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R. Schiller

Publications and source records attributed to R. Schiller.

7 recordsLinked to original sources
arXiv2001

Kondo-lattice model: Application to the temperature-dependent electronic structure of EuO(100) films

We present calculations for the temperature-dependent electronic structure and magnetic properties of thin ferromagnetic EuO films. The treatment is based on a combination of a multiband-Kondo lattice model with first-principles TB-LMTO band structure calculations. The method avoids the problem of double-counting of relevant interactions and takes into account the correct symmetry of the atomic orbitals. We discuss the temperature-dependent electronic structures of EuO(100) films in terms of quasiparticle densities of states and quasiparticle band structures. The Curie temperature T_C of the EuO films turns out to be strongly thickness-dependent, starting from a very low value = 15K for the monolayer and reaching the bulk value at about 25 layers.

cond-mat.str-el↗
arXiv2001

Temperature-dependent bandstructure of bulk EuO

We present calculations for the temperature-dependent electronic structure of bulk ferromagnetic EuO based on a parametrization of the d-f model Hamiltonian using results of first-principles TB-LMTO band structure calculations. The presented method avoids the problem of double-counting of relevant interactions and takes into account the symmetry of the atomic orbitals. It enables us to determine the temperature-dependent band structure of EuO over the entire temperature range.

cond-mat.str-el↗
arXiv2000

The temperature dependent behaviour of surface states in ferromagnetic semiconductors

We present a model calculation for the temperature dependent behaviour of surface states on a ferromagnetic local-moment film. The film is described within the s-f model featuring local magnetic moments being exchange coupled to the itinerant conduction electrons. The surface states are generated by modifying the hopping in the vicinity of the surface of the film. In the calculation for the temperature dependent behaviour of the surface states we are able to reproduce both Stoner-like and spin-mixing behaviour in agreement with recent (inverse) photoemission data on the temperature dependent behaviour of a Gd(0001) surface state.

cond-mat.str-el↗
arXiv1999

The temperature dependent bandstructure of a ferromagnetic semiconductor film

The electronic quasiparticle spectrum of a ferromagnetic film is investigated within the framework of the s-f model. Starting from the exact solvable case of a single electron in an otherwise empty conduction band being exchange coupled to a ferromagnetically saturated localized spin system we extend the theory to finite temperatures. Our approach is a moment-conserving decoupling procedure for suitable defined Green functions. The theory for finite temperatures evolves continuously from the exact limiting case. The restriction to zero conduction band occupation may be regarded as a proper model description for ferromagnetic semiconductors like EuO and EuS. Evaluating the theory for a simple cubic film cut parallel to the (100) crystal plane, we find some marked correlation effects which depend on the spin of the test electron, on the exchange coupling, and on the temperature of the local-moment system.

cond-mat.str-el↗
arXiv1999

Thickness dependent Curie temperatures of ferromagnetic Heisenberg films

We develop a procedure for calculating the magnetic properties of a ferromagnetic Heisenberg film with single-ion anisotropy which is valid for arbitrary spin and film thickness. Applied to sc(100) and fcc(100) films with spin S=7/2 the theory yields the layer dependent magnetizations and Curie temperatures of films of various thicknesses making it possible to investigate magnetic properties of films at the interesting 2D-3D transition.

cond-mat.str-el↗
arXiv1998

On the origin of surface states in a correlated local-moment film

The electronic quasiparticle structure of a ferromagnetic local moment film is investigated within the framework of the s-f model. For the special case of a single electron in an otherwise empty energy band being exchange coupled to a fully ordered localised spin system the problem can be solved exactly and, for the spin-down electron, some marked correlation effects can be found. We extend our model to incorporate the influence of the surface on the electronic structure. Therefore we modify the hopping integrals in the vicinity of the surface. This leads to the existence of surface states, both for the spin-up and the spin-down spectral density of states. The interplay between the modification of the hopping integrals and the existence of surface states and correlation effects is discussed in detail.

cond-mat.str-el↗