Spin-phonon coupling in the incommensurate magnetic ordered phase of orthorhombic TmMnO3

International audienceThe search for materials with strong magnetoelectric coupling has been intense since interesting properties were discovered in the perovskite TbMnO 3. Among the manganese-based perovskite family (RMnO 3), magnetic and electric orders coexist in the orthorhombic phase of the distorted perovskite TmMnO 3. The antiferromagnetic phase induces ferroelectricity, leading to type-II multiferroic behavior. Although the temperature-dependent behavior of the Raman-active phonons of other members of the orthorhombic RMnO 3 family was already reported, little information about orthorhombic TmMnO 3 has been published. In this paper, bulk samples of orthorhombic TmMnO 3 were obtained through HPHT treatment. Structural and magnetic properties of the synthesized samples were analyzed for phase con rmation. Temperature-dependent Raman spectra of bulk orthorhombic TmMnO 3 revealed weak spin-phonon coupling in the incommensurate antiferromagnetic ordered phase around 44 K. Raman spectra are also sensitive to the magnetic transition from the incommensurate to Etype antiferromagnetic phase, where the frequency renormalization due to the spin-phonon coupling vanishes. This feature shows the existence of an orbital-spin-phonon coupling based on the magnetic ordering of the lowtemperature phase