QUASI-PARTICLE SPECTRUM OF AN ANTIFERROMAGNETIC LOCAL MOMENT METAL

The s-f model is used to describe the temperature dependent electronic quasiparticle spectrum of a partially filled energy band which is exc hange coupled to an antiferromagnetically ordered local moment system. The self-energy of the band electrons is approximately calculated by the extension of a moment conserving decoupling procedure recently dev eloped for the description of the ferromagnetic counterpart. Results a re presented in terms of sublattice quasiparticle band structures, spe ctral densities. quasiparticle densities of states and characteristic interband (''mixed s-f'') correlations as functions of temperature T a nd band occupation n. The temperature dependence of the sublattice ban d structure is almost exclusively due to a redistribution of spectral weight between the various quasiparticle branches while their position s;Ire rather unaffected. As for the ferromagnet, the quasiparticle spl ittings can be addressed to the formation of a magnetic polaron (propa gating electron dressed by a virtual cloud of magnons) and to the appe arance of scattering states (magnon emission and absorption).