E. Blackburn — Page 3

arXiv2006

The magnetic multi-k form factor: an experimental signature of quantum correlators in USb0.88Te0.12?

Magnetic diffraction patterns which exhibit more than one discrete set of symmetry related peaks have been explained by the simultaneous coexistence of more than one magnetic polarisation and propagation vector, k, in the scattering amplitude. In this work we suggest using such multi-k magnetic structures as prototypical multiple order parameter systems. The examples studied are uranium rocksalts, which exhibit magnetic diffraction patterns, the indexing of which requires three orthogonal propagation wavevectors. In the cubic phase these systems exhibit, in addition to the three sets of symmetry related magnetic diffraction peaks, a set of additional Bragg peaks which have been observed by both neutron and x-ray resonant scattering. An interpretation of the neutron diffraction form factor of these peaks is presented, identifying these peaks as signatures of quantum coherence between the three orthogonal order parameters.

cond-mat.other↗

arXiv2003

Multi-$\vec{k}$ Configurations

Using resonant x-ray scattering to perform diffraction experiments at the U M$_{4}$ edge novel reflections of the generic form $ $ have been observed in UAs$_{0.8}$Se$_{0.2}$ where $\vec{k} = < k00>$, with $k = {1/2}$ reciprocal lattice units, is the wave vector of the primary (magnetic) order parameter. The $ $ reflections, with $10^{-4}$ of the $ $ magnetic intensities, cannot be explained on the basis of the primary order parameter within standard scattering theory. A full experimental characterisation of these reflections is presented including their energy, azimuthal and temperature dependencies. On this basis we establish that the reflections most likely arise from the electric dipole operator involving transitions between the core 3d and partially filled $5f$ states. The temperature dependence couples the $ $ peak to the triple-$\vec{k}$ region of the phase diagram: Below $\sim 50$ K, where previous studies have suggested a transition to a double-$\vec{k}$ state, the intensity of the $ $ is dramatically reduced. Whilst we are unable to give a definite explanation of how these novel reflections appear, this paper concludes with a discussion of possible ideas for these reflections in terms of the coherent superposition of the 3 primary (magnetic) order parameters.

cond-mat↗