Lattice and magnetic dynamics in perovskite YVO₃ Mott insulator investigated by neutron scattering

The spin wave and phonon in YVO₃ were investigated using powder inelastic neutron scattering. YVO₃ is an antiferromagnetic Mott insulator with a T_N = 118 K accompanied by a spin reorientation transition on warming from C-type to G-type at 77 K. This spin reorientation was observed from changes in the spin waves between 50 and 80 K. Using spinW, the magnetic exchange constants in the G- and C-type spin ordered structures are extracted to be J_ab = J_c = -5.8 meV at 5 and 50 K, J_ab = -3.8 meV, J_c = 7.6 meV at 80 K, J_ab = -3.8 meV, J_c = 6.0 meV at 100 K. Below 118 K, paramagnetic scattering appears in the dynamic structure function S(Q,E). The phonon spectrum up to 130 meV as a function of temperature was also obtained and compared to first-principles calculations. Phonon intensity changes were observed between 50 and 80 K, mainly from the energy shifts of the optical Oxygen branches above 40 meV, linked to the orthorhombic to monoclinic structural transition on warming at 77 K. By comparison, little phonon change was observed across T_N.