  A well-known connection between the magnetic susceptibility and the effective
exchange parameter is analyzed. It is shown that all current computational
schemes use a long-wave approximation which is suitable only for localized
moments systems. A corresponding smallness parameter is derived in real and
recipical space. General 'inverse susceptibility' approach is combined with a
multiple scattering theory and applied for the studies of elementary metals Fe,
Ni and Gd. It is shown that the proposed approach significantly improves the
description of the exchange coupling between nearest atoms, the spin wave
spectrum at large wave vectors for the itinerant degrees of freedom in metallic
magnets. A consistent usage of this method leads to the proper description of
magnetic short-range order effects.
