Magnetic Phase Diagrams of Manganites-like Local-Moment Systems with Jahn-Teller distortions (2008)
We use an extended two-band Kondo lattice model (KLM) to investigate the occurrence of different (anti-)ferromagnetic phases or phase separation depending on several model parameters. With regard to...
Ferromagnetism in multi-band Kondo lattice model (2008)
The ferromagnetic spin exchange interaction between the itinerant electrons and localized moments on a periodic lattice, studied within the so-called Kondo lattice model (KLM), is considered for...
Disordered Correlated Kondo-lattice model (2007)
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...
Sandschneider, N., Nolting, W.
Using the Keldysh formalism the tunneling current through a hybrid structure where a confined magnetic insulator (I) is sandwiched between two non-magnetic leads is calculated. The leads can be...
Green function theory versus Quantum Monte Carlo calculations for thin magnetic films (2007)
Henning, S., Koermann, F., Kienert, J., Schwieger, S., Nolting, W.
In this work we compare numerically exact Quantum Monte Carlo (QMC) calculations and Green function theory (GFT) calculations of thin ferromagnetic films including second order anisotropies. Thereby...
Schwieger, S., Kienert, J., Lenz, K., Lindner, J., Baberschke, K., Nolting, W.
Quantum mechanical calculations based on an extended Heisenberg model are compared with ferromagnetic resonance (FMR) experiments on prototype trilayer systems Ni_7/Cu_n/Co_2/Cu(001) in order to...
Kienert, J., Schwieger, S., Lenz, K., Lindner, J., Baberschke, K., Nolting, W.
Temperature dependent FMR-measurements of Ni and Co films are analysed using a microscopic theory for ultrathin metallic systems. The mechanism governing the temperature dependence of the magnetic...
A new type of temperature driven reorientation transition in magnetic thin films (2006)
Koermann, F., Schwieger, S., Kienert, J., Nolting, W.
We present a new type of temperature driven spin reorientation transition (SRT) in thin films. It can occur when the lattice and the shape anisotropy favor different easy directions of the...
Reddy, G. Gangadhar, Ramakanth, A., Ghatak, S. K., Behera, S. N., Nolting, W., Rao, T. Venkatappa
A model calculation is presented with the aim to study the interplay between magnetic and structural transitions. The model consists of an orbitally doubly degenerate conduction band and a periodic...
Temperature dependent electronic correlation effects in GdN (2006)
We investigate temperature dependent electronic correlation effects in the conduction bands of Gadolinium Nitride (GdN) based on the combination of many body analysis of the multi-band Kondo lattice...
Magnetic phase diagram of the Kondo lattice model with quantum localized spins (2006)
The magnetic phase diagram of the ferromagnetic Kondo lattice model is determined at T=0 in 1D, 2D, and 3D for various magnitudes of the quantum mechanical localized spins ranging from S=1/2 to...
Correlation effects in the valence bands of ferromagnetic semiconductor EuS (2005)
We present a many body analysis of the multi-band Kondo lattice model. The study is then combined with the first principles TB-LMTO band structure calculations, in order to investigate the...
Magnetic properties of a disordered Heisenberg binary spin system with long-range exchange (2005)
The influence of substitutional disorder on the magnetic properties of disordered Heisenberg binary spin systems with long-range exchange integrals is studied. The equation of motion for the magnon...
Electronic properties of EuB6 in the ferromagnetic regime: Half-metal versus semiconductor (2005)
To understand the halfmetallic ferromagnet EuB6 we use the Kondo lattice model for valence and conduction band. By means of a recently developed many-body theory we calculate the electronic...
The temperature dependence of interlayer exchange coupling - spin waves vs. spacer effects (2005)
Schwieger, S., Kienert, J., Nolting, W.
There are different mechanisms proposed to be responsible for the temperature dependence of the interlayer exchange coupling (IEC), namely a smearing out of the spacer or interface Fermi surface and...
Magnetism in (III, Mn)-V Diluted Magnetic Semiconductors: Effective Heisenberg Model (2005)
The magnetic properties of the diluted magnetic semiconductors (DMS) (Ga, Mn)As and (Ga, Mn)N are investigated by means of an effective Heisenberg model, whose exchange parameters are obtained from...
Theory of field induced spin reorientation transition in thin Heisenberg films (2004)
Schwieger, S., Kienert, J., Nolting, W.
We consider the spin reorientation transition in a ferromagnetic Heisenberg monolayer with a second order single ion anisotropy as a function of temperature and external field. Up to now analytical...
Disorder in Diluted Spin Systems (2004)
The influence of substitutional disorder on the magnetic properties of diluted Heisenberg spin systems is studied with regard to the magnetic stability of ferromagnetic diluted semiconductors (DMS)....
Carrier induced ferromagnetism in concentrated and diluted local-moment systems (2004)
Nolting, W., Hickel, T., Ramakanth, A., Reddy, G. G., Lipowczan, M.
For modeling the magnetic properties of concentrated and diluted magnetic semiconductors, we use the Kondo-lattice model. The magnetic phase diagram is derived by inspecting the static susceptibility...
On the origin of temperature dependence of interlayer exchange coupling in metallic trilayers (2004)
We study the influence of collective magnetic excitations on the interlayer exchange coupling (IEC) in metallic multilayers. The results are compared to other models that explain the temperature...
Ferromagnetism and temperature-dependent Electronic Structure of hcp Gadolinium (2004)
Santos, C., Eyert, V., Nolting, W.
We use a combination of a many-body model analysis with an ab initio band structure calculation to derive the temperature dependent electronic quasiparticle structure of the rare-earth metal...
Proper weak-coupling approach to the periodic s-d(f) exchange model (2003)
The periodic s-d(f) exchange model is characterized by a wide variety of interesting applications, a simple mathematical structure and a limited number of reliable approximations which take care of...
On details of the thermodynamical derivation of the Ginsburg--Landau equations (2003)
We examine the procedure of thermodynamical derivation of the Ginsburg--Landau equation for current, which is given unclear and contradictory interpretations in existing textbooks. We clarify all...
Metal-insulator transition in EuO (2003)
It is shown that the spectacular metal-insulator transition in Eu-rich EuO can be simulated within an extended Kondo lattice model. The different orders of magnitude of the jump in resistivity in...
The Correlated Kondo-lattice Model (2003)
Kienert, J., Santos, C., Nolting, W.
We investigate the ferromagnetic Kondo-lattice model (FKLM) with a correlated conduction band. A moment conserving approach is proposed to determine the electronic self-energy. Mapping the...
Ferromagnetic Kondo-Lattice Model (2003)
Nolting, W., Müller, W., Santos, C.
We present a many-body approach to the electronic and magnetic properties of the (multiband) Kondo-lattice model with ferromagnetic interband exchange. The coupling between itinerant conduction...
Correlation and surface effects in Vanadium Oxides (2003)
Schwieger, S., Potthoff, M., Nolting, W.
Recent photoemission experiments have shown strong surface modifications in the spectra from vanadium oxides as (V,Cr)_2O_3 or (Sr,Ca)VO_3. The effective mass is enhanced at the surface and the...
Exact solution for the two-site Kondo-Lattice Model - a limiting case for an insulator (2002)
Hickel, T., Roeseler, J., Nolting, W.
The Kondo-lattice model is well established as a method to describe an exchange coupling between single conduction electrons and localized magnetic moments. As a nontrivial exact result the...
Exact solution for the two-site correlated Kondo-Lattice Model - a limiting case for a metal (2002)
Hickel, T., Roeseler, J., Nolting, W.
The correlated Kondo-lattice model is used to describe the interaction of electrons in a single conduction band with localized magnetic moments as well as their mutual repulsion. It is our intension...
Self-energy approach to the correlated Kondo-lattice model (2002)
Nolting, W., Reddy, G. G., Ramakanth, A., Meyer, D., Kienert, J.
We develop an interpolating self-energy approach to the correlated Kondo-lattice model. The correlation of the band electrons is taken into account by a Hubbard interaction. The method is based on a...
Local Density of States in the Antiferromagnetic and Ferromagnetic Kondo Models (2002)
Sinjukow, P., Meyer, D., Nolting, W.
Based on a simple approximation scheme we have computed the local density of states (LDOS) of the antiferromagnetic and ferromagnetic Kondo models for the full range of band occupations and coupling...
Temperature-dependent quasiparticle band structure of the ferromagnetic semiconductor EuS (2002)
We present calculations for the temperature-dependent electronic structure of the ferromagnetic semiconductor EuS. A combination of a many-body evaluation of a multiband Kondo-lattice model and a...
Exact Mapping of Periodic Anderson Model to Kondo Lattice Model (2002)
It is shown that the Kondo lattice model, for any finite coupling constant J, can be obtained exactly from the periodic Anderson model in an appropriate limit. The mapping allows a direct proof of...
Long range superexchange - an exchange interaction through empty bands (2002)
We derive a generalization of the RKKY interaction to semiconductors using perturbation theory on a non-degenerated two-impurity Anderson model. In metals the interaction is mediated by excitations...
Hubbard Hamiltonian in the dimer representation. Large U limit (2002)
Matlak, M., Aksamit, J., Grabiec, B., Nolting, W.
We formulate the Hubbard model for the simple cubic lattice in the representation of interacting dimers applying the exact solution of the dimer problem. By eliminating from the considerations...
Temperature-dependent electronic structure and magnetic stability of thin ferromagnetic films (2002)
We study correlation effects and temperature dependencies in the electronic structure of thin ferromagnetic local-moment films. In a first step the Kondo-lattice model is investigated as a candidate...
Ferromagnetism in the Kondo-lattice model (2002)
We propose a modified RKKY-technique to evaluate the magnetic properties of the ferromagnetic Kondo-lattice model. Together with a previously developed selfenergy approach to the conduction electron...
Interlayer Exchange Coupling in M/N/M Multilayer (2001)
Jaya, S. Mathi, Valsakumar, M. C., Nolting, W.
The interlayer exchange coupling (IEC) of two local moment ferromagnetic layers separated by a non-magnetic spacer layer (M/N/M multilayer) is studied using the modified RKKY method along with the...
Ferromagnetism in the Hubbard model (2001)
Nolting, W., Potthoff, M., Herrmann, T., Wegner, T.
We investigate the possibility and stability of bandferromagnetism in the single-band Hubbard model. This model poses a highly non-trivial many-body problem the general solution of which has not been...
Low density approach to the Kondo-lattice model (2001)
Nolting, W., Reddy, G. G., Ramakanth, A., Meyer, D.
We propose a new approach to the (ferromagnetic) Kondo-lattice model in the low density region, where the model is thought to give a reasonable frame work for manganites with perovskite structure...
Stabilization of d-Band Ferromagnetism by Hybridization with Uncorrelated Bands (2001)
We investigate the influence of s-d or p-d hybridization to d-band ferromagnetism to estimate the importance of hybridization for the magnetic properties of transition metals. To focus our attention...
Schiller, R., Mueller, W., Nolting, W.
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...
Strong-coupling scenario of a metamagnetic transition (2001)
We investigate the periodic Anderson model in the presence of an external magnetic field, using dynamical mean-field theory in combination with the modified perturbation theory. A metamagnetic...
Temperature-dependent bandstructure of bulk EuO (2001)
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...
We calculate the temperature and layer-dependent electronic structure of a 20-layer EuO(100)-film using a combination of first-principles and model calculation based on the ferromagnetic...
Electron-correlation effects in appearance-potential spectra of Ni (2001)
Potthoff, M., Wegner, T., Nolting, W., Schlathölter, T., Vonbank, M., Ertl, K., ...
Spin-resolved and temperature-dependent appearance-potential spectra of ferromagnetic Nickel are measured and analyzed theoretically. The Lander self-convolution model which relates the line shape to...
Quantum effects in the quasiparticle structure of the ferromagnetic Kondo lattice model (2001)
Meyer, D., Santos, C., Nolting, W.
A new ``Dynamical Mean-field theory'' based approach for the Kondo lattice model with quantum spins is introduced. The inspection of exactly solvable limiting cases and several known approximation...
Electron-Correlation Effects in Appearance-Potential Spectra of Ni (2001)
Potthoff, M., Wegner, T., Nolting, W., Schlatholter, T., Vonbank, M., Ertl, K., ...
Magnons in the ferromagnetic Kondo-lattice model (2000)
Vogt, M., Santos, C., Nolting, W.
The magnetic properties of the ferromagnetic Kondo-lattice model (FKLM) are investigated. Starting from an analysis of the magnon spectrum in the spin-wave regime, we examine the ferromagnetic...
Ferromagnetism in the Periodic Anderson Model - a Modified Alloy Analogy (2000)
Reddy, G G, Meyer, D, Schwieger, S, Ramakanth, A, Nolting, W
We introduce a new aproximation scheme for the periodic Anderson model (PAM). The modified alloy approximation represents an optimum alloy approximation for the strong coupling limit, which can be...
We compare different approximation schemes for investigating ferromagnetism in the periodic Anderson model. The use of several approximations allows for a detailed analysis of the implications of the...
Dynamical mean-field study of ferromagnetism in the periodic Anderson model (2000)
The ferromagnetic phase diagram of the periodic Anderson model is calculated using dynamical mean-field theory in combination with the modified perturbation theory. Concentrating on the intermediate...
Kondo screening and exhaustion in the periodic Anderson model (2000)
We investigate the paramagnetic periodic Anderson model using the dynamical mean-field theory in combination with the modified perturbation theory which interpolates between the weak and strong...
The temperature dependent behaviour of surface states in ferromagnetic semiconductors (2000)
Schiller, R., Mueller, W., Nolting, W.
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...
Theory of Spin-Resolved Auger-Electron Spectroscopy from Ferromagnetic 3d-Transition Metals (1999)
Wegner, T., Potthoff, M., Nolting, W.
CVV Auger electron spectra are calculated for a multi-band Hubbard model including correlations among the valence electrons as well as correlations between core and valence electrons. The interest is...
Effects of Core-Hole Screening on Spin-Polarised Auger Spectra from Ferromagnetic Nickel (1999)
Wegner, T., Potthoff, M., Nolting, W.
We calculate the spin- and temperature-dependent local density of states for ferromagnetic Ni in the presence of a core hole at a distinguished site in the lattice. Correlations among the valence...
Relativistic photoemission theory for general nonlocal potentials (1999)
Meyer, C., Potthoff, M., Nolting, W., Borstel, G., Braun, J.
An improved formulation of the one-step model of photoemission from crystal surfaces is proposed which overcomes different limitations of the original theory. Considering the results of an...
On the magnetic stability at the surface in strongly correlated electron systems (1999)
The stability of ferromagnetism at the surface at finite temperatures is investigated within the strongly correlated Hubbard model on a semi-infinite lattice. Due to the reduced surface coordination...
Influence of uncorrelated overlayers on the magnetism in thin itinerant-electron films (1999)
Wu, J. H., Herrmann, T., Nolting, W.
The influence of uncorrelated (nonmagnetic) overlayers on the magnetic properties of thin itinerant-electron films is investigated within the single-band Hubbard model. The Coulomb correlation...
The temperature dependent bandstructure of a ferromagnetic semiconductor film (1999)
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...
Metallic surface of a Mott insulator - Mott insulating surface of a metal (1999)
The dynamical mean-field theory (DMFT) is employed to study the Mott transition in the semi-infinite Hubbard model at half-filling and zero temperature. We consider the low-index surfaces of the...
We investigate the influence of an interband exchange interaction on magnetism in a two-band Hubbard model. Our main emphasis lies on spin-flip scattering which is often neglected but is neccessary...
The asymmetric single-impurity Anderson model - the modified perturbation theory (1999)
Meyer, D., Wegner, T., Potthoff, M., Nolting, W.
We investigate the single-impurity Anderson model by means of the recently introduced modified perturbation theory. This approximation scheme yields reasonable results away from the symmetric case....
Thickness dependent Curie temperatures of ferromagnetic Heisenberg films (1999)
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)...
Ferromagnetism and the temperature-dependent electronic structure in thin Hubbard films (1998)
The magnetic behavior of thin ferromagnetic itinerant-electron films is investigated within the strongly correlated single-band Hubbard model. For its approximate solution we apply a generalization...
Surface metal-insulator transition in the Hubbard model (1998)
The correlation-driven metal-insulator (Mott) transition at a solid surface is studied within the Hubbard model for a semi-infinite lattice by means of the dynamical mean-field theory. The transition...
Effective mass at the surface of a Fermi liquid (1998)
Using the dynamical mean-field theory, we calculate the effective electron mass in the Hubbard model on a semi-infinite lattice. At the surface the effective mass is strongly enhanced. Near...
Dynamical mean-field study of the Mott transition in thin films (1998)
The correlation-driven transition from a paramagnetic metal to a paramagnetic Mott-Hubbard insulator is studied within the half-filled Hubbard model for a thin-film geometry. We consider simple-cubic...
The moment sum rule and its consequences for ferromagnetism in the Hubbard model (1998)
Potthoff, M., Herrmann, T., Wegner, T., Nolting, W.
The sum rule for the moments of the spectral density is discussed for the single-band Hubbard model. It is shown that respecting the sum rule up to the order m=3 is conceptually important for a...
Optimization of alloy-analogy-based approaches to the infinite-dimensional Hubbard model (1998)
Potthoff, M., Herrmann, T., Nolting, W.
An analytical expression for the self-energy of the infinite-dimensional Hubbard model is proposed that interpolates between different exactly solvable limits. We profit by the combination of two...
Ferromagnetism within the periodic Anderson model: A new approximation scheme (1998)
Meyer, D., Nolting, W., Reddy, G. G., Ramakanth, A.
We introduce a new approach to the periodic Anderson model (PAM) that allows a detailed investigation of the magnetic properties in the Kondo as well as the intermediate valence regime. Our method is...
Herrmann, T., Potthoff, M., Nolting, W.
The temperature-driven reorientation transition which, up to now, has been studied by use of Heisenberg-type models only, is investigated within an itinerant-electron model. We consider the Hubbard...
On the origin of surface states in a correlated local-moment film (1998)
Schiller, R., Mueller, W., Nolting, W.
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...
Wegner, T., Potthoff, M., Nolting, W.
The infinite-dimensional Hubbard model is studied by means of a modified perturbation theory. The approach reduces to the iterative perturbation theory for weak coupling. It is exact in the atomic...
One-step model of photoemission for non-local potentials (1997)
Potthoff, M., Lachnitt, J., Nolting, W., Braun, J.
The one-step model of valence-band photoemission and inverse photoemission from single-crystal surfaces is reformulated for generalized (non-local, complex and energy-dependent) potentials. Thereby,...
Weak-coupling approach to the semi-infinite Hubbard model: Non-locality of the self-energy (1997)
The Hubbard model on a semi-infinite three-dimensional lattice is considered to investigate electron-correlation effects at single-crystal surfaces. The standard second-order perturbation theory in...
Ferromagnetism in the Hubbard model: Influence of the lattice structure (1997)
By use of the spectral density approach the influence of the lattice structure on the possibility of ferromagnetism in the single band Hubbard model is investigated. The d=\infty hypercubic lattice...