ORCID Profile
0000-0002-6590-0136
Current Organisation
University of Oslo
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Publisher: IOP Publishing
Date: 11-1996
Publisher: Elsevier BV
Date: 2010
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2003
Publisher: World Scientific Pub Co Pte Lt
Date: 30-10-1996
DOI: 10.1142/S0217984996001413
Abstract: An additional broad peak in AC losses of Bi 2 Sr 2 Ca 1 Cu 2 O x tapes is observed. Using a new method based on the model of separated finite-size stacks of superconducting layers it is found that this peak reflects the presence of Bi 2 Sr 2 CuO x intergrowth in the s le. Kosterlitz-Thouless transition temperatures of pure Bi 2 Sr 2 Ca 1 Cu 2 O x and intergrowths of different thickness are defined. Our results are confirmed by the direct TEM measurements.
Publisher: American Physical Society (APS)
Date: 23-10-2006
Publisher: Royal Society of Chemistry (RSC)
Date: 1997
DOI: 10.1039/PC9969300363
Publisher: IOP Publishing
Date: 06-1997
Publisher: Elsevier BV
Date: 11-2010
Publisher: IEEE
Date: 05-09-2021
Publisher: IOP Publishing
Date: 06-2006
Publisher: Elsevier BV
Date: 08-1997
Publisher: Elsevier BV
Date: 08-1997
Publisher: Korean Physical Society
Date: 12-09-2008
DOI: 10.3938/JKPS.53.1498
Publisher: Springer Science and Business Media LLC
Date: 1997
Publisher: Elsevier BV
Date: 11-2010
Publisher: Elsevier BV
Date: 08-2004
Publisher: IOP Publishing
Date: 06-2010
Publisher: IOP Publishing
Date: 02-07-2012
Publisher: Springer Science and Business Media LLC
Date: 28-12-2012
Publisher: Elsevier BV
Date: 12-2010
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2007
Publisher: Elsevier BV
Date: 04-1998
Publisher: AIP Publishing
Date: 15-05-1996
DOI: 10.1063/1.362397
Abstract: Multijunction superconducting quantum interferometers can be created spontaneously by intrinsic junctions in granular high-Tc materials, and as a by-product of step-edge technology used to fabricate high-Tc thin film dc superconducting quantum interference devices. The properties of such systems are relatively little known. The theory predicts multivalued dependence of critical current Ic on applied magnetic flux Φe and the appearance of different stationary ‘‘phase states’’ related to different possible relationships between the phases of superconducting order parameter in in idual junctions. We report on the measurements performed on a (2×2) quantum interferometer, comprising a series array of two underd ed all-niobium tunnel junctions in each parallel arm. Experimental results closely follow the theoretical predictions and reveal several instability regions, in which noise generation takes place. These findings can possibly be related to the random telegraph noise observed in high-Tc materials.
Publisher: IEEE
Date: 11-09-2022
Publisher: IEEE
Date: 05-09-2021
Publisher: Elsevier BV
Date: 11-2000
Publisher: IOP Publishing
Date: 03-2011
Publisher: IOP Publishing
Date: 03-2011
Publisher: Elsevier BV
Date: 12-2019
Publisher: Elsevier BV
Date: 11-2000
Publisher: IOP Publishing
Date: 29-10-2010
Publisher: IOP Publishing
Date: 10-07-2017
Publisher: IOP Publishing
Date: 06-05-2008
Publisher: Elsevier BV
Date: 1993
Publisher: Elsevier BV
Date: 11-1993
Publisher: IOP Publishing
Date: 23-08-2007
Publisher: Springer Singapore
Date: 2020
Publisher: IOP Publishing
Date: 02-09-2013
Publisher: AIP Publishing
Date: 15-01-2001
DOI: 10.1063/1.1341229
Publisher: Springer Science and Business Media LLC
Date: 03-03-2009
Publisher: IEEE
Date: 09-11-2020
Publisher: American Physical Society (APS)
Date: 27-05-2005
Publisher: Springer Nature Singapore
Date: 2019
Publisher: Pleiades Publishing Ltd
Date: 09-2003
DOI: 10.1134/1.1630131
Publisher: American Physical Society (APS)
Date: 20-04-2007
Publisher: Springer Nature Singapore
Date: 2019
Publisher: Frontiers Media SA
Date: 10-08-2023
DOI: 10.3389/FNANO.2023.1216921
Abstract: Metal nanoparticles have attracted considerable attention due to their astounding potential for a wide range of commercial applications. From targeted drug delivery and antimicrobial agents to electronics, metal nanoparticles seem to have immeasurable prospects in all areas of science. However, modern industrial production frequently involves complex procedures, large amounts of energy, utilizes strong chemical solvents, or produces hazardous waste. Biological synthesis has been proposed as an alternative for simpler, inexpensive, and more eco-friendly metal nanoparticle production. Microorganisms possess multiple mechanisms to transport, regulate and bind metal ions that may result in the biosynthesis of nanoparticles. They can synthesize even complex bimetallic nanoparticles, which are difficult to produce with normal chemical and physical processes. A better understanding of bacteria-metal interactions might thus pave the way for a wide array of industrial applications. This review will summarize the current methods for metal nanoparticle synthesis, with a focus on the microbial (bio) synthesis of nanoparticles. We will describe the general mechanisms of bacteria-metal ion interactions, including cellular uptake and the subsequent reduction into nanoparticles. Protocols for the production of metal-based nanoparticles of relevant elements with different bacterial strains are compiled and the current challenges in bacterial synthesis of metal nanoparticles in the industry are discussed.
Publisher: Elsevier BV
Date: 02-2017
Publisher: IEEE
Date: 09-11-2020
Publisher: American Physical Society (APS)
Date: 07-11-2005
Publisher: Frontiers Media SA
Date: 18-11-2022
DOI: 10.3389/FNANO.2022.1062608
Abstract: Palladium (Pd) is a key component of many catalysts. Nanoparticles (NPs) offer a larger surface area than bulk materials, and with Pd cost increasing 5-fold in the last 10 years, Pd NPs are in increasing demand. Due to novel or enhanced physicochemical properties that Pd NPs exhibit at the nanoscale, Pd NPs have a wide range of applications not only in chemical catalysis, but also for ex le in hydrogen sensing and storage, and in medicine in photothermal, antibacterial, and anticancer therapies. Pd NPs, on the industrial scale, are currently synthesized using various chemical and physical methods. The physical methods require energy-intensive processes that include maintaining high temperatures and/or pressure. The chemical methods usually involve harmful solvents, hazardous reducing or stabilizing agents, or produce toxic pollutants and by-products. Lately, more environmentally friendly approaches for the synthesis of Pd NPs have emerged. These new approaches are based on the use of the reducing ability of phytochemicals and other biomolecules to chemically reduce Pd ions and form NPs. In this review, we describe the common physical and chemical methods used for the synthesis of Pd NPs and compare them to the plant- and bacteria-mediated biogenic synthesis methods. As size and shape determine many of the unique properties of Pd NPs on the nanoscale, special emphasis is given to the control of these parameters, clarifying how they impact current and future applications of this exciting nanomaterial.
Publisher: AIP Publishing
Date: 14-01-2013
DOI: 10.1063/1.4775693
Abstract: Combined voltage and magneto-optical study of magnetic flux flow in superconducting NbN films is reported. The nanosecond-scale voltage pulses appearing during thermomagnetic avalanches have been recorded in films partially coated by a metal layer. Simultaneous magneto-optical imaging and voltage measurements allowed the pulses to be associated with in idual flux branches penetrating the superconductor below the metal coating. From detailed characteristics of pulse and flux branches, the electrical field in the superconductor is found to be in the range of 5-50 kV/m, while the propagation speed of the avalanche during its final stage is found to be close to 5 km/s.
Publisher: Elsevier BV
Date: 07-1993
Publisher: IEEE
Date: 09-2016
Publisher: IEEE
Date: 09-2018
Publisher: Elsevier BV
Date: 08-2014
Publisher: Elsevier BV
Date: 10-2019
Publisher: World Scientific Pub Co Pte Lt
Date: 20-05-2003
DOI: 10.1142/S0217984903005639
Abstract: We report on experimental investigation of the effect of flux compression in superconducting YBa 2 Cu 3 O x (YBCO) films and YBCO/CMR (Colossal Magnetoresistive) multilayers. The flux compression produces positive magnetic moment (m) upon the cooling in a field from above to below the critical temperature. We found effect of compression in all measured films and multilayers. In accordance with theoretical calculations, m is proportional to applied magnetic field. The litude of the effect depends on the cooling rate, which suggests the inhomogeneous cooling as its origin. The positive moment is always very small, a fraction of a percent of the ideal diamagnetic response. A CMR layer in contact with HTS decreases the litude of the effect. The flux compression weakly depends on s le size, but sensitive to its form and topology. The positive magnetic moment does not appear in bulk s les at low rates of the cooling. Our results show that the main features of the flux compression are very different from those in Paramagnetic Meissner effect observed in bulk high temperature superconductors and Nb disks.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2016
Publisher: Wiley
Date: 29-01-2004
Publisher: IEEE
Date: 09-11-2020
Publisher: Elsevier BV
Date: 09-2007
Publisher: Elsevier BV
Date: 02-2018
Publisher: Elsevier BV
Date: 12-1994
Publisher: Elsevier BV
Date: 05-1992
Publisher: IOP Publishing
Date: 08-03-2017
Publisher: IOP Publishing
Date: 06-2010
Publisher: Springer Science and Business Media LLC
Date: 27-03-2020
DOI: 10.1038/S41598-020-62601-Y
Abstract: Scaling behaviour of dynamically driven vortex avalanches in superconducting YBa 2 Cu 3 O 7− δ films deposited on tilted crystalline substrates has been observed using quantitative magneto-optical imaging. Two films with different tilt angles are characterized by the probability distributions of avalanche size in terms of the number of moving vortices. It is found in both s les that these distributions follow power-laws over up to three decades, and have exponents ranging between 1.0 and 1.4. The distributions also show clear finite-size scaling, when the system size is defined by the depth of the flux penetration front – a signature of self-organized criticality. A scaling relation between the avalanche size exponent and the fractal dimension, previously derived theoretically from conservation of the number of magnetic vortices in the stationary state and shown in numerical simulations, is here shown to be satisfied also experimentally.
Publisher: IOP Publishing
Date: 10-1998
Publisher: AIP Publishing
Date: 12-11-2007
DOI: 10.1063/1.2814060
Abstract: Minute additions of a combination of Dy2O3 and B4C have been used to enhance both pinning and upper critical field in MgB2. A delicate balance of Dy2O3 and B4C additions is required to improve properties. The Dy2O3 nanoparticles react with B to form 10–15nm DyB4 nanoparticles, while B4C supplies carbon into the MgB2 crystal lattice and increases the upper critical field. The optimum level of Dy2O3 and B4C additions is ∼0.5wt% of Dy2O3 and 0.04wt% of B4C, yielding a Jc (20K) of 105Acm−2 at 2.7T.
Publisher: Elsevier BV
Date: 1997
Publisher: Elsevier BV
Date: 2021
Publisher: MDPI AG
Date: 24-08-2022
DOI: 10.3390/EN15176138
Abstract: Hydrogen as an energy carrier is a promising alternative to fossil fuels, and it becomes more and more popular in developed countries as a carbon-free fuel. The low boiling temperature of hydrogen (20 K or −253.15 °C) provides a unique opportunity to implement superconductors with a critical temperature above 20 K such as MgB2 or high-temperature superconductors. Superconductors increase efficiency and reduce the loss of energy, which could compensate for the high price of LH2 to some extent. Norway is one of the pioneer countries with adequate infrastructure for using liquid hydrogen in the industry, especially in marine technology where a superconducting propulsion system can make a remarkable impact on its economy. Using superconductors in the motor of a propulsion system can increase its efficiency from 95% to 98% when the motor operates at full power. The difference in efficiency is even greater when the motor does not work at full power. Here, we survey the applications of liquid hydrogen and superconductors and propose a realistic roadmap for their synergy, specifically for the Norwegian economy in the marine industry.
Publisher: IOP Publishing
Date: 07-1997
Publisher: Springer Science and Business Media LLC
Date: 18-12-2019
Publisher: World Scientific Pub Co Pte Lt
Date: 20-05-2003
DOI: 10.1142/S0217984903005524
Abstract: We report a range of experiments designed to test the efficacy of spin polarized injection from colossal magnetoresistive material (CMR) into high temperature superconductors (HTS). These include traditional transport measurements, studies of CMR/YBCO contacts, measurements of penetration depth and studies of the effect of spin-injection on the critical state of square thin films and rings. We have used pulsed currents to minimize heating and have made comparisons with the non-magnetic homologue of CMR LaNiO 3 . Our experiments provide evidence that there is a measurable effect, but that it is small and mainly confined to 10–20 nm of the YBCO surface. Current gain of about 0.2 has been observed.
Publisher: AIP Publishing
Date: 15-12-2005
DOI: 10.1063/1.2149489
Abstract: We report studies of cuprate∕manganate bilayers deposited onto SrTiO3 substrates by laser ablation. A significant difference in the properties of the in idual layers is observed depending on the material deposition sequence. The material which is on the bottom of the multilayer shows worse properties, e.g., a critical temperature of ∼60K for YBa2Cu3O7−δ (YBCO) covered by La2∕3Ca1∕3MnO3 (LCMO) as opposed to a value of ∼90K when YBCO is on the top. Similarly, the LCMO film has its metal-insulator transition temperature shifted below the Curie temperature when the YBCO is on top. We argue that the effect is not due to degraded crystal quality, cation substitution, or an electronic interaction, but results from a reduction in the oxygen content of the underlying layer. We find that this reduction is a feature of the complete LCMO layer and is not associated with the constituent elements. We discuss possible explanations for this effect.
Publisher: IEEE
Date: 09-2017
Publisher: AIP Publishing
Date: 07-2014
DOI: 10.1063/1.4887061
Abstract: The evolution of flux distribution in MgB2 single crystals during their remagnetization was imaged with magneto-optical technique. Meissner holes, formed as the areas where the annihilation of vortices and antivortices takes place, were found at the boundary between oppositely magnetized parts of the crystal. Gradient of magnetic induction in the vicinity of Meissner holes was found to be enhanced. Finger-like structures of convex shape, formed during the penetration of magnetic flux inside the crystal, were observed and explained as an effect of inhomogeneous pinning and demagnetizing field redistribution in the s le.
Publisher: World Scientific Pub Co Pte Lt
Date: 20-05-2003
DOI: 10.1142/S0217984903005664
Abstract: We report on a dynamical effect in YBa 2 Cu 3 O x (YBCO) films and YBCO/CMR (Colossal Magnetoresistive) multilayers, in which variations in the magnetic field sweep rate can change, or reverse the sign of, the magnetic moment. The effect occurs in thin films having a low critical current density, either intrinsically or as a result of operation near the critical temperature. We attribute this effect to the large demagnetizing field present in the films, leading to a relaxation in the non-equilibrium vortex distribution, in which current near the edge of the film changes direction. We have investigated this effect in a variety of systems by magnetometery, and provide some magneto-optical evidence of its mechanism.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2011
Publisher: IEEE
Date: 11-09-2022
Publisher: Elsevier BV
Date: 2014
Publisher: Elsevier BV
Date: 07-2022
Publisher: IEEE
Date: 05-09-2021
Publisher: AIP Publishing
Date: 03-2016
DOI: 10.1063/1.4943549
Abstract: Thermomagnetic avalanches in superconducting films propagating extremely fast while forming unpredictable patterns, represent a serious threat for the performance of devices based on such materials. It is shown here that a normal-metal frame surrounding a selected region inside the film area can provide efficient protection from the avalanches during their propagation stage. Protective behavior is confirmed by magneto-optical imaging experiments on NbN films equipped with Cu and Al frames, and also by performing numerical simulations. Experimentally, it is found that while conventional flux creep is not affected by the frames, the dendritic avalanches are partially or fully screened by them. The level of screening depends on the ratio of the sheet conductance of the metal and the superconductor in the resistive state, and for ratios much larger than unity the screening is very efficient.
Publisher: IOP Publishing
Date: 06-2006
Publisher: International Association of Advanced Materials
Date: 12-2017
Publisher: Springer Science and Business Media LLC
Date: 06-10-2010
Publisher: IEEE
Date: 11-09-2022
Publisher: IEEE
Date: 09-11-2020
Publisher: IOP Publishing
Date: 17-02-2009
Publisher: Elsevier BV
Date: 07-1999
Publisher: Korean Physical Society
Date: 05-2019
DOI: 10.3938/JKPS.74.984
Publisher: Elsevier BV
Date: 09-1993
Publisher: Informa UK Limited
Date: 11-1994
Publisher: IEEE
Date: 09-2017
Publisher: World Scientific Pub Co Pte Lt
Date: 20-05-2003
DOI: 10.1142/S0217984903005536
Abstract: It has recently been proposed that if phase incoherent preformed pairs exist above critical temperature (T c ), Andreev reflection should be observable above T c too. A distinctive feature of Andreev reflection is a zero bias conductance peak (ZBCP) in the conductance/voltage (G/V) characteristics. We have performed an extensive search for the ZBCP in HTS/normal-metal planar junctions including s les which have been annealed in Argon in an attempt to induce underdoping and enhancement of the pseudogap temperature. We have observed a maximum in the G/V characteristics above T c in a number of s les and contact configurations. In some s les this behavior persists up to room temperature, but has a very broad voltage scale, much greater than the gap voltage. In YBa 2 Cu 3 O x / Au and YBa 2 Cu 3 O x / Ag contacts the form and litude of the ZBCP is close to the theoretical prediction, but the origin of this effect could also be in s le heating. One particularly curious result comes from an Au/LSMO/YBCO s le that shows a clear sub-gap ZBCP over the temperature range 15–266 K.
Publisher: IEEE
Date: 09-2017
Publisher: IOP Publishing
Date: 17-03-2009
Publisher: Elsevier BV
Date: 2012
Publisher: Springer Science and Business Media LLC
Date: 02-10-2010
Publisher: AIP Publishing
Date: 02-2003
DOI: 10.1063/1.1542409
Abstract: The complex differential susceptibility of a YBCO film and YBCO–STO–LCMO structures with different thicknesses of the STO layer (0, 2, and 7 nm) is investigated. It is shown that for a YBCO–LCMO structure the temperature of the superconducting transition Tonset and the critical current density jc are observed to decrease in comparison with a pure YBCO film. In a YBCO–STO–LCMO structure, on the contrary, Tonset increases, while jc increases for the structure with the 2 nm thickness of STO and decreases for that with 7 nm of STO. It is conjectured that there is a change of the vortex pinning mechanism as the temperature is lowered.
Publisher: American Physical Society (APS)
Date: 23-02-2015
Publisher: IEEE
Date: 09-2019
Publisher: IOP Publishing
Date: 17-07-2004
Publisher: Springer Science and Business Media LLC
Date: 09-07-2009
Publisher: AIP Publishing
Date: 06-2009
DOI: 10.1063/1.3151990
Abstract: The mixed-state superconducting properties of bulk MgB2+2at.%TiO2 and +8at.%SiC, prepared by in situ solid state reaction, are investigated. Analysis of the mixed-state parameters, such as the upper critical field, the coherence length, and the Ginzburg-Landau parameter, proves that MgB2+2at.%TiO2 is a high-κ type-II superconductor in the dirty limit, while MgB2+8at.%SiC corresponds to that in the moderately clean limit. It is shown that the grain-boundary pinning realized in fine-grained doped MgB2 polycrystals is of the anisotropic rather than the electron-scattering type. The field-cooled temperature dependences of the magnetic moment reveal a transition of the s les to the paramagnetic state at certain applied magnetic fields, which is treated as manifestation of the paramagnetic Meissner effect. The experimental results are discussed on the base of modern theoretical approaches.
Publisher: IOP Publishing
Date: 17-07-2004
Publisher: Elsevier BV
Date: 11-1999
Publisher: American Physical Society (APS)
Date: 03-12-2004
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 08-1997
Publisher: Elsevier BV
Date: 11-2000
Publisher: Elsevier BV
Date: 07-2009
Publisher: World Scientific Pub Co Pte Lt
Date: 20-05-2003
DOI: 10.1142/S0217984903005706
Abstract: We report magnetization and transport measurements on MgB 2 in the form of powder, bulk ceramic, wire made by diffusion of Mg into B, and pulsed laser deposited thin films. Ceramic and wire forms show strong intergranular links, and we compare their properties with those of single crystals. The powder shows a magnetic moment versus temperature curve that scales with the moment at the lowest temperature, consistent with a distribution of grain sizes, on the scale of the London penetration depth. The ceramics shows anisotropic magnetization behavior, which is probably a consequence of the anisotropic compressional forces used in its manufacture. In both powder and ceramic, we have observed intriguing negative magnetic moments and steps therein upon changing temperature, well above the obvious superconducting transition. These could indicate small amounts of some higher T c superconducting phases. However, magnetization loops measured in this regime show ferromagnetism, which we suggest is the origin of the magnetic properties above T c . The wire shows a linear diamagnetic response up to an H c1 of 236 Oe, has a normal state resistivity of 2.6 × 10 -6 Ω·cm just above the transition and a resistivity ratio of 21, which is also similar to those of single crystals. The thin films are composed of large crystalline platelets, have a T c of 35 K, and are diamagnetic.
Publisher: Elsevier BV
Date: 10-2009
Publisher: Institute of Physics, Polish Academy of Sciences
Date: 07-1997
Publisher: Elsevier BV
Date: 06-2009
Publisher: Elsevier BV
Date: 1999
Publisher: IOP Publishing
Date: 20-03-2014
Publisher: Wiley
Date: 16-03-1994
Publisher: IOP Publishing
Date: 23-03-2009
Publisher: Springer Science and Business Media LLC
Date: 25-09-2010
Publisher: IOP Publishing
Date: 30-09-2013
Publisher: IOP Publishing
Date: 06-03-2012
Publisher: AIP Publishing
Date: 23-05-2002
DOI: 10.1063/1.1480888
Abstract: We report the influence of the magnetic state of thin films of La0.7Ca0.3MnO3 (LCMO) on the superconducting order parameter in LCMO/YBa2Cu3O7−δ (YBCO) thin-film bilayers. We find that the number density of Cooper pairs is enhanced at the coercive field of the LCMO layer relative to that where the magnetic moment is saturated. This effect is at most ∼10% and is only observable within a few degrees of the superconducting transition temperature. Experiments with thin SrTiO3 layers between the LCMO and YBCO layers provide strong evidence that the effect is a consequence of the spin-polarized nature of the electrons at the interface, rather than a direct magnetic effect.
Publisher: IOP Publishing
Date: 06-2006
Publisher: Elsevier BV
Date: 10-2010
Publisher: Elsevier BV
Date: 07-2001
Publisher: IEEE
Date: 05-09-2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
Publisher: IEEE
Date: 09-2016
Publisher: IEEE
Date: 09-2016
Publisher: IOP Publishing
Date: 10-1998
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Pavlo Mikheenko.