  A scheme to calculate the electronic structure of systems having a spiral
magnetic structure is presented. The approach is based on the KKR
(Korringa-Kohn-Rostoker) Green's function formalism which allows in combination
with CPA (Coherent Potential Approximation) alloy theory to deal with
chemically disordered materials. It is applied to the magnetic random alloys
Fe$_x$Ni$_{1-x}$, Fe$_x$Co$_{1-x}$ and Fe$_x$Mn$_{1-x}$. For these systems the
stability of their magnetic structure was analyzed. For Fe$_x$Ni$_{1-x}$ the
spin stiffness for was determined as a function of concentration that was found
in satisfying agreement with experiment. Performing spin spiral calculations
the longitudinal momentum-dependent magnetic susceptibility was calculated for
pure elemental systems (Cr, Ni) being in non-magnetic state as well as for
random alloys (Ag$_x$Pt$_{1-x}$). The obtained susceptibility was used to
analyze the stability of the paramagnetic state of these systems.
