Itinerant magnetism in hybridised degenerate electronic bands

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Abstract
Starting from a Hamiltonian for electrons which includes all hopping terms in the tight binding approximation, as well as all pair intra-atomic interactions, the authors show with the help of a canonical transformation that the non-diagonal hopping, mixing the degenerate bands, can be removed entirely. This leads to two hybridised bands for a twofold degenerate electronic system, which are used to derive the generalised Stoner criteria for the appearances of ferro- and antiferromagnetism. Analytical expressions for the magnetic moment at T=0 have been calculated under the Hartree-Fock approximation, independent of the explicit shape of the density of states.