Antiferroquadrupolar Order in the Magnetic Semiconductor TmTe

The physical properties of the antiferroquadrupolar state occurring in TmTe below T Q =1.8 K have been studied using neutron diffraction in applied magnetic fields. A field-induced antiferromagnetic component [ k =(1/2,1/2,1/2)] is observed and, from its magnitude and direction for different orientations of H , an O 2 2 quadrupole order parameter is inferred. Measurements below T N ≈0.5 K reveal that the magnetic structure is canted, in agreement with theoretical predictions for in-plane antiferromagnetism. Complex domain repopulation effects occur when the field is increased in the ordered phases, with discontinuities in the superstructure peak intensities above 4 T.