Antiferromagnetic order and lattice response in DyCuAs2.

We report high-resolution synchrotron x-ray diffraction and x-ray resonant magnetic scattering (XRMS) studies of the low-temperature crystal and magnetic structures of DyCuAs, a member of theRECuAsfamily exhibiting a resistivity minimum above the antiferromagnetic (AFM) transition temperature. Synchrotron diffraction measurements reveal that DyCuAspreserves tetragonal symmetry down to low temperature within the experimental resolution, although pronounced anomalies in both lattice parametersandare observed near the AFM transition temperature,K, indicating strong magnetoelastic coupling. XRMS measurements at the Dyedge establish commensurate AFM ordering belowwith AFM Bragg peaks atq= (0, 0, 0.5). Representation analysis and calculations of the AFM Bragg peak intensities identify the magnetic structure as therepresentation, consisting of in-plane Dy moments stacked along thecaxis in asequence. The magnetic structure is therefore identical to that previously reported for SmCuAs. Comparison among DyCuAs, SmCuAs, and GdCuAssuggests that in-plane AFM order and the associated magnetic frustration on the tetragonal lattice are closely connected to the emergence of the resistivity minimum in theRECuAsfamily. At the same time, the enhanced lattice response and stronger magnetic-field sensitivity observed in DyCuAsimply that magnetoelastic and spin-orbit interactions additionally play important roles in determining the robustness of this anomalous transport behavior.