| 1. |
- Magnus, Fridrik, et al.
(författare)
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Giant magnetic domains in amorphous SmCo thin films
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 89:22, s. 224420-1-224420-5
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Tidskriftsartikel (refereegranskat)abstract
- The potential for tuning of magnetic properties and the exceptional uniformity are among the features that make amorphous magnetic materials attractive for technology. Here it is shown that the magnetization reversal in amorphous SmCo thin films takes place through the formation of giant magnetic domains, over a centimeter across. The domain structure is found to be dictated by the direction of the imprinted in-plane easy axis and the film boundaries. This is a consequence of the size of the anisotropy and the structural uniformity of the films, which also allows the movement of millimeter-long domain walls over distances of several millimeters. The results demonstrate the possibility of tailoring the magnetic domain structure in amorphous magnets over a wide range of length scales, up to centimeters. Moreover, they highlight an important consequence of the structural perfection of amorphous films.
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| 2. |
- Magnus, Fridrik, et al.
(författare)
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Magnetostrictive properties of amorphous SmCo thin films with imprinted anisotropy
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 89:13, s. 134414-1-134414-6
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Tidskriftsartikel (refereegranskat)abstract
- We examine the magnetostriction in amorphous SmCo thin films with a composition in the range 4-27 at.% Sm. The magnetostriction increases significantly with increasing Sm content but is small compared to terbium-based ferromagnetic compounds, despite the large imprinted anisotropy. The magnetostriction and anisotropy both increase approximately linearly as the temperature is reduced. The magnetoelastic energy is found to be far smaller than the anisotropy energy so the magnetoelastic atomic displacements during growth cannot be the origin of the imprinted anisotropy. The anisotropy is only slightly altered by the application of large tensile stresses, indicating that the local strain fields involved in magnetostriction are not equivalent to the global strain produced by mechanical bending.
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| 3. |
- Magnus, Fridrik, et al.
(författare)
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Tunable giant magnetic anisotropy in amorphous SmCo thin films
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:16, s. 162402-
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Tidskriftsartikel (refereegranskat)abstract
- SmCo thin films have been grown by magnetron sputtering at room temperature with a composition of 2-35 at.% Sm. Films with 5 at.% or higher Sm are amorphous and smooth. A giant tunable uniaxial in-plane magnetic anisotropy is induced in the films which peaks in the composition range 11-22 at.% Sm. This cross-over behavior is not due to changes in the atomic moments but rather the local configuration changes. The excellent layer perfection combined with highly tunable magnetic properties make these films important for spintronics applications.
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| 4. |
- Moubah, Reda, et al.
(författare)
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Anisotropic Magnetostriction and Domain Wall Motion in Sm10Co90 Amorphous Films
- 2013
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Ingår i: APPL PHYS EXPRESS. - 1882-0778. ; 6:5, s. 053004-
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Tidskriftsartikel (refereegranskat)abstract
- We show that Sm10Co90 amorphous films exhibit anisotropic magnetostriction effects when a magnetic field is applied perpendicular to the imprinted easy axis of magnetization. At low applied fields (0-100 mT), we observe strong anisotropy in the field response. Parallel to the applied field, the strain scales linearly with the applied field while the strain perpendicular to the field direction ( easy axis) is close to the detection limit. This behavior is accompanied by zigzag domain wall motion with the corners pointing along the easy axis. The origin of the anisotropic magnetostriction is discussed.
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| 5. |
- Moubah, Reda, et al.
(författare)
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Antisymmetric magnetoresistance in SmCo5 amorphous films with imprinted in-plane magnetic anisotropy
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:5, s. 053911-
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Tidskriftsartikel (refereegranskat)abstract
- We report on magnetoresistance measurements in SmCo5 amorphous films with a giant imprinted magnetic anisotropy. At low applied field parallel to the easy axis, the magnetoresistance exhibits a hysteretic, square, and antisymmetric shape. The antisymmetry in the magnetoresistance is a result of the non-uniform distribution of the magnetization direction over the sample in conjunction with the extraordinary Hall effect. Moreover, the combination of anisotropic magnetoresistance measurements and magnetic domain imaging demonstrates that the symmetry depends on the magnetization orientation with respect to the applied field.
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| 6. |
- Moubah, Reda, et al.
(författare)
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Discrete Layer-by-Layer Magnetic Switching in Fe/MgO(001) Superlattices
- 2016
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Ingår i: Physical Review Applied. - : American physical society. - 2331-7019. ; 5:4
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Tidskriftsartikel (refereegranskat)abstract
- We report on a discrete layer-by-layer magnetic switching in Fe/MgO superlattices driven by an antiferromagnetic interlayer exchange coupling. The strong interlayer coupling is mediated by tunneling through MgO layers with thicknesses up to at least 1.8 nm, and the coupling strength varies with MgO thickness. Furthermore, the competition between the interlayer coupling and magnetocrystalline anisotropy stabilizes both 90 degrees and 180 degrees periodic alignment of adjacent layers throughout the entire superlattice. The tunable layer-by-layer switching, coupled with the giant tunneling magnetoresistance of Fe/MgO/Fe junctions, is an appealing combination for three-dimensional spintronic memories and logic devices.
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| 7. |
- Moubah, Reda, et al.
(författare)
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Strain enhanced magnetic anisotropy in SmCo/BaTiO3 multiferroic heterostructures
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:5, s. 053905-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the changes in magnetic properties of SmCo/BaTiO3 multiferroic heterostructures as the BaTiO3 substrate undergoes its structural phase transitions. The observations show that the macroscopic magnetization of the SmCo film is affected by the structural phase transitions of the BaTiO3 substrate. Kerr microscopy images show that the magnetic domains of SmCo films have a zigzag shape but their shape is not influenced by the strain transferred from the substrate during the structural phase transitions. Analysis of the magnetoelastic energy shows that the macroscopic change of the magnetization is accompanied by an enhancement of the magnetic anisotropy for the orthorhombic phase of the BaTiO3 substrate and not a change in symmetry of the anisotropy.
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| 8. |
- Moubah, Reda, et al.
(författare)
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Strain induced changes in magnetization of amorphous Co95Zr5 based multiferroic heterostructures
- 2013
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 3:2, s. 022113-
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Tidskriftsartikel (refereegranskat)abstract
- A clear change in the magnetic anisotropy in a layer of amorphous Co95Zr5 is obtained at the orthorhombic phase transition of the BaTiO3 substrate. The use of an amorphous buffer layer between the ferroelectric substrate and amorphous magnetic film shows that bulk strain governs the change in themagnetic anisotropy of our ferromagnetic-ferroelectric heterostructure. Moreover, we show that the thermal magnetization curves exhibit anisotropic behavior.
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| 9. |
- Moubah, Reda, et al.
(författare)
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Tailoring magnetism at the nanometer scale in SmCo5 amorphous films
- 2013
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 25:41, s. 416004-
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Tidskriftsartikel (refereegranskat)abstract
- The thickness dependence of magnetic properties has been studied in SmCo5 amorphous films with imprinted in-plane anisotropy for thicknesses ranging down to the nanometer scale (2.5-100 nm). The field induced in-plane magnetic anisotropy decreases considerably when the film thickness is below 20 nm. Analysis of the magnetic anisotropy energy shows that the decrease of the induced in-plane anisotropy is accompanied by the development of an out-of-plane interface anisotropy. Two different regimes for the coercivity (H-c) change are found: below 3.75 nm, the H-c decreases continuously with decrease of the film thickness, whereas at above 3.75 nm, the H-c decreases with increase of the film thickness. This change in Hc can be understood by considering the decrease of the short range chemical order for the thinnest films (<3.75 nm) and the relative decrease of the interface contribution with increasing film thickness. The changes in anisotropy have a profound influence on the domain structure, in which the angle of the zigzag domain boundaries decreases with the inverse thickness of the layers.
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