On the short range magnetic order of iron aboveT c

A derivation of the ordering part of the free energy functional based on an expansion about the free energy of a random CPA tight-binding paramagnetic effective medium is presented. Considering the dominant term of this functional, which is of Heisenberg form, the static magnetic correlation function is calculated within a spherical model approximation. For some parameters a behaviour characteristics for systems with tendency to form helicoidal ordered structure belowT _c is observed.