  Magnetic structures and their stability of the multiple helical spin density
waves (MHSDW) and related magnetic skyrmions in itinerant electron system have
been investigated on the basis of both the phenomenological and microscopic
theories. It is shown by using the Ginzburg-Landau (GL) theory and the
Application Visualization System (AVS) that the magnetic skyrmion structures
emerge as a MHSDW and can be stabilized in itinerant electron system on the fcc
lattice even if there is no Dzyaloshinskii-Moriya interaction. Moreover, by
using the generalized Hartree-Fock theory for the Hubbard model, the
antiferromagnetic skyrmion structure found in the GL theory is shown to be
stabilized on the fcc lattice in the vicinity of the half-filled electron
number.
