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“Stability of vortex-antivortex “molecules&rdquo, in mesoscopic superconducting triangles”. Misko VR, Fomin VM, Devreese JT, Moshchalkov VV, 3rd International Symposium on Mesoscopic Superconductivity and, Spintronics, MAR 01-04, 2004, Atsug, 191 (2005). http://doi.org/10.1142/9789812701619_0030
Abstract: We have revealed thermodynamically stable vortex-antivortex configurations in mesoscopic type I superconducting equilateral triangles. The revealed effect is explained by two factors: (i) vortex confinement in mesoscopic triangles and (ii) appearance of the vortex-antivortex repulsion in mesoscopic type I superconductor triangles in the vicinity of the dual point. The stability of the obtained solutions is examined as a function of material and external parameters – the Ginzburg-Landau parameter K and temperature – as well as a function of a distortion of the sample's shape. The vortex-antivortex. “molecule” turns out to be stable in a wide range of the parameters that makes it possible its experimental visualization.
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
DOI: 10.1142/9789812701619_0030
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“Stability of vortex-antivortex molecules in mesoscopic superconducting triangles”. Misko VR, Fomin VM, Devreese JT, Moshchalkov VV, Physica C-Superconductivity And Its Applications 404, 251 (2004). http://doi.org/10.1016/j.physc.2003.11.043
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 1.404
Times cited: 2
DOI: 10.1016/j.physc.2003.11.043
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“Stable vortex-antivortex molecules in mesoscopic superconducting triangles”. Misko VR, Fomin VM, Devreese JT, Moshchalkov VV, Physical Review Letters 90, 147003 (2003). http://doi.org/10.1103/PhysRevLett.90.147003
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 8.462
Times cited: 103
DOI: 10.1103/PhysRevLett.90.147003
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“Superconducting mesoscopic square loop”. Fomin VM, Misko VR, Devreese JT, Moshchalkov VV, Physical Review B 58, 11703 (1998). http://doi.org/10.1103/PhysRevB.58.11703
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 3.836
Times cited: 43
DOI: 10.1103/PhysRevB.58.11703
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“Superconducting mesoscopic square loops: phase boundaries and magnetization”. Devreese JT, Fomin VM, Misko VR, Moshchalkov VV, 1/2, 33 (1998)
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Times cited: 1
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“Temperature and magnetic field dependence of the voltagein GaAs films with superconducting Ga grains”. Willems BL, Taylor DMJ, Fritzsche J, Malfait M, Vanacken J, Moshchalkov VV, Montoya E, Van Tendeloo G, European physical journal : B : condensed matter and complex systems 66, 25 (2008). http://doi.org/10.1140/epjb/e2008-00386-3
Abstract: We have studied granular films consisting of nanoscale Ga droplets formed on GaAs films via a method of vacuum annealing to promote As evaporation. For temperatures and magnetic fields below the bulk Ga critical parameters, the samples are very sensitive towards external microwave radiation when two point voltage measurements are performed. Together with the observation of an oscillating magnetic field dependence of the voltage, a scenario in which the samples consist of Josephson-coupled loops seems to be the most likely one for explaining the obtained results.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.461
DOI: 10.1140/epjb/e2008-00386-3
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“Ultralow blocking temperature and breakdown of the giant spin model in Er3+-doped nanoparticles”. van den Heuvel W, Tikhomirov VK, Kirilenko D, Schildermans N, Chibotaru LF, Vanacken J, Gredin P, Mortier M, Van Tendeloo G, Moshchalkov VV, Physical review : B : condensed matter and materials physics 82, 094421 (2010). http://doi.org/10.1103/PhysRevB.82.094421
Abstract: The magnetization of luminescent Er3+-doped PbF2 nanoparticles (formula Er0.3Pb0.7F2.3) has been studied. Despite the high concentration of the doping Er3+ ions and relatively large size (8 nm) of these nanoparticles we have found no deviation between field-cooled and zero-field-cooled magnetization curves down to T=0.35 K, which points out an ultralow blocking temperature for the reversal of magnetization. We also have found strongly deviating magnetization curves M(H/T) for different temperatures T. These results altogether show that the investigated nanoparticles are not superparamagnetic, but rather each Er3+ ion in these nanoparticles is found in a paramagnetic state down to very low temperatures, which implies the breakdown of the Néel-Brown giant spin model in the case of these nanoparticles. Calculations of magnetization within a paramagnetic model of noninteracting Er3+ ions completely support this conclusion. Due to the ultralow blocking temperature, these nanoparticles have a potential for magnetic field-induced nanoscale refrigeration with an option of their optical localization and temperature control.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 11
DOI: 10.1103/PhysRevB.82.094421
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“Vortex states in a mescopic superconducting triangle”. Misko VR, Fomin VM, Devreese JT, Moshchalkov VV, Physica C-Superconductivity And Its Applications 369, 361 (2002). http://doi.org/10.1016/S0921-4534(01)01277-1
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 1.404
Times cited: 14
DOI: 10.1016/S0921-4534(01)01277-1
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“In situ tailoring of superconducting junctions via electro-annealing”. Lombardo J, Jelić, ŽL, Baumans XDA, Scheerder JE, Nacenta JP, Moshchalkov VV, Van de Vondel J, Kramer RBG, Milošević, MV, Silhanek AV, Nanoscale 10, 1987 (2018). http://doi.org/10.1039/C7NR08571K
Abstract: We demonstrate the in situ engineering of superconducting nanocircuitry by targeted modulation of material properties through high applied current densities. We show that the sequential repetition of such customized electro-annealing in a niobium (Nb) nanoconstriction can broadly tune the superconducting critical temperature T-c and the normal-state resistance R-n in the targeted area. Once a sizable R-n is reached, clear magneto-resistance oscillations are detected along with a Fraunhofer-like field dependence of the critical current, indicating the formation of a weak link but with further adjustable characteristics. Advanced Ginzburg-Landau simulations fully corroborate this picture, employing the detailed parametrization from the electrical characterization and high resolution electron microscope images of the region within the constriction where the material has undergone amorphization by electro-annealing.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 7.367
Times cited: 23
DOI: 10.1039/C7NR08571K
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“0 and &pi, phase Josephson coupling through an insulating barrier with magnetic impurities”. Vávra O, Gaži S, Golubović, DS, Vávra I, Dérer J, Verbeeck J, Van Tendeloo G, Moshchalkov VV, Physical review : B : condensed matter and materials physics 74, 020502 (2006). http://doi.org/10.1103/PhysRevB.74.020502
Abstract: We have studied the temperature and field dependencies of the critical current I(C) in the Nb-Fe(0.1)Si(0.9)-Nb Josephson junction with a tunneling barrier formed by a paramagnetic insulator. We demonstrate that in these junctions coexistence of both the 0 and the pi states within one tunnel junction occurs, and leads to the appearance of a sharp cusp in the temperature dependence I(C)(T), similar to the I(C)(T) cusp found for the 0-pi transition in metallic pi junctions. This cusp is not related to the 0-pi temperature-induced transition itself, but is caused by the different temperature dependencies of the opposing 0 and pi supercurrents through the barrier.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 27
DOI: 10.1103/PhysRevB.74.020502
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“Preparation, structural and optical characterization of nanocrystalline ZnO doped with luminescent Ag-nanoclusters”. Kuznetsov AS, Lu Y-G, Turner S, Shestakov MV, Tikhomirov VK, Kirilenko D, Verbeeck J, Baranov AN, Moshchalkov VV, Optical materials express 2, 723 (2012). http://doi.org/10.1364/OME.2.000723
Abstract: Nanocrystalline ZnO doped with Ag-nanoclusters has been synthesized by a salt solid state reaction. Three overlapping broad emission bands due to the Ag nanoclusters have been detected at about 570, 750 and 900 nm. These emission bands are excited by an energy transfer from the exciton state of the ZnO host when pumped in the wavelength range from 250 to 400 nm. The 900 nm emission band shows characteristic orbital splitting into three components pointing out that the anisotropic crystalline wurtzite host of ZnO is responsible for this feature. Heat-treatment and temperature dependence studies confirm the origin of these emission bands. An energy level diagram for the emission process and a model for Ag nanoclusters sites are suggested. The emission of nanocrystalline ZnO doped with Ag nanoclusters may be applied for white light generation, displays driven by UV light, down-convertors for solar cells and luminescent lamps.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.591
DOI: 10.1364/OME.2.000723
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“Onset, evolution, and magnetic braking of vortex lattice instabilities in nanostructured superconducting films”. Adami O-A, Jelić, ŽL, Xue C, Abdel-Hafiez M, Hackens B, Moshchalkov VV, Milošević, MV, Van de Vondel J, Silhanek AV, Physical review: B: condensed matter and materials physics 92, 134506 (2015). http://doi.org/10.1103/PhysRevB.92.134506
Abstract: In 1976, Larkin and Ovchinnikov [Zh. Eksp. Teor. Fiz. 68, 1915 (1975) [Sov. Phys.–JETP 41, 960 (1976)]] predicted that vortex matter in superconductors driven by an electrical current can undergo an abrupt dynamic transition from a flux-flow regime to a more dissipative state at sufficiently high vortex velocities. Typically, this transition manifests itself as a large voltage jump at a particular current density, so-called instability current density J∗, which is smaller than the depairing current. By tuning the effective pinning strength in Al films, using an artificial periodic pinning array of triangular holes, we show that a unique and well-defined instability current density exists if the pinning is strong, whereas a series of multiple voltage transitions appear in the relatively weaker pinning regime. This behavior is consistent with time-dependent Ginzburg-Landau simulations, where the multiple-step transition can be unambiguously attributed to the progressive development of vortex chains and subsequently phase-slip lines. In addition, we explore experimentally the magnetic braking effects, caused by a thick Cu layer deposited on top of the superconductor, on the instabilities and the vortex ratchet effect.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 21
DOI: 10.1103/PhysRevB.92.134506
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“Nematic superconducting state in iron pnictide superconductors”. Li J, Pereira PJ, Yuan J, Lv Y-Y, Jiang M-P, Lu D, Lin Z-Q, Liu Y-J, Wang J-F, Li L, Ke X, Van Tendeloo G, Li M-Y, Feng H-L, Hatano T, Wang H-B, Wu P-H, Yamaura K, Takayama-Muromachi E, Vanacken J, Chibotaru LF, Moshchalkov VV, Nature communications 8, 1880 (2017). http://doi.org/10.1038/s41467-017-02016-y
Abstract: Nematic order often breaks the tetragonal symmetry of iron-based superconductors. It arises from regular structural transition or electronic instability in the normal phase. Here, we report the observation of a nematic superconducting state, by measuring the angular dependence of the in-plane and out-of-plane magnetoresistivity of Ba 0.5 K 0.5 Fe 2 As 2 single crystals. We find large twofold oscillations in the vicinity of the superconducting transition, when the direction of applied magnetic field is rotated within the basal plane. To avoid the influences from sample geometry or current flow direction, the sample was designed as Corbino-shape for in-plane and mesa-shape for out-of-plane measurements. Theoretical analysis shows that the nematic superconductivity arises from the weak mixture of the quasi-degenerate s-wave and d-wave components of the superconducting condensate, most probably induced by a weak anisotropy of stresses inherent to single crystals.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.124
Times cited: 8
DOI: 10.1038/s41467-017-02016-y
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“Superconductor-insulator transition driven by pressure-tuned intergrain coupling in nanodiamond films”. Zhang G, Zhou Y, Korneychuk S, Samuely T, Liu L, May PW, Xu Z, Onufriienko O, Zhang X, Verbeeck J, Samuely P, Moshchalkov VV, Yang Z, Rubahn H-G, Physical review materials 3, 034801 (2019). http://doi.org/10.1103/PHYSREVMATERIALS.3.034801
Abstract: We report on the pressure-driven superconductor-insulator transition in heavily boron-doped nanodiamond films. By systematically increasing the pressure, we suppress the Josephson coupling between the superconducting nanodiamond grains. The diminished intergrain coupling gives rise to an overall insulating state in the films, which is interpreted in the framework of a parallel-series circuit model to be the result of bosonic insulators with preserved localized intragrain superconducting order parameters. Our investigation opens up perspectives for the application of high pressure in research on quantum confinement and coherence. Our data unveil the percolative nature of the electrical transport in nanodiamond films, and highlight the essential role of grain boundaries in determining the electronic properties of this material.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.926
Times cited: 5
DOI: 10.1103/PHYSREVMATERIALS.3.034801
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“Comment on “Transverse rectification in superconducting thin films with arrays of asymmetric defects””. Silhanek AV, van de Vondel J, Moshchalkov VV, Metlushko V, Ilic B, Misko VR, Peeters FM, Applied physics letters 92 (2008). http://doi.org/10.1063/1.2920078
Keywords: Editorial; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 20
DOI: 10.1063/1.2920078
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“Controlling flux flow dissipation by changing flux pinning in superconducting films”. Grimaldi G, Leo A, Nigro A, Silhanek AV, Verellen N, Moshchalkov VV, Milošević, MV, Casaburi A, Cristiano R, Pace S, Applied physics letters 100, 202601 (2012). http://doi.org/10.1063/1.4718309
Abstract: We study the flux flow state in superconducting materials characterized by rather strong intrinsic pinning, such as Nb, NbN, and nanostructured Al thin films, in which we drag the superconducting dissipative state into the normal state by current biasing. We modify the vortex pinning strength either by ion irradiation, by tuning the measuring temperature or by including artificial pinning centers. We measure critical flux flow voltages for all materials and the same effect is observed: switching to low flux flow dissipations at low fields for an intermediate pinning regime. This mechanism offers a way to additionally promote the stability of the superconducting state. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4718309]
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 33
DOI: 10.1063/1.4718309
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“Guided nucleation of superconductivity on a graded magnetic substrate”. Milošević, MV, Gillijns W, Silhanek AV, Libál A, Peeters FM, Moshchalkov VV, Applied physics letters 96, 032503 (2010). http://doi.org/10.1063/1.3293300
Abstract: We demonstrate the controlled spatial nucleation of superconductivity in a thin film deposited on periodic arrays of ferromagnetic dots with gradually increasing diameter. The perpendicular magnetization of the dots induces vortex-antivortex molecules in the sample, with the number of (anti)vortices increasing with magnet size. The resulting gradient of antivortex density between the dots predetermines local nucleation of superconductivity in the sample as a function of the applied external field and temperature. In addition, the compensation between the applied magnetic field and the antivortices results in an unprecedented enhancement of the critical temperature.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 15
DOI: 10.1063/1.3293300
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“Influence of the morphology on the magneto-transport properties of laser-ablated ultrathin La0.7Ba0.3MnO3 films”. Das A, Gordon I, Wagner P, Cannaerts M, Moshchalkov VV, Bruynseraede Y, Schuddinck W, Van Tendeloo G, Borghs G, Journal of applied physics 90, 1429 (2001). http://doi.org/10.1063/1.1380217
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 2
DOI: 10.1063/1.1380217
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“Preparing polymer films doped with magnetic nanoparticles by spin-coating and melt-processing can induce an in-plane magnetic anisotropy”. Wouters J, Lebedev OI, Van Tendeloo G, Yamada H, Sato N, Vanacken J, Moshchalkov VV, Verbiest T, Valev VK, Journal of applied physics 109, 076105 (2011). http://doi.org/10.1063/1.3572048
Abstract: Faraday rotation has been used to investigate a series of polymer films doped with magnetic iron oxide nanoparticles. The films have been prepared by spin-coating and melt-processing. In each case, upon varying the angle of optical incidence on the films, an in-plane magnetic anisotropy is observed. The effect of such an anisotropy on the Faraday rotation as a function of the angle of optical incidence is verified by comparison with magnetically poled films. These results demonstrate that care should be taken upon analyzing the magnetic behavior of such films on account of the sample preparation techniques themselves being able to affect the magnetization.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 10
DOI: 10.1063/1.3572048
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“The size and structure of Ag particles responsible for surface plasmon effects and luminescence in Ag homogeneously doped bulk glass”. Shestakov MV, Meledina M, Turner S, Tikhomirov VK, Verellen N, Rodríguez VD, Velázquez JJ, Van Tendeloo G, Moshchalkov VV, Journal of applied physics 114, 073102 (2013). http://doi.org/10.1063/1.4818830
Abstract: As-prepared and heat-treated oxyfluoride glasses, co-doped with Ag nanoclusters/nanoparticles, are prepared at 0.15 at. % Ag concentration. The as-prepared glass shows an absorption band in the UV/violet attributed to the presence of amorphous Ag nanoclusters with an average size of 1.1 nm. The luminescence spectra of the untreated glass can also be ascribed to these Ag nanoclusters. Upon heat-treatment, the clusters coalesce into Ag nanoparticles with an average size of 2.3 nm, and the glasses show an extra surface plasmon absorption band in the visible. These particles, however, cease to emit due to ascribing plasmonic properties of bulk silver.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 19
DOI: 10.1063/1.4818830
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“Symmetry and electronic states of Mn2+ in ZnS nanowires with mixed hexagonal and cubic stacking”. Chen L, Kirilenko D, Stesmans A, Nguyen XS, Binnemans K, Goderis B, Vanacken J, Lebedev O, Van Tendeloo G, Moshchalkov VV, Applied physics letters 97, 041918 (2010). http://doi.org/10.1063/1.3475017
Abstract: Electron spin resonance and electronic spectroscopy techniques were used to study the symmetry and electronic structure of Mn2+ dopants in solvothermally synthesized ZnS nanowires. The average diameter of ∼ 5 nm leads to the observable quantum confinement effects in the photoluminescence excitation spectra. The results clearly demonstrate the three symmetry locations of Mn2+ incorporation. Together with the inferred Mn2+ center densities, these data indicate a much higher efficiency of Mn2+ substitution in the nanowire sample with about two times larger diameter.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 5
DOI: 10.1063/1.3475017
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“Luminescence of fixed site Ag nanoclusters in a simple oxyfluoride glass host and plasmon absorption of amorphous Ag nanoparticles in a complex oxyfluoride glass host”. Shestakov MV, Meledina M, Turner S, Baekelant W, Verellen N, Chen X, Hofkens J, Van Tendeloo G, Moshchalkov VV, Proceedings of the Society of Photo-optical Instrumentation Engineers
T2 –, 8th International Conference on Photonics, Devices, and System VI, AUG 27-29, 2014, Prague, CZECH REPUBLIC , Unsp 94501n (2015). http://doi.org/10.1117/12.2068198
Abstract: Ag nanocluster-doped glasses have been prepared by a conventional melt-quenching method. The effect of melt temperature and dwell time on the formation of Ag nanoclusters and Ag nanoparticles in simple host oxyfluoride glasses has been studied. The increase of melt temperature and dwell time results in the dissolution of Ag nanoparticles and substantial red-shift of absorption and photoluminescence spectra of the prepared glasses. The quantum yield of the glasses is similar to 5% and does not depend on melt temperature and dwell time. The prepared glasses may be used as red phosphors or down-conversion layers for solar-cells.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
DOI: 10.1117/12.2068198
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“Polarity-dependent vortex pinning and spontaneous vortex-antivortex structures in superconductor/ferromagnet hybrids”. Bending SJ, Milošević MV, Moshchalkov VV Springer, Berlin, page 299 (2010).
Keywords: H1 Book chapter; Condensed Matter Theory (CMT)
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