Magnetic excitations in charge-ordered Nd _0.5 Ca _0.5 MnO ₃ : A Brillouin scattering study

Brillouin scattering studies on single crystals of a charge-ordered manganite, Nd0.5Ca0.5MnO3, have been carried out for the first time. The spectra show two modes at (B-mode) and 60 GHz (S-mode). The B-mode frequency and intensity from 300 K to 27 K, covering both the charge ordering transition at 250 K and the antiferromagnetic transition, at 170 K, exactly follow the same temperature dependence as the d.c. magnetic susceptibility. The B-mode is associated with bulk magnetic excitations and the S-mode with surface magnetic excitations of the manganite with ferromagnetic correlations. The study is strongly indicative of the presence of ferromagnetic inhomogeneities in the charge-ordered as well as antiferromagnetic phases.