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Sökning: WFRF:(Hjörvarsson B.)

  • Resultat 1-10 av 67
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1.
  • Ingason, Arni Sigurdur, et al. (författare)
  • Magnetic Self-Organized Atomic Laminate from First Principles and Thin Film Synthesis
  • 2013
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 110
  • Tidskriftsartikel (refereegranskat)abstract
    • he first experimental realization of a magnetic Mn+1AXn (MAX) phase, (Cr0.75Mn0.25)2GeC, is presented, synthesized as a heteroepitaxial single crystal thin film, exhibiting excellent structural quality. This self-organized atomic laminate is based on the well-known Cr2GeC, with Mn, a new element in MAX phase research, substituting Cr. The compound was predicted using first-principles calculations, from which a variety of magnetic behavior is envisaged, depending on the Mn concentration and Cr/Mn atomic configuration within the sublattice. The analyzed thin films display a magnetic signal at room temperature.
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2.
  • Zamani, A., et al. (författare)
  • Magnetic properties of amorphous Fe93Zr7 films : Effect of light ion implantation
  • 2015
  • Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 117:14
  • Tidskriftsartikel (refereegranskat)abstract
    • The Curie temperature (Tc) of amorphous FeZr alloys can be greatly enhanced by doping with light elements. In this investigation, ion implantation is used to dope Fe93Zr7 thin films with H, He, B, C, and N. Extended X-ray absorption fine structure measurements confirm that the amorphous structure is preserved upon implantation for all samples, except for the N-implanted sample which is partially crystallized. The Curie temperature increases from 124 K for the pristine FeZr sample to about 400 K for the (FeZr)B0.11 sample. The increase of Tc is proportional to the increase in the average Fe-Fe distance, which allows us to conclude that the dominant cause of the Tc enhancement of amorphous Fe93Zr7 upon doping is a volume effect.
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3.
  • Dahlqvist, Martin, et al. (författare)
  • Magnetically driven anisotropic structural changes in the atomic laminate Mn2GaC
  • 2016
  • Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 93:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Inherently layered magnetic materials, such as magnetic M(n+1)AX(n) (MAX) phases, offer an intriguing perspective for use in spintronics applications and as ideal model systems for fundamental studies of complex magnetic phenomena. The MAX phase composition M(n+1)AX(n) consists of M(n+1)AX(n) blocks separated by atomically thin A-layers where M is a transition metal, A an A-group element, X refers to carbon and/or nitrogen, and n is typically 1, 2, or 3. Here, we show that the recently discovered magnetic Mn2GaC MAX phase displays structural changes linked to the magnetic anisotropy, and a rich magnetic phase diagram which can be manipulated through temperature and magnetic field. Using first-principles calculations and Monte Carlo simulations, an essentially one-dimensional (1D) interlayer plethora of two-dimensioanl (2D) Mn-C-Mn trilayers with robust intralayer ferromagnetic spin coupling was revealed. The complex transitions between them were observed to induce magnetically driven anisotropic structural changes. The magnetic behavior as well as structural changes dependent on the temperature and applied magnetic field are explained by the large number of low energy, i.e., close to degenerate, collinear and noncollinear spin configurations that become accessible to the system with a change in volume. These results indicate that the magnetic state can be directly controlled by an applied pressure or through the introduction of stress and show promise for the use of Mn2GaC MAX phases in future magnetoelectric and magnetocaloric applications.
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4.
  • Baldi, A., et al. (författare)
  • Mg/Ti multilayers : Structural and hydrogen absorption properties
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:22, s. 224203-
  • Tidskriftsartikel (refereegranskat)abstract
    • Mg-Ti alloys have uncommon optical and hydrogen absorbing properties, originating from a "spinodal-like" microstructure with a small degree of chemical short-range order in the atomic distribution. In the present study we artificially engineer short-range order by depositing Pd-capped Mg/Ti multilayers with different periodicities. Notwithstanding the large lattice mismatch between Mg and Ti, the as-deposited metallic multilayers show good structural coherence. On exposure to H-2 gas a two-step hydrogenation process occurs with the Ti layers forming the hydride before Mg. From in situ measurements of the bilayer thickness Lambda at different hydrogen pressures, we observe large out-of-plane expansions of Mg and Ti layers on hydrogenation, indicating strong plastic deformations in the films and a consequent shortening of the coherence length. On unloading at room temperature in air, hydrogen atoms remain trapped in the Ti layers due to kinetic constraints. Such loading/unloading sequence can be explained in terms of the different thermodynamic properties of hydrogen in Mg and Ti, as shown by diffusion calculations on a model multilayered systems. Absorption isotherms measured by hydrogenography can be interpreted as a result of the elastic clamping arising from strongly bonded Mg/Pd and broken Mg/Ti interfaces.
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5.
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6.
  • Melander, Emil, et al. (författare)
  • Influence of the magnetic field on the plasmonic properties of transparent Ni anti-dot arrays
  • 2012
  • Ingår i: Applied Physics Letters. - 0003-6951 .- 1077-3118. ; 101:6, s. 063107-
  • Tidskriftsartikel (refereegranskat)abstract
    • Extraordinary optical transmission is observed due to the excitation of surface plasmon polaritons in 2-dimensional hexagonal anti-dot patterns of pure Ni thin films, grown on sapphire substrates. A strong enhancement of the polar Kerr rotation is recorded at the surface plasmon related transmission maximum. Angular resolved reflectivity measurements under an applied field reveal an enhancement and a shift of the normalized reflectivity difference upon reversal of the magnetic saturation (transverse magneto-optical Kerr effect-TMOKE). The change of the TMOKE signal clearly shows the magnetic field modulation of the dispersion relation of SPPs launched in a 2D patterned ferromagnetic Ni film. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4742931]
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7.
  • Moubah, Reda, et al. (författare)
  • Discrete Layer-by-Layer Magnetic Switching in Fe/MgO(001) Superlattices
  • 2016
  • Ingår i: Physical Review Applied. - : American physical society. - 2331-7019. ; 5:4
  • 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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8.
  • Palonen, H., et al. (författare)
  • The magnetization profile induced by the double magnetic proximity effect in an Fe/Fe0.30V0.70 superlattice
  • 2019
  • Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 115:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The double magnetic proximity effect (MPE) in an Fe/Fe0.30V0.70 superlattice is studied by a direct measurement of the magnetization profile using polarized neutron reflectivity. The experimental magnetization profile is shown to qualitatively agree with a profile calculated using density functional theory. The profile is divided into a short range interfacial part and a long range tail. The interfacial part is explained by charge transfer and induced magnetization, while the tail is attributed to the inhomogeneous nature of the FeV alloy. The long range tail in the magnetization persists up to 170% above the intrinsic ordering temperature of the FeV alloy. The observed effects can be used to design systems with a direct exchange coupling between layers over long distances through a network of connected atoms. When combined with the recent advances in tuning and switching, the MPE with electric fields and currents, the results can be applied in spintronic devices. Published under license by AIP Publishing.
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9.
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10.
  • Qviller, A. J., et al. (författare)
  • Direct observation of magnetic proximity effects in amorphous exchange-spring magnets by neutron reflectometry
  • 2020
  • Ingår i: Physical Review Materials. - 2475-9953. ; 4:10
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we report a direct observation of a magnetic proximity effect in an amorphous thin-film exchange-spring magnet by the use of neutron reflectometry. The exchange-spring magnet is a trilayer consisting of two ferromagnetic layers with high T-c separated by a ferromagnetic layer, which is engineered to have a significantly lower T-c than the embedding layers. This enables us to measure magnetization depth profiles at which the low-T-c material is in a ferromagnetic or paramagnetic state, while the embedding layers are ferromagnetic. A clear proximity effect is observed 7 K above the intrinsic T-c of the embedded layer, with a range extending 50 angstrom.
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  • Resultat 1-10 av 67
  • [1]234567Nästa

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