Temperature and pressure dependence of the ordered magnetic U moment of USe

In the U monochalcogenides, the magnetic properties are characterised by an interplay between localised, rare-earth-like magnetic moments and itinerant, electron-band-like magnetism due to hybridisation effects. Using neutron powder diffraction, we have measured the temperature dependence of the ordered magnetic U moments. The magnetic ordering below TC=176 K was found to be accompanied by a strong rhombohedral distortion of the NaCl-type lattice. The application of pressure below 1 GPa leads to a drastic reduction of the measured magnetic neutron intensity by about 40%, which is presumably caused by a domain reorientation associated with the rhombohedral distortion. Up to pressures of 7.4 GPa, no further significant change of magnetic intensity was observed.