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| 2. |
- Andersson, Gabriella, et al.
(författare)
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Perpendicular magnetocrystalline anisotropy in tetragonally distorted Fe-Co alloys
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 96:3
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Tidskriftsartikel (refereegranskat)abstract
- We report on the experimental realization of tetragonal Fe-Co alloys as a constituent of Fe(0.36)Co(0.64)/Pt superlattices with huge perpendicular magnetocrystalline anisotropy energy, reaching 210 mu eV/atom, and a saturation magnetization of 2.5 mu(B)/atom at 40 K, in qualitative agreement with theoretical predictions. At room temperature the corresponding values 150 mu eV/atom and 2.2 mu(B)/atom are achieved. This suggests that Fe-Co alloys with carefully chosen combinations of composition and distortion are good candidates for high-density perpendicular storage materials.
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| 3. |
- Andersson, Gabriella, et al.
(författare)
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Structure of Fe-Co/Pt(001) superlattices : a realization of tetragonal Fe-Co alloys
- 2007
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 19:1, s. 016008-
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Tidskriftsartikel (refereegranskat)abstract
- The structural properties of a tetragonally distorted Fe1-xCox alloy, in the form of Fe1-xCox/Pt(001) superlattices with x = 0.64, have been investigated experimentally. The study follows recent theoretical predictions on the enhanced uniaxial magnetocrystalline anisotropy of such alloys with specific combinations of chemical composition and tetragonal distortion. The ratio between out-of-plane and in-plane lattice parameters in the Fe0.36Co0.64 layers, c/a, was found to vary between 1.18 and 1.31, depending on the thickness ratio between the alloy and the spacer. This covered the range of interest c/a = 1.20-1.25 in the previous calculations and should be compared to c/a = 1 in the original bcc alloy lattice. Simulations of x-ray diffraction patterns as well as density functional calculations support the derivation of the Fe0.36Co0.64 lattice parameters.
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| 6. |
- Hjörvarsson, Björgvin, et al.
(författare)
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The influence of weak links on magnetic ordering in layered structures
- 2008
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 61:1, s. 17008-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the magnetic ordering in layered magnets with two different inherent ordering temperatures. A [V(12 ML)Fe(2 ML)/V(12 ML)(/Fe(3 ML)](70) superlattice with anti-ferromagnetic interlayer exchange coupling is used for this purpose. The more rapid decrease of the magnetic moment in the 2 monolayer thick Fe layers influences the ordering in a non-trivial way. A distribution of the effective ordering temperature is inferred, originating from a more rapid decrease of the magnetic moment in the near-surface region, as compared to the interior of the sample. The results clearly demonstrate the need to consider all energy and length scales when addressing ordering in materials with finite extension.
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| 9. |
- Johansson, Emil, et al.
(författare)
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Hydrogen uptake and optical properties of sputtered Mg-Ni thin films
- 2004
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 16, s. 7649-
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogen uptake and distribution in wedged Mg–Ni films, with composition ranging from Mg0.85Ni0.15 to Mg0.55Ni0.45, were investigated. Upon hydrogen loading at 298 K these films undergo a transition from a mirror-like metallic to a semiconducting transparent state. After exposure to a hydrogen pressure of 1 bar, the samples exhibit large variation in optical appearance, ranging from a pale yellowish (Mg rich side) to a brownish shade (Ni rich side). The change in the effective optical band gap Egeff as a function of sample composition and hydrogen concentration was determined; it showed changes from 3.6 eV in the Ni poor domain to 2.4 eV in the Ni rich domain. Composition analysis using the 15N nuclear resonance method showed close to homogeneous hydrogen distribution throughout the film and close to linear increase in the hydrogen uptake with increasing Mg content. The thermal stability of the films is limited; annealing above 393 K results in significant redistribution of the constituents. Mg is enriched at the surface, reacting with Pd and thereby degrading the capping layer through the formation of Mg6Pd and MgO, as determined by x-ray diffraction, x-ray photoelectron spectroscopy and Rutherford backscattering studies. This redistribution results in a severe decrease of the hydrogen uptake rate, as monitored by in situ resistivity measurements.
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