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Direct and indirect magnetocaloric properties of first- and second-order phase transition materials
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics. Uppsala University.ORCID iD: 0000-0003-2790-116x
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Description
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 [en]
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: urn:nbn:se:uu:diva-487266ISBN: 978-91-513-1644-4 (print)OAI: oai:DiVA.org:uu-487266DiVA, id: diva2:1706621
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
List of papers
1. Field induced crossover in critical behaviour and direct measurement of the magnetocaloric properties of La0.4Pr0.3Ca0.1Sr0.2MnO3
Open this publication in new window or tab >>Field induced crossover in critical behaviour and direct measurement of the magnetocaloric properties of La0.4Pr0.3Ca0.1Sr0.2MnO3
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2020 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, article id 19485Article in journal (Refereed) Published
Abstract [en]

La0.4Pr0.3Ca0.1Sr0.2MnO3 has been investigated as a potential candidate for room temperature magnetic refrigeration. Results from X-ray powder diffraction reveal an orthorhombic structure with Pnma space group. The electronic and chemical properties have been confirmed by X-ray photoelectron spectroscopy and ion-beam analysis. A second-order paramagnetic to ferromagnetic transition was observed near room temperature (289 K), with a mean-field like critical behaviour at low field and a tricritical mean-field like behaviour at high field. The field induced crossover in critical behaviour is a consequence of the system being close to a first-order magnetic transition in combination with a magnetic field induced suppression of local lattice distortions. The lattice distortions consist of interconnected and weakly distorted pairs of Mn-ions, where each pair shares an electron and a hole, dispersed by large Jahn–Teller distortions at Mn3+ lattice sites. A comparatively high value of the isothermal entropy-change (3.08 J/kg-K at 2 T) is observed and the direct measurements of the adiabatic temperature change reveal a temperature change of 1.5 K for a magnetic field change of 1.9 T.

National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-424925 (URN)10.1038/s41598-020-76321-w (DOI)000595151600039 ()33173113 (PubMedID)
Available from: 2020-11-10 Created: 2020-11-10 Last updated: 2022-10-27Bibliographically approved
2. Large room temperature relative cooling power in La0.5Pr0.2Ca0.1Sr0.2MnO3
Open this publication in new window or tab >>Large room temperature relative cooling power in La0.5Pr0.2Ca0.1Sr0.2MnO3
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2020 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 827, article id 154292Article in journal (Refereed) Published
Abstract [en]

The La0.5Pr0.2Ca0.1Sr0.2MnO3 compound has been investigated as a potential candidate for room temperature magnetocaloric refrigeration. The Rietveld refinement of X-ray powder diffraction patterns confirms that the compound crystalizes in an orthorhombic phase with the Pnma space group. Rutherford backscattering spectrometry and time-of-flight elastic recoil detection analysis, verified the desired ratio of the elements in the compound. Using X-ray photoelectron spectroscopy two oxidation states of manganese (Mn), Mn4+ and Mn3+ were identified in the compound with relative amounts of 32% and 68%, respectively. The observed spin orbit splitting of the Mn-2p3/2 and Mn-2p1/2 levels was obtained as 11.7 eV. A ferromagnetic to paramagnetic transition was observed around 296 K, which makes the material interesting for magnetic cooling near room temperature. In addition, the absence of magnetic hysteresis provides another argument in favor of the studied compound. The isothermal entropy change (-deltaSm) and the relative cooling power (RCP) for a magnetic field change of 5 T were found to be 4 J/kg K and 372 J/kg, respectively. From the comparison of the values of (-deltaSm) and RCP with those obtained for the archetypal magnetocaloric material gadolinium, it is argued that our material can be considered as a potential candidate in cooling systems based on magnetic refrigeration.

National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-406043 (URN)10.1016/j.jallcom.2020.154292 (DOI)000520405900059 ()
Funder
Swedish Foundation for Strategic Research , EM-16-0039Swedish Foundation for Strategic Research , RIF14-0053Swedish Research Council, 2017-00646_9
Available from: 2020-03-04 Created: 2020-03-04 Last updated: 2022-10-27Bibliographically approved
3. Effect of reduced local lattice disorder on the magnetic properties of B-site substituted La0.8Sr0.2MnO3
Open this publication in new window or tab >>Effect of reduced local lattice disorder on the magnetic properties of B-site substituted La0.8Sr0.2MnO3
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2021 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 529, article id 167893Article in journal (Refereed) Published
Abstract [en]

Disorder induced by chemical inhomogeneity and Jahn-Teller (JT) distortions is often observed in mixed valence perovskite manganites. The main reasons for the evolution of this disorder are connected with the cationic size differences and the ratio between JT active and non-JT active ions. The quenched disorder leads to a spin-cluster state above the magnetic transition temperature. The effect of Cu, a B-site substitution in the La0.8Sr0.2MnO3 compound, on the disordered phase has been addressed here. X-ray powder diffraction reveals rhombohedral (R-3c) structures for both the parent and B-site substituted compound with negligible change of lattice volume. The chemical compositions of the two compounds were verified by ion beam analysis technique. With the change of electronic bandwidth, the magnetic phase transition temperature has been tuned towards room temperature (318 K), an important requirement for room temperature magnetic refrigeration. However, a small decrease of the isothermal entropy change was observed with Cu-substitution, related to the decrease of the saturation magnetization.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Griffiths phase, Jahn-Teller effect, Dimerons, Magnetocaloric effect, Spin cluster state
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-439303 (URN)10.1016/j.jmmm.2021.167893 (DOI)000636608000047 ()
Funder
Swedish Foundation for Strategic Research , EM-16-0039Swedish Research Council, 201700646_9Swedish Foundation for Strategic Research , RIF14-0053
Available from: 2021-03-31 Created: 2021-03-31 Last updated: 2024-01-15Bibliographically approved
4. Evolution of Griffiths phase and critical behaviour of La1-xPbxMnO3 +/- y solid solutions
Open this publication in new window or tab >>Evolution of Griffiths phase and critical behaviour of La1-xPbxMnO3 +/- y solid solutions
2021 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 33, no 14, article id 145801Article in journal (Refereed) Published
Abstract [en]

Polycrystalline La1-xPbxMnO3 +/- y (x = 0.3, 0.35, 0.4) solid solutions were prepared by solid state reaction method and their magnetic properties have been investigated. Rietveld refinement of x-ray powder diffraction patterns showed that all samples are single phase and crystallized with the rhombohedral structure in the R-3c space group. A second order paramagnetic to ferromagnetic (FM) phase transition was observed for all materials. The Griffiths phase (GP), identified from the temperature dependence of the inverse susceptibility, was suppressed by increasing magnetic field and showed a significant dependence on A-site chemical substitution. The critical behaviour of the compounds was investigated near to their Curie temperatures, using intrinsic magnetic field data. The critical exponents (beta, gamma and delta) are close to the mean-field approximation values for all three compounds. The observed mean-field like behaviour is a consequence of the GP and the formation of FM clusters. Long-range FM order is established as the result of long-range interactions between FM clusters. The magnetocaloric effect was studied in terms of the isothermal entropy change. Our study shows that the material with the lowest chemical substitution (x = 0.3) has the highest potential (among the three compounds) as magnetic refrigerant, owing to its higher relative cooling power (258 J kg(-1) at 5 T field) and a magnetic phase transition near room temperature.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP)IOP PUBLISHING LTD, 2021
Keywords
Griffiths phase, critical scaling, long range order
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-437727 (URN)10.1088/1361-648X/abdd64 (DOI)000616511900001 ()33565421 (PubMedID)
Funder
Swedish Foundation for Strategic Research , EM-16-0039Swedish Research Council, 2017-00646_9Swedish Foundation for Strategic Research , RIF14-0053
Available from: 2021-03-15 Created: 2021-03-15 Last updated: 2024-01-15Bibliographically approved
5. Effect of small cation occupancy and anomalous Griffiths phase disorder in nonstoichiometric magnetic perovskites
Open this publication in new window or tab >>Effect of small cation occupancy and anomalous Griffiths phase disorder in nonstoichiometric magnetic perovskites
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2022 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 895, article id 162714Article in journal (Refereed) Published
Abstract [en]

The structural, magnetic, magnetocaloric and Griffiths phase (GP) disorder of non-stoichiometric perovskite manganites La0.8-xSr0.2-yMn1+x+yO3 are reported here. Determination of valence states and structural phases evidenced that the smaller cations Mn2+ and Mn3+ will not occupy the A-site of a perovskite under atmospheric synthesis conditions. The same analysis also supports that the vacancy in the A-site of a perovskite induces a similar vacancy in the B-site. The La3+ and Sr2+ cation substitutions in the A-site with vacancy influences the magnetic phase transition temperature (TC) inversely, which is explained in terms of the electronic bandwidth change. An anomalous non-linear change of the GP has been observed in the Sr substituted compounds. The agglomeration of Mn3+-Mn4+ pairs (denoted as dimerons), into small ferromagnetic clusters, has been identified as the reason for the occurrence of the GP. A threshold limit of the dimeron formation explains the observed non-linear behaviour of the GP formation. The Sr-substituted compounds show a relatively large value of isothermal entropy change (maximum 3.27 J/kgK at mu H-0 = 2T) owing to its sharp magnetic transition, while the broad change of magnetization in the La-substituted compound enhances the relative cooling power (maximum 98 J/kg at mu H-0 = 2T).

Place, publisher, year, edition, pages
ElsevierElsevier BV, 2022
Keywords
Manganites, Magnetocaloric effect, Griffiths phase, Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, Nonstoichiometric perovskites
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-467380 (URN)10.1016/j.jallcom.2021.162714 (DOI)000749451300004 ()
Funder
Swedish Foundation for Strategic Research , EM-16-0039Swedish Foundation for Strategic Research , RIF14-0053Swedish Research Council, 2017-00646_9
Available from: 2022-02-14 Created: 2022-02-14 Last updated: 2024-01-15Bibliographically approved
6. Site-specific atomic substitution in a giant magnetocaloric Fe2P-type system
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
7. A setup for direct measurement of the adiabatic temperature change in magnetocaloric materials
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
8. Magneto-structural coupling strength dependent giant magnetocaloric effect in (Mn,Fe)NiSi-system
Open this publication in new window or tab >>Magneto-structural coupling strength dependent giant magnetocaloric effect in (Mn,Fe)NiSi-system
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(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-487269 (URN)
Available from: 2022-10-27 Created: 2022-10-27 Last updated: 2022-11-02
9. Magnetocaloric properties of nonstoichiometric Fe2P-type intermetallics near room temperature
Open this publication in new window or tab >>Magnetocaloric properties of nonstoichiometric Fe2P-type intermetallics near room temperature
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(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-487268 (URN)
Available from: 2022-10-27 Created: 2022-10-27 Last updated: 2022-11-02

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