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 DyCuAs2, a member of theRECuAs2family exhibiting a resistivity minimum above the antiferromagnetic transition temperature. Synchrotron diffraction measurements reveal that DyCuAs2preserves tetragonal symmetry down to low temperature within the experimental resolution, although pronounced anomalies in both lattice parametersaandcare observed near the antiferromagnetic transition temperature, TN≈ 7 K, indicating strong magnetoelastic coupling. XRMS measurements at the Dy L3edge establish commensurate antiferromagnetic ordering below TNwith AFM Bragg peaks atq= (0, 0, 0.5). Representation analysis and calculations of the AFM Bragg peak intensities identify the magnetic structure as the Γ10representation, consisting of in-plane Dy moments stacked along the c axis in a + +-- sequence. The magnetic structure is therefore identical to that previously reported for SmCuAs2. Comparison among DyCuAs2, SmCuAs2, and GdCuAs2suggests 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 theRECuAs2family. At the same time, the enhanced lattice response and stronger magnetic-field sensitivity observed in DyCuAs2imply that magnetoelastic and spin-orbit interactions additionally play important roles in determining the robustness of this anomalous transport behavior.