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Temperature-dependent Gilbert damping of Co2FeAl thin films with different degree of atomic order
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
KTH Royal Institute of Technology, School of Engineering Sciences, Department of Applied Physics; KTH Royal Institute of Technology, Swedish e-Science Research Center.
Indian Institute of Technology Delhi, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 224425Article in journal (Refereed) Published
Abstract [en]

Half-metallicity and low magnetic damping are perpetually sought for spintronics materials, and full Heusler compounds in this respect provide outstanding properties. However, it is challenging to obtain the well-ordered half-metallic phase in as-deposited full Heusler compound thin films, and theory has struggled to establish a fundamental understanding of the temperature-dependent Gilbert damping in these systems. Here we present a study of the temperature-dependent Gilbert damping of differently ordered as-deposited Co2FeAl full Heusler compound thin films. The sum of inter- and intraband electron scattering in conjunction with the finite electron lifetime in Bloch states governs the Gilbert damping for the well-ordered phase, in contrast to the damping of partially ordered and disordered phases which is governed by interband electronic scattering alone. These results, especially the ultralow room-temperature intrinsic damping observed for the well-ordered phase, provide fundamental insights into the physical origin of the Gilbert damping in full Heusler compound thin films.

Place, publisher, year, edition, pages
American Physical Society, 2017. Vol. 96, no 224425
Keywords [en]
Gilbert damping, full Heusler compound, Temperature Dependent Gilbert damping, Thin Films, Density of states
National Category
Condensed Matter Physics Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
URN: urn:nbn:se:uu:diva-337305DOI: 10.1103/PhysRevB.96.224425ISI: 000418572700007OAI: oai:DiVA.org:uu-337305DiVA, id: diva2:1169001
Funder
Knut and Alice Wallenberg Foundation, KAW 2012.0031Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology, GGS1403ASwedish National Infrastructure for Computing (SNIC)Available from: 2017-12-22 Created: 2017-12-22 Last updated: 2018-03-12
In thesis
1. Magnetization Dynamics in Ferromagnetic Thin Films: Evaluation of Different Contributions to Damping in Co2FeAl and FeCo Film Structures
Open this publication in new window or tab >>Magnetization Dynamics in Ferromagnetic Thin Films: Evaluation of Different Contributions to Damping in Co2FeAl and FeCo Film Structures
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Static and dynamic magnetic properties of Co2FeAl and Fe65Co35 alloys have been investigated. Co2FeAl films were deposited at different temperatures and the deposition parameters were optimized with respect to structural and magnetic properties. As a result, a film with B2 crystalline phase was obtained without any post-annealing process. A lowest magnetic damping parameter of  was obtained for the film deposited at 573K. This obtained low value is comparable to the lowest values reported in research literature.  After optimizing the deposition parameters of this alloy, different seed layers and capping layers were added adjacent to the Co2FeAl layer and the effect of these layers on the magnetic relaxation was investigated. In addition to adding nonmagnetic layers to Co2FeAl, the dependence of the magnetic damping parameter with respect to the thickness of Co2FeAl was investigated by depositing films with different thicknesses. A temperature dependent study of the magnetic damping parameter was also performed and the measured damping parameters were compared with theoretically calculated intrinsic Gilbert damping parameters. Different extrinsic contributions to the magnetic damping, such as two magnon scattering, spin pumping, eddy-current damping and radiative damping, were identified and subtracted from the experimentally obtained damping parameter. Hence, it was possible to obtain the intrinsic damping parameter, that is called the Gilbert damping parameter.

In the second part of the thesis, Fe65Co35 alloys were investigated in terms of static and dynamic magnetic properties. Fe65Co35 films were deposited without and with different seed layers in order to first understand the effect of the seed layer on static magnetic properties of the films, such as the coercivity of the films. Then the films with seed layers yielding the lowest coercivity were investigated in terms of dynamic magnetic properties. Fe65Co35 films with different rhenium dopant concentrations and with ruthenium as the seed and capping layer were also investigated. The purpose of this study was to increase the damping parameter of the films and an increase of about ~230% was obtained by adding the dopant to the structure. This study was performed at different temperatures and after subtraction of the extrinsic contributions to the damping, the experimental values were compared with theoretically calculated values of the Gilbert damping parameter. During the thesis work, magnetic looper and superconducting quantum interference device magnetometers set-ups were used for static magnetic measurements and cavity, broadband in-plane and broadband out-of-plane ferromagnetic resonance set-ups were used for dynamic measurements.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 74
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1644
Keywords
spintronics, Gilbert damping parameter, magnetization dynamics, ferromagnetic resonance, Heusler alloys, magnetic thin films
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-345856 (URN)978-91-513-0268-3 (ISBN)
Public defence
2018-05-03, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-04-09 Created: 2018-03-12 Last updated: 2018-05-16

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Akansel, SerkanSvedlindh, Peter

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