| 1. |
- Arnalds, Unnar B., et al.
(författare)
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Magnetic structure and diffracted magneto-optics of patterned amorphous multilayers
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:14, s. 144434-1-144434-8
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Tidskriftsartikel (refereegranskat)abstract
- We present magneto-optical Kerr effect measurements of patterned arrays of Co68Fe24Zr8 / Al2O3 amorphous multilayers. The multilayers were patterned in two dimensions into two different arrangements of circular and ellipsoidal islands. Magnetization loops were recorded in a longitudinal geometry using both the specularly reflected beam as well as diffracted beams scattered off the patterned films. The magnetization of the patterned structures is significantly different from the magnetization of a continuous multilayer owing to the lateral confinement of the pattern and the introduction of additional dipolar coupling between the layers at the edges of the islands. By investigating the magnetic response at the different diffraction orders from the two different configurations of islands we are able to observe the magnetization at different length scales and determine the magnetic response of the circular and ellipsoidal islands individually.
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| 2. |
- Arnalds, Unnar, et al.
(författare)
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X-ray resonant magnetic scattering from patterned multilayers
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:6, s. 064426-
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Tidskriftsartikel (refereegranskat)abstract
- We report on x-ray resonant magnetic scattering from laterally patterned arrays of amorphous Co68Fe24Zr8/Al2O3 multilayers. The arrays are composed of circular and ellipsoidal elements which display distinct individual magnetic responses enabling the investigation of the dependence of the observed magnetization on the scattering condition. We focus our attention to special points in reciprocal space, relating to the lateral and perpendicular structure of the samples, thereby revealing the magnetic structure of the multilayered arrays. This allows a comparison of the observed magnetization under different scattering conditions to magneto-optical measurements. The scattering data are supported by micromagnetic simulations which further enhance our understanding of the intricate charge and magnetic scattering from three dimensional patterns.
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| 3. |
- Fu, Yu, et al.
(författare)
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Tailored magnetic anisotropy in an amorphous trilayer
- 2011
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 109:11, s. 113908-
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Tidskriftsartikel (refereegranskat)abstract
- An amorphous Co68Fe24Zr8(3 nm)/Al70Zr30(3 nm)/Co68Fe24Zr8(3 nm) trilayer system has been investigated using in-plane and out-of-plane angular dependent ferromagnetic resonance at different frequencies. The in-plane magnetic anisotropy is uniaxial, retaining its value of (2.9 +/- 0.1) x 10(3) J/m(3) for each magnetic layer, whereas its direction was tailored independently in an arbitrary manner by applying an external magnetic field during the film deposition. The perpendicular anisotropy constant, supposed to reflect the interface quality, is nearly identical for both layers. Furthermore, the magnetic layers act independently upon each other due to the absence of interlayer coupling.
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| 4. |
- Hase, Thomas, et al.
(författare)
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Spin and orbital moment in amorphous Co68Fe24Zr8 layers
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 80:13, s. 134402-
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Tidskriftsartikel (refereegranskat)abstract
- The ratio of the orbital to the spin magnetic moment was determined for both Fe and Co in amorphous Co68 Fe24 Zr8 layers using x-ray circular dichroism. The investigations were performed on both thick Co68 Fe24 Zr8 layers as well as on amorphous Co68 Fe24 Zr8 / Al70 Zr30 multilayers grown by dc sputtering. Structural characterization was performed using x-ray reflectometry, x-ray diffraction, and transmission electron microscopy. X-ray circular dichroism, x-ray magnetic scattering as well as the magneto-optic Kerr effect were used to characterize the magnetic properties of the amorphous materials. The ratio of the orbital to spin moments in the single CoFeZr-layer sample was 0.012±0.005 for Fe and 0.078±0.005 for Co. Substantial reduction in the the ratio of the orbital to spin moments was observed with decreasing CoFeZr-layer thickness.
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| 5. |
- Lidbaum, Hans, et al.
(författare)
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Structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers
- 2010
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 312:4, s. 580-586
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Tidskriftsartikel (refereegranskat)abstract
- The structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers grown by using magnetron Sputtering were investigated with X-ray reflectivity, transmission electron microscopy and magnetooptical Kerr effect. The Co68Fe24Zr8 form amorphous islands when the nominal thickness of the Co68Fe24Zr8 layers is 10 angstrom, exhibiting an isotropic superparamagnetic behavior. Continuous layers with mostly a nano-crystalline structure are instead formed when the nominal thickness of the Co68Fe24Zr8 layers is increased to 20 angstrom. The continuous layers exhibit random, in-plane, magnetic anisotropy resulting from the growth Process. However, induced uniaxial anisotropy is obtained when growing the sample in the presence of an applied magnetic field, regardless of the combination of amorphous and nano-crystalline material.
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| 6. |
- Pálsson, Gunnar K., et al.
(författare)
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Influence of Titanium and Vanadium on the Hydrogen transport through amorphous alumina films
- 2010
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 494:1-2, s. 239-244
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Tidskriftsartikel (refereegranskat)abstract
- The influence of titanium and vanadium on the hydrogen transport rate through thin amorphous alumina films is addressed. Only small changes in the transport rate are observed when the Al2O3 are covered with titanium or vanadium. This is in stark contrast to results with a Pd overlayer, which enhances the transport by an order of magnitude. Similarly, when titanium is embedded into the alumina the transport rate is faster than for the covered case but still slower than the undoped reference. Embedding vanadium in the alumina does not yield an increase in uptake rate compared to the vanadium covered oxide layers. These results add to the understanding of the hydrogen uptake of oxidized metals, especially the alanates, where the addition of titanium has been found to significantly enhance the rate of hydrogen uptake. The current findings eliminate two possible routes for the catalysis of alanates by Ti, namely dissociation and effective diffusion short-cuts formed by Ti. Finally, no photocatalytic enhancement was noticed on the titanium covered samples.
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| 7. |
- Raanaei, Hossein, et al.
(författare)
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Imprinting layer specific magnetic anisotropies in amorphous multilayers
- 2009
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Ingår i: Journal of Applied Physics. - : AIP. - 0021-8979 .- 1089-7550. ; 106:2, s. 023918-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate how layer specific in-plane magnetic anisotropy can be imprinted in amorphous multilayers. The anisotropy is obtained by growing the magnetic layers in the presence of an external field and the anisotropy direction can thereby be arbitrarily chosen for each of the magnetic layers. We used Co68Fe24Zr8 and Al70Zr30 layers as building blocks for demonstrating this effect. The imprinting is expected to be obtainable for a wide range of amorphous materials when grown at temperatures below the magnetic ordering temperature.
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| 8. |
- Raanaei, Hossein, et al.
(författare)
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Structural coherence and layer perfection in Fe/MgO multilayers
- 2008
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 20:5, s. 055212-
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Tidskriftsartikel (refereegranskat)abstract
- A series of Fe/MgO multilayers was grown on single-crystal MgO(001) substrates at different temperatures using magnetron sputtering. The structural quality of the samples was investigated by x-ray reflectometry, x-ray diffraction and transmission electron microscopy. The results show a strong dependence of the structural quality on the growth temperature. Although good epitaxial layers are obtained at 165 ◦C, the sample does not exhibit any superlattice diffraction peaks. This effect is shown to be related to a continuous variation of the distance between the Fe layers as well as between the MgO layers.
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| 9. |
- Raanaei, Hossein, 1968-
(författare)
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Tailoring Properties of Materials at the Nanoscale
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The knowledge of growth and characterizing techniques is essential for the preparation of high quality thin films and multilayers. Here, structural properties have been investigated by X-ray reflectivity, X-ray diffraction, and transmission electron microscopy while the composition was determined by Rutherford backscattering spectrometry. For the magnetic studies, magneto-optical Kerr effect and X-ray magnetic circular dichroism have been used. The structural properties of the metal/insulator multilayer system, Fe/MgO, have been investigated. The coherency of the layers was influenced by the difference of the atomic distance in the Fe and MgO layers, resulting in long range strain fields. As a consequence, the coherency between the layers is not maintained. The atomic steps can not exist in amorphous materials, due to the absence of well defined atomic distances. Furthermore, the magnetic properties of amorphous materials allow a tuning of magnetic properties such as magnetic anisotropy and ordering temperature. The possibility to imprint arbitrary magnetic anisotropy in nanolaminated magnetic amorphous Co68Fe24Zr8 was demonstrated. The ratio of the orbital to spin moments for both Fe and Co was determined, for both thick and thin layers embedded in amorphous Al70Zr30 layers. When growing Co68Fe24Zr8 /Al2O3 the layers exhibit large changes in layer quality with thickness of the layers, ultimately affecting the magnetic properties of the stack. The use of protective layers is of large importance when performing ex-situ measurements. Most of the materials used were capped by Al2O3, effectively hindering both the reaction with oxygen and water. The penetration of hydrogen through different thicknesses of alumina was investigated. The experiments confirmed high degree of passivation as well as the possibility to selectively diffuse hydrogen through these layers. The use of element specific diffusion barriers allows the tailoring of magnetic properties of magnetic thin films and multilayers.
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| 10. |
- Wang, Yuntao, et al.
(författare)
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The influence of amorphous Al2O3 coating on the hydrogen uptake properties of materials
- 2008
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 464:1-2, s. L13-L16
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Tidskriftsartikel (refereegranskat)abstract
- An experimental exploration of the transport rate of hydrogen through amorphous Al2O3 layers is presented. Significant changes in the transport rate were observed when changing the thickness of the oxide from 1 to 3 nm. By coating the oxide with a catalytically active Pd layer, a fast dissociation of hydrogen is allowed, enabling a separation between the limitation imposed by dissociation and the transport through the oxide.
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