Antiferromagnetic order and lattice response in DyCuAs 2

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Abstract 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 2 , a member of the RE CuAs 2 family exhibiting a resistivity minimum above the antiferromagnetic (AFM) transition temperature. Synchrotron diffraction measurements reveal that DyCuAs 2 preserves tetragonal symmetry down to low temperature within the experimental resolution, although pronounced anomalies in both lattice parameters a and c are observed near the AFM transition temperature, T N ≈ 7 K, indicating strong magnetoelastic coupling. XRMS measurements at the Dy L 3 edge establish commensurate AFM ordering below T N with AFM Bragg peaks at q = (0, 0, 0.5). Representation analysis and calculations of the AFM Bragg peak intensities identify the magnetic structure as the Γ 10 representation, 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 SmCuAs 2 . Comparison among DyCuAs 2 , SmCuAs 2 , and GdCuAs 2 suggests that in-plane AFM order and the associated magnetic frustration on the tetragonal lattice are closely connected to the emergence of the resistivity

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