Fe 3+ S = 5/2 ions form saw-tooth like chains along the a axis of the oxo-selenite Fe2O(SeO3)2 and an onset of long-range magnetic order is observed for temperatures below TC = 105 K. This order leads to distinct fingerprints in phonon mode linewidths and energies as resolved by Raman scattering. In addition, new excitations with small linewidths emerge below T = 150 K, and are assigned to two-magnon scattering processes with the participation of flat-band and high energy magnon branches. From this a set of exchange coupling constants is estimated. The specific ratio of the saw-tooth spine-spine and spine-vertex interactions may explain the instability of the dimer quantum ground state against an incommensurate 3D magnetic order. arXiv:1901.09617v1 [cond-mat.str-el]

We report a Raman scattering study of single-crystalline homometallic oxyborate Mn2OBO3, a compound realizing a one-dimensional ribbon-structure. Phonon excitations as a function of temperature and light polarization are compared to lattice dynamical calculations, giving evidence for a strong coupling between lattice and magnetic degrees of freedom. Furthermore, a broader feature with a distinct structure emerges at low temperatures. Based on our theoretical analysis, we assign this signal to specific two-magnon scattering processes related to high energy flat-band magnon branches.

No abstract

No abstract