Facility, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015
Lausanne, Switzerland
[6
]Magnetic Spectroscopy
Group, Diamond Light Source, Didcot OX11 0DE, United Kingdom