  The pyrovanadate alpha-Cu2V2O7 belongs to the orthorhombic (Fdd2) class of
crystals with noncentrosymmetric crystal structure. Recently, the compound has
been identified to be a magnetic multiferroic with a substantial electric
polarization below the magnetic transition temperature TC = 35 K. Here we
report the results of our inelastic neutron scattering (INS) studies on a
polycrystalline sample of alpha-Cu2V2O7. Our INS data clearly show the
existence of dispersive spin wave excitations below TC with a zone-boundary
energy of 11 meV at 5 K.We have analyzed the data using linear spin wave
theory, which shows good agreement between the experiment and calculation. The
analysis is consistent with the third nearest neighbor exchange interaction
playing a dominant role in the magnetism of the material.
