Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 74: Correlated Electrons: Quantum Impurities, Kondo Physics

TT 74.5: Vortrag

Mittwoch, 2. April 2014, 16:00–16:15, BEY 81

Finite-Temperature Studies of Inverse Indirect Magnetic Exchange — •Maximilian Aulbach, Irakli Titvinidze, Andrej Schwabe, and Michael Potthoff — Universität Hamburg, Hamburg, Deutschland

The standard Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction emerges as an effective low-energy coupling in systems where the magnetic moments of impurities are coupled via a weak local exchange J to the spins of a system of itinerant conduction electrons. Contrary, in the case of antiferromagnetic and strong J, the impurity spins are screened individually by the formation of almost local Kondo singlets. In confined magnetic nanostructures, this results in a localization of conduction electrons and a corresponding formation of local magnetic moments which are indirectly coupled via virtual excitations of the Kondo singlets. This new "inverse" indirect magnetic exchange (IIME) [1] can also be studied in Anderson-lattice models with diluted impurities and results in a ferromagnetic ground state.

Here we focus on the finite-temperature properties. Using dynamical mean-field theory and a continuous-time quantum Monte-Carlo impurity solver, we calculate the temperature-dependent magnetization at the different inequivalent sites as well as the Curie temperature. The QMC results are compared with the predictions of static mean-field theory applied to an effective low-energy spin-only Hamiltonian that is derived in fourth-order strong-coupling perturbation theory.
A. Schwabe, I. Titvinidze and M. Potthoff, Phys. Rev. B 88, 121107(R) (2013)