The magnetic order in multiferroic DyMnO₃

With flexibility in tuning their electric and magnetic properties, multiferroics can be used in information exchange and storage in ways that are very different from the present electronic materials. Here we use resonant soft X-ray scattering spectroscopy to study the F-type (0,τ,0) and C-type (0, 1–2τ, 0) diffraction peaks from sinusoidal antiferromagnetic spin order in multiferroic DyMnO₃. By comparing the temperature dependence of ordering wave vectors τ, peak intensities I, and correlation lengths λ measured at Mn L₂-, O K-, and Dy M₅-edges, we show that the nearly perfect locking between the ordering wave vectors from Dy 4f states and Mn 3d orbitals manifesting the second harmonic diffraction peak implies the notable orbital involvement in the coupling between Mn and Dy spins. Our DFT calculations further suggest that the lattice response to different antiferromagnetic ground states (A-type versus E-type) is much weaker in TbMnO₃, in agreement with previous claim that the symmetric exchange interaction can be an important factor for understanding the ferroelectricity in DyMnO₃ than in TbMnO₃.