Quadrupolar ordered state at high fields in PrPb3

PrPb3 exhibits an antiferroquadrupolar transition at TQ=0.4K. In the present work, in order to reveal the order parameters of the ordered states in much higher fields than 5 T applied along the [1 1¯ 0] direction, we performed neutron diffraction experiments in the temperature range between 50 mK and 0.8 K in magnetic fields up to 14.5 T. Above 7 T, we observed magnetic reflections at q=(δδ0.5)(δ∼0.02) and its equivalents. The field-induced antiferromagnetic components were normal to the applied field, indicating that the quadrupolar order parameter in the high field phase should be of O22-type.