Two-magnon Raman scattering in LiMnPO4

Two-magnon Raman scattering is observed in the orthophosphate LiMnPO4, carrying quantitative information on the magnetic interactions between local Mn2+ moments. A simulated annealing fitting procedure of the Raman signal to theoretical curves derived from a magnetic Hamiltonian was carried out, taking exchange and anisotropy constants as free fitting parameters. Previously reported inelastic neutron scattering (INS) data [J. Li et al., Phys. Rev. B 79, 144410 (2009)] were also used in the fit. It is shown that the combined application of INS and Raman scattering data in the fit reduces the ambiguity of the determined set of exchange parameters with respect to fitting procedures using INS or Raman data independently. The temperature dependence of the Raman signal does not show a collapse of the two-magnon excitations at the long-range magnetic ordering temperature, TN=34K, supporting significant short-range spin correlations above TN.