11 results on '"Peddis, Davide"'
Search Results
2. Time and temperature dependent magnetic viscosity experiments on Sr/Co nanoferrite particles.
- Author
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Maltoni, Pierfrancesco, Varvaro, Gaspare, Abdolrahimi, Maryam, Peddis, Davide, and Mathieu, Roland
- Subjects
VISCOSITY ,MAGNETIZATION reversal ,ACTIVATION energy ,MAGNETIC fields ,FERRITES ,TEMPERATURE - Abstract
Magnetic viscosity experiments have been performed in order to investigate the magnetization reversal in Sr nanoferrite particles (nanoscale SrFe
12 O19 ) and interacting Sr/Co nanoferrite particles (SrFe12 O19 –CoFe2 O4 nanocomposites). The magnetic viscosity S = d M (t) / d l n (t) , where M (t) is the magnetization as a function of time, has been collected. For Sr nanoferrite S shows a maximum close to the coercive field, reflecting the relation between S and the energy barrier distribution. We evidence that magnetic viscosity experiments on Sr nanoferrite and interacting Sr/Co nanoferrite particles provide reliable qualitative results for the different magnetic field sweep rate and saturating field H s a t considered. In addition, the activation volumes extracted from the magnetic viscosity experiments performed at different temperatures on Sr nanoferrite are quantitatively correlated to anisotropy changes. [ABSTRACT FROM AUTHOR]- Published
- 2023
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3. Towards bi-magnetic nanocomposites as permanent magnets through the optimization of the synthesis and magnetic properties of SrFe12O19 nanocrystallites
- Author
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Maltoni, Pierfrancesco, Sarkar, Tapati, Varvaro, Gaspare, Barucca, Gianni, Ivanov, Sergey, Peddis, Davide, and Mathieu, Roland
- Subjects
Permanent magnets ,nanocomposites ,Sol-gel chemistry ,permanent magnets ,Materials Chemistry ,Materialkemi ,Ferrites ,Nanocomposites ,sol-gel chemistry ,Condensed Matter Physics ,Den kondenserade materiens fysik ,ferrites - Abstract
Sol-gel synthesis was used in order to obtain nanocrystallites of the SrFe12O19 (SFO) hexaferrite in an efficient and reliable way. By optimizing the initial synthetic conditions, we were able to control the size of the nanoparticles (NPs), at lower annealing temperature. The x-ray powder diffraction, transmission electron microscopy (TEM), and magnetic measurements have demonstrated a significant relation between the morphology, size, and magnetic properties of the nanoscale SFO, revealing a definite dependence on the crystallite size along the c-axis. The obtained NPs appear almost isotropic, in the form of platelets and exhibit similar magnetic performance, in terms of the energy product (BH)(MAX), thus, demonstrating the suitability of reducing the annealing temperature without any deterioration in the magnetic properties. Additionally, this work illustrates the feasibility of the sol-gel bottom-up approach to employ magnetic NPs as building-blocks for designing hard/soft exchange-coupled bi-magnetic nanocomposites, combining the high coercivity of a hard phase (SFO) and the high saturation magnetization of a soft phase (CoFe2O4); in this regard, we discuss the tunability of the magnetic anisotropy by symbiotically restricting the growth of both phases.
- Published
- 2021
4. High-Moment FeCo Magnetic Nanoparticles Obtained by Topochemical H 2 Reduction of Co-Ferrites.
- Author
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Omelyanchik, Alexander, Varvaro, Gaspare, Maltoni, Pierfrancesco, Rodionova, Valeria, Murillo, Jean-Pierre Miranda, Locardi, Federico, Ferretti, Maurizio, Sangregorio, Claudio, Canepa, Fabio, Chernavsky, Petr, Perov, Nikolai, and Peddis, Davide
- Subjects
METAL nanoparticles ,NANOPARTICLE size ,MAGNETIC materials ,MAGNETIC field effects ,MAGNETIZATION measurement ,FERRITES ,MAGNETIC nanoparticles - Abstract
Featured Application: Metallic nanoparticles with a high value of magnetization have potential interest for application in biomedicine, catalysis, composite permanent magnets, and other fields. Cobalt ferrite nanoparticles of different stoichiometries synthesized by a sol–gel autocombustion method were used as a starting material to obtain high-moment Fe
50 Co50 and Fe66 Co34 metal nanoparticles by topochemical hydrogen reduction. Structural and magnetic investigations confirmed the formation of FeCo nanoparticles with crystallite sizes of about 30 nm and magnetization at 0.5 T of ~265 Am2 /kg (0 K), which was larger than the expected bulk value, likely because of the incorporation in the body-centered cubic (bcc) FeCo structure of the residual C atoms present on the surface of the oxide particles. Temperature-dependent magnetization measurements in the H2 atmosphere were also performed to investigate in detail the reduction mechanism and the effect of an external magnetic field on the process efficiency. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
5. Exchange bias and surface effects in bimagnetic CoO-core/Co0.5Ni0.5Fe2 O4 -shell nanoparticles
- Author
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Lavorato, Gabriel Carlos, Winkler, Elin Lilian, Ghirri, Alberto, Lima, Enio Junior, Peddis, Davide, Troiani, Horacio Esteban, Fiorani, Dino, Agostinelli, Elisabetta, Rinaldi, Daniele, and Zysler, Roberto Daniel
- Subjects
CORE/SHELL NANOPARTICLES ,purl.org/becyt/ford/1 [https] ,MAGNETIC NANOPARTICLES ,purl.org/becyt/ford/2 [https] ,FERRITES ,purl.org/becyt/ford/2.10 [https] ,EXCHANGE-BIAS ,purl.org/becyt/ford/1.3 [https] - Abstract
Bimagnetic nanoparticles have been proposed for the design of new materials with controlled properties, which requires a comprehensive investigation of their magnetic behavior due to multiple effects arising from their complex structure. In this work we fabricated bimagnetic core/shell nanoparticles formed by an ∼3-nm antiferromagnetic (AFM) CoO core encapsulated within an ∼1.5-nm ferrimagnetic (FiM) Co0.5Ni0.5Fe2O4 shell, aiming at studying the enhancement of the magnetic anisotropy and the surface effects of a ferrimagnetic oxide shell. The magnetic properties of as-synthesized and annealed samples were analyzed by ac and dc magnetization measurements. The results indicate that the magnetic response of the as-synthesized particles is governed by the superparamagnetic behavior of the interacting nanoaggregates of spins that constitute the disordered ferrimagnetic shell, whose total moments block at (TB)=49 K and collectively freeze in a superspin-glass-type state at (Tg)=3 K. On the other hand, annealed nanoparticles are superparamagnetic at room temperature and behave as an exchange-coupled system below the blocking temperature (TB)=70 K, with enhanced coercivity HC(10K)∼14.6 kOe and exchange bias field HEB(10K)∼2.3 kOe, compared with the as-synthesized system where HC(10K)∼5.5 kOe and HEB(10K)∼0.8 kOe. Our results, interpreted using different models for thermally activated and surface relaxation processes, can help clarify the complex magnetic behavior of many core/shell and hollow nanoparticle systems. Fil: Lavorato, Gabriel Carlos. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Winkler, Elin Lilian. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Ghirri, Alberto. Consiglio Nazionale delle Ricerche; Italia Fil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Peddis, Davide. Consiglio Nazionale delle Ricerche; Italia Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Fiorani, Dino. Consiglio Nazionale delle Ricerche; Italia Fil: Agostinelli, Elisabetta. Consiglio Nazionale delle Ricerche; Italia Fil: Rinaldi, Daniele. Universita Politecnica delle Marche via Brecce Bianche; Italia Fil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina
- Published
- 2016
6. Interparticle Interactionsand Magnetic Anisotropyin Cobalt Ferrite Nanoparticles: Influence of Molecular Coating.
- Author
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Peddis, Davide, OrruÌ, Federica, Ardu, Andrea, Cannas, Carla, Musinu, Anna, and Piccaluga, Giorgio
- Subjects
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FERRITES , *COBALT compounds , *ANISOTROPY , *NANOPARTICLES , *SURFACE coatings , *OLEIC acid , *SURFACES (Technology) - Abstract
Molecular coating of nanoparticles represents probablythe mostimportant and, at the same time, critical step to design new nanostructuredmagnetic materials. The interaction between molecules and surfaceatoms leads to a strong modification of surface magnetic properties,that are one of the key points in the physics of magnetic nanoparticles.In this paper the magnetic properties of CoFe2O4nanoparticles (â¨Dâ© â 4â8 nm) coatedwith oleic acid have been investigated in order to clarify the roleof the molecular coating on the interparticle interactions and surfaceanisotropy. An increase of magnetic anisotropy (i.e., coercive fieldand anisotropy constant) with particle size is observed in coatednanoparticles, indicating that the magnetic anisotropy is governedmainly by its magneto-crystalline component. The removal of molecularcoating induces a strong increase of anisotropy, because of the increaseof its surface component, as indicated by the increase of exchangebias field. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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7. Mn-ferrite nanoparticles via reverse microemulsions: synthesis and characterization.
- Author
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Scano, Alessandra, Ennas, Guido, Frongia, Francesca, Barbera, Aurelio, López-Quintela, M., Marongiu, Giaime, Paschina, Giorgio, Peddis, Davide, Pilloni, Martina, and Vázquez-Vázquez, Carlos
- Subjects
FERRITES ,NANOPARTICLES ,EMULSIONS ,INORGANIC synthesis ,HEAT treatment of metals ,TEMPERATURE effect ,HYDROXIDES ,SURFACE active agents ,SOLUTION (Chemistry) - Abstract
Mn-ferrite nanoparticles were synthesized by thermal treatment at 800 °C of manganese and iron oxo-hydroxides obtained via water-in-oil microemulsions consisting of n-hexanol as continuous phase, cetyl trimethyl ammonium bromide (CTAB) as the cationic surfactant and aqueous solutions of metal salts and precipitant agent (tetramethyl ammonium hydroxide) as reagents. Nanoparticles were synthesized using a multi-microemulsion approach. Two different co-precipitation routes are described depending on the Fe(II) or Fe(III) precursor salts. The influence of salt concentration and digestion process on the final products was examined. The nanoparticles were characterized by X-ray diffraction accompanied by Rietveld analysis, transmission electron microscopy, thermal analysis, infrared spectroscopy, and SQUID magnetometry. In all the synthesis reported in this study MnFeO was observed only after thermal treatment at 800 °C of the as-prepared precursors. Almost spherical nanocrystalline MnFeO ranging from 12 to 39 nm was obtained starting from chlorides or mixed chloride-sulfate salts as precursors. Low values of reduced remanent magnetization ( M/ M) and coercive field ( H) induce to believe that a fraction of superparamagnetic particle is present at room temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
8. Green Synthesis of Co-Zn Spinel Ferrite Nanoparticles: Magnetic and Intrinsic Antimicrobial Properties.
- Author
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Omelyanchik, Alexander, Levada, Kateryna, Pshenichnikov, Stanislav, Abdolrahim, Maryam, Baricic, Miran, Kapitunova, Anastasiya, Galieva, Alima, Sukhikh, Stanislav, Astakhova, Lidiia, Antipov, Sergey, Fabiano, Bruno, Peddis, Davide, and Rodionova, Valeria
- Subjects
MAGNETIC nanoparticles ,MAGNETIC structure ,FERRITES ,MAGNETIC properties ,ZINC ferrites ,SPINEL ,NANOPARTICLES - Abstract
Spinel ferrite magnetic nanoparticles have attracted considerable attention because of their high and flexible magnetic properties and biocompatibility. In this work, a set of magnetic nanoparticles of cobalt ferrite doped with zinc was synthesized via the eco-friendly sol-gel auto-combustion method. Obtained particles displayed a room-temperature ferromagnetic behavior with tuned by chemical composition values of saturation magnetization and coercivity. The maximal values of saturation magnetization ~74 Am
2 /kg were found in cobalt ferrite nanoparticles with a 15–35% molar fraction of cobalt replaced by zinc ions. At the same time, the coercivity exhibited a gradually diminishing trend from ~140 to ~5 mT whereas the concentration of zinc was increased from 0 to 100%. Consequently, nanoparticles produced by the proposed method possess highly adjustable magnetic properties to satisfy the requirement of a wide range of possible applications. Further prepared nanoparticles were tested with bacterial culture to display the influence of chemical composition and magnetic structure on nanoparticles-bacterial cell interaction. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
9. Magnetocrystalline and Surface Anisotropy in CoFe2O4 Nanoparticles.
- Author
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Omelyanchik, Alexander, Salvador, María, D'Orazio, Franco, Mameli, Valentina, Cannas, Carla, Fiorani, Dino, Musinu, Anna, Rivas, Montserrat, Rodionova, Valeria, Varvaro, Gaspare, and Peddis, Davide
- Subjects
MAGNETIC anisotropy ,MAGNETIC properties ,FERRITES ,NANOPARTICLES ,SILICA ,MAGNETIZATION ,ANNEALING of metals - Abstract
The effect of the annealing temperature T
ann on the magnetic properties of cobalt ferrite nanoparticles embedded in an amorphous silica matrix (CoFe2 O4 /SiO2 ), synthesized by a sol-gel auto-combustion method, was investigated by magnetization and AC susceptibility measurements. For samples with 15% w/w nanoparticle concentration, the particle size increases from ~2.5 to ~7 nm, increasing Tann from 700 to 900 °C. The effective magnetic anisotropy constant (Keff ) increases with decreasing Tann , due to the increase in the surface contribution. For a 5% w/w sample annealed at 900 °C, Keff is much larger (1.7 × 106 J/m3 ) than that of the 15% w/w sample (7.5 × 105 J/m3 ) annealed at 700 °C and showing comparable particle size. This indicates that the effect of the annealing temperature on the anisotropy is not only the control of the particle size but also on the core structure (i.e., cation distribution between the two spinel sublattices and degree of spin canting), strongly affecting the magnetocrystalline anisotropy. The results provide evidence that the magnetic anisotropy comes from a complex balance between core and surface contributions that can be controlled by thermal treatments. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
10. Surfactant-assisted route to fabricate CoFe2O4 individual nanoparticles and spherical assemblies
- Author
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Cannas, Carla, Ardu, Andrea, Peddis, Davide, Sangregorio, Claudio, Piccaluga, Giorgio, and Musinu, Anna
- Subjects
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SURFACE active agents , *MICROFABRICATION , *COBALT compounds , *FERRITES , *NANOCRYSTALS , *SURFACE area , *POROUS materials , *TRANSMISSION electron microscopy - Abstract
Abstract: A surfactant-assisted route in aqueous media has been shown to be suitable to prepare either individual primary CoFe2O4 nanocrystals or secondary spherical nanoporous assemblies with a high surface area. The formation of primary nanoparticles or of spherical assemblies is found to be dependent on the presence of the surfactant and on the particle size, but is shown that the nanoparticle–surfactant interface plays a dominant role. The size of the primary CoFe2O4 particles is controlled by the type of salt, the synthesis temperature and the concentration of the precursors. A detailed characterization evidences the shape and size of the primary particles, the way in which the primary particles assemble and their features in terms of morphological, textural and magnetic properties. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
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11. Tunable magnetic properties of Ni-doped CoFe2O4 nanoparticles prepared by the sol–gel citrate self-combustion method.
- Author
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Omelyanchik, Alexander, Singh, Gurvinder, Volochaev, Mikhail, Sokolov, Alexey, Rodionova, Valeria, and Peddis, Davide
- Subjects
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COBALT , *FERRITES , *X-ray diffraction , *MAGNETIC properties , *NANOSTRUCTURED materials - Abstract
Highlights • The obtained samples show relatively high values of M S and H C without any thermal treatment. • Magnetic properties of cobalt ferrite nanoparticle were strongly affected when there are doped with nickel. • The higher value of magnetization saturation was found for the Ni 0.25 Co 0.75 Fe 2 O 4 sample. Abstract The nanostructured spinel ferrites with complex stoichiometry are an important family of the materials in a number of applications, especially in electronics through their good electrical and magnetic properties. In the framework of this study, a set of mixed cobalt and nickel ferrites was prepared with the sol–gel self-combustion route. The structural and morphological features of particles were studied with X-ray diffraction (XRD), Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive X-ray analysis (EDX) techniques. The prepared particles show a crystalline nature with a monotonic distribution of the elements and particles size distribution in the range of 17–29 nm. The obtained particles demonstrate good magnetic properties with tunable saturation magnetization and magnetic anisotropy, i.e., coercivity depending on chemical composition. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
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