uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Di Marco, Igor
Alternative names
Publications (10 of 49) Show all publications
Di Marco, I., Held, A., Keshavarz, S., Kvashnin, Y. O. & Chioncel, L. (2018). Half-metallicity and magnetism in the Co2MnAl/CoMnVAl heterostructure. Physical Review B, 97(3), Article ID 035105.
Open this publication in new window or tab >>Half-metallicity and magnetism in the Co2MnAl/CoMnVAl heterostructure
Show others...
2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 3, article id 035105Article in journal (Refereed) Published
Abstract [en]

We present a study of the electronic structure and magnetism of Co2MnAl, CoMnVAl, and their heterostructure. We employ a combination of density-functional theory and dynamical mean-field theory (DFT+DMFT). We find that Co2MnAl is a half-metallic ferromagnet, whose electronic and magnetic properties are not drastically changed by strong electronic correlations, static or dynamic. Nonquasiparticle states are shown to appear in the minority spin gap without affecting the spin polarization at the Fermi level predicted by standard DFT. We find that CoMnVAl is a semiconductor or a semimetal, depending on the employed computational approach. We then focus on the electronic and magnetic properties of the Co2MnAl/CoMnVAl heterostructure, predicted by previous first-principle calculations as a possible candidate for spin-injecting devices. We find that two interfaces, Co-Co/V-Al and Co-Mn/Mn-Al, preserve the half-metallic character, with and without including electronic correlations. We also analyze the magnetic exchange interactions in the bulk and at the interfaces. At the Co-Mn/Mn-Al interface, competing magnetic interactions are likely to favor the formation of a noncollinear magnetic order, which is detrimental for the spin polarization.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-341501 (URN)10.1103/PhysRevB.97.035105 (DOI)000419230600004 ()
Available from: 2018-02-13 Created: 2018-02-13 Last updated: 2018-02-13Bibliographically approved
Kanski, J., Ilver, L., Karlsson, K., Ulfat, I., Leandersson, M., Sadowski, J. & Di Marco, I. (2017). Electronic structure of (Ga, Mn) As revisited. New Journal of Physics, 19, Article ID 023006.
Open this publication in new window or tab >>Electronic structure of (Ga, Mn) As revisited
Show others...
2017 (English)In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 19, article id 023006Article in journal (Refereed) Published
Abstract [en]

The detailed nature of electronic states mediating ferromagnetic coupling in dilute magnetic semiconductors, specifically (Ga, Mn) As, has been an issue of long debate. Two confronting models have been discussed emphasizing host band versus impurity band carriers. Using angle resolved photoemission we show that the electronic structure of the (Ga, Mn) As system is significantly modified from that of GaAs throughout the valence band. Close to the Fermi energy, the presence of Mninduces a strong mixing of the bulk bands of GaAs, which results in the appearance of a highly dispersive band in the gap region of GaAs. ForMnconcentrations above1% the band reaches the Fermi level, and can thus host the delocalized holes needed for ferromagnetic coupling. Overall, our data provide a firm evidence of delocalized carriers belonging to the modified host valence band.

Keyword
dilute magnetic semiconductors, band structure, magnetic coupling
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-331901 (URN)10.1088/1367-2630/aa5a42 (DOI)000405916900002 ()
Available from: 2017-10-24 Created: 2017-10-24 Last updated: 2017-11-29Bibliographically approved
Ivanov, S. A., Bush, A. A., Ritter, C., Behtin, M. A., Cherepanov, V. M., Autieri, C., . . . Mathieu, R. (2017). Evolution of the structural and multiferroic properties of PbFe2/3W1/3O3 ceramics upon Mn-doping. Materials Chemistry and Physics, 187, 218-232.
Open this publication in new window or tab >>Evolution of the structural and multiferroic properties of PbFe2/3W1/3O3 ceramics upon Mn-doping
Show others...
2017 (English)In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 187, p. 218-232Article in journal (Refereed) Published
Abstract [en]

The perovskite system Pb(Fe1-xMnx)(2/3)W1/3O3 (0 <= x <= 1, PFMWO) has been prepared by conventional solid-state reaction under different sintering conditions. Structures and phase composition as well as thermal, magnetic and dielectric properties of the compounds have been systematically investigated experimentally and by first-principles density functional calculations. A clean perovskite phase is established at room temperature for compositions 0 <= x <= 0.4. Rietveld refinements of X-ray and neutron powder diffraction patterns demonstrate that the compounds crystallize in space group Pm-3m (0 <= x <= 0.4). The degree of ordering of the Fe and W/Mn cations was found to depend on the concentration of Mn. First-principles calculations suggest that the structural properties of PFMWO are strongly influenced by the Jahn Teller effect. The PFMWO compounds behave as relaxor ferroelectrics at weak Mn-doping with a dielectric constant that rapidly decreases with increasing Mn content. A low temperature antiferromagnetic G-type order with propagation vector k = (1/2,1/2,1/2) is derived from neutron powder diffraction data for the samples with x <= 0.4. However with increasing doping concentration, the magnetic order is perturbed. First principles calculations show that the dominant exchange coupling is antiferromagnetic and occurs between nearest neighbor Fe atoms. When the system is doped with Mn, a relatively weak ferromagnetic (FM) interaction between Fe and Mn atoms emerges. However, due to the presence of this FM interaction, the correlation length of the magnetic order is greatly shortened already at rather low doping levels.

Keyword
Oxides, Dielectric properties, Magnetic properties, Magnetic structures
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-316943 (URN)10.1016/j.matchemphys.2016.12.003 (DOI)000392786900026 ()
Funder
Swedish Research CouncilGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyThe Swedish Foundation for International Cooperation in Research and Higher Education (STINT)Knut and Alice Wallenberg FoundationCarl Tryggers foundation , CTS 12:419 13:413
Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2017-11-29Bibliographically approved
Keshavarz, S., Kvashnin, Y. O., Rodrigues, D. C. M., Pereiro, M., Di Marco, I., Autieri, C., . . . Eriksson, O. (2017). Exchange interactions of CaMnO3 in the bulk and at the surface. Physical Review B Condensed Matter, 95, Article ID 115120.
Open this publication in new window or tab >>Exchange interactions of CaMnO3 in the bulk and at the surface
Show others...
2017 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 95, article id 115120Article in journal (Refereed) Published
Abstract [en]

We present electronic and magnetic properties of CaMnO3 (CMO) as obtained from ab initio calculations. We identify the preferable magnetic order by means of density functional theory plus Hubbard U calculations and extract the effective exchange parameters (Jij ' s) using the magnetic force theorem. We find that the effects of geometrical relaxation at the surface as well as the change of crystal field are very strong and are able to influence the lower-energymagnetic configuration. In particular, our analysis reveals that the exchange interaction between the Mn atoms belonging to the surface and the subsurface layers is very sensitive to the structural changes. An earlier study [A. Filippetti and W. E. Pickett, Phys. Rev. Lett. 83, 4184 (1999)] suggested that this coupling is ferromagnetic and gives rise to the spin-flip (SF) process on the surface of CMO. In our work, we confirm their finding for an unrelaxed geometry, but once the structural relaxations are taken into account, this exchange coupling changes its sign. Thus, we suggest that the surface of CMO should have the same G-type antiferromagnetic order as in the bulk. Finally, we show that the suggested SF can be induced in the system by introducing an excess of electrons.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-319934 (URN)10.1103/PhysRevB.95.115120 (DOI)000396008300003 ()
Funder
Swedish Research CouncileSSENCE - An eScience CollaborationKnut and Alice Wallenberg Foundation
Available from: 2017-04-11 Created: 2017-04-11 Last updated: 2017-11-29Bibliographically approved
Cardias, R., Szilva, A., Bergman, A., Di Marco, I., Katsnelson, M. I., Lichtenstein, A. I., . . . Kvashnin, Y. O. (2017). The Bethe-Slater curve revisited; new insights from electronic structure theory. Scientific Reports, 7, Article ID 4058.
Open this publication in new window or tab >>The Bethe-Slater curve revisited; new insights from electronic structure theory
Show others...
2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 4058Article in journal (Refereed) Published
Abstract [en]

The Bethe-Slater (BS) curve describes the relation between the exchange coupling and interatomic distance. Based on a simple argument of orbital overlaps, it successfully predicts the transition from antiferromagnetism to ferromagnetism, when traversing the 3d series. In a previous article [Phys. Rev. Lett. 116, 217202 (2016)] we reported that the dominant nearestneighbour (NN) interaction for 3d metals in the bcc structure indeed follows the BS curve, but the trends through the series showed a richer underlying physics than was initially assumed. The orbital decomposition of the inter-site exchange couplings revealed that various orbitals contribute to the exchange interactions in a highly non-trivial and sometimes competitive way. In this communication we perform a deeper analysis by comparing 3d metals in the bcc and fcc structures. We find that there is no coupling between the E-g orbitals of one atom and T-2g orbitals of its NNs, for both cubic phases. We demonstrate that these couplings are forbidden by symmetry and formulate a general rule allowing to predict when a similar situation is going to happen. In gamma-Fe, as in alpha-Fe, we find a strong competition in the symmetry-resolved orbital contributions and analyse the differences between the high-spin and low-spin solutions.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-330728 (URN)10.1038/s41598-017-04427-9 (DOI)000403874900041 ()28642615 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2017-10-10 Created: 2017-10-10 Last updated: 2017-10-10Bibliographically approved
Lüder, J., Schött, J., Brena, B., Haverkort, M. W., Thunström, P., Eriksson, O., . . . Kvashnin, Y. (2017). Theory of L-edge spectroscopy of strongly correlated systems. Physical Review B, 96(24), Article ID 245131.
Open this publication in new window or tab >>Theory of L-edge spectroscopy of strongly correlated systems
Show others...
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 24, article id 245131Article in journal (Refereed) Published
Abstract [en]

X-ray absorption spectroscopy measured at the L edge of transition metals (TMs) is a powerful element-selective tool providing direct information about the correlation effects in the 3d states. The theoretical modeling of the 2p→3d excitation processes remains to be challenging for contemporary ab initio electronic structure techniques, due to strong core-hole and multiplet effects influencing the spectra. In this work, we present a realization of the method combining the density-functional theory with multiplet ligand field theory, proposed in Haverkort et al. [Phys. Rev. B 85, 165113 (2012)]. In this approach, a single-impurity Anderson model (SIAM) is constructed, with almost all parameters obtained from first principles, and then solved to obtain the spectra. In our implementation, we adopt the language of the dynamical mean-field theory and utilize the local density of states and the hybridization function, projected onto TM 3d states, in order to construct the SIAM. The developed computational scheme is applied to calculate the L-edge spectra for several TM monoxides. A very good agreement between the theory and experiment is found for all studied systems. The effect of core-hole relaxation, hybridization discretization, possible extensions of the method as well as its limitations are discussed.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-339767 (URN)10.1103/PhysRevB.96.245131 (DOI)000418573600012 ()
Funder
Knut and Alice Wallenberg Foundation, 2013.0020; 2012.0031Carl Tryggers foundation
Available from: 2018-02-02 Created: 2018-02-02 Last updated: 2018-02-02Bibliographically approved
Schött, J., Locht, I. L. M., Lundin, E., Grånäs, O., Eriksson, O. & Di Marco, I. (2016). Analytic continuation by averaging Pade approximants. PHYSICAL REVIEW B, 93(7), Article ID 075104.
Open this publication in new window or tab >>Analytic continuation by averaging Pade approximants
Show others...
2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 7, article id 075104Article in journal (Refereed) Published
Abstract [en]

The ill-posed analytic continuation problem for Green's functions and self-energies is investigated by revisiting the Pade approximants technique. We propose to remedy the well-known problems of the Pade approximants by performing an average of several continuations, obtained by varying the number of fitted input points and Pade coefficients independently. The suggested approach is then applied to several test cases, including Sm and Pr atomic self-energies, the Green's functions of the Hubbard model for a Bethe lattice and of the Haldane model for a nanoribbon, as well as two special test functions. The sensitivity to numerical noise and the dependence on the precision of the numerical libraries are analyzed in detail. The present approach is compared to a number of other techniques, i.e., the nonnegative least-squares method, the nonnegative Tikhonov method, and the maximum entropy method, and is shown to perform well for the chosen test cases. This conclusion holds even when the noise on the input data is increased to reach values typical for quantum Monte Carlo simulations. The ability of the algorithm to resolve fine structures is finally illustrated for two relevant test functions.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-279570 (URN)10.1103/PhysRevB.93.075104 (DOI)000369399500001 ()
Funder
Swedish Research CouncileSSENCE - An eScience CollaborationKnut and Alice Wallenberg Foundation, KAW-2013.0020
Available from: 2016-03-02 Created: 2016-03-02 Last updated: 2016-11-29
Schött, J., van Loon, E., Locht, I. L. M., Katsnelson, M. & Di Marco, I. (2016). Comparison between methods of analytical continuation for bosonic functions. Physical Review B. Condensed Matter and Materials Physics, 94, Article ID 245140.
Open this publication in new window or tab >>Comparison between methods of analytical continuation for bosonic functions
Show others...
2016 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 94, article id 245140Article in journal (Refereed) Published
Abstract [en]

In this article we perform a critical assessment of different known methods for the analytical con- tinuation of bosonic functions, namely the maximum entropy method, the non-negative least-square method, the non-negative Tikhonov method, the Pad ́e approximant method, and a stochastic sam- pling method. Four functions of different shape are investigated, corresponding to four physically relevant scenarios. They include a simple two-pole model function, two flavours of the tight bind- ing model on a square lattice, i.e. a single-orbital metallic system and a two-orbitals insulating system, and the Hubbard dimer. The effect of numerical noise in the input data on the analytical continuation is discussed in detail. Overall, the stochastic method by Mishchenko et al. [Phys. Rev. B 62, 6317 (2000)] is shown to be the most reliable tool for input data whose numerical precision is not known. For high precision input data, this approach is slightly outperformed by the Pad ́e approximant method, which combines a good resolution power with a good numerical stability. Although none of the methods retrieves all features in the spectra in the presence of noise, our analysis provides a useful guideline for obtaining reliable information of the spectral function in cases of practical interest. 

Keyword
Green's functions, analytical continuation
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-308693 (URN)10.1103/PhysRevB.94.245140 (DOI)000391012400012 ()
Funder
Swedish Research CouncileSSENCE - An eScience CollaborationKnut and Alice Wallenberg FoundationEU, European Research Council, 338957 FEMTO/NANOSwedish National Infrastructure for Computing (SNIC)
Available from: 2016-11-29 Created: 2016-11-29 Last updated: 2017-11-29Bibliographically approved
Bhandary, S., Schueler, M., Thunstroem, P., di Marco, I., Brena, B., Eriksson, O., . . . Sanyal, B. (2016). Correlated electron behavior of metal-organic molecules: Insights from density functional theory combined with many-body effects using exact diagonalization. PHYSICAL REVIEW B, 93(15), Article ID 155158.
Open this publication in new window or tab >>Correlated electron behavior of metal-organic molecules: Insights from density functional theory combined with many-body effects using exact diagonalization
Show others...
2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 15, article id 155158Article in journal (Refereed) Published
Abstract [en]

A proper theoretical description of the electronic structure of the 3d orbitals in the metal centers of functional metalorganics is a challenging problem. We apply density functional theory and an exact diagonalization method in a many-body approach to study the ground-state electronic configuration of an iron porphyrin (FeP) molecule. Our study reveals that the consideration of multiple Slater determinants is important, and FeP is a potential candidate for realizing a spin crossover due to a subtle balance of crystal-field effects, on-site Coulomb repulsion, and hybridization between the Fe-d orbitals and ligand N-p states. The mechanism of switching between two close-lying electronic configurations of Fe-d orbitals is shown. We discuss the generality of the suggested approach and the possibility to properly describe the electronic structure and related low-energy physics of the whole class of correlated metal-centered organometallic molecules.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-297348 (URN)10.1103/PhysRevB.93.155158 (DOI)000374948400003 ()
Funder
Carl Tryggers foundation Swedish Research CouncilKnut and Alice Wallenberg FoundationeSSENCE - An eScience CollaborationGerman Research Foundation (DFG), FOR 1346
Available from: 2016-06-23 Created: 2016-06-22 Last updated: 2017-01-25Bibliographically approved
Panda, S. K., Di Marco, I., Delin, A. & Eriksson, O. (2016). Correlated electronic structure of CeN. Journal of Electron Spectroscopy and Related Phenomena, 208, 111-115.
Open this publication in new window or tab >>Correlated electronic structure of CeN
2016 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 208, p. 111-115Article in journal (Refereed) Published
Abstract [en]

We have studied in detail the electronic structure of CeN including spin orbit coupling (SOC) and electron electron interaction, within the dynamical mean-field theory combined with density-functional theory in generalized gradient approximation (GGA+DMFT). The effective impurity problem has been solved through the spin-polarized T-matrix fluctuation-exchange (SPTF) solver and the Hubbard I approximation (HIA). The calculated l-projected atomic partial densities of states and the converged potential were used to obtain the X-ray-photoemission-spectra (XPS) and Bremstrahlung Isochromat spectra (BIS). Following the spirit of Gunnarsson-Schonhammer model, we have coupled the SPTF and HIA 4f spectral functions to explain the various spectroscopic manifestations of CeN. Our computed spectra in such a coupled scheme explain the experimental data remarkably well, establishing the validity of our theoretical model in analyzing the electronic structure of CeN. The contribution of the various l-states in the total spectra and the importance of cross sections are also analyzed in detail.

Keyword
Electronic properties, GGA plus DMFT, CeN
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-297923 (URN)10.1016/j.elspec.2015.10.004 (DOI)000375738900020 ()
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research eSSENCE - An eScience Collaboration
Available from: 2016-06-29 Created: 2016-06-28 Last updated: 2017-11-28Bibliographically approved
Organisations

Search in DiVA

Show all publications