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Sökning: WFRF:(Kapaklis V.)

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1.
  • Tarnavich, V., et al. (författare)
  • Magnetic field induced chirality in Ho/Y multilayers with gradually decreasing anisotropy
  • 2017
  • Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 96:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Metal rare-earth magnetic/nonmagnetic Ho/Y superlattice structures possess a coherent spin helix propagating through many superlattice layer repetitions. An externalmagnetic field applied in the film plane induces a nonzero average chirality of the helices. It is shown that the direction of the applied in-plane field can modify the value and sign of the chirality parameter.. The dependence of. on the relative angle of applied field during the field`-cooling procedure has an oscillatory character and can be described by simple sinusoidal function with p periodicity. The experimental finding is discussed from the point of view of an interbalance between Zeeman energy, magnetocrystalline anisotropy, and induced uniaxial anisotropy.
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2.
  • Ukleev, V, et al. (författare)
  • Coherent charge and magnetic ordering in Ho/Y superlattice revealed by element-selective x-ray scattering
  • 2019
  • Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 100:13
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic rare-earth/nonmagnetic metal superlattices are well-known to display chiral spin helices in the rare-earth layers that propagate coherently across the nonmagnetic layers. However, the underlying mechanism that preserves the magnetic phase and chirality coherence across the nonmagnetic layers has remained elusive. In this paper, we use resonant and element-specific x-ray scattering to evidence directly the formation of two fundamentally different long-range modulations in a holmium/yttrium (Ho/Y) multilayer: the known Ho chiral spin helix with periodicity 25 angstrom and a newly observed charge density wave with periodicity 16 angstrom that propagates through both the Ho and nonmagnetic Y layer. With x-ray circular magnetic dichroism measurements ruling out the existence of a magnetic proximity effect induced moment in the nonmagnetic Y layers, we propose that the charge density wave is also chiral, thus providing the means for the transmittance of magnetic chirality coherence between Ho layers.
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3.
  • Maccaferri, N., et al. (författare)
  • Nanoscale magnetophotonics
  • 2020
  • Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 127:8
  • Tidskriftsartikel (refereegranskat)abstract
    • This Perspective surveys the state-of-the-art and future prospects of science and technology employing nanoconfined light (nanophotonics and nanoplasmonics) in combination with magnetism. We denote this field broadly as nanoscale magnetophotonics. We include a general introduction to the field and describe the emerging magneto-optical effects in magnetoplasmonic and magnetophotonic nanostructures supporting localized and propagating plasmons. Special attention is given to magnetoplasmonic crystals with transverse magnetization and the associated nanophotonic non-reciprocal effects and to magneto-optical effects in periodic arrays of nanostructures. We also give an overview of the applications of these systems in biological and chemical sensing, as well as in light polarization and phase control. We further review the area of nonlinear magnetophotonics, the semiconductor spin-plasmonics, and the general principles and applications of opto-magnetism and nano-optical ultrafast control of magnetism and spintronics. © 2020 Author(s).
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4.
  • 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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5.
  • Tarnavich, V. V., et al. (författare)
  • Field-induced chirality in the helix structure of Ho/Y multilayers
  • 2014
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 89:5, s. 054406-
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the net chirality in the spin helix structure of Ho/Y multilayers induced by an in-plane applied magnetic field. The lifting of degeneracy of the chiral symmetry was revealed by means of polarized neutron reflectometry. Three samples of different thicknesses of the Ho and Y layers were grown by molecular-beam epitaxy. The chiral states are degenerated upon zero field cooling below the critical temperature TN=115±3 K. The chirality parameter γ rises during the field cooling procedure in the field range from 0 to 1 T and saturates at a value of 0.12±0.01. The chirality appears stepwise below TN and depends weakly on temperature. The phenomenon is interpreted in terms of the Dzyaloshinskii-Moriya interaction appearing at the interface between the Ho and Y layers.
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6.
  • Magnfält, Daniel, et al. (författare)
  • Synthesis of tunable plasmonic metal-ceramic nanocomposite thin films by temporally modulated sputtered fluxes
  • 2017
  • Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 121:17
  • Tidskriftsartikel (refereegranskat)abstract
    • The scientific and technological interest for metal-dielectric nanocomposite thin films emanates from the excitation of localized surface plasmon resonances (LSPRs) on the metal component. The overall optical response of the nanocomposite is governed by the refractive index of the dielectric matrix and the properties of the metallic nanoparticles in terms of their bulk optical properties, size, and shape, and the inter-particle distance of separation. In order to tune the film morphology and optical properties, complex synthesis processes which include multiple steps-i. e., film deposition followed by post-deposition treatment by thermal or laser annealing-are commonly employed. In the present study, we demonstrate that the absorption resonances of Ag/AlOxNy nanocomposite films can be effectively tuned from green (similar to 2.4 eV) to violet (similar to 2.8 eV) using a single-step synthesis process that is based on modulating the arrival pattern of film forming species with sub-monolayer resolution, while keeping the amount of Ag in the films constant. Our data indicate that the optical response of the films is the result of LSPRs on isolated Ag nanoparticles that are seemingly shifted by dipolar interactions between neighboring particles. The synthesis strategy presented may be of relevance for enabling integration of plasmonic nanocomposite films on thermally sensitive substrates. Published by AIP Publishing.
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7.
  • Ciuciulkaite, Agne, MSc, 1991-, et al. (författare)
  • Magnetic and all-optical switching properties of amorphous TbxCo100-x alloys
  • 2020
  • Ingår i: Physical Review Materials. - : American Physical Society (APS). - 2475-9953. ; 4:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Amorphous TbxCo100-x magnetic alloys exhibit a list of intriguing properties, such as perpendicular magnetic anisotropy, high magneto-optical activity, and magnetization switching using ultrashort optical pulses. Varying the Tb:Co ratio in these alloys allows for tuning properties such as the saturation magnetic moment, coercive field, and the performance of light-induced magnetization switching. In this paper, we investigate the magnetic, optical, and magneto-optical properties of various TbxCo100-x thin-film alloy compositions. We report on the effect the choice of different seeding layers has on the structural and magnetic properties of TbxCo100-x layers. We also demonstrate that for a range of alloys, deposited on fused silica substrates, with Tb content of 24-30 at. %, helicity-dependent all-optical switching of magnetization can be achieved, albeit in a multishot framework. We explain this property to arise from the helicity-dependent laser-induced magnetization on the Co sublattice due to the inverse Faraday effect. Our paper provides an insight into material aspects for future potential hybrid magnetoplasmonic TbCo-based architectures.
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8.
  • Cooper-Jensen, Carsten, et al. (författare)
  • "m=1" coatings for neutron guides
  • 2014
  • Ingår i: International Workshop on Neutron Optics and Detectors (NOP&D 2013) 2–5 July 2013, Munich, Germany. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 528, s. 012005-012005
  • Konferensbidrag (refereegranskat)abstract
    • A substantial fraction of the price for a supermirror neutron guide system is the shielding, which is needed because of the gamma radiation produced as a result of neutron absorption in the supermirror layers. Traditional coatings have been made of nickel-titanium heterostructures, but Ni and Ti also have a fairly high absorption cross section for cold and thermal neutrons. We examine a number of alternatives to Ni as part of a study to reduce the gamma radiation from neutron guides. Materials such as diamond and Be have higher neutron scattering density than Ni, smaller absorption cross section, and when a neutron is absorbed they emit gamma photons with lower energies. We present reflectivity data comparing Ni with Be and preliminary results from diamond coatings showing there use as neutron guide coatings. Calculations show that Be and diamond coatings emit two orders of magnitude fewer gamma photons compared to Ni, mainly because of the lower absorption cross section.
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9.
  • Hellsing, Maja S., et al. (författare)
  • Crystalline order of polymer nanoparticles over large areas at solid/liquid interfaces
  • 2012
  • Ingår i: Applied Physics Letters. - 0003-6951 .- 1077-3118. ; 100:22, s. 221601-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the formation of large two-dimensional domains (about 20 cm2) of oriented and ordered structures of polystyrene particles dispersed in water at a solid/liquid interface.  Gentle flow of the dispersed sample into the holder at a shear strain rate of about 0.1 s−1 caused particles at the air/latex meniscus to self-assemble in a regular structure on both solid silica or alumina surfaces.  Scattering experiments show that the particle separation at the surface was the same as in the bulk and determined by repulsion arising from the charges on the particles.  Close-packed planes formed parallel to the interface.
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10.
  • Jishiashvili, D., et al. (författare)
  • Germanium Nitride Nanowires Produced by Thermal Annealing in Hydrazine Vapor
  • 2009
  • Ingår i: Advanced Science Letters. - 1936-6612. ; 2:1, s. 40-44
  • Tidskriftsartikel (refereegranskat)abstract
    • A simple pyrolytic: technology was developed in this paper for producing Germanium nitride nanowires. Hydrazine was used as the nitriding agent, while the 3 mol.% of water diluted in it served for producing volatile GeO molecules and for the accomplishment of mass transfer. The Ge3N4 nuclei appeared on the surfaces of GeOx clusters, formed after redeposition of GeO molecules. The growth of two types of nanowires was observed. The ball-shaped Ge tip surrounded with the amorphous GeO2 sheath served as a catalyst during the vapor-liquid-solid growth of tapered nanowires. Straight nanowires were produced through the oxide-assisted method. Tentative results on the blue-green photoluminescence of nanowires were obtained.
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