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, T_N≈ 7 K, indicating strong magnetoelastic coupling. XRMS measurements at the Dy L₃edge establish commensurate antiferromagnetic ordering below T_Nwith 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.