H Ebert

Publications (129)195.21 Total impact

• Article: Enhanced iron magnetic moment in the ThFe11C2 intermetallic compound

  D Benea, O Isnard, J Minár, H Ebert, V Pop
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  ABSTRACT: Detailed theoretical investigations on the electronic and magnetic properties of the ThFe11C2 compound have been performed using both the linear muffin-tin orbital and Korringa–Kohn–Rostocker methods of band structure calculation. The structure of the ThFe11C2 compound has three inequivalent iron sites with different local environment. A strongly enhanced magnetic moment is observed on certain Fe positions, coexisting with much lower magnetic moments on other iron positions of the lattice. Band structure calculations indeed show that the Fe magnetic moments depend strongly on the local environment. The average Fe magnetic moment obtained from these calculations is in good agreement with the experimental average Fe moment obtained from magnetization measurements. The orbital contribution to the magnetic moment is found to be especially large on the Fe 4b position. Comparing calculated hyperfine fields with experimental results, it is found that the calculated and experimental hyperfine fields are correlated. However, similarly to the results reported before for elemental Fe, the magnitude of all calculated Fe hyperfine fields is about 25% smaller. The agreement with the Mössbauer measurements is improved by scaling the core polarization contribution and by estimating the orbital valence d-electrons contribution to the magnetic hyperfine fields using the local spin density approximation + dynamical mean field theory calculated orbital moments.
  Journal of Applied Physics 02/2013; 109:083909-083909. · 2.17 Impact Factor
• Source

  Available from: Diana Benea

  Article: Magnetic Compton profiles of Fe and Ni corrected by dynamical electron correlations

  D Benea, J. Minár, S. Mankovsky, L. Chioncel, H Ebert
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  ABSTRACT: Magnetic Compton profiles (MCPs) of Ni and Fe along [111] direction have been calculated using a combined Density Functional and many-body theory approach. At the level of the local spin density approximation the theoretical MCPs does not describe correctly the experimental results around the zero momentum transfer. In this work we demonstrate that inclusion of electronic correlations as captured by Dynamical Mean Field Theory (DMFT) improves significantly the agreement between the theoretical and the experimental MCPs. In particular, an energy decomposition of Ni MCPs gives indication of spin polarization and intrinsic nature of Ni 6 eV satellite, a genuine many-body feature.
  Physical Review B 02/2013; 85:085109. · 3.69 Impact Factor
• Article: First-principles calculation of the Gilbert damping parameter via the linear response formalism with application to magnetic transition-metals and alloys

  S. Mankovsky, D. Koedderitzsch, G. Woltersdorf, H. Ebert
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  ABSTRACT: A method for the calculations of the Gilbert damping parameter $\alpha$ is presented, which based on the linear response formalism, has been implemented within the fully relativistic Korringa-Kohn-Rostoker band structure method in combination with the coherent potential approximation alloy theory. To account for thermal displacements of atoms as a scattering mechanism, an alloy-analogy model is introduced. This allows the determination of $\alpha$ for various types of materials, such as elemental magnetic systems and ordered magnetic compounds at finite temperature, as well as for disordered magnetic alloys at $T = 0$ K and above. The effects of spin-orbit coupling, chemical and temperature induced structural disorder are analyzed. Calculations have been performed for the 3$d$ transition-metals bcc Fe, hcp Co, and fcc Ni, their binary alloys bcc Fe$_{1-x}$Co$_{x}$, fcc Ni$_{1-x}$Fe$_x$, fcc Ni$_{1-x}$Co$_x$ and bcc Fe$_{1-x}$V$_{x}$, and for 5d impurities in transition-metal alloys. All results are in satisfying agreement with experiment.
  01/2013;
• Article: Electronic structure and magnetic properties of CrSb$_2$ and FeSb$_2$ investigated via ab-initio calculations

  G. Kuhn, S. Mankovsky, H. Ebert, M. Regus, W. Bensch
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  ABSTRACT: The electronic structure and magnetic properties of CrSb$_2$ have been investigated by ab-initio calculations with an emphasis on the role of the magnetic structure for the ground state. The influence of correlation effects has been investigated by performing fixed spin moment (FSM) calculations showing their important role for the electronic and magnetic properties. The details of the electronic structure of CrSb$_2$ are analyzed by a comparison with those of FeSb$_2$. The results obtained contribute in particular to the understanding of the temperature dependence of transport and magnetic behavior observed experimentally.
  07/2012;
• Article: Magnetic properties of CrSb compounds with zinc-blende and wurtzite structures.

  G Kuhn, S Polesya, S Mankovsky, J Minár, H Ebert, M Regus, W Bensch
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  ABSTRACT: The electronic structure and magnetic properties of Cr-Sb compounds with zinc-blende and wurtzite structure have been studied by means of the Korringa-Kohn-Rostoker (KKR) band structure method. The occurrence of a half-metallic behavior has been investigated for the bulk systems as a function of lattice parameter, as well as for thin films deposited on different substrates. In the latter case the influence of the surface and interface on the electronic structure is discussed in addition. To study magnetic order in the bulk and within the films, exchange coupling parameters have been calculated from first principles. They have been used for subsequent Monte Carlo simulations, based on a classical Heisenberg Hamiltonian, to obtain the Curie temperature.
  Journal of Physics Condensed Matter 07/2012; 24(30):306005. · 2.55 Impact Factor
• Article: Trends in the magnetic properties of Fe, Co and Ni clusters and monolayers on Ir(111), Pt(111) and Au(111)

  S. Bornemann, O. Šipr, S. Mankovsky, S. Polesya, J. B. Staunton, W. Wurth, H. Ebert, J. Minár
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  ABSTRACT: We present a detailed theoretical investigation on the magnetic properties of small single-layered Fe, Co and Ni clusters deposited on Ir(111), Pt(111) and Au(111). For this a fully relativistic {\em ab-initio} scheme based on density functional theory has been used. We analyse the element, size and geometry specific variations of the atomic magnetic moments and their mutual exchange interactions as well as the magnetic anisotropy energy in these systems. Our results show that the atomic spin magnetic moments in the Fe and Co clusters decrease almost linearly with coordination on all three substrates, while the corresponding orbital magnetic moments appear to be much more sensitive to the local atomic environment. The isotropic exchange interaction among the cluster atoms is always very strong for Fe and Co exceeding the values for bulk bcc Fe and hcp Co, whereas the anisotropic Dzyaloshinski-Moriya interaction is in general one or two orders of magnitude smaller when compared to the isotropic one. For the magnetic properties of Ni clusters the magnetic properties can show quite a different behaviour and we find in this case a strong tendency towards noncollinear magnetism.
  04/2012;
• Article: Magnetic properties of Co clusters deposited on Pt(111)

  J. Minár, S. Bornemann, O. Šipr, S. Polesya, H. Ebert
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  ABSTRACT: Using the fully relativistic version of the Korringa–Kohn–Rostoker method for electronic structure calculations within local spin density functional theory, the magnetic and spectroscopic properties of Co clusters deposited on Pt(111) have been investigated. Of central interest was the role of spin–orbit coupling, since it influences the spontaneous formation and orientation of magnetic moments and gives rise among other things to the occurrence of orbital magnetic moments, magnetic anisotropy energy and magnetic circular dichroism in X-ray absorption. The results have been complemented by calculations of the exchange coupling parameters Jij used within Monte Carlo simulations on the basis of the extended classical Heisenberg Hamiltonian. This allowed us to simulate the magnetic properties at finite temperatures, which are of central importance for applications.
  Applied Physics A 04/2012; 82(1):139-144. · 1.63 Impact Factor
• Article: Electronic and magnetic trends in martensitically transforming Fe--Pd alloys

  ME Gruner, P Entel, J Minár, S Polesya, S Mankovsky, H Ebert
  Journal of Magnetism and Magnetic Materials 01/2012; · 1.78 Impact Factor
• Article: Correlation effects in magnetic materials: an ab-initio investigation on electronic structure and spectroscopy

  J Minár, J Braun, H Ebert
  Journal of Electron Spectroscopy and Related Phenomena 01/2012; · 1.96 Impact Factor
• Article: Effects of spin-dependent quasiparticle renormalization in Fe, Co, and Ni photoemission spectra: An experimental and theoretical study

  J Sanchez-Barriga, J Braun, J Minar, I Di Marco, A Varykhalov, O Rader, V Boni, V Bellini, F Manghi, H Ebert, M I Katsnelson, A I Lichtenstein, O Eriksson, W Eberhardt, H A Duerr, J Fink
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  ABSTRACT: We have investigated the spin-dependent quasiparticle lifetimes and the strength of electron correlation effects in the ferromagnetic 3d transition metals Fe, Co, and Ni by means of spin- and angle-resolved photoemission spectroscopy. The experimental data are accompanied by state-of-the-art many-body calculations within the dynamical mean-field theory and the three-body scattering approximation, including fully relativistic calculations of the photoemission process within the one-step model. Our quantitative analysis reveals that inclusion of local many-body Coulomb interactions are of ultimate importance for a realistic description of correlation effects in ferromagnetic 3d transition metals. However, we found that more sophisticated many-body calculations with larger modifications in the case of Fe and Co are still needed to improve the quantitative agreement between experiment and theory. In general, it turned out that not only the dispersion behavior of energetic structures should be affected by nonlocal correlations but also the line widths of most of the photoemission peaks are underestimated by the current theoretical approaches. The increasing values of the on-site Coulomb interaction parameter U and the band narrowing of majority spin states obtained when moving from Fe to Ni indicate that the effect of nonlocal correlations becomes weaker with increasing atomic number, whereas correlation effects tend to be stronger.
  Physical Review B 01/2012; 85(20). · 3.69 Impact Factor
• Article: Recent developments in the theory of HARPES

  J Minár, J Braun, H Ebert
  Journal of Electron Spectroscopy and Related Phenomena 01/2012; · 1.96 Impact Factor
• Article: Structural and magnetic properties of CrSb compounds: NiAs structure.

  S Polesya, G Kuhn, S Mankovsky, H Ebert, M Regus, W Bensch
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  ABSTRACT: The structural and magnetic properties of CrSb compounds with NiAs structure have been studied by means of the Korringa-Kohn-Rostoker (KKR) band structure method. An analysis of the structural and magnetic stability has been performed on the basis of total energy calculations for various magnetic states. The magnetic properties at finite temperature have been investigated by means of Monte Carlo simulations on the basis of a classical Heisenberg Hamiltonian and the exchange coupling parameters calculated from first principles. This approach allowed us to determine the critical temperature in good agreement with experiment.
  Journal of Physics Condensed Matter 12/2011; 24(3):036004. · 2.55 Impact Factor
• Source

  Available from: Jan Minar

  Article: Spin-orbit coupling effect in (Ga,Mn)As films: anisotropic exchange interactions and magnetocrystalline anisotropy

  S. Mankovsky, S. Polesya, S. Bornemann, J. Minár, F. Hoffmann, C H Back, H Ebert
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  ABSTRACT: The magneto-crystalline anisotropy (MCA) of (Ga,Mn)As films has been studied on the basis of ab-initio electronic structure theory by performing magnetic torque calculations. An appreciable contribution to the in-plane uniaxial anisotropy can be attributed to an extended region adjacent to the surface. Calculations of the exchange tensor allow to ascribe a significant part to the MCA to the exchange anisotropy, caused either by a tetragonal distortion of the lattice or by the presence of the surface or interface.
  08/2011;
• Article: Calculating condensed matter properties using the KKR-Green's function method—recent developments and applications

  H Ebert, D Ködderitzsch, J Minár
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  ABSTRACT: The modern version of the KKR (Korringa–Kohn–Rostoker) method represents the electronic structure of a system directly and efficiently in terms of its single-particle Green's function (GF). This is in contrast to its original version and many other traditional wave-function-based all-electron band structure methods dealing with periodically ordered solids. Direct access to the GF results in several appealing features. In addition, a wide applicability of the method is achieved by employing multiple scattering theory. The basic ideas behind the resulting KKR-GF method are outlined and the different techniques to deal with the underlying multiple scattering problem are reviewed. Furthermore, various applications of the KKR-GF method are reviewed in some detail to demonstrate the remarkable flexibility of the approach. Special attention is devoted to the numerous developments of the KKR-GF method, that have been contributed in recent years by a number of work groups, in particular in the following fields: embedding schemes for atoms, clusters and surfaces, magnetic response functions and anisotropy, electronic and spin-dependent transport, dynamical mean field theory, various kinds of spectroscopies, as well as first-principles determination of model parameters.
  Reports on Progress in Physics 08/2011; 74(9):096501. · 14.72 Impact Factor
• Source

  Available from: ArXiv

  Article: Ab initio calculation of the Gilbert damping parameter via the linear response formalism.

  H Ebert, S Mankovsky, D Ködderitzsch, P J Kelly
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  ABSTRACT: A Kubo-Greenwood-like equation for the Gilbert damping parameter α is presented that is based on the linear response formalism. Its implementation using the fully relativistic Korringa-Kohn-Rostoker band structure method in combination with coherent potential approximation alloy theory allows it to be applied to a wide range of situations. This is demonstrated with results obtained for the bcc alloy system Fe(1-x)Co(x) as well as for a series of alloys of Permalloy with 5d transition metals. To account for the thermal displacements of atoms as a scattering mechanism, an alloy-analogy model is introduced. The corresponding calculations for Ni correctly describe the rapid change of α when small amounts of substitutional Cu are introduced.
  Physical Review Letters 08/2011; 107(6):066603. · 7.37 Impact Factor
• Article: Electronic and transport properties of disordered transition‐metal alloys

  D. Ködderitzsch, S. Lowitzer, J. B. Staunton, H. Ebert
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  ABSTRACT: We present a first-principles approach to describe electronic transport of disordered alloys in a material specific way. The electronic structure is represented in terms of the relativistic multiple scattering KKR-Green function. Disorder with possible inclusion of short-ranged order effects is taken into account by the coherent-potential approximation or its non-local formulation. A salient feature of the presented method is the possibility to combine it with a linear response Kubo framework, allowing for a detailed investigation of many transport phenomena which are of immediate relevance for applications in which electrons and/or their spin are manipulated. This is illustrated by several examples and developments, among them the description of the residual resistivity of K-state- and ferromagnetic alloys. Inclusion of relativistic effects by using the Dirac-formalism represents the basis to deal with the anomalous Hall effect and to derive a relativistic spin-projection scheme for currents.
  physica status solidi (b) 06/2011; 248(10):2248 - 2265. · 1.32 Impact Factor
• Source

  Available from: Jan Minar

  Article: Many-body effects in x-ray absorption and magnetic circular dichroism spectra within the LSDA+DMFT framework

  O. Sipr, J. Minar, A Scherz, H Wende, H Ebert
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  ABSTRACT: The theoretical description of photoemission spectra of transition metals was greatly improved recently by accounting for the correlations between the d electrons within the local spin density approximation (LSDA) plus dynamical mean field theory (DMFT). We assess the improvement of the LSDA+DMFT over the plain LSDA in x-ray absorption spectroscopy, which --- unlike the photoemission spectroscopy --- is probing unocccupied electronic states. By investigating the L2,3-edge x-ray absorption near-edge structure (XANES) and x-ray magnetic circular dichroism (XMCD) of Fe, Co, and Ni, we find that the LSDA+DMFT improves the LSDA results, in particular concerning the asymmetry of the L3 white line. Differences with respect to the experiment, nevertheless, remain --- particularly concerning the ratio of the intensities of the L3 and L2 peaks. The changes in the XMCD peak intensities invoked by the use of the LSDA+DMFT are a consequence of the improved description of the orbital polarization and are consistent with the XMCD sum rules. Accounting for the core hole within the final state approximation does not generally improve the results. This indicates that to get more accurate L2,3-edge XANES and XMCD spectra, one has to treat the core hole beyond the final state approximation.
  05/2011;
• Article: Magnetocrystalline anisotropy and Gilbert damping in iron-rich Fe-Si thin films

  I. Barsukov, S. Mankovsky, A. Rubacheva, R. Meckenstock, D. Spoddig, J. Lindner, N. Melnichak, B. Krumme, S. I. Makarov, H. Wende, H. Ebert, M. Farle
  Physical Review B 01/2011; 84:180405(R). · 3.69 Impact Factor
• Article: d-and sp-like surface states on fcc Co (001) with distinct sensitivity to surface roughness

  T Allmers, M Donath, J Braun, J Minár, H Ebert
  Physical Review B. 01/2011; 84(24):245426.
• Article: Semiconductors I: Bulk-Spin-orbit coupling effect in (Ga, Mn) As films: Anisotropic exchange interactions and magnetocrystalline anisotropy (5 pages) 201201 (R)

  S Mankovsky, S Polesya, S Bornemann, J Minár, F Hoffmánn, CH Back, H Ebert
  Physical Review-Section B-Condensed Matter. 01/2011; 84(20).