arXiv subjects

Karol Szałowski

Publications and source records attributed to Karol Szałowski.

22 records · Page 2Linked to original sources

arXiv2012

Indirect RKKY interaction in armchair graphene nanoribbons

A form of an indirect Ruderman-Kittel-Kasuya-Yosida (RKKY)-like coupling between magnetic on-site impurities in armchair graphene nanoribbons is studied theoretically. The calculations are based on a tight-binding model for a finite nanoribbon system with periodic boundary conditions. A pronounced Friedel-oscillation-like dependence of the coupling magnitude on the impurity position within the nanoribbon resulting from quantum size effects is found and investigated. In particular, the distance dependence of coupling is analysed. For semiconducting nanoribbons, this dependence is exponential-like, resembling the Bloembergen-Rowland interaction. In particular, for metallic nanoribbons, interesting behaviour is found for finite length systems, in which zero-energy states make an important contribution to the interaction. In such situation, the coupling decay with the distance can be then substantially slower.

cond-mat.mes-hall↗

arXiv2011

The RKKY Coupling between Impurity Spins in Graphene Nanoflakes

We calculate the indirect charge carrier mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between magnetic impurities for two selected graphene nanoflakes containing four hexagonal rings in their structure, differing by their geometry. We describe the electronic structure of either charge-neutral or doped nanoflakes using the tight-binding approximation with the Hubbard term, which is treated within the molecular-field approximation. We find pronounced differences in the RKKY coupling energies, dependent on the placement of the pair of magnetic moments in the nanostructure and on the edge form. For an odd total number of electrons in the structure, we predict in some circumstances the existence of ferromagnetic coupling with leading first-order perturbational contribution, while for an even number of charge carriers the usual, second-order mechanism dominates. Therefore, doping of the nanoflake with a single charge carrier is found to be able to change the coupling from an antiferromagnetic to a ferromagnetic one for some geometries.

cond-mat.mes-hall↗

arXiv2009

In search of antiferromagnetic interlayer coupling in diluted magnetic thin films with RKKY interaction

We study a model thin film containing diluted bilayer structure with the RKKY long-range interaction. The magnetic subsystem is composed of two magnetically doped layers, separated by an undoped nonmagnetic spacer and placed inside a wider film modelled by a quantum well of infinite depth. We focus our study on the range of parameters for which the antiferromagnetic coupling between the magnetic layers can be expected. The critical temperatures for such system are found and their dependence on magnetic layer thickness and charge carriers concentration is discussed. The magnetization distribution within each magnetic layer is calculated as a function of layer thickness. The external field required to switch the mutual orientation of layer magnetizations from antiferromagnetic to ferromagnetic state is also discussed.

cond-mat.mtrl-sci↗

arXiv2007

The influence of structural short-range order on the phase diagrams of diluted FCC magnet with arbitrary spin and modified RKKY interaction

A diluted FCC magnet with modified long-range RKKY interaction and arbitrary Ising spin S is considered within two-sublattice model. In the molecular field approximation the Gibbs free-energy is derived, from which all magnetic thermodynamic properties can be self-consistently obtained. In particular, the phase diagrams are studied for different magnetic ion and free-charge concentration, the atomic short-range-order (Warren-Cowley) parameter being taken into account.

cond-mat.stat-mech↗