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Your search keyword '"Paturi, Petriina"' showing total 233 results
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233 results on '"Paturi, Petriina"'

52. Uniform size Y-Ba-Cu-O particles obtained by laser ablation and post-annealing

Author

Paturi, Petriina, Huhtinen, Hannu, Laiho, Reino, and Raittila, Jussi

Subjects
High temperature superconductors -- Research, Semiconductor films -- Research, Business, Electronics, Electronics and electrical industries
Abstract

A new study investigates the effect of post-annealing on the distributions and sizes of single Y-Ba-Cu-O particles on SrTiO3 substrates.

Published
2001

53. High Critical Current Density and Enhanced Pinning in Superconducting Films of YBa2Cu3O7−δ Nanocomposites with Embedded BaZrO3, BaHfO3, BaTiO3, and SrZrO3 Nanocrystals

Author

Díez-Sierra, Javier, primary, López-Domínguez, Pedro, additional, Rijckaert, Hannes, additional, Rikel, Mark, additional, Hänisch, Jens, additional, Khan, Mukarram Zaman, additional, Falter, Martina, additional, Bennewitz, Jan, additional, Huhtinen, Hannu, additional, Schäfer, Sebastian, additional, Müller, Robert, additional, Schunk, Stephan Andreas, additional, Paturi, Petriina, additional, Bäcker, Michael, additional, De Buysser, Klaartje, additional, and Van Driessche, Isabel, additional

Published
2020
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55. Self-assembled nanorods in YBCO matrix - a computational study of their effects on critical current anisotropy

Author

Rivasto, Elmeri, Khan, Mukarram Zaman, Malmivirta, Mika, Rijckaert, Hannes, Aye, Moe Moe, Hynninen, Teemu, Huhtinen, Hannu, Van Driessche, Isabel, and Paturi, Petriina

Subjects
Chemistry, Electronic properties and materials, Surfaces, interfaces and thin films, Physics and Astronomy, Condensed Matter::Superconductivity, lcsh:R, Computational methods, lcsh:Medicine, lcsh:Q, FILMS, lcsh:Science, Article, Superconducting properties and materials
Abstract

In order to understand how the doping with self-assembled nanorods of different sizes and concentrations as well as applied magnetic fields affect the critical current anisotropy in YBa2Cu3O7−x (YBCO) thin films close to YBCO c-axis, we present an extensive and systematic computational study done by molecular dynamics simulation. The simulations are also used to understand experimentally measured J c (θ) curves for BaHfO3, BaZrO3 and BaSnO3 doped YBCO thin films with the help of nanorod parameters obtained from transmission electron microscopy measurements. Our simulations reveal that the relation between applied and matching field plays a crucial role in the formation of J c (θ)-peak around YBCO c-axis (c-peak) due to vortex-vortex interactions. We also find how different concentrations of different size nanorods effect the shape of the c-peak and explain how different features, such as double c-peak structures, arise. In addition to this, we have quantitatively explained that, even in an ideal superconductor, the overdoping of nanorods results in decrease of the critical current. Our results can be widely used to understand and predict the critical current anisotropy of YBCO thin films to improve and develop new pinscapes for various transport applications.

Published
2019

56. Iron oxide nanocomposite magnets produced by partial reduction of strontium hexaferrite

Author

Tikkanen Jussi and Paturi Petriina

Subjects
Physics, QC1-999
Abstract

Isotropic bulk nanocomposite permanent magnets were produced with strontium hexaferrite, SrO·6Fe2O3, and magnetite, Fe3O4, as the magnetically hard and soft components. A novels synthesis scheme based on the partial reduction of SrO·6Fe2O3 was employed. In two parallel experiments, nano- and microcrystalline SrO·6Fe2O3 particles were compacted into pellets along with a controlled, understoichiometric amount of potato starch as a reducing agent. The pellets were then sintered in a passive atmosphere. Based on XRD and room temperature magnetic hysteresis measurements, it was concluded that a fraction of the SrO·6Fe2O3 input material had been reduced into Fe3O4. In comparison with pure SrO·6Fe2O3 control pellets, these composites exhibited maximum energy product increases in excess of 5 % due to remanence boosting. The improvement of magnetic properties was attributed to an efficient exchange spring coupling between the magnetic phases. Interestingly, as the synthesis scheme also worked for microcrystalline SrO·6Fe2O3 , the method could presumably be adapted to yield crystallographically oriented bulk nanocomposite magnets.

Published
2014
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58. The effect of film thickness on the magnetic and magneto-transport properties of Sr2FeMoO6 thin films

Author

Huhtinen Hannu, Majumdar Sayani, Saloaro Minnamari, and Paturi Petriina

Subjects
Physics, QC1-999
Abstract

Magnetoresistive Sr2FeMoO6 thin films were grown by pulsed laser deposition with three different thicknesses 150 nm, 270 nm and 500 nm. Structural, magnetic and magneto-transport properties of the films were measured. Structural properties showed that impurity phases are formed when the film thickness exceed limiting thickness over 300 nm. Otherwise no major differences were observed in structural and magnetic properties between the films. The semiconductive upturn was observed in all ρ(T) curves, but it was notably smaller for the two thickest films. At 350 K the magnetoresistive (MR) behaviour was very similar for all the films, but at 10 K the negative MR was clearly largest for the thickest film and also the shape of the curve in low fields deviated from others.

Published
2013
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64. Weak links inYBCO nanopowder

Author

Paturi, Petriina, Raittila, Jussi, and Huhtinen, Hannu

Subjects
Magnetization -- Analysis, Superconductivity -- Analysis, Superconductors -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Investigating the preparation of two batches of YBCO powder and determine their magnetic properties with a SQUID-magnetometer and microwave absorption measurement is discussed. It is found that adding annealing times strengthens the interparticle weak links and reduces their number, which is observed as a higher critical field of the weak links and less curvature in the field dependency of the magnetization is presented.

Published
2003

65. Solar UV index and UV dose determination with photochromic hackmanites : from the assessment of the fundamental properties to the device

Author

Norrbo, Isabella, Curutchet, Antton, Kuusisto, Ari, Makela, Jaakko, Laukkanen, Pekka, Paturi, Petriina, Laihinen, Tero, Sinkkonen, Jari, Wetterskog, Erik, Mamedov, Fikret, Le Bahers, Tangui, Lastusaari, Mika, Norrbo, Isabella, Curutchet, Antton, Kuusisto, Ari, Makela, Jaakko, Laukkanen, Pekka, Paturi, Petriina, Laihinen, Tero, Sinkkonen, Jari, Wetterskog, Erik, Mamedov, Fikret, Le Bahers, Tangui, and Lastusaari, Mika

Abstract

Extended exposure to sunlight or artificial UV sources is a major cause of serious skin and eye diseases such as cancer. There is thus a great need for convenient materials for the easy monitoring of UV doses. While organic photochromic molecules are tunable for responses under different wavelengths of UV radiation, they suffer from rather poor durability because the color changes involve drastic changes in molecular structure. Inorganic materials, on the other hand, are durable, but they have lacked tunability. Here, by combining computational and empirical data, we confirm the mechanism of coloration in the hackmanites, nature-based materials, and introduce a new technique called thermotenebrescence. With knowledge of the mechanism, we show that we can control and thus tune the energy of electronic states of synthetic hackmanites (Na,M)(8)Al6Si6O24(Cl,S)(2) so that their body color is sensitive to the solar UV index as well as UVA, UVB or UVC radiation levels. Finally, we demonstrate that it is possible to use images taken with an inexpensive cell phone to quantify the radiation dose or UV index. The hackmanite materials thus show great potential for use in portable healthcare both in everyday life and in laboratories.

Published
2018
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66. Enhanced flux pinning in YBCO multilayer films with BCO nanodots and segmented BZO nanorods

Author

Malmivirta, Mika, Rijckaert, Hannes, Paasonen, Ville, Huhtinen, Hannu, Hynninen, Teemu, Jha, Rajveer, Awana, Veerpal Singh, Van Driessche, Isabel, and Paturi, Petriina

Subjects
HIGH-TEMPERATURE SUPERCONDUCTORS, Chemistry, THIN-FILMS, MOLECULAR-DYNAMICS, CURRENT DENSITIES, YBA2CU3O7-X FILMS, Condensed Matter::Superconductivity, lcsh:R, lcsh:Medicine, lcsh:Q, lcsh:Science, VORTICES, Article
Abstract

The flux pinning properties of the high temperature superconductor YBa2Cu3O7−δ (YBCO) have been conventionally improved by creating both columnar and dot-like pinning centres into the YBCO matrix. To study the effects of differently doped multilayer structures on pinning, several samples consisting of a multiple number of individually BaZrO3 (BZO) and BaCeO3 (BCO) doped YBCO layers were fabricated. In the YBCO matrix, BZO forms columnar and BCO dot-like defects. The multilayer structure improves pinning capability throughout the whole angular range, giving rise to a high critical current density, J c. However, the BZO doped monolayer reference still has the most isotropic J c. Even though BZO forms nanorods, in this work the samples with multiple thin layers do not exhibit a c axis peak in the angular dependence of J c. The angular dependencies and the approximately correct magnitude of J c were also verified using a molecular dynamics simulation.

Published
2017

67. High Critical Current Density and Enhanced Pinning in Superconducting Films of YBa2Cu3O7-δ Nanocomposites with Embedded BaZrO3, BaHfO3, BaTiO3, and SrZrO3 Nanocrystals.

Author

Díez-Sierra, Javier, López-Domínguez, Pedro, Rijckaert, Hannes, Rikel, Mark, Hänisch, Jens, Khan, Mukarram Zaman, Falter, Martina, Bennewitz, Jan, Huhtinen, Hannu, Schäfer, Sebastian, Müller, Robert, Schunk, Stephan Andreas, Paturi, Petriina, Bäcker, Michael, De Buysser, Klaartje, and Van Driessche, Isabel

Published
2020
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70. Pair Distribution Function Analysis of ZrO2 Nanocrystals and Insights in the Formation of ZrO2-YBa2Cu3O7 Nanocomposites

Author

Rijckaert, Hannes, primary, De Roo, Jonathan, additional, Van Zele, Matthias, additional, Banerjee, Soham, additional, Huhtinen, Hannu, additional, Paturi, Petriina, additional, Bennewitz, Jan, additional, Billinge, Simon, additional, Bäcker, Michael, additional, De Buysser, Klaartje, additional, and Van Driessche, Isabel, additional

Published
2018
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71. Solar UV index and UV dose determination with photochromic hackmanites: from the assessment of the fundamental properties to the device

Author

Norrbo, Isabella, primary, Curutchet, Antton, additional, Kuusisto, Ari, additional, Mäkelä, Jaakko, additional, Laukkanen, Pekka, additional, Paturi, Petriina, additional, Laihinen, Tero, additional, Sinkkonen, Jari, additional, Wetterskog, Erik, additional, Mamedov, Fikret, additional, Le Bahers, Tangui, additional, and Lastusaari, Mika, additional

Published
2018
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72. A Structural Optimization of Ferrite/YBCO Bilayers

Author

Malmivirta, Mika, Jyrinki, Jaakko, Huhtinen, Hannu, Pan, Alexey V, Rubanov, Sergey, Jha, R, Awana, V P, Paturi, Petriina, Malmivirta, Mika, Jyrinki, Jaakko, Huhtinen, Hannu, Pan, Alexey V, Rubanov, Sergey, Jha, R, Awana, V P, and Paturi, Petriina

Abstract

Magnetic particles can be used to take advantage of both defect and magnetic pinning in high-temperature superconductors. We combined layers of ferrite+cerium oxide with YBCO to see their effect both on the structure of the YBCO and on flux pinning. The deposition temperature of the ferrite greatly affects its structure and also the saturation magnetization. Combined with YBCO, the magnetic layer distorts the structure of YBCO, although, for example, the critical temperature remains rather unchanged. According to the structural results achieved here, the magnetic pinning layer is best positioned on the top of YBCO. This way, an improvement in Jc(B) is seen in all the field range, and also, a clear improvement of the accommodation field was measured. However, it does not play a huge role whether the ferrite is CoFe2O4, NiFe2O4, or ZnFe2O4, all mixed with CeO2.

Published
2017

73. Optimizing Nanocomposites through Nanocrystal Surface Chemistry: Superconducting YBa2Cu3O7 Thin Films via Low-Fluorine Metal Organic Deposition and Preformed Metal Oxide Nanocrystals

Author

Rijckaert, Hannes, primary, Pollefeyt, Glenn, additional, Sieger, Max, additional, Hänisch, Jens, additional, Bennewitz, Jan, additional, De Keukeleere, Katrien, additional, De Roo, Jonathan, additional, Hühne, Ruben, additional, Bäcker, Michael, additional, Paturi, Petriina, additional, Huhtinen, Hannu, additional, Hemgesberg, Maximilian, additional, and Van Driessche, Isabel, additional

Published
2017
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77. Comparison of Chemical, Electronic, and Optical Properties of Mg-Doped AlGaN

Author

Mäkelä, Jaakko, primary, Tuominen, Marjukka, additional, Nieminen, Tiina, additional, Yasir, Muhammad, additional, Kuzmin, Mikhail, additional, Dahl, Johnny, additional, Punkkinen, Marko, additional, Laukkanen, Pekka, additional, Kokko, Kalevi, additional, Osiecki, Jacek, additional, Schulte, Karina, additional, Lastusaari, Mika, additional, Huhtinen, Hannu, additional, and Paturi, Petriina, additional

Published
2016
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80. Toward Versatile Sr2FeMoO6-Based Spintronics by Exploiting Nanoscale Defects

Author

Saloaro, Minnamari, primary, Hoffmann, Martin, additional, Adeagbo, Waheed A., additional, Granroth, Sari, additional, Deniz, Hakan, additional, Palonen, Heikki, additional, Huhtinen, Hannu, additional, Majumdar, Sayani, additional, Laukkanen, Pekka, additional, Hergert, Wolfram, additional, Ernst, Arthur, additional, and Paturi, Petriina, additional

Published
2016
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87. Effect of Partial Crystallization on the Structural and Luminescence Properties of Er3+-Doped Phosphate Glasses.

Author

Lopez-Iscoa, Pablo, Salminen, Turkka, Hakkarainen, Teemu, Petit, Laeticia, Janner, Davide, Boetti, Nadia G., Lastusaari, Mika, Pugliese, Diego, Paturi, Petriina, and Milanese, Daniel

Subjects
PHOSPHATE glass, CERAMICS, NUCLEATION, LUMINESCENCE, CRYSTALLIZATION
Abstract

Er-doped phosphate glass ceramics were fabricated by melt-quenching technique followed by a heat treatment. The effect of the crystallization on the structural and luminescence properties of phosphate glasses containing Al2O3, TiO2, and ZnO was investigated. The morphological and structural properties of the glass ceramics were characterized by Field Emission-Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), and micro-Raman spectroscopy. Additionally, the luminescence spectra and the lifetime values were measured in order to study the influence of the crystallization on the spectroscopic properties of the glasses. The volume ratio between the crystal and the glassy phases increased along with the duration of the heat treatment. The crystallization of the glass ceramics was confirmed by the presence of sharp peaks in the XRD patterns and different crystal phases were identified depending on the glass composition. Sr(PO3)2 crystals were found to precipitate in all the investigated glasses. As evidenced by the spectroscopic properties, the site of the Er3+ ions was not strongly affected by the heat treatment except for the fully crystallized glass ceramic which does not contain Al2O3, TiO2, and ZnO. An increase of the lifetime was also observed after the heat treatment of this glass. Therefore, we suspect that the Er3+ ions are incorporated in the precipitated crystals only in this glass ceramic [ABSTRACT FROM AUTHOR]

Published
2017
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91. Paturi, Petriina

Author

Paturi, Petriina and Paturi, Petriina

Published
2012

92. Defining B-c, B* and B-phi for YBCO Thin Films

Author

Paturi, Petriina, Irjala, Matti, Abrahamsen, Asger Bech, Huhtinen, Hannu, Paturi, Petriina, Irjala, Matti, Abrahamsen, Asger Bech, and Huhtinen, Hannu

Abstract

The accommodation field, B* , is generally defined to be the field at which the cross over from single vortex pinning to collective pinning occurs. It is determined from magnetization curves as the point where the J c plateau ends and it used as a convenient way of comparing the pinning properties of superconducting films. Similarly, the characteristic field, B c, can be obtained from magneto-optical (MO) images from when the flux fronts meet in the middle of the film. The matching field, B phi, at which there is one vortex line per pinning site, is sometimes thought to be the same as B*, but in BaZrO3-doped YBa2Cu3O7 films the calculated B phi is much higher than the observed B*. B phi can be determined from angular dependent transport measurements. All of the field values correspond to some special case in the flux pinning in the film and relate to J c. In this work we have determined B c, B* and B phi for different kinds of YBCO films using MO, magnetization and transport measurements to reveal the deeper meaning of the special fields.

Published
2009

95. Ferromagnetism induced in ZnO nanorods by morphology changes under a nitrogen–carbon atmosphere

Author

Sieber, Brigitte, primary, Salonen, Jarno, additional, Makila, Ermei, additional, Tenho, Mikko, additional, Heinonen, Markku, additional, Huhtinen, Hannu, additional, Paturi, Petriina, additional, Kukk, Edwin, additional, Perry, Guillaume, additional, Addad, Ahmed, additional, Moreau, Myriam, additional, Boussekey, Luc, additional, and Boukherroub, Rabah, additional

Published
2013
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96. The phase diagram of YBCo nano-particles

Author

Hjøllum, Jari í, Kuhn, L.T., Lefmann, K., Niedermayer, C., Raittila, J., Andersen, Niels Hessel, Abrahamsen, Asger Bech, Grivel, Jean-Claude, Lebech, Bente, Christensen, Niels Bech, Paturi, Petriina, Hjøllum, Jari í, Kuhn, L.T., Lefmann, K., Niedermayer, C., Raittila, J., Andersen, Niels Hessel, Abrahamsen, Asger Bech, Grivel, Jean-Claude, Lebech, Bente, Christensen, Niels Bech, and Paturi, Petriina

Published
2007

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