Quadrupolar and Magnetic Ordering in (U,Np)Pd3

UPd3 exhibits four phase transitions between 8 K and 4 K which have been attributed to a succession of antiferroquadrupolar ordered structures of the uranium 5f2 electrons. These structures have been studied by resonant X-ray scattering techniques.We present new measurements of the azimuthal dependence of the superlattice intensities from which we have deduced the order parameter in the phase immediately below T0 = 7:6 K to be Qzx. We also report studies of dhcp NpPd3 with results for the magnetic susceptibility, heat capacity and electrical resistivity. Two phase transitions have been observed at 30 K and 10 K. The evolution of the quadrupolar phases in UPd3 has been determined in samples of (U1¡xNpx)Pd3.JRC.E.6-Actinides researc