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Publications (10 of 249) Show all publications
Ulusoy, S., Feygenson, M., Thersleff, T., Uusimaeki, T., Valvo, M., Roca, A. G., . . . Salazar Alvarez, G. (2024). Elucidating the Lithiation Process in Fe3−δO4 Nanoparticles by Correlating Magnetic and Structural Properties. ACS Applied Materials and Interfaces, 16(12), 14799-14808
Open this publication in new window or tab >>Elucidating the Lithiation Process in Fe3−δO4 Nanoparticles by Correlating Magnetic and Structural Properties
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2024 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 16, no 12, p. 14799-14808Article in journal (Refereed) Published
Abstract [en]

Due to their high potential energy storage, magnetite (Fe3O4) nanoparticles have become appealing as anode materials in lithium-ion batteries. However, the details of the lithiation process are still not completely understood. Here, we investigate chemical lithiation in 70 nm cubic-shaped magnetite nanoparticles with varying degrees of lithiation, x = 0, 0.5, 1, and 1.5. The induced changes in the structural and magnetic properties were investigated using X-ray techniques along with electron microscopy and magnetic measurements. The results indicate that a structural transformation from spinel to rock salt phase occurs above a critical limit for the lithium concentration (xc), which is determined to be between 0.5< xc ≤ 1 for Fe3−δO4. Diffraction and magnetization measurements clearly show the formation of the antiferromagnetic LiFeO2 phase. Upon lithiation, magnetization measurements reveal an exchange bias in the hysteresis loops with an asymmetry, which can be attributed to the formation of mosaic-like LiFeO2 subdomains. The combined characterization techniques enabled us to unambiguously identify the phases and their distributions involved in the lithiation process. Correlating magnetic and structural properties opens the path to increasing the understanding of the processes involved in a variety of nonmagnetic applications of magnetic materials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2024
Keywords
iron oxide, lithiation, structural transformation, diffraction, magnetism
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-526226 (URN)10.1021/acsami.3c18334 (DOI)001184842100001 ()38478774 (PubMedID)
Funder
Swedish Research Council, 2016-06959
Available from: 2024-04-05 Created: 2024-04-05 Last updated: 2024-04-24Bibliographically approved
Ravensburg, A. L., Brucas, R., Music, D., Spode, L., Pálsson, G. K., Svedlindh, P. & Kapaklis, V. (2024). Epitaxy enhancement in oxide/tungsten heterostructures by harnessing the interface adhesion. Applied Physics A: Materials Science & Processing, 130(2), Article ID 74.
Open this publication in new window or tab >>Epitaxy enhancement in oxide/tungsten heterostructures by harnessing the interface adhesion
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2024 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 130, no 2, article id 74Article in journal (Refereed) Published
Abstract [en]

The conditions whereby epitaxy is achieved are commonly believed to be mostly governed by misfit strain. We report on a systematic investigation of growth and interface structure of single crystalline tungsten thin films on two different metal oxide substrates, Al2O3 (11‾20) and MgO (001). We demonstrate that despite a significant mismatch, enhanced crystal quality is observed for tungsten grown on the sapphire substrates. This is promoted by stronger adhesion and chemical bonding with sapphire compared to magnesium oxide, along with the restructuring of the tungsten layers close to the interface. The latter is supported by ab initio calculations using density functional theory. Finally, we demonstrate the growth of magnetic heterostructures consisting of high-quality tungsten layers in combination with ferromagnetic CoFe layers, which are relevant for spintronic applications.

Place, publisher, year, edition, pages
Springer, 2024
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-520683 (URN)10.1007/s00339-023-07212-w (DOI)001137900100005 ()
Funder
Swedish Research Council, 2019-03581Swedish Research Council, 2021-0465Swedish Energy Agency, 2020-005212Olle Engkvists stiftelse, 217-0023National Academic Infrastructure for Supercomputing in Sweden (NAISS)Swedish Research Council, 2022-06725
Available from: 2024-01-14 Created: 2024-01-14 Last updated: 2024-01-31Bibliographically approved
Dutta, S., Husain, S., Kumar, P., Gupta, N. K., Chaudhary, S., Svedlindh, P. & Barman, A. (2024). Manipulating ultrafast magnetization dynamics of ferromagnets using the odd-even layer dependence of two-dimensional transition metal di-chalcogenides. Nanoscale, 16(8), 4105-4113
Open this publication in new window or tab >>Manipulating ultrafast magnetization dynamics of ferromagnets using the odd-even layer dependence of two-dimensional transition metal di-chalcogenides
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2024 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 16, no 8, p. 4105-4113Article in journal (Refereed) Published
Abstract [en]

Two-dimensional transition metal dichalcogenides (TMDs) have drawn immense interest due to their strong spin-orbit coupling and unique layer number dependence in response to spin-valley coupling. This leads to the possibility of controlling the spin degree of freedom of the ferromagnet (FM) in thin film heterostructures and may prove to be of interest for next-generation spin-based devices. Here, we experimentally demonstrate the odd-even layer dependence of WS2 nanolayers by measurements of the ultrafast magnetization dynamics in WS2/Co3FeB thin film heterostructures by using time-resolved Kerr magnetometry. The fluence (photon energy per unit area) dependent magnetic damping (alpha) reveals the existence of broken symmetry and the dominance of inter- and intraband scattering for odd and even layers of WS2, respectively. The higher demagnetization time, tau m, in 3 and 5 layers of WS2 is indicative of the interaction between spin-orbit and spin-valley coupling due to the broken symmetry. The lower tau m in even layers as compared to the bare FM layer suggests the presence of a spin transport. By correlating tau m and alpha, we pinpointed the dominant mechanisms of ultrafast demagnetization. The mechanism changes from spin transport to spin-flip scattering for even layers of WS2 with increasing fluence. A fundamental understanding of the two-dimensional material and its odd-even layer dependence at ultrashort timescales provides valuable information for designing next-generation spin-based devices. Odd-even WS2 layer number dependent ultrafast demagnetization and damping are studied by varying the pump fluence.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2024
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-525486 (URN)10.1039/d3nr06197c (DOI)001167762200001 ()38349614 (PubMedID)
Available from: 2024-03-25 Created: 2024-03-25 Last updated: 2024-03-25Bibliographically approved
Montero Amenedo, J., Svedlindh, P. & Österlund, L. (2024). Photo-induced reversible modification of the Curie-Weiss temperature in paramagnetic gadolinium compounds. Solid State Communications, 378, Article ID 115419.
Open this publication in new window or tab >>Photo-induced reversible modification of the Curie-Weiss temperature in paramagnetic gadolinium compounds
2024 (English)In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 378, article id 115419Article in journal (Refereed) Published
Abstract [en]

Gadolinium oxyhydride GdHO is a photochromic material that darkens under illumination and bleaches back by thermal relaxation. As an inorganic photochromic material that can be easily deposited by magnetron sputtering, GdHO has very interesting potential applications as a functional material, specially for smart glazing applications. However, the underlying reasons behind the photochromic mechanism - which can be instrumental for the correct optimisation of GdHO for different applications - are not completely understood. In this paper, we rely on the well-established magnetic properties of Gd3+ to shed light on this matter. GdHO thin films present paramagnetic behaviour similar to other Gd3+ compounds such as Gd2O3. Illumination of the films result in a reversible increase of the Curie-Weiss temperature pointing to Ruderman-Kittel-Kasuya-Yosida RKKY interactions, which is consistent with the resistivity decrease observed in the photodarkened films.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Oxyhydrides, Photochromism, RKKY
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-522889 (URN)10.1016/j.ssc.2023.115419 (DOI)001150127700001 ()
Funder
Swedish Energy Agency, P2022-00859
Available from: 2024-02-12 Created: 2024-02-12 Last updated: 2024-02-12Bibliographically approved
Ngaloy, R., Zhao, B., Ershadrad, S., Gupta, R., Davoudiniya, M., Bainsla, L., . . . Dash, S. P. (2024). Strong In-Plane Magnetization and Spin Polarization in (Co0.15Fe0.85)5GeTe2/Graphen e van der Waals Heterostructure Spin-Valve at Room Temperature. ACS Nano, 18(7), 5240-5248
Open this publication in new window or tab >>Strong In-Plane Magnetization and Spin Polarization in (Co0.15Fe0.85)5GeTe2/Graphen e van der Waals Heterostructure Spin-Valve at Room Temperature
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2024 (English)In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 18, no 7, p. 5240-5248Article in journal (Refereed) Published
Abstract [en]

Van der Waals (vdW) magnets are promising, because of their tunable magnetic properties with doping or alloy composition, where the strength of magnetic interactions, their symmetry, and magnetic anisotropy can be tuned according to the desired application. However, so far, most of the vdW magnet-based spintronic devices have been limited to cryogenic temperatures with magnetic anisotropies favoring out-of-plane or canted orientation of the magnetization. Here, we report beyond room-temperature lateral spin-valve devices with strong in-plane magnetization and spin polarization of the vdW ferromagnet (Co0.15Fe0.85)5GeTe2 (CFGT) in heterostructures with graphene. Density functional theory (DFT) calculations show that the magnitude of the anisotropy depends on the Co concentration and is caused by the substitution of Co in the outermost Fe layer. Magnetization measurements reveal the above room-temperature ferromagnetism in CFGT and clear remanence at room temperature. Heterostructures consisting of CFGT nanolayers and graphene were used to experimentally realize basic building blocks for spin valve devices, such as efficient spin injection and detection. Further analysis of spin transport and Hanle spin precession measurements reveals a strong in-plane magnetization with negative spin polarization at the interface with graphene, which is supported by the calculated spin-polarized density of states of CFGT. The in-plane magnetization of CFGT at room temperature proves its usefulness in graphene lateral spin-valve devices, thus revealing its potential application in spintronic technologies.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2024
Keywords
van der Waals magnet, spin-valve, graphene, van der Waals heterostructures, 2Dmagnets, in-plane magnetization, spin polarization
National Category
Condensed Matter Physics Other Physics Topics
Identifiers
urn:nbn:se:uu:diva-528480 (URN)10.1021/acsnano.3c07462 (DOI)001167191800001 ()38330915 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council, 2018-07046Swedish Research Council, 2021-04821Swedish Research Council, 2021-0465Swedish Research Council, 2021-05925Swedish Research Council, 2022-04309
Available from: 2024-05-23 Created: 2024-05-23 Last updated: 2024-05-23Bibliographically approved
Zhao, B., Ngaloy, R., Ghosh, S., Ershadrad, S., Gupta, R., Ali, K., . . . Dash, S. P. (2023). A Room-Temperature Spin-Valve with van der Waals Ferromagnet Fe5GeTe2/Graphene Heterostructure. Advanced Materials, 35(16), Article ID 2209113.
Open this publication in new window or tab >>A Room-Temperature Spin-Valve with van der Waals Ferromagnet Fe5GeTe2/Graphene Heterostructure
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2023 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 35, no 16, article id 2209113Article in journal (Refereed) Published
Abstract [en]

The discovery of van der Waals (vdW) magnets opened a new paradigm for condensed matter physics and spintronic technologies. However, the operations of active spintronic devices with vdW ferromagnets are limited to cryogenic temperatures, inhibiting their broader practical applications. Here, the robust room-temperature operation of lateral spin-valve devices using the vdW itinerant ferromagnet Fe5GeTe2 in heterostructures with graphene is demonstrated. The room-temperature spintronic properties of Fe5GeTe2 are measured at the interface with graphene with a negative spin polarization. Lateral spin-valve and spin-precession measurements provide unique insights by probing the Fe5GeTe2/graphene interface spintronic properties via spin-dynamics measurements, revealing multidirectional spin polarization. Density functional theory calculations in conjunction with Monte Carlo simulations reveal significantly canted Fe magnetic moments in Fe5GeTe2 along with the presence of negative spin polarization at the Fe5GeTe2/graphene interface. These findings open opportunities for vdW interface design and applications of vdW-magnet-based spintronic devices at ambient temperatures.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2023
Keywords
2D magnets, Fe5GeTe2, graphene, Hanle spin precession, spin-valve, van der Waals heterostructures, van der Waals magnets
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-511082 (URN)10.1002/adma.202209113 (DOI)000945738100001 ()36641649 (PubMedID)
Funder
Vinnova, 2019-00068Swedish Research Council, 2021-04821Knut and Alice Wallenberg FoundationSwedish Research Council, 2022-04309Swedish Research Council, 2021-04658Swedish Research Council, 2018-05973Swedish National Infrastructure for Computing (SNIC), SNIC 2021/3-38
Available from: 2023-09-07 Created: 2023-09-07 Last updated: 2023-09-07Bibliographically approved
Ghorai, S., Hedlund, D., Kapuscinski, M. & Svedlindh, P. (2023). A setup for direct measurement of the adiabatic temperature change in magnetocaloric materials. IEEE Transactions on Instrumentation and Measurement, 72, 1-9
Open this publication in new window or tab >>A setup for direct measurement of the adiabatic temperature change in magnetocaloric materials
2023 (English)In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 72, p. 1-9Article in journal (Refereed) Published
Abstract [en]

In order to find a highly efficient, environmentally-friendly magnetic refrigerant, direct measurements of the adiabatic temperature change ΔTadb are required. Here, in this work, a simple setup for the ΔTadb measurement is presented. Using a permanent magnet Halbach array with a maximum magnetic field of 1.8 T and a rate of magnetic field change of 5 T/s, accurate determination of ΔTadb is possible in this system. The operating temperature range of the system is from 100 to 400 K, designed for the characterization of materials with potential for room temperature magnetic refrigeration applications. Using the setup, ΔTadb of a first-order and two second-order compounds have been studied. Results from the direct measurement for the first-order compound have been compared with ΔTadb calculated from the temperature and magnetic field-dependent specific heat data. By comparing results from direct and indirect measurements, it is concluded that for a reliable characterization of the magnetocaloric effect (MCE), direct measurement of ΔTadb should be adopted.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-487263 (URN)10.1109/TIM.2023.3272387 (DOI)000991806800037 ()
Funder
Swedish Foundation for Strategic Research, EM−16−0039
Available from: 2022-10-26 Created: 2022-10-26 Last updated: 2023-08-14Bibliographically approved
Jana, S., Knut, R., Delczeg-Czirjak, E. K., Malik, R. S., Stefanuik, R., Terschlüsen, J. A., . . . Karis, O. (2023). Atom-specific magnon-driven ultrafast spin dynamics in Fe1-xNix alloys. Physical Review B, 107(18), Article ID L180301.
Open this publication in new window or tab >>Atom-specific magnon-driven ultrafast spin dynamics in Fe1-xNix alloys
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2023 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 107, no 18, article id L180301Article in journal (Refereed) Published
Abstract [en]

By employing element-specific spectroscopy in the ultrafast time scale in Fe1-xNix alloys, we find a composition-dependent effect in the demagnetization that we relate to electron-magnon scattering and changes in the spin-wave stiffness. In all six measured alloys of different composition, the demagnetization of Ni compared to Fe exhibits a delay, an effect which we find is inherent in alloys but not in elemental Fe and Ni. Using a model based on electron-magnon scattering, we extract a spin-wave stiffness from all alloys that show excellent agreement with values obtained from other techniques.

Place, publisher, year, edition, pages
American Physical Society (APS), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-503182 (URN)10.1103/PhysRevB.107.L180301 (DOI)000987750800002 ()
Funder
Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic ResearchSwedish Research Council, 2016-04524Swedish Research Council, 2013-08316Swedish Research Council, 2021-5395Knut and Alice Wallenberg FoundationEU, European Research Council, 101002772 -SPINNER
Available from: 2023-06-26 Created: 2023-06-26 Last updated: 2023-06-26
Mottamchetty, V., Rani, P., Brucas, R., Rydberg, A., Svedlindh, P. & Gupta, R. (2023). Direct evidence of terahertz emission arising from anomalous Hall effect. Scientific Reports, 13(1), Article ID 5988.
Open this publication in new window or tab >>Direct evidence of terahertz emission arising from anomalous Hall effect
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2023 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 5988Article in journal (Refereed) Published
Abstract [en]

A detailed understanding of the different mechanisms being responsible for terahertz (THz) emission in ferromagnetic (FM) materials will aid in designing efficient THz emitters. In this report, we present direct evidence of THz emission from single layer Co0.4Fe0.4B0.2 (CoFeB) FM thin films. The dominant mechanism being responsible for the THz emission is the anomalous Hall effect (AHE), which is an effect of a net backflow current in the FM layer created by the spin polarized current reflected at the interfaces of the FM layer. The THz emission from the AHE-based CoFeB emitter is optimized by varying its thickness, orientation, and pump fluence of the laser beam. Results from electrical transport measurements show that skew scattering of charge carriers is responsible for the THz emission in the CoFeB AHE-based THz emitter.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-509239 (URN)10.1038/s41598-023-33143-w (DOI)001034742000077 ()37045934 (PubMedID)
Funder
Swedish Research Council, 2021-04658Swedish Research Council, 2018-04918Swedish Research Council, 201703725
Available from: 2023-08-21 Created: 2023-08-21 Last updated: 2023-08-21Bibliographically approved
Ghorai, S., Vieira, R. M., Shtender, V., Delczeg-Czirjak, E. K., Herper, H. C., Björkman, T., . . . Svedlindh, P. (2023). Giant magnetocaloric effect in the (Mn,Fe)NiSi-system.
Open this publication in new window or tab >>Giant magnetocaloric effect in the (Mn,Fe)NiSi-system
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2023 (English)Manuscript (preprint) (Other academic)
Abstract [en]

The search for energy-efficient and environmentally friendly cooling technologies is a key driver for the development of magnetic refrigeration based on the magnetocaloric effect (MCE). This phenomenon arises from the interplay between magnetic and lattice degrees of freedom that is strong in certain materials, leading to a change in temperature upon application or removal of a magnetic field. Here we report on a new material, Mn1−xFexNiSi0.95Al0.05, with an exceptionally large isothermal entropy at room temperature. By combining experimental and theoretical methods we outline the microscopic mechanism behind the large MCE in this material. It is demonstrated that the competition between the Ni2In-type hexagonal phase and the MnNiSi-type orthorhombic phase, that coexist in this system, combined with the distinctly different magnetic properties of these phases, is a key parameter for the functionality of this material for magnetic cooling.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-525213 (URN)10.48550/arXiv.2307.00128 (DOI)
Available from: 2024-03-19 Created: 2024-03-19 Last updated: 2024-03-19
Projects
Low-dimensional magnetism [2010-03340_VR]; Uppsala UniversitySpin currents and interface effects in magnetic heterostructures [2017-03799_VR]; Uppsala UniversityMagnetic and structural characterization of magnetic materials for green energy technology [2019-03604_ VINNOVA]; Uppsala University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3049-6831

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