Determination of the Antiferroquadrupolar Order Parameters in UPd3

الأصل · EN

By combining accurate heat capacity and X-ray resonant scattering results we have resolved the long standing question regarding the nature of the quadrupolar ordered phases in UPd₃. The order parameter of the highest temperature quadrupolar phase has been uniquely determined to be antiphase Qzx in contrast to the previous conjecture of Qₓ₂₋y₂. The azimuthal dependence of the X-ray scattering intensity from the quadrupolar superlattice reflections indicates that the lower temperature phases are described by a superposition of order parameters. The heat capacity features associated with each of the phase transitions characterize their order, which imposes restrictions on the matrix elements of the quadrupolar operators.