  The dielectric constant of the Kagome staircase-like Co3V2O8 polycrystalline
compound has been measured as function of temperature and magnetic field up to
14T. It is found that the application of an external magnetic field suppresses
the anomaly for the dielectric constant beyond 6.1K. Furthermore, its magnetic
field dependence reveals a negative magnetocapacitance which is proportional to
the magnetic susceptibility, suggesting a common magnetostrictive origin for
the magnetic field dependence of the two quantities. This result is very
different from that obtained from the isostructural compound Ni3V2O8 that
presents a peak in the dielectric constant at the incommensurate magnetic phase
transition coupled to a sign change of the magnetocapacitance.
