| 31. |
- Rusz, Jan, 1979-, et al.
(författare)
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Local electronic structure information contained in energy-filtered diffraction patterns
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:6, s. 064444-
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the information contained in energy-filtered diffraction patterns measured on core-level edges. By inversion of the sum rules for electron energy loss near edge structures we calculate the reciprocal space distribution of the contribution to the total signal originating from spin moment, orbital moment, spin-orbital interaction, and individual components of magnetic and spin-orbital anisotropy tensors. We demonstrate, in particular, that the diffraction patterns contain information about all three vector components of the spin and orbital magnetic moments.
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| 32. |
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| 33. |
- Rusz, Jan, et al.
(författare)
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Quantitative magnetic measurements with transmission electron microscope
- 2010
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 322:9-12, s. 1478-1480
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Tidskriftsartikel (refereegranskat)abstract
- We briefly review the state-of-the-art electronmagnetic chiraldichroism experiments and theory with focus on quantitative measurements of the atom-specific orbital to spin moment ratio m(1)/m(s). Our approach of quantitative method, based on reciprocal space mapping of the magnetic signal, is described. We discuss additional symmetry considerations for m(1)/m(s) measurements, which are present due to dynamical diffraction effects. The selead to a preference for the 3-beam orientation of the sample. Further on, we describe a method of correcting a symmetries present due to imperfect 3-beam orientation-the so-called double-difference correction.
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| 34. |
- Rusz, Jan, et al.
(författare)
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Spin and orbital moment sum-rules for the electron energy loss chiral magnetic dichroism
- 2008
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 403:5-9, s. 1614-1615
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Tidskriftsartikel (refereegranskat)abstract
- We present analytical sum-rules for the electron energy loss chiral magnetic dichroism experiment. Predictions of the sum-rules are simulated for Fe, Co and Ni crystals with artificialy varied spin and orbital moments by means of the LDA + U method. These are then compared to directly calculated magnetic moments and found to be in close agreement. (C) 2007 Elsevier B.V. All rights reserved.
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| 35. |
- Rusz, Jan, et al.
(författare)
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Sum rules for electron energy loss near edge spectra
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:6, s. 060408-
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Tidskriftsartikel (refereegranskat)abstract
- We derive four sum-rule expressions for spectra measured in electron energy loss near edge structure experiments. These sum rules permit the determination of spin and orbital magnetic moments, spin-orbit interaction, and number of states, analogously to the sum rules of x-ray magnetic circular dichroism. The derivation of the sum rules is based on dynamical electron diffraction theory and the properties of the mixed dynamic form factor. The accuracy of the sum rules is tested by a complete evaluation of the thickness-dependent electron energy loss spectra for iron, cobalt, and nickel crystals. We find that the sum rules reproduce both spin and orbital moments with very good accuracy. Our results provide a foundation for the use of the energy loss magnetic chiral dichroism technique as a quantitative probe of element-specific magnetic properties.
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| 36. |
- Salikhov, R., et al.
(författare)
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Enhanced spin-orbit coupling in tetragonally strained Fe-Co-B films
- 2017
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 29:27
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Tidskriftsartikel (refereegranskat)abstract
- Tetragonally strained interstitial Fe-Co-B alloys were synthesized as epitaxial films grown on a 20 nm thick Au0.55Cu0.45 buffer layer. Different ratios of the perpendicular to in-plane lattice constant c/a = 1.013, 1.034 and 1.02 were stabilized by adding interstitial boron with different concentrations 0, 4, and 10 at.%, respectively. Using ferromagnetic resonance (FMR) and x-ray magnetic circular dichroism (XMCD) we found that the total orbital magnetic moment significantly increases with increasing c/a ratio, indicating that reduced crystal symmetry and interstitial B leads to a noticeable enhancement of the effect of spin-orbit coupling (SOC) in the Fe-Co-B alloys. First-principles calculations reveal that the increase in orbital magnetic moment mainly originates from B impurities in octahedral position and the reduced symmetry around B atoms. These findings offer the possibility to enhance SOC phenomena - namely the magnetocrystalline anisotropy and the orbital moment - by stabilizing anisotropic strain by doping 4 at.% B. Results on the influence of B doping on the Fe-Co film microstructure, their coercive field and magnetic relaxation are also presented.
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| 37. |
- Thersleff, Thomas, 1980-, et al.
(författare)
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Towards sub-nanometer real-space observation of spin and orbital magnetism at the Fe/MgO interface
- 2017
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- While the performance of magnetic tunnel junctions based on metal/oxide interfaces is determined by hybridization, charge transfer, and magnetic properties at the interface, there are currently only limited experimental techniques with sufficient spatial resolution to directly observe these effects simultaneously in real-space. In this letter, we demonstrate an experimental method based on Electron Magnetic Circular Dichroism (EMCD) that will allow researchers to simultaneously map magnetic transitions and valency in real-space over interfacial cross-sections with sub-nanometer spatial resolution. We apply this method to an Fe/MgO bilayer system, observing a significant enhancement in the orbital to spin moment ratio that is strongly localized to the interfacial region. Through the use of first-principles calculations, multivariate statistical analysis, and Electron Energy-Loss Spectroscopy (EELS), we explore the extent to which this enhancement can be attributed to emergent magnetism due to structural confinement at the interface. We conclude that this method has the potential to directly visualize spin and orbital moments at buried interfaces in magnetic systems with unprecedented spatial resolution.
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| 38. |
- Vinogradov, Nikolay, et al.
(författare)
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Formation and Structure of Graphene Waves on Fe(110)
- 2012
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 109:2
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Tidskriftsartikel (refereegranskat)abstract
- A very rich Fe-C phase diagram makes the formation of graphene on iron surfaces a challenging task. Here we demonstrate that the growth of graphene on epitaxial iron films can be realized by chemical vapor deposition at relatively low temperatures, and that the formation of carbides can be avoided in excess of the carbon-containing precursors. The resulting graphene monolayer creates a novel periodically corrugated pattern on Fe(110). Using low-energy electron microscopy and scanning tunneling microscopy, we show that it is modulated in one dimension forming long waves with a period of similar to 4 nm parallel to the [001] direction of the substrate, with an additional height modulation along the wave crests. The observed topography of the graphene/Fe superstructure is well reproduced by density functional theory calculations, and found to result from a unique combination of the lattice mismatch and strong interfacial interaction, as probed by core-level photoemission and x-ray absorption spectroscopy.
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| 39. |
- Wasilewski, Bartosz, et al.
(författare)
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Electronic specific heat coefficient and magnetic properties of Y(Fe1-xCox)(2) Laves phases : A combined experimental and first-principles study
- 2019
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 100:13
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Tidskriftsartikel (refereegranskat)abstract
- We investigated experimentally and computationally the concentration dependence of the electronic specific heat coefficient gamma in the Y(Fe1-xCox)(2) pseudobinary Laves phase system. The experimentally observed maximum in gamma(x) around the magnetic phase transition was interpreted within the local density approximation combined with the virtual crystal approximation. To explain the formation of the observed maximum, we analyzed theoretically the dependence of the magnetic energy, magnetic moments, densities of states, and Fermi surfaces on the Co concentration. Furthermore, we carried out the calculations of the density of states (DOS) at the Fermi level as a function of fixed spin moment. The calculated Co concentration at which gamma takes the maximum value (x(max-LDA-VCA) = 0.91) stays in good agreement with the measured value (x(max-expt) = 0.925). We conclude that the observed maximum in gamma(x) results from the presence of the sharp DOS peak in the vicinity of the Fermi level.
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| 40. |
- Werwinski, Miroslaw, et al.
(författare)
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Magnetic properties of Fe5SiB2 and its alloys with P, S, and Co
- 2016
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Ingår i: PHYSICAL REVIEW B. - 2469-9950. ; 93:17
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Tidskriftsartikel (refereegranskat)abstract
- Fe5SiB2 has been synthesized and magnetic measurements have been carried out, revealing that M-sat = 0.92 MA/mat T = 300 K. The M versus T curve shows a broad peak around T = 160 K. The anisotropy constant K-1, estimated at T = 300 K, is 0.25 MJ/m(3). Theoretical analysis of Fe5SiB2 system has been carried out and extended to the full range of Fe5Si1-xPxB2, Fe5P1-xSxB2, and (Fe1-xCox)(5)SiB2 compositions. The electronic band structures have been calculated using the full-potential local-orbital minimum-basis scheme (FPLO-14). The calculated total magnetic moments are 9.20, 9.15, 9.59, and 2.42 mu(B) per formula units of Fe5SiB2, Fe5PB2, Fe5SB2, and Co5SiB2, respectively. In agreement with experiment, magnetocrystalline anisotropy energies (MAE's) calculated for T = 0 K change from a negative (easy-plane) anisotropy -0.28 MJ/m(3) for Fe5SiB2 to the positive (easy-axis) anisotropy 0.35 MJ/m(3) for Fe5PB2. Further increase of the number of p electrons in Fe5P1-xSxB2 leads to an increase of MAE up to 0.77 MJ/m(3) for the hypothetical Fe5P0.4S0.6B2 composition. Volume variation and fixed spin moment calculations (FSM) performed for Fe5SiB2 show an inverse relation between MAE and magnetic moment in the region down to about 15% reduction of the spin moment. The alloying of Fe5SiB2 with Co is proposed as a practical realization of magnetic moment reduction, which ought to increase MAE. MAE calculated in virtual crystal approximation (VCA) for a full range of (Fe1-xCox)(5)SiB2 compositions reaches the maximum value of 1.16 MJ/m(3) at Co concentration x = 0.3, with the magnetic moment 7.75 mu(B) per formula unit. Thus, (Fe0.7Co0.3)(5)SiB2 is suggested as a candidate for a rare-earth free permanent magnet. For the stoichiometric Co5SiB2 there is an easy-plane magnetization, with the value of MAE = -0.15 MJ/m(3).
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