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- Akansel, Serkan, 1983-
(författare)
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Magnetization Dynamics in Ferromagnetic Thin Films : Evaluation of Different Contributions to Damping in Co2FeAl and FeCo Film Structures
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 2. |
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| 3. |
- Andersson, Cecilia, 1976-
(författare)
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Exploring the Magnetism of Ultra Thin 3d Transition Metal Films
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis the magnetic and structural properties of ultra-thin 3d transition metals films have been investigated, in particular Fe, Ni and Co films. X-ray Magnetic Circular Dichroism (XMCD) has provided element specific spin (ms ) and orbital (ml ) moments per atom by utilizing the magneto optic sum-rules. Element specific hysteresis curves have been measured by means of X-ray Resonant Magnetic Scattering (XRMS), and the local crystallographic structure has been investigated using Extended X-ray Absorption Fine Structure (EXAFS).By performing XMCD on Fe/Ag(100) we observe a spin reorientation from in-plane to out-of-plane as the Fe thickness is lowered. At temperatures below 300K it occurs around 5-7 mono layers (ML) of Fe. While reorienting the magnetization out-of-plane the orbital moment increases with 125% but only a minor increase (5%) of the spin moment is observed. Extended X-ray Absorption Fine Structure (EXAFS) measurements indicate that films 6 ML and thicker have a bulk-like bcc structure. For the thin out-of-plane films, the local crystallographic structure is more complicated.The spin reorientation of the Au/Co/Au tri-layer system has been studied as a function of temperature, Co layer and Au cap thickness. An unexpected behavior of the orbital moment upon spin reorientation is found in these systems. An ex-situ prepared sample shows a smooth spin reorientation from an in-plane to an out-of-plane easy magnetization direction as the temperature is lowered from 300K to 200K. In-situ prepared samples have also been investigated and a novel phase diagram has been identified. The Au/Co interface has been explored during the Au capping by means of photoemission measurements.In the bi- and tri-layer system of Fe and Ni we have been able to manipulate the spin reorientation by varying the Fe and Ni thickness. A novel non-collinear interlayer exchange interaction for 3d ferro magnets in direct contact has been discovered for a set of samples. This exchange interaction is found to be strongly dependant on the preparation conditions.
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| 5. |
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| 6. |
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| 7. |
- Andersson, Gabriella, et al.
(författare)
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Aktiverande problemlösningsövningar i grupp.
- 2010
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Ingår i: Att undervisa med vetenskaplig förankring – i praktiken!. - Uppsala : Universitetstryckeriet. ; , s. 103-113
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Anil Kumar, Puri, et al.
(författare)
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Magnetic polarons and spin-glass behavior in insulating La1-xSrxCoO3 (x = 0.125 and 0.15)
- 2020
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Ingår i: Physical Review Research. - : AMER PHYSICAL SOC. - 2643-1564. ; 2:4
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of magnetic polarons in Sr doped LaCoO3 (La1-xSrxCoO3) single crystal and polycrystalline samples are investigated by employing dc and ac magnetic measurement and small angle neutron scattering (SANS) techniques. The effect of magnetic field and temperature on magnetic polarons is experimentally studied for La0.875Sr0.125CoO3 and La0.85Sr0.15CoO3 compounds that belong to the spin glass insulating regime of the broader compositional phase diagram of this system. Langevin analyses of the isothermal magnetization curves in the notional paramagnetic regime prove the existence of magnetic polarons with large moments. The dc field superimposed ac susceptibility data and the analysis of the glassy dynamics prove that the size of polarons in 15% Sr doped crystal increase as the field is increased while the field effect is not visible in the 12.5% Sr doped crystal. A polycrystalline sample of La0.85Sr0.15CoO3 is analyzed by SANS experiments, which confirm nonzero correlation length at temperatures far above the macroscopic ordering temperature and hence the presence of magnetic polarons.
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| 9. |
- Arvanitis, Dimitri, et al.
(författare)
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Influence of ligand states on the relationship between orbital moment and magnetocrystalline anisotropy
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:17, s. 177207-
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Tidskriftsartikel (refereegranskat)abstract
- The spin and orbital moments of Au/Co/Au trilayers grown on a W(110) single crystal substrate have been investigated by means of x-ray magnetic circular dichroism. Our findings suggest that the orbital moment of Co does not obtain a maximum value along the easy axis, in contrast with previous experience. This is attributed to the large spin-orbit interaction within the Au caps. Both second order perturbation theory and first principles calculations show how the magnetocrystalline anisotropy (MCA) is dramatically influenced by this effect, and how this leads to the fact that the orbital moment anisotropy is not proportional to the MCA.
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| 10. |
- Bailey, W. E., et al.
(författare)
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Detection of microwave phase variation in nanometre-scale magnetic heterostructures
- 2013
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 2025-
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Tidskriftsartikel (refereegranskat)abstract
- The internal phase profile of electromagnetic radiation determines many functional properties of metal, oxide or semiconductor heterostructures. In magnetic heterostructures, emerging spin electronic phenomena depend strongly upon the phase profile of the magnetic field (H) over tilde at gigahertz frequencies. Here we demonstrate nanometre-scale, layer-resolved detection of electromagnetic phase through the radio frequency magnetic field (H) over tilde (rf) in magnetic heterostructures. Time-resolved X-ray magnetic circular dichroism reveals the local phase of the radio frequency magnetic field acting on individual magnetizations (M) over tilde (i) through the susceptibility as (M) over tilde = (chi) over tilde(H) over tilde (rf). An unexpectedly large phase variation, similar to 40 degrees, is detected across spin-valve trilayers driven at 3 GHz. The results have implications for the identification of novel effects in spintronics and suggest general possibilities for electromagnetic-phase profile measurement in heterostructures.
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