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Eriksson, Olle
Publications (10 of 15) Show all publications
Shirinyan, A. A., Kozin, V. K., Hellsvik, J., Pereiro, M., Eriksson, O. & Yudin, D. (2019). Self-organizing maps as a method for detecting phase transitions and phase identification. Physical Review B, 99(4), Article ID 041108.
Open this publication in new window or tab >>Self-organizing maps as a method for detecting phase transitions and phase identification
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 4, article id 041108Article in journal (Refereed) Published
Abstract [en]

Originating from image recognition, methods of machine learning allow for effective feature extraction and dimensionality reduction in multidimensional datasets, thereby providing an extraordinary tool to deal with classical and quantum models in many-body physics. In this study, we employ a specific unsupervised machine learning technique-self-organizing maps-to create a low-dimensional representation of microscopic states, relevant for macroscopic phase identification and detecting phase transitions. We explore the properties of spin Hamiltonians of two archetype model systems: a two-dimensional Heisenberg ferromagnet and a three-dimensional crystal, Fe in the body-centered-cubic structure. The method of self-organizing maps, which is known to conserve connectivity of the initial dataset, is compared to the cumulant method theory and is shown to be as accurate while being computationally more efficient in determining a phase transition temperature. We argue that the method proposed here can be applied to explore a broad class of second-order phase-transition systems, not only magnetic systems but also, for example, order-disorder transitions in alloys.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:oru:diva-71885 (URN)10.1103/PhysRevB.99.041108 (DOI)000455825600002 ()2-s2.0-85059904004 (Scopus ID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationSwedish Energy AgencySwedish Foundation for Strategic Research
Note

Funding Agencies:

Russian Science Foundation  17-12-01359 

Horizon2020 RISE project CoExAN 

eSSENCE  

STandUPP 

Available from: 2019-01-29 Created: 2019-01-29 Last updated: 2019-01-29Bibliographically approved
Vekilova, O. Y., Fayyazi, B., Skokov, K. P., Gutfleisch, O., Echevarria-Bonet, C., Barandiarán, J. M., . . . Herper, H. C. (2019). Tuning the magnetocrystalline anisotropy of Fe3Sn by alloying. Physical Review B, 99(2), Article ID 024421.
Open this publication in new window or tab >>Tuning the magnetocrystalline anisotropy of Fe3Sn by alloying
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 2, article id 024421Article in journal (Refereed) Published
Abstract [en]

The electronic structure, magnetic properties, and phase formation of hexagonal ferromagnetic Fe3Sn-based alloys have been studied from first principles and by experiment. The pristine Fe3Sn compound is known to fulfill all the requirements for a good permanent magnet, except for the magnetocrystalline anisotropy energy (MAE). The latter is large, but planar, i.e., the easy magnetization axis is not along the hexagonal c direction, whereas a good permanent magnet requires the MAE to be uniaxial. Here we consider Fe3Sn0.75M0.25, where M = Si, P, Ga, Ge, As, Se, In, Sb, Te, Pb, and Bi, and show how different dopants affect the MAE and can alter it from planar to uniaxial. The stability of the doped Fe3Sn phases is elucidated theoretically via the calculations of their formation enthalpies. A micromagnetic model is developed to estimate the energy density product (BH)(max) and coercive field mu H-0(c) of a potential magnet made of Fe3Sn0.75M0.25, the most promising candidate from theoretical studies. The phase stability and magnetic properties of the Fe3Sn compound doped with Sb and Mn have been checked experimentally on the samples synthesised using the reactive crucible melting technique as well as by solid state reaction. The Fe3Sn-Sb compound is found to be stable when alloyed with Mn. It is shown that even small structural changes, such as a change of the c/a ratio or volume, that can be induced by, e.g., alloying with Mn, can influence anisotropy and reverse it from planar to uniaxial and back.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Materials Engineering Condensed Matter Physics
Identifiers
urn:nbn:se:oru:diva-72084 (URN)10.1103/PhysRevB.99.024421 (DOI)000456301900005 ()2-s2.0-85060392732 (Scopus ID)
Funder
Swedish Research Council
Note

Funding Agencies:

NOVAMAG project, EU Horizon 2020 Framework Programme  686056 

STandUPP  

eSSENCE  

KAW foundation  2012.0031  2013.0020 

Available from: 2019-02-05 Created: 2019-02-05 Last updated: 2019-02-05Bibliographically approved
Koumpouras, K., Yudin, D., Adelmann, C., Bergman, A., Eriksson, O. & Pereiro, M. (2018). A majority gate with chiral magnetic solitons. Journal of Physics: Condensed Matter, 30(37), Article ID 375801.
Open this publication in new window or tab >>A majority gate with chiral magnetic solitons
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2018 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 30, no 37, article id 375801Article in journal (Refereed) Published
Abstract [en]

In magnetic materials, nontrivial spin textures may emerge due to the competition among different types of magnetic interactions. Among such spin textures, chiral magnetic solitons represent topologically protected spin configurations with particle-like properties. Based on atomistic spin dynamics simulations, we demonstrate that these chiral magnetic solitons are ideal to use for logical operations, and we demonstrate the functionality of a three- input majority gate, in which the input states can be controlled by applying an external electromagnetic field or spin-polarized currents. One of the main advantages of the proposed device is that the input and output signals are encoded in the chirality of solitons, that may be moved, allowing to perform logical operations using only minute electric currents. As an example we illustrate how the three input majority gate can be used to perform logical relations, such as Boolean AND and OR.

Place, publisher, year, edition, pages
IOP Publishing, 2018
Keywords
magnonics, majority gate, solitons, spin dynamics, magnetic nanodevices
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:oru:diva-68752 (URN)10.1088/1361-648X/aad82f (DOI)000442630600001 ()30079893 (PubMedID)
Funder
Swedish Research Council
Note

Funding Agencies:

KAW foundation  2013.0020  2012.0031 

eSSENCE  

CEA Enhanced Eurotalents program  

Russian Science Foundation  17-12-01359 

imecs Industrial Affiliation Program on Beyond CMOS devices  

Available from: 2018-09-10 Created: 2018-09-10 Last updated: 2018-09-10Bibliographically approved
Pervishko, A. A., Baglai, M. I., Eriksson, O. & Yudin, D. (2018). Another view on Gilbert damping in two-dimensional ferromagnets. Scientific Reports, 8, Article ID 17148.
Open this publication in new window or tab >>Another view on Gilbert damping in two-dimensional ferromagnets
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 17148Article in journal (Refereed) Published
Abstract [en]

A keen interest towards technological implications of spin-orbit driven magnetization dynamics requests a proper theoretical description, especially in the context of a microscopic framework, to be developed. Indeed, magnetization dynamics is so far approached within Landau-Lifshitz-Gilbert equation which characterizes torques on magnetization on purely phenomenological grounds. Particularly, spin-orbit coupling does not respect spin conservation, leading thus to angular momentum transfer to lattice and damping as a result. This mechanism is accounted by the Gilbert damping torque which describes relaxation of the magnetization to equilibrium. In this study we work out a microscopic Kubo-Streda formula for the components of the Gilbert damping tensor and apply the elaborated formalism to a two-dimensional Rashba ferromagnet in the weak disorder limit. We show that an exact analytical expression corresponding to the Gilbert damping parameter manifests linear dependence on the scattering rate and retains the constant value up to room temperature when no vibrational degrees of freedom are present in the system. We argue that the methodology developed in this paper can be safely applied to bilayers made of non- and ferromagnetic metals, e.g., CoPt.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:oru:diva-70496 (URN)10.1038/s41598-018-35517-x (DOI)000450766300006 ()30464318 (PubMedID)2-s2.0-85056969363 (Scopus ID)
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research Knut and Alice Wallenberg Foundation
Note

Funding Agencies:

Russian Science Foundation  18-72-00058  17-12-01359 

eSSENCE 

Available from: 2018-12-05 Created: 2018-12-05 Last updated: 2018-12-05Bibliographically approved
Shaw, J. M., Delczeg-Czirjak, E. K., Edwards, E. R. J., Kvashnin, Y., Thonig, D., Schoen, M. A. W., . . . Nembach, H. T. (2018). Magnetic damping in sputter-deposited Co2MnGe Heusler compounds with A2, B2, and L2(1) orders: Experiment and theory. Physical Review B, 97(9), Article ID 094420.
Open this publication in new window or tab >>Magnetic damping in sputter-deposited Co2MnGe Heusler compounds with A2, B2, and L2(1) orders: Experiment and theory
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2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 9, article id 094420Article in journal (Refereed) Published
Abstract [en]

We show that very low values of the magnetic damping parameter can be achieved in sputter deposited polycrystalline films of Co2MnGe annealed at relatively low temperatures ranging from 240 degrees C to 400 degrees C. Damping values as low as 0.0014 are obtained with an intrinsic value of 0.0010 after spin-pumping contributions are considered. Of importance to most applications is the low value of inhomogeneous linewidth that yields measured linewidths of 1.8 and 5.1 mT at 10 and 40 GHz, respectively. The damping parameter monotonically decreases as the B2 order of the films increases. This trend is reproduced and explained by ab initio calculations of the electronic structure and damping parameter. Here, the damping parameter is calculated as the structure evolves from A2 to B2 to L2(1) orders. The largest decrease in the damping parameter occurs during the A2 to B2 transition as the half-metallic phase becomes established.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:oru:diva-66385 (URN)10.1103/PhysRevB.97.094420 (DOI)000427798500002 ()2-s2.0-85044408058 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation, 2012.0031 2013.0030Swedish Research Council, 2016-04524 2016-06955 2013-08316
Note

Funding Agencies:

STandUP  

eSSENCE  

IARPA Cryogenic Computing Complexity program 

Available from: 2018-04-09 Created: 2018-04-09 Last updated: 2018-08-20Bibliographically approved
Keshavarz, S., Kontos, S., Wardecki, D., Kvashnin, Y. O., Pereiro, M., Panda, S. K., . . . Svedlindh, P. (2018). Magnetic properties of Ruddlesden-Popper phases Sr3−x Yx (Fe1.25 Ni0.75) O7−δ: A combined experimental and theoretical investigation. Physical Review Materials, 2(4), Article ID 044005.
Open this publication in new window or tab >>Magnetic properties of Ruddlesden-Popper phases Sr3−x Yx (Fe1.25 Ni0.75) O7−δ: A combined experimental and theoretical investigation
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2018 (English)In: Physical Review Materials, E-ISSN 2475-9953, Vol. 2, no 4, article id 044005Article in journal (Refereed) Published
Abstract [en]

We present a comprehensive study of the magnetic properties of Sr3-xYx(Fe1.25Ni0.75)O-7(-delta )(0 <= x <= 0.75). Experimentally, the magnetic properties are investigated using superconducting quantum interference device (SQUID) magnetometry and neutron powder diffraction (NPD). This is complemented by a theoretical study based on density functional theory as well as the Heisenberg exchange parameters. Experimental results show an increase in the Ned temperature (T-N) with an increase of Y concentrations and O occupancy. The NPD data reveal that all samples are antiferromagnetically ordered at low temperatures, which has been confirmed by our theoretical simulations for the selected samples. Our first-principles calculations suggest that the three-dimensional magnetic order is stabilized due to finite interlayer exchange couplings. The latter give rise to finite interlayer spin-spin correlations, which disappear above T-N.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:oru:diva-66838 (URN)10.1103/PhysRevMaterials.2.044005 (DOI)000430385300001 ()
Funder
Swedish Research Council
Note

Funding Agencies:

eSSENCE  

KAW Foundation 

Available from: 2018-05-02 Created: 2018-05-02 Last updated: 2018-09-04Bibliographically approved
Huang, S., Holmstrom, E., Eriksson, O. & Vitos, L. (2018). Mapping the magnetic transition temperatures for medium- and high-entropy alloys. Intermetallics (Barking), 95, 80-84
Open this publication in new window or tab >>Mapping the magnetic transition temperatures for medium- and high-entropy alloys
2018 (English)In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 95, p. 80-84Article in journal (Refereed) Published
Abstract [en]

Tailorable magnetic state near room temperature is very promising for several technological, including magnetocaloric applications. Here using first-principle alloy theory, we determine the Curie temperature (T-C) of a number of equiatomic medium- and high-entropy alloys with solid solution phases. All calculations are performed at the computed lattice parameters, which are in line with the available experimental data. Theory predicts a large crystal structure dependence of T-C, which explains the experimental observations under specified conditions. The sensitivity of the magnetic state to the crystal lattice is reflected by the magnetic exchange interactions entering the Heisenberg Hamiltonian. The analysis of the effect of composition on T-C allows researchers to explore chemistry-dependent trends and design new multi-component alloys with pre-assigned magnetic properties.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Curie temperature, High-entropy alloys, First-principle calculations, Monte-Carlo simulations
National Category
Metallurgy and Metallic Materials Physical Chemistry
Identifiers
urn:nbn:se:oru:diva-66647 (URN)10.1016/j.intermet.2018.01.016 (DOI)000428975100010 ()2-s2.0-85041415212 (Scopus ID)
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research VINNOVA, 2014-03374Swedish Energy AgencyCarl Tryggers foundation
Note

Funding Agencies:

Swedish Foundation for International Cooperation in Research and Higher Education

China Scholarship Council  

Hungarian Scientific Research Fund  OTKA 109570 

Available from: 2018-04-19 Created: 2018-04-19 Last updated: 2018-04-19Bibliographically approved
Thonig, D., Kvashnin, Y., Eriksson, O. & Pereiro, M. (2018). Nonlocal Gilbert damping tensor within the torque-torque correlation model. Physical Review Materials, 2(1), Article ID 013801.
Open this publication in new window or tab >>Nonlocal Gilbert damping tensor within the torque-torque correlation model
2018 (English)In: Physical Review Materials, ISSN 2475-9953, Vol. 2, no 1, article id 013801Article in journal (Refereed) Published
Abstract [en]

An essential property of magnetic devices is the relaxation rate in magnetic switching, which depends strongly on the damping in the magnetization dynamics. It was recently measured that damping depends on the magnetic texture and, consequently, is a nonlocal quantity. The damping enters the Landau-Lifshitz-Gilbert equation as the phenomenological Gilbert damping parameter a, which does not, in a straightforward formulation, account for nonlocality. Efforts were spent recently to obtain Gilbert damping from first principles for magnons of wave vector q. However, to the best of our knowledge, there is no report about real-space nonlocal Gilbert damping aij. Here, a torque-torque correlation model based on a tight-binding approach is applied to the bulk elemental itinerant magnets and it predicts significant off-site Gilbert damping contributions, which could be also negative. Supported by atomistic magnetization dynamics simulations, we reveal the importance of the nonlocal Gilbert damping in atomistic magnetization dynamics. This study gives a deeper understanding of the dynamics of the magnetic moments and dissipation processes in real magnetic materials. Ways of manipulating nonlocal damping are explored, either by temperature, materials doping, or strain.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:oru:diva-64122 (URN)10.1103/PhysRevMaterials.2.013801 (DOI)000419105000001 ()
Funder
Swedish Research Council
Note

Funding Agencies:

eSSENCE  

KAW Foundation  2012.0031  2013.0020 

Available from: 2018-01-15 Created: 2018-01-15 Last updated: 2018-01-15Bibliographically approved
Eriksson, O. (2018). Searching for materials with reduced dimension. Nature Nanotechnology, 13(3), 180-181
Open this publication in new window or tab >>Searching for materials with reduced dimension
2018 (English)In: Nature Nanotechnology, ISSN 1748-3387, E-ISSN 1748-3395, Vol. 13, no 3, p. 180-181Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:oru:diva-64915 (URN)10.1038/s41565-017-0060-4 (DOI)000427009000007 ()29402978 (PubMedID)2-s2.0-85041617757 (Scopus ID)
Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-04-03Bibliographically approved
Schmitz-Antoniak, C., Schmitz, D., Warland, A., Darbandi, M., Haldar, S., Bhandary, S., . . . Wende, H. (2018). Suppression of the Verwey Transition by Charge Trapping. Annalen der Physik, 530(3), Article ID 1700363.
Open this publication in new window or tab >>Suppression of the Verwey Transition by Charge Trapping
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2018 (English)In: Annalen der Physik, ISSN 0003-3804, E-ISSN 1521-3889, Vol. 530, no 3, article id 1700363Article in journal (Refereed) Published
Abstract [en]

The Verwey transition in Fe3O4 nanoparticles with a mean diameter of 6.3 nm is suppressed after capping the particles with a 3.5 nm thick shell of SiO2. By X-ray absorption spectroscopy and its associated X-ray magnetic circular dichroism this suppression can be correlated to localized Fe2+ states and a reduced double exchange visible in different site-specific magnetization behavior in high magnetic fields. The results are discussed in terms of charge trapping at defects in the Fe3O4/ SiO2 interface and the consequent difficulties in the formation of the common phases of Fe3O4. By comparison to X-ray absorption spectra of bare Fe3O4 nanoparticles in course of the Verwey transition, particular changes in the spectral shape could be correlated to changes in the number of unoccupied d states for Fe ions at different lattice sites. These findings are supported by density functional theory calculations.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2018
Keywords
magnetite, nanoparticles, Verwey transition, X-ray absorption spectroscopy
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:oru:diva-66576 (URN)10.1002/andp.201700363 (DOI)000428350500010 ()2-s2.0-85042457108 (Scopus ID)
Note

Funding Agencies:

BMBF  05 ES3XBA/5 

DFG  WE 2623/3-1 

Helmholtz Association (Young Investigator's Group Borderline Magnetism)  VH-NG-1031 

Available from: 2018-04-13 Created: 2018-04-13 Last updated: 2018-09-04Bibliographically approved
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