Observation of magnons and its state density by Brillouin scattering in substituted garnets

Magnon spectra were obtained by Brillouin scattering from single crystals of BCVIG(Bi 3-2 x Ca 2 x Fe 5- y V y O 12 , x = 1.2, y = 1.3 ). For the first time we have observed the bulk magnons and continuous spin wave band. The measured dispersion relation of bulk magnon shows good agreement with the theory of spin waves, but with a very large spin-wave stiffness constant D . The continuous band demonstrates the characteristics of the density of state of the spin wave.