T = 0 Magnetic Polaron in f‐Systems with Antiferromagnetic s‐f Exchange

The s‐f model is used for investigating ferromagnetic f‐systems with an antiferromagnetic s‐f exchange interaction between conduction electrons and localized magnetic f‐moments. Particularily the electronic excitation spectrum is discussed for the exactly solvable limiting case of an empty conduction band at T = 0, and that via physical quantities such as the one‐electron spectral density, the quasiparticle density of states, and the electronic selfenergy. The ↑‐spectrum is simple, consisting of one single, only rigidly shifted band. The ↓‐spectrum, however, is built up by two quasiparticle subbands of quite different physical meaning. The gap between them closes if the Bloch band width exceeds a critical value. The ↓‐spectral density consists of one low‐energy δ‐peak and a relatively broad, high‐energy scattering part, which results from magnon emission processes. The dependence on model parameters and the distinction from f‐systems with ferromagnetic s‐f exchange is discussed in detail.