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Publications (10 of 141) Show all publications
Zeiger, P. & Rusz, J. (2020). Efficient and Versatile Model for Vibrational STEM-EELS. Physical Review Letters, 124(2), Article ID 025501.
Open this publication in new window or tab >>Efficient and Versatile Model for Vibrational STEM-EELS
2020 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 2, article id 025501Article in journal (Refereed) Published
Abstract [en]

We introduce a novel method for the simulation of the impact scattering in vibrational scanning transmission electron microscopy electron energy loss spectroscopy simulations. The phonon-loss process is modeled by a combination of molecular dynamics and elastic multislice calculations within a modified frozen phonon approximation. The key idea is thereby to use a so-called S thermostat in the classical molecular dynamics simulation to generate frequency dependent configurations of the vibrating specimen's atomic structure. The method includes correlated motion of atoms and provides vibrational spectrum images at a cost comparable to standard frozen phonon calculations. We demonstrate good agreement of our method with simulations and experiments for a 15 nm flake of hexagonal boron nitride.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-404696 (URN)10.1103/PhysRevLett.124.025501 (DOI)000506852200008 ()32004041 (PubMedID)
Funder
Swedish Research CouncilSwedish National Infrastructure for Computing (SNIC)
Available from: 2020-02-25 Created: 2020-02-25 Last updated: 2020-02-25Bibliographically approved
Duan, Y.-X., Zhang, C., Rusz, J., Oppeneer, P. M., Durakiewicz, T., Sassa, Y., . . . Meng, J.-Q. (2019). Crystal electric field splitting and f-electron hybridization in heavy-fermion CePt2In7. Physical Review B, 100(8), Article ID 085141.
Open this publication in new window or tab >>Crystal electric field splitting and f-electron hybridization in heavy-fermion CePt2In7
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 8, article id 085141Article in journal (Refereed) Published
Abstract [en]

We use high-resolution angle-resolved photoemission spectroscopy to investigate the electronic structure of the antiferromagnetic heavy fermion compound CePt2In7, which is amember of the CeIn3-derived heavy fermion material family. Weak hybridization among 4f electron states and conduction bands was identified in CePt2In7 at low temperature much weaker than that in the other heavy fermion compounds like CeIrIn5 and CeRhIn5. The Ce 4f spectrum shows fine structures near the Fermi energy, reflecting the crystal electric field splitting of the 4f(5/2)(1) and 4f(7/2)(1) states. Also, we find that the Fermi surface has a strongly three-dimensional topology, in agreement with density-functional theory calculations.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-398850 (URN)10.1103/PhysRevB.100.085141 (DOI)000482582200008 ()
Funder
Swedish Research Council, 2017-05078Swedish Research Council, INCA-2014-6426Knut and Alice Wallenberg FoundationSwedish Research Council, 2016-06955Swedish Research CouncilCarl Tryggers foundation , CTS-16: 324Carl Tryggers foundation , CTS-17:325
Available from: 2019-12-18 Created: 2019-12-18 Last updated: 2019-12-18Bibliographically approved
Negi, D. S., Datta, R. & Rusz, J. (2019). Defect driven spin state transition and the existence of half-metallicity in CoO. Journal of Physics: Condensed Matter, 31(11), Article ID 115602.
Open this publication in new window or tab >>Defect driven spin state transition and the existence of half-metallicity in CoO
2019 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 31, no 11, article id 115602Article in journal (Refereed) Published
Abstract [en]

We unveil the native defect induced high spin to low spin state transition in Co+3 and half- metallicity in CoO. First principles calculations unravel that, defect density holds a key role in dictating the spin-state transition in Co+3 ion in CoO, and introducing the half-metallicity. Charge transfer in the vicinity of vacancy plane favors the stabilization and coexistence of bivalent Co+2 and trivalent Co+3 ion in CoO. We propose that defect engineering could serve as a route to design the half metallicity in transition metal mono-oxides.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Keywords
half-metallicty, transition metal oxides, spin state transition
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-376709 (URN)10.1088/1361-648X/aafd11 (DOI)000456850300002 ()30625423 (PubMedID)
Funder
Swedish Research CouncilGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyCarl Tryggers foundation Swedish National Infrastructure for Computing (SNIC)
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2019-02-13Bibliographically approved
Wasilewski, B., Sniadecki, Z., Werwinski, M., Pierunek, N., Rusz, J. & Eriksson, O. (2019). Electronic specific heat coefficient and magnetic properties of Y(Fe1-xCox)(2) Laves phases: A combined experimental and first-principles study. Physical Review B, 100(13), Article ID 134436.
Open this publication in new window or tab >>Electronic specific heat coefficient and magnetic properties of Y(Fe1-xCox)(2) Laves phases: A combined experimental and first-principles study
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 13, article id 134436Article in journal (Refereed) Published
Abstract [en]

We investigated experimentally and computationally the concentration dependence of the electronic specific heat coefficient gamma in the Y(Fe1-xCox)(2) pseudobinary Laves phase system. The experimentally observed maximum in gamma(x) around the magnetic phase transition was interpreted within the local density approximation combined with the virtual crystal approximation. To explain the formation of the observed maximum, we analyzed theoretically the dependence of the magnetic energy, magnetic moments, densities of states, and Fermi surfaces on the Co concentration. Furthermore, we carried out the calculations of the density of states (DOS) at the Fermi level as a function of fixed spin moment. The calculated Co concentration at which gamma takes the maximum value (x(max-LDA-VCA) = 0.91) stays in good agreement with the measured value (x(max-expt) = 0.925). We conclude that the observed maximum in gamma(x) results from the presence of the sharp DOS peak in the vicinity of the Fermi level.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-397299 (URN)10.1103/PhysRevB.100.134436 (DOI)000493513000003 ()
Funder
Swedish Research CouncilStandUpKnut and Alice Wallenberg Foundation
Available from: 2019-12-06 Created: 2019-12-06 Last updated: 2019-12-06Bibliographically approved
Rotunno, E., Zanfrognini, M., Frabboni, S., Rusz, J., Borkowski, R. E. D., Karimi, E. & Grillo, V. (2019). Orbital angular momentum resolved electron magnetic chiral dichroism. Physical Review B, 100(22), Article ID 224409.
Open this publication in new window or tab >>Orbital angular momentum resolved electron magnetic chiral dichroism
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 22, article id 224409Article in journal (Refereed) Published
Abstract [en]

We propose to use the recently introduced orbital angular momentum spectrometer in a transmission electron microscope to perform electron magnetic chiral dichroism experiments, dispersing the inelastically scattered electrons from a magnetic material in both energy and angular momentum. The technique offers several advantages over previous formulations of electron magnetic chiral dichroism as it requires much simpler experimental conditions in terms of specimen orientation and thickness. A simulation algorithm, based on the multislice description of the beam propagation, is used to anticipate the advantages of the approach over current electron magnetic chiral dichroism implementations. Numerical calculations confirm an increased magnetic signal to noise ratio with in plane atomic resolution.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-400763 (URN)10.1103/PhysRevB.100.224409 (DOI)000501542400004 ()
Funder
EU, Horizon 2020, 766970
Available from: 2020-01-03 Created: 2020-01-03 Last updated: 2020-01-03Bibliographically approved
Negi, D. S., Spiegelberg, J., Muto, S., Thersleff, T., Ohtsuka, M., Schonstrom, L., . . . Rusz, J. (2019). Proposal for Measuring Magnetism with Patterned Apertures in a Transmission Electron Microscope. Physical Review Letters, 122(3), Article ID 037201.
Open this publication in new window or tab >>Proposal for Measuring Magnetism with Patterned Apertures in a Transmission Electron Microscope
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2019 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 122, no 3, article id 037201Article in journal (Refereed) Published
Abstract [en]

We propose a magnetic measurement method utilizing a patterned postsample aperture in a transmission electron microscope. While utilizing electron magnetic circular dichroism, the method circumvents previous needs to shape the electron probe to an electron vortex beam or astigmatic beam. The method can be implemented in standard scanning transmission electron microscopes by replacing the spectrometer entrance aperture with a specially shaped aperture, hereafter called a ventilator aperture. The proposed setup is expected to work across the whole range of beam sizes-from wide parallel beams down to atomic resolution magnetic spectrum imaging.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Atom and Molecular Physics and Optics Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-376816 (URN)10.1103/PhysRevLett.122.037201 (DOI)000456782500011 ()
Funder
Swedish Research Council, 2016-05113Knut and Alice Wallenberg Foundation, 3DEM-NATUR 2012.0112Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyCarl Tryggers foundation
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-02-19Bibliographically approved
Negi, D. S., Zeiger, P., Jones, L., Idrobo, J.-C., van Aken, P. A. & Rusz, J. (2019). Prospect for detecting magnetism of a single impurity atom using electron magnetic chiral dichroism. Physical Review B, 100(10), Article ID 104434.
Open this publication in new window or tab >>Prospect for detecting magnetism of a single impurity atom using electron magnetic chiral dichroism
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 10, article id 104434Article in journal (Refereed) Published
Abstract [en]

Dopants, even single atoms, can influence the electrical and magnetic properties of materials. Here we demonstrate the opportunity for detecting the magnetic response of an embedded magnetic impurity in a nonmagnetic host material. We combine a depth sectioning approach with electron magnetic circular dichroism in scanning transmission electron microscopy to compute the depth-resolved magnetic inelastic-scattering cross section of single Co impurity buried in the host crystal of GaAs. Our calculations suggest that the magnetic dichroic signal intensity is sensitive to the depth and lateral position of the electron probe relative to the magnetic impurity. Additionally, a more precise dichroic signal localization can be achieved via choosing higher-collection-angle (beta) apertures. Quantitative evaluation of the inelastic-scattering cross section and signal-to-noise ratio indicates that the magnetic signal from a single Co atom is on the verge of being detectable with today's state-of-the-art instrumentation.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-395834 (URN)10.1103/PhysRevB.100.104434 (DOI)000488252600004 ()
Funder
Swedish Research Council, 2017-04026Swedish National Infrastructure for Computing (SNIC)EU, Horizon 2020, 823717 ESTEEM3Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25Bibliographically approved
Edstrom, A., Lubk, A. & Rusz, J. (2019). Quantum mechanical treatment of atomic-resolution differential phase contrast imaging of magnetic materials. Physical Review B, 99(17), Article ID 174428.
Open this publication in new window or tab >>Quantum mechanical treatment of atomic-resolution differential phase contrast imaging of magnetic materials
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 17, article id 174428Article in journal (Refereed) Published
Abstract [en]

Utilizing the Pauli equation based multislice method, introduced in a previous paper [A. Edstrom, A. Lubk, and J. Rusz, Phys. Rev. Lett. 116, 127203 (2016)], we study the atomic-resolution differential phase contrast (DPC) imaging on an example of a hard magnet FePt with in-plane magnetization. Simulated center-of-mass pattern in a scanning transmission electron microscopy experiment carries information about both electric and magnetic fields. The momentum transfer remains curl free, which has consequences for interpretation of the integrated DPC technique. The extracted magnetic component of the pattern is compared to the expected projected microscopic magnetic field as obtained by density functional theory calculation. Qualitative agreement is obtained for low sample thicknesses and a suitable range of collection angles.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-387586 (URN)10.1103/PhysRevB.99.174428 (DOI)000469324500002 ()
Funder
Swedish Research Council
Available from: 2019-06-26 Created: 2019-06-26 Last updated: 2019-06-26Bibliographically approved
Thersleff, T., Schönström, L., Tai, C.-W., Adam, R., Burgler, D. E., Schneider, C. M., . . . Rusz, J. (2019). Single-pass STEM-EMCD on a zone axis using a patterned aperture: progress in experimental and data treatment methods. Scientific Reports, 9, Article ID 18170.
Open this publication in new window or tab >>Single-pass STEM-EMCD on a zone axis using a patterned aperture: progress in experimental and data treatment methods
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2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 18170Article in journal (Refereed) Published
Abstract [en]

Measuring magnetic moments in ferromagnetic materials at atomic resolution is theoretically possible using the electron magnetic circular dichroism (EMCD) technique in a (scanning) transmission electron microscope ((S)TEM). However, experimental and data processing hurdles currently hamper the realization of this goal. Experimentally, the sample must be tilted to a zone-axis orientation, yielding a complex distribution of magnetic scattering intensity, and the same sample region must be scanned multiple times with sub-atomic spatial registration necessary at each pass. Furthermore, the weak nature of the EMCD signal requires advanced data processing techniques to reliably detect and quantify the result. In this manuscript, we detail our experimental and data processing progress towards achieving single-pass zone-axis EMCD using a patterned aperture. First, we provide a comprehensive data acquisition and analysis strategy for this and other EMCD experiments that should scale down to atomic resolution experiments. Second, we demonstrate that, at low spatial resolution, promising EMCD candidate signals can be extracted, and that these are sensitive to both crystallographic orientation and momentum transfer.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-400667 (URN)10.1038/s41598-019-53373-1 (DOI)000500806400001 ()31796786 (PubMedID)
Funder
Swedish Research Council, 2017-04026Swedish Foundation for Strategic Research , ITM17-0301
Available from: 2020-01-03 Created: 2020-01-03 Last updated: 2020-01-03Bibliographically approved
Wang, Z., Tavabi, A. H., Jin, L., Rusz, J., Tyutyunnikov, D., Jiang, H., . . . Zhong, X. (2018). Atomic scale imaging of magnetic circular dichroism by achromatic electron microscopy. Nature Materials, 17(3), 221-225
Open this publication in new window or tab >>Atomic scale imaging of magnetic circular dichroism by achromatic electron microscopy
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2018 (English)In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 17, no 3, p. 221-225Article in journal (Refereed) Published
Abstract [en]

In order to obtain a fundamental understanding of the interplay between charge, spin, orbital and lattice degrees of freedom in magnetic materials and to predict and control their physical properties1-3, experimental techniques are required that are capable of accessing local magnetic information with atomic-scale spatial resolution. Here, we show that a combination of electron energy-loss magnetic chiral dichroism(4) and chromatic-aberration-corrected transmission electron microscopy, which reduces the focal spread of inelastically scattered electrons by orders of magnitude when compared with the use of spherical aberration correction alone, can achieve atomic-scale imaging of magnetic circular dichroism and provide element-selective orbital and spin magnetic moments atomic plane by atomic plane. This unique capability, which we demonstrate for Sr2FeMoO6, opens the door to local atomic-level studies of spin configurations in a multitude of materials that exhibit different types of magnetic coupling, thereby contributing to a detailed understanding of the physical origins of magnetic properties of materials at the highest spatial resolution.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-350057 (URN)10.1038/s41563-017-0010-4 (DOI)000426012000009 ()29403052 (PubMedID)
Funder
EU, FP7, Seventh Framework Programme, 320832Swedish Research Council
Available from: 2018-05-09 Created: 2018-05-09 Last updated: 2018-05-09Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-0074-1349

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