| 1. |
- Akansel, Serkan, et al.
(författare)
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Effect of seed layers on dynamic and static magnetic properties of Fe65Co35 thin films
- 2018
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 51:30
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Tidskriftsartikel (refereegranskat)abstract
- Fe65Co35 thin films have been deposited on SiO2 substrates using sputtering technique with different choices of seed layer; Ru, Ni82.5Fe17.5, Rh, Y and Zr. Best soft magnetic properties were observed with seed layers of Ru, Ni82.5Fe17.5 and Rh. Adding these seed layers, the coercivity of the Fe65Co35 films decreased to values of around 1.5 mT, which can be compared to the value of 12.5 mT obtained for films deposited without seed layer. Further investigations were performed on samples with these three seed layers in terms of dynamic magnetic properties, both on as prepared and annealed samples, using constant frequency cavity and broadband ferromagnetic resonance measurements. Damping parameters of around 8.0X10-3 and 4.5X10-3 were obtained from in-plane and out-of-plane measurements, respectively, for as prepared samples, values that were reduced to 6.5X10-3 and 4.0X10-3 for annealed samples.
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| 2. |
- Akansel, Serkan, et al.
(författare)
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Enhanced Gilbert damping in Re-doped FeCo films : Combined experimental and theoretical study
- 2019
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 99:17
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Tidskriftsartikel (refereegranskat)abstract
- 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 focusing on the change of the saturation magnetization (M-s) and the Gilbert damping parameter (alpha). Both experimental and theoretical results show that M-s decreases with increasing Re-doping level, while at the same time alpha increases. The experimental low temperature saturation magnetic induction exhibits a 29% decrease, from 2.31 to 1.64 T, 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 2.1 x 10(-3), which is close to the theoretically calculated Gilbert damping parameter. With 10 at.% Re doping, the damping parameter increases to 7.8 x 10(-3), which is in good agreement with the theoretical value of 7.3 x 10(-3). The increase in damping parameter with Re doping is explained by the increase in the density of states at the Fermi level, mostly contributed by the spin-up channel of Re. Moreover, both experimental and theoretical values for the damping parameter weakly decrease with decreasing temperature.
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| 3. |
- Akansel, Serkan, et al.
(författare)
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Enhanched Gilbert Damping in Re doped FeCo Films : A combined experimental and theoretical study
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 4. |
- Akansel, Serkan, 1983-, et al.
(författare)
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Thickness dependent enhancement of damping in Co2FeAl/β-Ta thin films
- 2018
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 97:13
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Tidskriftsartikel (refereegranskat)abstract
- In the present work Co2FeAl (CFA) thin films were deposited by ion beam sputtering on Si (100) substrates at the optimized deposition temperature of 300°C. A series of CFA films with different thickness (tCFA ); 8, 10, 12, 14, 16, 18 and 20 nm were prepared and all samples were capped with a 5 nm thick b-Ta layer. The thickness dependent static and dynamic properties of the films were studied by SQUID magnetometry, in-plane as well as out-of-plane broadband VNA-FMR measurements and angle dependent cavity FMR measurements. The saturation magnetization and the coercive field were found to be weakly thickness dependent and lie in the range 900 – 950 kA/m and 0.53 – 0.87 kA/m, respectively. The effective damping parameter ( αeff) extracted from in-plane and out-of-plane FMR results reveal a 1/tCFA dependence, the values for the in-plane αeff being larger due to two-magnon scattering (TMS). The origin of the αeff thickness dependence is spin pumping into the non-magnetic b-Ta layer and in case of the in-plane αeff also a thickness dependent TMS contribution. From the out-of-plane FMR results, it was possible to disentangle the different contributions to αeff and to the extract values for the intrinsic Gilbert damping (αG ) and the effective spin-mixing conductance (g_eff^↑↓ ) of the CFA/ b-Ta interface, yielding αG=1.1X10-3 and g_eff^↑↓=2.90x1019 m-2.
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| 5. |
- Bejhed Stjernberg, Rebecca, et al.
(författare)
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Magnetophoretic Transport Line System for Rapid On-Chip Attomole Protein Detection
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:37, s. 10296-10302
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Tidskriftsartikel (refereegranskat)abstract
- A lab-on-a-chip traveling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micrometer-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized, forming a sandwich-type assay. The MBs were transported across a detection area, and the presence of target molecules resulted in the immobilization of MBs within this area. Target quantification was accomplished by MB counting in the detection area using an optical microscope. In order to demonstrate the versatility of the microarray, biotinylated antiavidin was selected as the target protein. In this case, avidin-functionalized MBs and an avidin-functionalized detection area were used. With a total assay time of 1 to 1.5 h (depending on the labeling approach used), a limit of detection in the attomole range was achieved. Compared to on-chip surface plasmon resonance biodetection systems, our method has a larger dynamic range and is about a factor of 500 times more sensitive. Furthermore, our MB transportation system can operate in any chip-based biosensor platform, thereby significantly improving traditional biosensors.
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| 6. |
- Bloch, J., et al.
(författare)
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Reversible structural change and thermodynamic properties of hydrogen in thin vanadium films
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:16, s. 165418-
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Tidskriftsartikel (refereegranskat)abstract
- The absorption of H in 50nm V(001) films under pressures of 1–104Pa H2 and at temperatures between 310 and 530K was studied using in situ combined x-ray diffraction (XRD) and electrical resistivity measurements. The H-induced XRD peak shifts clearly indicate a fully reversible and nondeteriorating first-order phase transformation for the film. The H-induced residual resistivity changes in the V film demonstrate several extreme points (maxima and minima) apparently associated with some special points on the pressure isotherms of the film both below and above the critical temperature (Tc=460±20K) . Correlating these extreme points with the known V(bulk)-H phase diagram indicates that, in addition to the first-order transformation, two additional reversible second-order transitions exist in the film. The enthalpy and entropy of this transformation, obtained from the temperature dependence of the plateau pressures, are ‑39±1kJ/mol°K , and ‑60±2J/mol , respectively. The thermodynamic constants and the lattice parameters of the phases for the first-order transformation in the film closely correspond to the α→β phase transformation in bulk V.
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| 7. |
- Brucas, Rimantas, 1965, et al.
(författare)
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Magnetic and transport properties of discontinuous Ni81 Fe19/Al2O3 multilayers
- 2007
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 310:2 SUPPL. PART 3, s. 2521-2523
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Tidskriftsartikel (refereegranskat)abstract
- The structural percolation and its correlation with the magnetic and transport properties of Ni 81 Fe 19 / Al 2 O 3 multilayer films were studied by varying the thickness (t) of the Ni 81 Fe 19 (permalloy, Py) layers in the range of 10-16 Å, while keeping the Al 2 O 3 layer thickness constant at 16 Å. Low-angle X-ray reflectivity and transmission electron microscopy measurements revealed a good structural quality of the multilayers and showed the transition from continuous Py layers (t = 16 over(A, ̊)) separated by Al 2 O 3 layers to grains (t = 10 over(A, ̊)) dispersed in the insulating matrix. Magnetization measurements showed the gradual transition from ferromagnetic layers (t = 16 over(A, ̊)) to superparamagnetic clusters (t = 12 over(A, ̊)) and isolated grains (t = 10 over(A, ̊)) that successively become blocked as the temperature decreases. The temperature dependence of the current in-plane (CIP) resistance of the samples reveals a change from typical metallic (d R / d T > 0) to dielectric (d R / d T
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| 8. |
- Bručas, Rimantas, et al.
(författare)
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Magnetic and transport properties of Ni81Fe19/Al2O3 granular multilayers approaching the superparamagnetic limit
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:7, s. 073907-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic and transport properties of Ni81Fe 19/Al2O3 granular multilayer films were studied in relation to their structural properties as the nominal thickness t of the permalloy (Ni81Fe19) layer was varied near the percolation limit: in the range of 8≤t≤ 16 Å while keeping the nominal thickness of the Al2O3 layers constant at 16 Å. A good structural quality of the multilayers was demonstrated by low angle x-ray reflectivity measurements, and transmission electron microscopy showed the transition from continuous permalloy layers separated by aluminium oxide layers for t= 16 Å to metal grains dispersed in the insulator at t=8 Å. Magnetization measurements showed the gradual transition from ferromagnetic layers to superparamagnetic clusters and grains that successively become blocked as the temperature decreases. A strong correlation between transport and structural properties was observed in the temperature (T) dependence of the electrical resistance measured with the current in the plane in the range of 2 ≤T≤300 K: a gradual change of behavior from continuous permalloy layers with conducting interlayer connections for t=16 Å. to isolated permalloy grains in a dielectric for the film with t= 10 Å. The percolation occurs between 12 and 10 Å, as deduced both from the magnetic and resistive properties. The discontinuous metal films were analyzed within models for thermally assisted tunneling, yielding estimates of the tunneling barrier for intralayer conduction of about 20 meV for t= 10 Å. A significant magnetic field dependence of the resistance increasing with decreasing temperature was observed in all samples.
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| 9. |
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| 10. |
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