Magnetic Materials for Cool Applications 1150878/... Magnetic Materials for Cool Applications. Relations

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  • ACTA UNIVERSITATIS

    UPSALIENSIS UPPSALA

    2017

    Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1585

    Magnetic Materials for Cool Applications

    Relations between Structure and Magnetism in Rare Earth Free Alloys

    JOHAN CEDERVALL

    ISSN 1651-6214 ISBN 978-91-513-0123-5 urn:nbn:se:uu:diva-331762

  • Dissertation presented at Uppsala University to be publicly examined in Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, Friday, 8 December 2017 at 09:00 for the degree of Doctor of Philosophy. The examination will be conducted in English. Faculty examiner: Prof. Paul Henry (The ISIS Facility, STFC Rutherford Appleton Laboratory).

    Abstract Cedervall, J. 2017. Magnetic Materials for Cool Applications. Relations between Structure and Magnetism in Rare Earth Free Alloys. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1585. 70 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-513-0123-5.

    New and more efficient magnetic materials for energy applications are a big necessity for sustainable future. Whether the application is energy conversion or refrigeration, materials based on sustainable elements should be used, which discards all rare earth elements. For energy conversion, permanent magnets with high magnetisation and working temperature are needed whereas for refrigeration, the entropy difference between the non-magnetised and magnetised states should be large. For this reason, magnetic materials have been synthesised with high temperature methods and structurally and magnetically characterised with the aim of making a material with potential for large scale applications. To really determine the cause of the physical properties the connections between structure (crystalline and magnetic) and, mainly, the magnetic properties have been studied thoroughly.

    The materials that have been studied have all been iron based and exhibit properties with potential for the applications in mind. The first system, for permanent magnet applications, was Fe5SiB2. It was found to be unsuitable for a permanent magnet, however, an interesting magnetic behaviour was studied at low temperatures. The magnetic behaviour arose from a change in the magnetic structure which was solved by using neutron diffraction. Substitutions with phosphorus (Fe5Si1-xPxB2) and cobalt (Fe1-xCox)5PB2 were then performed to improve the permanent magnet potential. While the permanent magnetic potential was not improved with cobalt substitutions the magnetic transition temperature could be greatly controlled, a real benefit for magnetic refrigeration. For this purpose AlFe2B2 was also studied, and there it was found, conclusively, that the material undergoes a second order transition, making it unsuitable for magnetic cooling. However, the magnetic structure was solved with two different methods and was found to be ferromagnetic with all magnetic moments aligned along the crystallographic a-direction. Lastly, the origin of magnetic cooling was studied in Fe2P, and can be linked to the interactions between the magnetic and atomic vibrations.

    Keywords: Magnetism, Diffraction, X-ray scattering, Neutron Scattering, Permanent magnets, Magnetocalorics

    Johan Cedervall, Department of Chemistry - Ångström, Box 523, Uppsala University, SE-75120 Uppsala, Sweden.

    © Johan Cedervall 2017

    ISSN 1651-6214 ISBN 978-91-513-0123-5 urn:nbn:se:uu:diva-331762 (http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331762)

  • ”That which does not kill us makes us stronger.” - Friedrich Nietzsche

  • List of papers

    This thesis is based on the following papers, which are referred to in the text by their roman numerals.

    I Magnetostructural transition in Fe5SiB2 observed with neutron diffraction J. Cedervall, S. Kontos, T. C. Hansen, O. Balmes, F. J. Martinez-Casado, Z. Matej, P. Beran, P. Svedlindh, K. Gunnarsson, M. Sahlberg. Journal of Solid State Chemistry, 235, 113-118 (2016)

    II Magnetic properties of the Fe5SiB2-Fe5PB2 system D. Hedlund, J. Cedervall, A. Edström, M. Werwiński, S. Kontos, O. Eriksson, J. Rusz, P. Svedlindh, M. Sahlberg, K. Gunnarsson. Physical Review B. 96 094433 (2017)

    III Influence of cobalt substitution on the magnetic properties of Fe5PB2 J. Cedervall, E. Nonnet, D. Hedlund, L. Häggström, T. Ericsson, A. Edström, M. Werwiński, J. Rusz, P. Svedlindh, K. Gunnarsson, M. Sahlberg. Submitted

    IV Magnetic structure of the magnetocaloric compound AlFe2B2 J. Cedervall, M. S. Andersson, T. Sarkar, E. K. Delczeg-Czirjak, L. Bergqvist, T. C. Hansen, P. Beran, P. Nordblad, M. Sahlberg. Journal of Alloys and Compounds, 664, 784-791 (2016)

    V Mössbauer study of the magnetocaloric compound AlFe2B2 J. Cedervall, L. Häggström, T. Ericsson, M. Sahlberg. Hyperfine Interactions, 237, 18 (2016)

    VI Magnetic and mechanical effects of Mn substitutions in AlFe2B2 J. Cedervall, M. S. Andersson, P Berastegui, S. Shafeie, U. Jansson, P. Nordblad, M. Sahlberg. In manuscript

  • VII Towards an understanding of the magnetocaloric effect in Fe2P J. Cedervall, M. S. Andersson, E. K. Delczeg-Czirjak, D. Iuşan, M. Pereiro, P. Roy, T. Ericsson, L. Häggström, W. Lohstroh, H. Mutka, M. Sahlberg, P. Nordblad, P. P. Deen. In manuscript

    Reprints were made with permission from the publishers.

  • My contributions to the papers

    The authors contribution to the papers in this thesis:

    Paper I. I planned the study, synthesised the samples and performed all struc- tural characterisations, except for the representational analysis. I wrote the main part of the manuscript and was involved in all discussions.

    Paper II. I was involved in the planning of the study, synthesised the samples and performed all structural characterisations. I was involved in all dis- cussions and approved the final manuscript.

    Paper III. I planned the study, synthesised the samples and performed all structural characterisations. I wrote the main part of the manuscript and was involved in all discussions.

    Paper IV. I planned the study, synthesised the samples and performed all structural characterisations, except for the representational analysis. I wrote the main part of the manuscript and was involved in all discus- sions.

    Paper V. I, together with the other authors, planned the study. I synthesised the samples and performed all structural characterisations. I was in- volved in the writing of the manuscript and all discussions.

    Paper VI. I planned the study, synthesised the samples and performed all structural and mechanical characterisations. I wrote the main part of the manuscript and was involved in all discussions.

    Paper VII. I synthesised the samples and performed all structural character- isations. I took part in the neutron experiments and was involved in the data analysis. I also took part in the writing of the manuscript and all discussions.

  • Other publications to which the author has contributed.

    i Irreversible structure change of the as prepared FeMnP1-xSix- struc- ture on the initial cooling through the curie temperature V. Höglin, J. Cedervall, M. S. Andersson, T. Sarkar, P. Nordblad, M. Sahlberg. Journal of Magnetism and Magnetic Materials, 374, 455-458 (2015)

    ii Phase diagram, structures and magnetism of the FeMnP1-xSix V. Höglin, J. Cedervall, M. S. Andersson, T. Sarkar, M. Hudl, P. Nord- blad, Y. Andersson, M. Sahlberg. RSC Advances, 5, 8278-8284 (2015)

    iii Directly obtained τ-phase MnAl, a high performance magnetic ma- terial for permanent magnets H. Fang, S. Kontos, J. Ångström, J. Cedervall, P. Svedlindh, K. Gun- narsson, M. Sahlberg. Journal of Solid State Chemistry 237, 300-306 (2016)

    iv Low temperature magneto-structural transitions in Mn3Ni20P6 J. Cedervall, P. Beran, M. Vennström, T. Danielsson, S. Ronneteg, V. Höglin, D. Lindell, O. Eriksson, G. André, Y. Andersson, P. Nordblad, M. Sahlberg. Journal of Solid State Chemistry 237, 343-348 (2016)

    v Magnetic properties of Fe5SiB2 and its alloys with P, S, and Co M. Werwiński, S. Kontos, K. Gunnarsson, P. Svedlindh, J. Cedervall, V. Höglin, M. Sahlberg, A. Edström, O. Eriksson, J. Rusz. Physical Review B, 93, 174412 (2016)

    vi Short-range magnetic correlations and spin dynamics in the para- magnetic regime of (Mn,Fe)2(P,Si) X. F. Miao, L. Caron, J. Cedervall, P. C. M. Gubbens, P. Dalmas de Réotier, A. Yaouanc, F. Qian, A. R. Wildes, H. Luetkens, A. Amato, N. H. van Dijk, E. Brück. Physical Review B 94, 014426 (2016)

    vii Insights into formation and stability of τ-MnAlZx (Z = C and B) H. Fang, J. Cedervall, F. J. Martinez-Casado, Z. Matej, J. Bednarcik, J. Ångström, P. Berastegui, M. Sahlberg. Journal of Alloys and Compounds 692, 198-203 (2017)

  • viii AlM2B2 (M=Cr, Mn, Fe, Co, Ni): a group of nanolaminated materi- als K. Kádas, D. Iuşan, J. Hellsvik, J. Cedervall, P. Berastegui, M. Sahlberg, U. Jansson, O. Eriksson. Journal of Physics: Condensed Matter 29, 155402 (2017)

  • Contents

    1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.1 Magnetic materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

    1.1.1 Magnetostructural properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1.1.2 Permanent magnets . . . . . . . . . . . . .