Heavy fermions in transition metals and transition-metal oxides

Heavy-fermion formation in transition metals and transition-metal oxides is reviewed and compared to observations in canonical f-derived heavy-fermion systems. The work focuses on the dynamic susceptibilities which reveal a characteristic temperature and frequency dependence and which can be unambiguously determined via nuclear magnetic resonance and electron-spin resonance measurements as well as via quasielastic neutron-scattering studies. Different routes to heavy-fermion behaviour are discussed, amongst them Kondo systems, frustrated magnets, and electronically correlated systems close to a metal-insulator transition. From a theoretical point of view, utilizing dynamical mean-field theory, we show that dynamic susceptibilities as calculated for the Hubbard model and for the periodic Anderson model look qualitatively rather similar. These different theoretical concepts describe an universal behaviour of the temperature dependent dynamic susceptibility. Copyright Springer-Verlag Berlin/Heidelberg 2003