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Effect of small cation occupancy and anomalous Griffiths phase disorder in nonstoichiometric magnetic perovskites
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.ORCID iD: 0000-0003-2790-116x
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.ORCID iD: 0000-0002-8690-9957
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.ORCID iD: 0000-0001-9299-3262
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
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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
Elsevier BV Elsevier, 2022. Vol. 895, article id 162714
Keywords [en]
Manganites, Magnetocaloric effect, Griffiths phase, Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, Nonstoichiometric perovskites
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-467380DOI: 10.1016/j.jallcom.2021.162714ISI: 000749451300004OAI: oai:DiVA.org:uu-467380DiVA, id: diva2:1637451
Funder
Swedish Foundation for Strategic Research , EM-16-0039Swedish Foundation for Strategic Research , RIF14-0053Swedish Research Council, 2017-00646_9Available from: 2022-02-14 Created: 2022-02-14 Last updated: 2024-01-15Bibliographically approved
In thesis
1. Direct and indirect magnetocaloric properties of first- and second-order phase transition materials
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)
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Available from: 2022-11-22 Created: 2022-10-27 Last updated: 2022-11-22

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Ghorai, SagarShtender, VitaliiStröm, PetterSkini, RidhaSvedlindh, Peter

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