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Enhanched Gilbert Damping in Re doped FeCo Films: A combined experimental and theoretical study
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The effects of rhenium doping in the range 0 – 10 at% on the static and dynamic magnetic properties of Fe65Co35 thin films have been studied experimentally as well as with first principles electronic structure calculations focussing on the change of the saturation magnetization (Ms ) and the Gilbert damping parameter (α ). Both experimental and theoretical results show that Ms decreases with increasing Re doping level, while at the same time α increases.  The experimental low temperature saturation magnetic induction exhibits a 29% decrease, from 2.31T to 1.64T, in the investigated doping concentration range, which is more than predicted by the theoretical calculations. The room temperature value of the damping parameter obtained from ferromagnetic resonance measurements, correcting for extrinsic contributions to the damping, is for the undoped sample 2.7X103, which is close to the Gilbert damping parameter extracted from the theoretical calculations. The room temperature experimental value for the damping parameter increases to  9X103 when doping with 10 at% Re; the corresponding increase of the Gilbert damping parameter obtained from theoretical calculations is 7.3X103. Both experimental and theoretical values for the damping parameter weakly decrease with decreasing temperature.

Keywords [en]
Magnetization dynamics, magnetic thin films, Gilbert damping, ferromagnetic resonance
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-345854OAI: oai:DiVA.org:uu-345854DiVA, id: diva2:1189791
Funder
Knut and Alice Wallenberg Foundation, 2012.0031Available from: 2018-03-12 Created: 2018-03-12 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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