Disordered correlated Kondo-lattice model |
| |
Authors: | V. Bryksa W. Nolting |
| |
Affiliation: | Institut für Physik, Humboldt-Universität zu Berlin, Newtonstraße 15, D-12489 Berlin, Germany |
| |
Abstract: | We propose a self-consistent approximate solution of the disordered Kondo-lattice model (KLM) to get the interconnected electronic and magnetic properties of ‘local-moment’ systems like diluted ferromagnetic semiconductors. Aiming at (A1-xMx) compounds, where magnetic (M) and non-magnetic (A) atoms distributed randomly over a crystal lattice, we present a theory which treats the subsystems of itinerant charge carriers and localized magnetic moments in a homologous manner. The coupling between the localized moments due to the itinerant electrons (holes) is treated by a modified RKKY-theory which maps the KLM onto an effective Heisenberg model. The exchange integrals turn out to be functionals of the electronic self-energy guaranteeing self-consistency of our theory. The disordered electronic and magnetic moment systems are both treated by CPA-type methods. We discuss in detail the dependencies of the key-terms such as the long-range and oscillating effective exchange integrals, ‘the local-moment’ magnetization, the electron spin polarization, the Curie temperature as well as the electronic and magnonic quasiparticle densities of states on the concentration x of magnetic ions, the carrier concentration n, the exchange coupling J, and the temperature. The shape and the effective range of the exchange integrals turn out to be strongly x-dependent. The disorder causes anomalies in the spin spectrum especially in the low-dilution regime, which are not observed in the mean field approximation. |
| |
Keywords: | 75.50.Pp 71.23.&minus k 75.30.Hx 85.75.&minus d |
本文献已被 ScienceDirect 等数据库收录! |
|