Quasiparticles in Magnetic Metals
The properties of a low-density electron gas are calculated, with all two-body scattering processes included in the t-matrix approximation. This yield a phase diagram indicating the possibility of itinerant electron ferromagnetism or antiferromagnetism. The results are confirmed at high density by an analysis of Nagaoka’s model of a half-filled band. The collective excitations are electron- and hole-like quasiparticles having an interaction-dependent effective mass, and magons. The role of the atomic exchange forces (“Hund’s rules”) are assessed quantitatively in a two-band model. Without such exchange, no magnetic moments can exist. This chapter highlights some of the distinctions between magnetism in metals and in non-metals.
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