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Self‐Consistent CPA Treatment of the Conduction Electron Spin Polarization of Degenerate Ferromagnetic Semiconductors
Author(s) -
Borgieł W.,
Nolting W.,
Borstel G.
Publication year - 1986
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221360115
Subject(s) - condensed matter physics , quasiparticle , electron , curie temperature , spin polarization , ferromagnetism , physics , thermal conduction , quantum mechanics , superconductivity
A theory for the temperature and charge carrier concentration dependence of the electronic quasiparticle spectrum, of a ferromagnetic 4f‐system is presented. The s‐f model is used with inclusion of a Coulomb interaction between the conduction electrons. The full analytical solution of the zero band width limit of this model is used to formulate an alloy analogy, which is then treated by a conventional CPA‐procedure. In this way in a selfconsistent manner basic quantities are determined like the quasiparticle density of states and the conduction electron spin polarization. The quasiparticle spectrum is shown to be composed of three subbands which can be interpreted as consequence of different simple elementary processes. The spin polarization is almost complete for small band occupations n and temperatures below the Curie‐temperature. It drops down quite abruptly at a certain critical concentration, reaching again a relative maximum for the exactly half‐filled conduction band. The temperature dependence of the spin polarization for fixed n explains recently performed field emission experiments.