Abstract
Landau formalism is used to investigate the surface effect of multiferroic BiMnO3. This multiferroics have a polarization and magnetization below magnetic transition temperature. Magnetic extrapolation length parameter Delta(m) and electric extrapolation length parameter delta(p) express the surface effect in Landau free energy. These two parameters control the magnetic transition temperature, where delta(p) control the ferroelectric transition temperature. The values of magnetization and polarization are reduced by decreasing the values of these surface parameters. Electric and magnetic susceptibilities are calculated. Stepwise behavior of electric susceptibility at magnetic transition temperatures is expressed. The values of susceptibilities for the films are lesser than that of the bulk due to surface effect coming from magnetism and ferroelectricity of multiferroics.