Magnetoelectric susceptibility (ξ) of classical magnetoelectrics is always substantially smaller that the geometric average of the electric (χ <Subscript> e </Subscript>) and magnetic (χ <Subscript> m </Subscript>) susceptibilities. Materials reaching the equality ξ <Superscript>2</Superscript>=χ <Subscript> e </Subscript> χ <Subscript> m </Subscript> as a limiting value may thus be considered as ideal...</subscript></subscript></superscript></subscript></subscript>