Magnetic and structural correlations in the warwickite Mn2OBO3

Gnezdilov, V; Pashkevich, Yu; Kurnosov, V; Zhuravlev, O., V; Wulferding, D.; Lemmens, P.; Kazak, N., V; Knyazev, Yu, V; Ovchinnikov, S. G. Source: LOW TEMPERATURE PHYSICS, 45 (9):1046-1052; 10.1063/1.5121280 SEP 2019

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.