Abstract
In the rare-earth compound PrPb3, it was proposed that antiferroquadrupolar (AFQ) ordering occurs at TQ=0.4K only by means of macroscopic measurements. Recently, we have performed neutron diffraction measurements in a magnetic field to confirm the existence of the AFQ ordered state. In magnetic fields applied along the [001] axis, antiferromagnetic components with q=(1/2±δ1/2 0), (1/2 1/2±±0)(±-1/8) are observed below TQ (0.4K at H=0) whose amplitudes vary linear with H and vanish at zero field, providing the first evidence for a modulated quadrupolar phase. For H<1, a nonsquare modulated state persists even below 100 mK, suggesting quadrupole moments associated with a Γ3 doublet ground state to be partially quenched by hybridization with conduction electrons.
