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Magnetic order and energy-scale hierarchy in articial spin ice structures
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.ORCID iD: 0000-0002-1527-8668
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
Department of Physics, University of Warwick, Coventry, United Kingdom.
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2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, article id 014435Article in journal (Refereed) Published
Abstract [en]

In order to explain and predict the properties of many physical systems, it is essential to understand the interplay of different energy scales. Here we present investigations of the magnetic order in thermalized artificial spin-ice structures, with different activation energies of the interacting Ising-like elements. We image the thermally equilibrated magnetic states of the nanostructures using synchrotron-based magnetic microscopy. By comparing results obtained from structures with one or two different activation energies, we demonstrate a clear impact on the resulting magnetic order. The differences are obtained by the analysis of the magnetic spin structure factors, in which the role of the activation energies is manifested by distinct short-range order. These results highlight the potential of artificial spin-ice structures to serve as model systems for designing various energy-scale hierarchies and investigating their impact on the collective dynamics and magnetic order.

Place, publisher, year, edition, pages
2018. Vol. 98, article id 014435
Keywords [en]
artificial spin ice, magnetic nano-structures, mesoscopic spin systems, mesospins, model systems, Shakti, engineering of energy-landscape, multiple energy-scales
National Category
Condensed Matter Physics Nano Technology
Research subject
Physics
Identifiers
URN: urn:nbn:se:uu:diva-329016DOI: 10.1103/PhysRevB.98.014435ISI: 000440137800003OAI: oai:DiVA.org:uu-329016DiVA, id: diva2:1148136
Funder
The Swedish Foundation for International Cooperation in Research and Higher Education (STINT)Knut and Alice Wallenberg FoundationSwedish Research Council
Note

Title in thesis list of papers: Magnetic order and energy-scale hierarchy in articial spin ice

Available from: 2017-10-10 Created: 2017-10-10 Last updated: 2018-10-08Bibliographically approved
In thesis
1. Tailoring the magnetic order in mesoscopic spin systems
Open this publication in new window or tab >>Tailoring the magnetic order in mesoscopic spin systems
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mesoscopic spin systems can be designed and fabricated using modern nano-fabrication techniques. These systems can contain large numbers of patterned ferromagnetic elements, for which the shape will generally determine their effective mesospin dimensionality. The lateral arrangement of these mesospins can be further used to tune the interactions between them.

With an appropriate choice of material, it is possible to define a temperature range where thermal fluctuations of these mesospins are experimentally accessible. To actively define this range, we use δ-doped Palladium, a three-layer system of Palladium—Iron—Palladium, for which the Curie-temperature scales with the Iron layer thickness. The patterned mesoscopic elements used in this work have a stadium-like shape that promotes a single magnetic domain state, thus making these islands behave as one-dimensional Ising-like mesospins that can be observed using magnetic imaging techniques.

We investigate the impact on the magnetic order resulting from modifications of the square spin ice geometry. By adding, removing and merging elements in the square artificial spin ice architecture, energy-landscape variations can be realized. Firstly, an added interaction modifier is used to equilibrate the interactions between the mesospins at the vertex level, which can restore the degenerate ground state of the square spin ice model. Secondly, the removal of elements can lead to topologically frustrated spin systems, as not all building blocks can simultaneously be in their lowest energy state. Furthermore, the merging results in multiple element sizes in the mesospin system. As the magnetization reversal barrier is dependent on the element size, these mesospin systems have different energy barriers. The thermal ordering process in such a system differs from a single-size element system with its unique energy barrier. Using reciprocal space analysis tools like the magnetic spin structure factor we show that systems with multiple element sizes achieve a higher short-range order then their single-size element references. The magnetic order in mesoscopic spin systems could successfully be tailored by modifications of the lattice geometry.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 78
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1574
Keywords
artificial spin ice, magnetic nano-structures, mesoscopic spin systems, mesospins, model systems, Shakti, Saint George, interaction modifier, engineering of energy-landscape, multiple energy-scales
National Category
Condensed Matter Physics Nano Technology
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-328790 (URN)978-91-513-0099-3 (ISBN)
Public defence
2017-11-28, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Available from: 2017-11-03 Created: 2017-10-10 Last updated: 2017-11-03

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Stopfel, HenryÖstman, ErikChioar, Ioan-AugustinHjörvarsson, BjörgvinKapaklis, Vassilios

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