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Publications (10 of 18) Show all publications
Dürr, R. N., Maltoni, P., Feng, S., Ghorai, S., Ström, P., Tai, C.-W., . . . Edvinsson, T. (2024). Clearing Up Discrepancies in 2D and 3D Nickel Molybdate Hydrate Structures. Inorganic Chemistry, 63(5)
Open this publication in new window or tab >>Clearing Up Discrepancies in 2D and 3D Nickel Molybdate Hydrate Structures
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2024 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 63, no 5Article in journal (Refereed) Published
Abstract [en]

When electrocatalysts are prepared, modification of the morphology is a common strategy to enhance their electrocatalytic performance. In this work, we have examined and characterized nanorods (3D) and nanosheets (2D) of nickel molybdate hydrates, which previously have been treated as the same material with just a variation in morphology. We thoroughly investigated the materials and report that they contain fundamentally different compounds with different crystal structures, chemical compositions, and chemical stabilities. The 3D nanorod structure exhibits the chemical formula NiMoO4·0.6H2O and crystallizes in a triclinic system, whereas the 2D nanosheet structures can be rationalized with Ni3MoO5–0.5x(OH)x·(2.3 – 0.5x)H2O, with a mixed valence of both Ni and Mo, which enables a layered crystal structure. The difference in structure and composition is supported by X-ray photoelectron spectroscopy, ion beam analysis, thermogravimetric analysis, X-ray diffraction, electron diffraction, infrared spectroscopy, Raman spectroscopy, and magnetic measurements. The previously proposed crystal structure for the nickel molybdate hydrate nanorods from the literature needs to be reconsidered and is here refined by ab initio molecular dynamics on a quantum mechanical level using density functional theory calculations to reproduce the experimental findings. Because the material is frequently studied as an electrocatalyst or catalyst precursor and both structures can appear in the same synthesis, a clear distinction between the two compounds is necessary to assess the underlying structure-to-function relationship and targeted electrocatalytic properties.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2024
Keywords
nickel molybdate hydrate; nanorods, nanosheets layered nickel molybdate, α-NiMoO4, molybdenum leaching, Raman spectroscopy
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-476769 (URN)10.1021/acs.inorgchem.3c03261 (DOI)001158182800001 ()38242537 (PubMedID)
Funder
EU, Horizon 2020, 765376
Available from: 2022-06-13 Created: 2022-06-13 Last updated: 2024-03-01Bibliographically 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
Atak, G., Ghorai, S., Granqvist, C. G., Niklasson, G. A. & Bayrak Pehlivan, I. (2023). Cycling durability and potentiostatic rejuvenation of electrochromic tungsten oxide thin films: Effect of silica nanoparticles in LiClO4-Propylene carbonate electrolytes. Solar Energy Materials and Solar Cells, 250, Article ID 112070.
Open this publication in new window or tab >>Cycling durability and potentiostatic rejuvenation of electrochromic tungsten oxide thin films: Effect of silica nanoparticles in LiClO4-Propylene carbonate electrolytes
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2023 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 250, article id 112070Article in journal (Refereed) Published
Abstract [en]

Electrochromic (EC) technology allows control of the transmission of visible light and solar radiation through thin-film devices. When applied to “smart” windows, EC technology can significantly diminish energy use for cooling and air conditioning of buildings and simultaneously provide good indoor comfort for the buildings’ occupants through reduced glare. EC “smart” windows are available on the market, but it is nevertheless important that their degradation under operating conditions be better understood and, ideally, prevented. In the present work, we investigated EC properties, voltammetric cycling durability, and potentiostatic rejuvenation of sputter-deposited WO3 thin films immersed in LiClO4–propylene carbonate electrolytes containing up to 3.0 wt% of ∼7-nm-diameter SiO2 nanoparticles. Adding about 1 wt% SiO2 led to a significant improvement in cycling durability in the commonly used potential range of 2.0–4.0 V vs. Li/Li+. Furthermore, X-ray photoemission spectroscopy indicated that O–Si bonds were associated with enhanced durability in the presence of SiO2 nanoparticles.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Electrochromism, Cycling durability, Potentiostatic rejuvenation, Tungsten oxide, Silica nanoparticles, Smart windows
National Category
Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-488940 (URN)10.1016/j.solmat.2022.112070 (DOI)000878840800005 ()
Funder
Swedish Research Council, 2019-00207
Available from: 2022-11-25 Created: 2022-11-25 Last updated: 2023-04-13Bibliographically 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
Rani, P., Jönsson, P. E., Ghorai, S., N'Diaye, A. T. & Andersson, G. (2023). Magnetic Properties versus Interface Density in Rigid-Exchange-Coupled Amorphous Multilayers with Induced Uniaxial Anisotropy. Journal of Applied Physics, 133(7), Article ID 073903.
Open this publication in new window or tab >>Magnetic Properties versus Interface Density in Rigid-Exchange-Coupled Amorphous Multilayers with Induced Uniaxial Anisotropy
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2023 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 133, no 7, article id 073903Article in journal (Refereed) Published
Abstract [en]

We demonstrate the possibility to tune the saturation magnetization, coercivity, and uniaxial in-plane anisotropy constant in amorphous bilayers and multilayers of Co85(Al70Zr30)15 and Sm11Co82Ti7 through the interface density. From magnetometry and x-ray circular dichroism (XMCD) measurements, we conclude that the easy-axis coercivity 𝜇0𝐻𝑐 increases four times when the number of bilayer repetitions, 𝑁, increases from 1 to 10 within a constant total sample thickness of 20 nm. At the same time, the anisotropy constant 𝐾𝑢 also increases by a factor four, whereas the saturation magnetization 𝑀𝑠 decreases slightly. The Co spin and orbital moments, 𝑚𝑠 and 𝑚𝑙, are found to be approximately constant within the sample series. The average total Co moment is only 0.8–0.9 𝜇𝐵/atom, but the 𝑚𝑙/𝑚𝑠 ratio is strongly enhanced compared to pure Co. Magnetization curves extracted from XMCD measurements show that the Co and Sm moments are ferromagnetically coupled for all samples.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-495566 (URN)10.1063/5.0137889 (DOI)000958356700008 ()
Funder
Swedish Research Council, 2017-03725Swedish Foundation for Strategic Research, EM-16-0039
Available from: 2023-01-30 Created: 2023-01-30 Last updated: 2023-05-02Bibliographically approved
Ibrayeva, A., Lind, E., Silva, M. D., Ghorai, S. & Eriksson, S. (2023). Measurement and Modelling of Hysteresis Curves for Nonlinear Permanent Magnets at Different Inclination Angles. In: 2023 IEEE International Magnetic Conference (INTERMAG): . Paper presented at IEEE International Magnetic Conference (INTERMAG), May 15-19, 2023, Sendai, Japan. Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Measurement and Modelling of Hysteresis Curves for Nonlinear Permanent Magnets at Different Inclination Angles
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2023 (English)In: 2023 IEEE International Magnetic Conference (INTERMAG), Institute of Electrical and Electronics Engineers (IEEE), 2023Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the measurement results of the BH/MH curves of the Alnico 8 (LNGT40) with recoil loops and a mathematical model for the calculation of the average magnetic flux density in a cubic permanent magnet. The measurements were performed with a Vibrating Sample Magnetometer (VSM). The magnet samples have a cubic shape with 3 mm sides. BH curves in preferred (easy) and transverse directions and recoil loops were measured and compared to Alnico 9 (LNGT72) as well as to the data from the supplier. The load line of the cubic magnet in 0 A/m applied magnetic field was found. A mathematical model was developed which can approximate the MH a curve for an applied field with an arbitrarily chosen angle between the field and easy axis, given MH a curves for 0o and 90o. Also, a simplified general model of a cubic permanent magnet in the air and calculation results of stored energy and hysteresis losses were presented.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
Series
International Conference on Magnetics, ISSN 2150-4598, E-ISSN 2150-4601
Keywords
Alnico magnets, BH curve, Demagnetization, Permanent Magnet, Recoil Line
National Category
Other Physics Topics Other Electrical Engineering, Electronic Engineering, Information Engineering Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-520985 (URN)10.1109/INTERMAG50591.2023.10265100 (DOI)001090594700054 ()979-8-3503-3246-9 (ISBN)979-8-3503-3247-6 (ISBN)
Conference
IEEE International Magnetic Conference (INTERMAG), May 15-19, 2023, Sendai, Japan
Funder
Swedish Research Council, 2018-04617StandUp
Available from: 2024-01-18 Created: 2024-01-18 Last updated: 2024-04-22Bibliographically approved
Silva, M. D., Lind, E., Ibrayeva, A., Ghorai, S. & Eriksson, S. (2023). Model for Angular Dependency of the Intrinsic Coercivity of Ferrite Permanent Magnets. In: 2023 IEEE International Magnetic Conference, INTERMAG: . Paper presented at IEEE International Magnetic Conference (INTERMAG), MAY 15-19, 2023, Sendai, JAPAN. Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Model for Angular Dependency of the Intrinsic Coercivity of Ferrite Permanent Magnets
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2023 (English)In: 2023 IEEE International Magnetic Conference, INTERMAG, Institute of Electrical and Electronics Engineers (IEEE), 2023Conference paper, Published paper (Refereed)
Abstract [en]

In internal permanent magnet synchronous machines (IPMSM), the use of ferrite permanent magnets is being studied as an alternative to rare-earth elements-based permanent magnets, such as NdFeB. However, demagnetization measurements of ferrite magnets are rarely published and such information is crucial for an efficient electrical machine design with ferrite magnets. In this paper, we present measurements of partial demagnetization on ferrite permanent magnets subject to inclined external magnetic fields. From the measurements done, mathematical models are developed for Y30 and Y40 samples that defines a relationship between the intrinsic coercivity and the inclination of the external demagnetizing field. Furthermore, from the primary results, the angular dependency of hysteresis losses and relative permeability are also explored, as well as their impact on the design of IPMSM.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
Series
International Conference on Magnetics, ISSN 2150-4598
Keywords
Angular Demagnetization, Ferrite Magnets, Intrinsic Coercivity, Magnetic Field Modeling
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-520987 (URN)10.1109/INTERMAG50591.2023.10265092 (DOI)001090594700046 ()979-8-3503-3246-9 (ISBN)
Conference
IEEE International Magnetic Conference (INTERMAG), MAY 15-19, 2023, Sendai, JAPAN
Funder
StandUp
Available from: 2024-01-18 Created: 2024-01-18 Last updated: 2024-02-09Bibliographically approved
Ghorai, S., Cedervall, J., Clulow, R., Huang, S., Ericsson, T., Häggström, L., . . . Svedlindh, P. (2023). Site-specific atomic substitution in a giant magnetocaloric Fe2P-type system. Physical Review B, 107(10), Article ID 104409.
Open this publication in new window or tab >>Site-specific atomic substitution in a giant magnetocaloric Fe2P-type system
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2023 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 107, no 10, article id 104409Article in journal (Refereed) Published
Abstract [en]

Giant magnetocaloric (GMC) materials constitute a requirement for near room temperature magnetic refrigeration. (Fe,Mn)2(P,Si) is a GMC compound with strong magnetoelastic coupling. The main hindrance towards application of this material is a comparably large temperature hysteresis, which can be reduced by metal site substitution with a nonmagnetic element. However, the (Fe,Mn)2(P,Si) compound has two equally populated metal sites, the tetrahedrally coordinated 3f and the pyramidally coordinated 3g sites. The magnetic and magnetocaloric properties of such compounds are highly sensitive to the site specific occupancy of the magnetic atoms. Here we have attempted to study separately the effect of 3f and 3g site substitution with equal amounts of vanadium. Using formation energy calculations, the site preference of vanadium and its influence on the magnetic phase formation are described. A large difference in the isothermal entropy change (as high as 44\%) with substitution in the 3f and 3g sites is observed. The role of the lattice parameter change with temperature and the strength of the magnetoelastic coupling on the magnetic properties are highlighted.

Place, publisher, year, edition, pages
American Physical Society, 2023
National Category
Condensed Matter Physics Materials Chemistry
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-487262 (URN)10.1103/PhysRevB.107.104409 (DOI)000974419900006 ()
Funder
Swedish Foundation for Strategic Research, EM-16-0039Swedish Research Council, 2019-00645StandUpeSSENCE - An eScience CollaborationSwedish National Infrastructure for Computing (SNIC)
Available from: 2022-10-26 Created: 2022-10-26 Last updated: 2023-05-26Bibliographically approved
Nayak, S., Ghorai, S., Padhan, A. M., Hajra, S., Svedlindh, P. & Murugavel, P. (2022). Cationic redistribution induced spin-glass and cluster-glass states in spinel ferrite. Physical Review B, 106(17), Article ID 174402.
Open this publication in new window or tab >>Cationic redistribution induced spin-glass and cluster-glass states in spinel ferrite
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2022 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 106, no 17, article id 174402Article in journal (Refereed) Published
Abstract [en]

The effect of the cationic redistribution on the complex spinel structure and magnetic properties were investigated in Zn0.7Cu0.3Fe2O4 ferrite. X-ray photoelectron spectroscopy and x-ray diffraction studies revealed that the system exhibits a mixed spinel structure with Fe3+, Zn2+, and Cu2+ occupying both tetrahedral and octahedral sublattices. The DC magnetization results revealed the absence of long-range magnetic order in the system. Furthermore, the AC susceptibility data analysis using dynamic scaling laws suggests that the system exhibits magnetic relaxation below two different temperatures: (i) a spin-glass–like transition at low temperature (∼49.2K) with critical exponent 10.3 and spin-flip time ∼10−11s, and (ii) a cluster-glass–like transition at higher temperature (∼317K) with critical exponent 4.6 and spin-flip time ∼10−10s. The existence of glassy behavior and magnetic memory effects below the spin-glass transition temperature proves that the system is in nonequilibrium dynamical state. The coexistence of spin-glass and cluster-glass along with the thermal hysteresis between these two transitions could widen the technological applications of these systems.

Place, publisher, year, edition, pages
American Physical Society, 2022
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-488050 (URN)10.1103/physrevb.106.174402 (DOI)000885897100002 ()
Available from: 2022-11-08 Created: 2022-11-08 Last updated: 2022-12-12Bibliographically approved
Ghorai, S. (2022). Direct and indirect magnetocaloric properties of first- and second-order phase transition materials. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Direct and indirect magnetocaloric properties of first- and second-order phase transition materials
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The energy-efficient and environmentally friendly alternative cooling technology based on the magnetocaloric effect (MCE) is discussed in this thesis. The thesis has two major parts, one devoted to material characterization and the other to instrument development. Different magnetic oxides and intermetallic compounds with second-order and first-order magnetic transitions, respectively, were studied with the aim of finding materials suitable for magnetic refrigeration. For the application of the MCE, a high value of the isothermal entropy changes and the relative cooling power (RCP), along with minimal temperature hysteresis are required. The temperature hysteresis is negligible for all studied second-order compounds, while an almost ten times higher value of the isothermal entropy change has been observed for the first-order compounds. The highest value of isothermal entropy change (20 J/kgK at 2 T applied magnetic field) has been observed for the MnNiSi-type compounds exhibiting magneto-structural phase transitions, while the largest value of the RCP (176 J/kg at 2 T applied magnetic field) has been observed for the Fe2P-type compounds exhibiting magneto-elastic phase transitions.

For the characterization of magnetocaloric properties, one important parameter is the adiabatic temperature change, which is often not reported in literature owing to the lack of experimental setups for direct measurements of the magnetocaloric effect. This thesis also includes the development of a setup for the direct measurement of the adiabatic temperature change upon a change in a magnetic field.  

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2022. p. 63
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2212
Keywords
Magnetocaloric effect, Adiabatic temperature change, Direct measurement of magnetocaloric effect, Griffiths phase, Magneto-elastic transition, Magneto-structural transition, Second-order magnetic phase transition, First-order magnetic phase transition, Isothermal magnetic entropy change
National Category
Natural Sciences
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-487266 (URN)978-91-513-1644-4 (ISBN)
Public defence
2022-12-14, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala , 75237 Sweden, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2022-11-22 Created: 2022-10-27 Last updated: 2022-11-22
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2790-116x

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