Magnetic Excitation of Cu₂(MoO₄)(SeO₃)

One-dimensional spin chain systems have been attracting renewed interest in terms of a magnon or spinon-band splitting, which is found in ??-Cu₂V₂O₇ and Cs₂CuCl₄. A key parameter for the band splitting is an intrachain antisymmetric Dzyaloshinskii-Moriya interaction. To expand the variety of materials that can exhibit the band splitting, we have further searched for a possible quasi one-dimensional antiferromagnet and found Cu₂(MoO₄)(SeO₃) is a candidate. Single crystal magnetic susceptibility measurements show an anomaly at T_N ~ 23 K in all directions. A broad peak near 50 K suggested one dimensionality. The negative Curie-Weiss temperature Θ = -95.6(3) K confirms that the dominant exchange interaction between Cu²⁺ ions in Cu2(MoO4)(SeO3) is antiferromagnetic. By neutron powder diffraction experiment, we determined that Cu₂(MoO₄)(SeO₃) orders with antiferromagnetic structure, where the magnetic moments are mostly parallel (or antiparallel) to the one-dimensional direction. The inelastic neutron scattering experiment revealed the magnon dispersion along the (11L) direction. A continuum like excitation around (110) was observed. Additionally, the magnetic  excitation has a gap of ~ 1.0 meV suggesting the presence of an anisotropy in this compound.