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Potapkin, V., Dubrovinsky, L., Sergueev, I., Ekholm, M., Kantor, I., Bessas, D., . . . Abrikosov, I. (2016). Magnetic interactions in NiO at ultrahigh pressure. PHYSICAL REVIEW B, 93(20), 201110
Open this publication in new window or tab >>Magnetic interactions in NiO at ultrahigh pressure
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2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 20, p. 201110-Article in journal (Refereed) Published
Abstract [en]

Magnetic properties of NiO have been studied in the multimegabar pressure range by nuclear forward scattering of synchrotron radiation using the 67.4 keV Mossbauer transition of Ni-61. The observed magnetic hyperfine splitting confirms the antiferromagnetic state of NiO up to 280 GPa, the highest pressure where magnetism has been observed so far, in any material. Remarkably, the hyperfine field increases from 8.47 T at ambient pressure to similar to 24 T at the highest pressure, ruling out the possibility of a magnetic collapse. A joint x-ray diffraction and extended x-ray-absorption fine structure investigation reveals that NiO remains in a distorted sodium chloride structure in the entire studied pressure range. Ab initio calculations support the experimental observations, and further indicate a complete absence of Mott transition in NiO up to at least 280 GPa.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-129492 (URN)10.1103/PhysRevB.93.201110 (DOI)000376638400001 ()
Note

Funding Agencies|National Science Foundation-Earth Sciences [EAR-1128799]; Department of Energy-GeoSciences [DE-FG02-94ER14466]; DOE Office of Science [DE-AC02-06CH11357]; Helmholtz Association; Materials Sciences and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy; Swedish Government Strategic Research Area Grants Swedish e-Science Research Center (SeRC) and in Materials Science on Functional Materials at Linkoping University [2009 00971]; Knut and Alice Wallenbergs Foundation project Strong Field Physics and New States of Matter; Swedish Foundation for Strategic Research program SRL Grant [10-0026]; Swedish Research Council (VR) [2015-04391]; Grant of Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; Tomsk State University Academic D.I. Mendeleev Fund Program

Available from: 2016-06-20 Created: 2016-06-20 Last updated: 2018-08-29
Tal, A., Katsnelson, M. I., Ekholm, M., Jönsson, J., Dubrovinsky, L., Dubrovinskaia, N. & Abrikosov, I. (2016). Pressure-induced crossing of the core levels in 5d metals. Physical Review B, 93(20), 205150
Open this publication in new window or tab >>Pressure-induced crossing of the core levels in 5d metals
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2016 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 93, no 20, p. 205150-Article in journal (Refereed) Published
Abstract [en]

A pressure-induced interaction between core electrons, the core-level crossing (CLC) transition, has been observed in hcp Os at P approximate to 400 GPa [L. Dubrovinsky et al., Nature (London) 525, 226 (2015)]. By carrying out a systematic theoretical study for all metals of the 5d series (Hf, Ta, W, Re, Os, Ir, Pt, Au) we have found that the CLC transition is a general effect for this series of metals. While in Pt it occurs at approximate to 1500 GPa, at a pressure substantially higher than in Os, in Ir it occurs already at 80 GPa. Moreover, we predict that in Re the CLC transition may take place already at ambient pressure. We explain the effect of the CLC and analyze the shift of the transition pressure across the series within the Thomas-Fermi model. In particular, we show that the effect has many common features with the atomic collapse in rare-earth elements.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-129490 (URN)10.1103/PhysRevB.93.205150 (DOI)000376638700004 ()
Note

Funding Agencies|Swedish Government Strategic Research Area Grant Swedish e-Science Research Centre (SeRC); Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of MISiS; Swedish Foundation for Strategic Research (SSF) program SRL [10-0026]; Swedish Research Council (VR) [2015-04391]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; German Research Foundation (DFG); Federal Ministry of Education and Research (BMBF), Germany; DFG [DU 954-8/1]; BMBF (PT-DESY) [5K13WC3, O5K2013, 2]; Act 211 Government of the Russian Federation [02.A03.21.0006]; Knut and Alice Wallenberg Foundation [2012.0083, 2014-2019]

Available from: 2016-06-21 Created: 2016-06-20 Last updated: 2017-11-28
Dubrovinsky, L., Dubrovinskaia, N., Bykova, E., Bykov, M., Prakapenka, V., Prescher, C., . . . Abrikosov, I. (2015). The most incompressible metal osmium at static pressures above 750 gigapascals. Nature, 525(7568), 226-+
Open this publication in new window or tab >>The most incompressible metal osmium at static pressures above 750 gigapascals
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2015 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 525, no 7568, p. 226-+Article in journal (Refereed) Published
Abstract [en]

Metallic osmium (Os) is one of the most exceptional elemental materials, having, at ambient pressure, the highest known density and one of the highest cohesive energies and melting temperatures(1). It is also very incompressible(2-4), but its high-pressure behaviour is not well understood because it has been studied(2-6) so far only at pressures below 75 gigapascals. Here we report powder X-ray diffraction measurements on Os at multi-megabar pressures using both conventional and double-stage diamond anvil cells(7), with accurate pressure determination ensured by first obtaining self-consistent equations of state of gold, platinum, and tungsten in static experiments up to 500 gigapascals. These measurements allow us to show that Os retains its hexagonal close-packed structure upon compression to over 770 gigapascals. But although its molar volume monotonically decreases with pressure, the unit cell parameter ratio of Os exhibits anomalies at approximately 150 gigapascals and 440 gigapascals. Dynamical mean-field theory calculations suggest that the former anomaly is a signature of the topological change of the Fermi surface for valence electrons. However, the anomaly at 440 gigapascals might be related to an electronic transition associated with pressure-induced interactions between core electrons. The ability to affect the core electrons under static high-pressure experimental conditions, even for incompressible metals such as Os, opens up opportunities to search for new states of matter under extreme compression.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-121742 (URN)10.1038/nature14681 (DOI)000360927400033 ()26302297 (PubMedID)
Note

Funding Agencies|Deutsche Forschungsgemeinschaft (DFG); Federal Ministry of Education and Research (BMBF), Germany; DFG through Heisenberg Program; DFG [DU 954-8/1]; BMBF [5K13WC3, O5K2013]; Swedish Foundation for Strategic Research programme SRL [10-0026]; Swedish Research Council (VR) [621-2011-4426]; Swedish Government Strategic Research Area Grant Swedish e-Science Research Centre (SeRC); Materials Science "Advanced Functional Materials" (AFM); Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; ERC [338957]; NWO; National Science Foundation - Earth Sciences [EAR-1128799]; Department of Energy - GeoSciences [DE-FG02-94ER14466]; DOE Office of Science by Argonne National Laboratory [DE-AC02-06CH11357]

Available from: 2015-10-06 Created: 2015-10-05 Last updated: 2017-12-01
Reeh, S., Kasprzak, M., Klusmann, C. D., Stalf, F., Music, D., Ekholm, M., . . . Schneider, J. M. (2013). Elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys studied by the combinatorial thin film approach and ab initio calculations. Journal of Physics: Condensed Matter, 25(24)
Open this publication in new window or tab >>Elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys studied by the combinatorial thin film approach and ab initio calculations
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2013 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 24Article in journal (Refereed) Published
Abstract [en]

The elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys with additions of up to 8 at.% X were studied by combinatorial thin film growth and characterization and by ab initio calculations using the disordered local moments (DLM) approach. The lattice parameter and Youngs modulus values change only marginally with X. The calculations and experiments are in good agreement. We demonstrate that the elastic properties of transition metal alloyed Fe-Mn can be predicted by the DLM model.

Place, publisher, year, edition, pages
Institute of Physics: Hybrid Open Access, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-95499 (URN)10.1088/0953-8984/25/24/245401 (DOI)000319673800009 ()
Note

Funding Agencies|Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Center|(SFB) 761|Swedish Research Council|621-2011-4426|Swedish Foundation for Strategic Research|SRL 10-0026|Swedish e-Science Research Centre (SeRC)||

Available from: 2013-07-05 Created: 2013-07-05 Last updated: 2017-12-06
Reeh, S., Music, D., Ekholm, M., Abrikosov, I. & Schneider, J. M. (2013). Elastic properties of fcc Fe-Mn-X (X=Cr, Co, Ni, Cu) alloys from first-principles calculations. Physical Review B. Condensed Matter and Materials Physics, 87(22)
Open this publication in new window or tab >>Elastic properties of fcc Fe-Mn-X (X=Cr, Co, Ni, Cu) alloys from first-principles calculations
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2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 22Article in journal (Refereed) Published
Abstract [en]

The influence of the valence electron concentration of X in fcc Fe-Mn-X (X=Cr, Co, Ni, Cu) alloys on the elastic and magnetic properties has been studied by means of ab initio calculations for alloy element concentrations of up to 8 at. % X. We observe that Cu increases the bulk-to-shear modulus (B/G) ratio by 19.2%. Simultaneously magnetic moments of Fe and Mn increase strongly. The other alloying elements induce less significant changes in B/G. The trends in B/G may be understood by considering the changes in G induced by the variation in valence electron concentration (VEC). As the VEC is increased, more pronounced metallic bonds are formed, giving rise to smaller shear modulus values. The changes in magnetic moments may be explained by the magnetovolume effect. Alloys with smaller VEC as Fe-Mn exhibit a decrease in local magnetic moments and equilibrium lattice parameters, while alloys with larger VEC as Fe-Mn demonstrate an increase in local magnetic moments and equilibrium lattice parameters. These data provide the basis for the design of Mn-rich steels with enhanced elastic properties.

Place, publisher, year, edition, pages
American Physical Society, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-96471 (URN)10.1103/PhysRevB.87.224103 (DOI)000320103700002 ()
Available from: 2013-08-23 Created: 2013-08-20 Last updated: 2017-12-06
Sergueev, I., Dubrovinsky, L., Ekholm, M., Vekilova, O., Chumakov, A. I., Zając, M., . . . Ruffer, R. (2013). Hyperfine Splitting and Room-Temperature Ferromagnetism of Ni at Multimegabar Pressure. Physical Review Letters, 111(15)
Open this publication in new window or tab >>Hyperfine Splitting and Room-Temperature Ferromagnetism of Ni at Multimegabar Pressure
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2013 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 111, no 15Article in journal (Refereed) Published
Abstract [en]

Magnetic and elastic properties of Ni metal have been studied up to 260 GPa by nuclear forward scattering of synchrotron radiation with the 67.4 keV Mossbauer transition of Ni-61. The observed magnetic hyperfine splitting confirms the ferromagnetic state of Ni up to 260 GPa, the highest pressure where magnetism in any material has been observed so far. Ab initio calculations reveal that the pressure evolution of the hyperfine field, which features a maximum in the range of 100 to 225 GPa, is a relativistic effect. The Debye energy obtained from the Lamb-Mossbauer factor increases from 33 me V at ambient pressure to 60 me V at 100 GPa. The change of this energy over volume compression is well described by a Gruneisen parameter of 2.09.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-97381 (URN)10.1103/PhysRevLett.111.157601 (DOI)000326051100011 ()
Available from: 2013-09-11 Created: 2013-09-11 Last updated: 2017-12-06Bibliographically approved
Glazyrin, K., Pourovskii, L., Dubrovinsky, L., Narygina, O., McCammon, C., Hewener, B., . . . Abrikosov, I. (2013). Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition. Physical Review Letters, 110(11)
Open this publication in new window or tab >>Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition
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2013 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, no 11Article in journal (Refereed) Published
Abstract [en]

We discover that hcp phases of Fe and Fe0.9Ni0.1 undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mossbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe. DOI: 10.1103/PhysRevLett.110.117206

Place, publisher, year, edition, pages
American Physical Society, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-78777 (URN)10.1103/PhysRevLett.110.117206 (DOI)000316172500027 ()
Note

Funding Agencies|Swedish e-Science Research Centre (SeRC)||Swedish Research Council|621-2011-4426|Swedish Foundation for Strategic Research (SSF) programs SRL Grant|10-0026|German Science Foundation (DFG)||German Ministry for Education and Research (BMBF)||National Science Foundation-Earth Sciences|EAR-1128799|Department of Energy-Geosciences|DE-FG02-94ER14466|U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences|DE-AC02-06CH11357|

Available from: 2012-06-20 Created: 2012-06-20 Last updated: 2017-12-07Bibliographically approved
Abrikosov, I., Ekholm, M., Ponomareva, A. V. & Barannikova, S. A. (2012). Importance of Thermally Induced Magnetic Excitations in First-principles Simulations of Elastic Properties of Transition Metal Alloys. Solid State Phenomena, 190, 291-294
Open this publication in new window or tab >>Importance of Thermally Induced Magnetic Excitations in First-principles Simulations of Elastic Properties of Transition Metal Alloys
2012 (English)In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 190, p. 291-294Article in journal (Refereed) Published
Abstract [en]

We demonstrate the importance of accounting for the complex magnetic ground state and finite temperature magnetic excitations in theoretical simulations of structural and elastic properties of transition metal alloys. Considering Fe72Cr16Ni12 face centered cubic (fcc) alloy, we compare results of first-principles calculations carried out for ferromagnetic and non-magnetic states, as well as for the state with disordered local moments. We show that the latter gives much more accurate description of the elastic properties for paramagnetic alloys. We carry out a determination of the magnetic ground state for fcc Fe-Mn alloys, considering collinear, as well as non-collinear states, and show the sensitively of structural and elastic properties in this system to the detailed alignment between magnetic moments. We therefore conclude that it is essential to develop accurate models of the magnetic state for the predictive description of properties of transition metal alloys.

Keywords
Magnetic transition metal alloys, magnetic ground state, disordered local moments, elastic properties, first-principles simulations
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78775 (URN)10.4028/www.scientific.net/SSP.190.291 (DOI)000308061600070 ()
Available from: 2012-06-20 Created: 2012-06-20 Last updated: 2017-12-07Bibliographically approved
Ekholm, M. (2012). Theoretical Descriptions of Complex Magnetism in Transition Metals and Their Alloys. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Theoretical Descriptions of Complex Magnetism in Transition Metals and Their Alloys
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, various methods for studying solids by simulations of quantummechanical equations, have been applied to transition metals and their alloys. Transition metals such as Fe, Ni, and Mn, are not only cornerstones in modern technology, but also key components in the very fabric of the Earth interior. Such systems show highly complex magnetic properties. As shown within this thesis, to understand and predict their properties from a microscopic level, is still a highly demanding task for the the quantum theory of solids. This is especially crucial at elevated temperature and pressure.

It is found that the magnetic degrees of freedom are inseparable from the structural, elastic and chemical properties of such alloy systems. This requires theoretical descriptions capable of handling this interplay. Such schemes are discussed and demonstrated.

Furthermore, the importance of the description of Coulomb correlation effects is demonstrated by DFT calculations and also by going beyond the one-electron description by the LDA+DMFT method.

It is also shown how magnetic interactions in the half-metallic compound NiMnSb can be manipulated by alloying. The stability of these alloys is  also evaluated in calculations, and verified by experimental synthesis at ambient conditions.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. p. 130
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1452
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78781 (URN)978-91-7519-885-9 (ISBN)
Public defence
2012-06-14, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2012-06-20 Created: 2012-06-20 Last updated: 2019-12-08Bibliographically approved
Ekholm, M., Mikhaylushkin, A., Simak, S., Johansson, B. & Abrikosov, I. (2011). Configurational thermodynamics of Fe-Ni alloys at Earths core conditions. Earth and Planetary Science Letters, 308(1-2), 90-96
Open this publication in new window or tab >>Configurational thermodynamics of Fe-Ni alloys at Earths core conditions
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2011 (English)In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 308, no 1-2, p. 90-96Article in journal (Refereed) Published
Abstract [en]

By means of ab-initio calculations, we perform an analysis of the configurational thermodynamics, effects of disorder, and structural energy differences in Fe-Ni alloys at the pressure and temperature conditions of the Earths core. We show from ab-initio calculations that the ordering energies of fcc and hcp-structured Fe-Ni solid solutions at these conditions depend sensitively on the alloy configuration, i.e., on the degree of chemical disorder, and are on a scale comparable with the structural energy differences. From configurational thermodynamic simulations we find that a distribution of Fe and Ni atoms in the solutions should be very close to completely disordered at these conditions. Using this model of the Fe-Ni system, we have calculated the fcc-hcp structural free energy difference in a wide pressure-temperature range of 120-360 GPa and 1000-6600K. Our calculations show that alloying of Fe with Ni below 3000 K favours stabilisation of the fcc phase over the hcp, in agreement with experiments. However, above 3000 K the effect is reversed, and at conditions corresponding to those of the Earths inner core, Ni acts as an agent to stabilise the hcp phase.

Place, publisher, year, edition, pages
Elsevier, 2011
Keywords
Earths inner core, Fe-Ni alloy, ab-initio calculations, crystal structure
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-70218 (URN)10.1016/j.epsl.2011.05.035 (DOI)000293486100009 ()
Note
Original Publication: Marcus Ekholm, Arkady Mikhaylushkin, Sergey Simak, B Johansson and Igor Abrikosov, Configurational thermodynamics of Fe-Ni alloys at Earths core conditions, 2011, Earth and Planetary Science Letters, (308), 1-2, 90-96. http://dx.doi.org/10.1016/j.epsl.2011.05.035 Copyright: Elsevier http://www.elsevier.com/Available from: 2011-08-26 Created: 2011-08-26 Last updated: 2017-12-08Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7563-1494

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