F. Laviano's research while affiliated with Politecnico di Torino and other places

Publications (143)

Article
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A microwave technique suitable for investigating the AC magnetic susceptibility of small samples in the GHz frequency range is presented. The method—which is based on the use of a coplanar waveguide resonator, within the resonator perturbation approach—allows one to obtain the absolute value of the complex susceptibility, from which the penetration...
Article
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Superconductors are strategic materials for the fabrication of magnetic shields, and within this class, MgB2 has been proven to be a very promising option. However, a successful approach to produce devices with high shielding ability also requires the availability of suitable simulation tools guiding the optimization process. In this paper, we repo...
Article
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In this work, we presented the design of a module of a 10 MW toroidal SMES, tailored for a charge/discharge time of 1s aimed at compensating the intermittency of a solar photovoltaic system. The design is performed through an approach based on the functional analysis: first, the functions that must be satisfied by the SMES are identified, together...
Article
The use of superconducting (SC) materials is crucial for shielding quasi-static magnetic fields. However, the frequent requisite of space-saving solutions with high shielding performance requires the development of a 3D modelling procedure capable of predicting the screening properties for different orientations of the applied field. In this paper,...
Article
Ion irradiation of superconductors allows both the establishment of their radiation hardness and the modification and optimization of their properties useful for applications. In this work, we investigate the effects of proton irradiation with different energies on Fe(Se,Te) thin films grown on CaF<sub>2</sub> and on buffered YSZ substrates. These...
Article
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Zinc oxide nanoparticles (ZnO NPs) are currently among the most promising nanomaterials for theranostics. However, they suffer from some drawbacks that could prevent their application in nanomedicine as theranostic agents. The doping of ZnO NPs can be effectively exploited to enhance the already-existing ZnO properties and introduce completely new...
Article
Nanomedicine have gained huge attention in recent years with new approaches in medical diagnosis and therapy. Particular consideration has been devoted to the nanoparticles in theranostic field with specific interest for magnetic and gold nanoparticles (MNPs and GNPs) due to their peculiar properties under exposition to electromagnetic fields. In t...
Article
Copper-containing ferrimagnetic glass-ceramic with the following composition: 24.7% SiO2-8.5% CaO-13.5% Na2O-3.3% P2O5-31% Fe2O3-14% FeO–5CuO (wt%) was synthesized by means melt and quenching process both in powder and bulk form. The obtained samples were characterized and compared by means morphological, compositional and structural analyses. The...
Article
Rare heart substituted iron garnets (REIGs) are interesting material which may present large in-plane magnetization. In correspondence of defects, domain walls (DWs) undergo nucleation, segmentation and pinning. In such cases, the Néel spike domain structure may appear, and its DWs can produce not negligible stray fields above the REIG. Experimenta...
Article
In this work an innovative formulation of bone cement for the treatment of bone tumor and its associated complications has been designed by preparing a new class of Fe3O4-Ag nanostructures, using gallic acid as a reducing agent. The obtained nanoparticles have been introduced in polymethyl methacrylate (PMMA)-based composite cement evaluating the i...
Preprint
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We perform electric double-layer gating experiments on thin films of niobium nitride. Thanks to a cross-linked polymer electrolyte system of improved efficiency, we induce surface charge densities as high as $\approx 2.8 \times 10^{15}\,\mathrm{cm}^{-2}$ in the active channel of the devices. We report a reversible modulation of the superconducting...
Article
YBa 2 Cu 3 O 7 -based coated conductors (CCs) achieve the highest critical current densities ( J c ) of any known superconductor and are a key technology for applications such as rotatory machines, high-field magnets and power transmission. Incorporation of nano-sized non-superconducting second phases as additional vortex pinning centers has been c...
Article
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Zinc oxide nanocrystals (ZnO-NCs) doped with transition metal elements or rare earth elements can be probed for magnetic resonance imaging to be used as a molecular imaging technique for accurate diagnosis of various diseases. Herein, we use Mn as a candidate of transition metal elements and Gd as a presenter of rare earth elements. We report an ea...
Article
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We present the characterization and the numerical simulation of a high-temperature superconducting bolometer based on an YBa 2 Cu 3 O 7-x (YBCO) film, which is patterned in serpentine elements and selectively modified by means of micro-collimated high-energy heavy-ion irradiation. The local irradiation of YBCO yields to a controlled reduction of th...
Article
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Magnetic-optical methods are used to investigate the magnetic microstructure of an epitaxial film of (Lu,Bi) substituted rare earth iron garnet. In particular, we focused our study on a bi-dimensional domain configuration, the Néel spike, which is induced and pinned at defects inside the sample or at its edges. Imaging of magnetic domains and domai...
Article
Magnetite-based nanoparticles (NPs) were synthesized by co-precipitation process and coated with a thin layer of silica, eventually doped with calcium, by a modified Stöber method. The potential bioactive behavior of NPs was investigated by dipping samples in simulated body fluid (SBF) and analyzing them with Field-Emission Scanning Electron Micros...
Article
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During the last decades the applications of nanotechnology in the biomedical field have attracted a lot of attention. Magnetic and gold nanoparticles (MNPs and GNPs) became a new area of interest as selective tools for tumour treatment, due to their unique properties and biocompatibility. In this paper Superparamagnetic-Iron Oxide Nanoparticles (MN...
Article
We report on a combined experimental and modelling approach towards the design and fabrication of efficient bulk shields for low-frequency magnetic fields. To this aim, MgB 2 is a promising material when its growing technique allows the fabrication of suitably shaped products and a realistic numerical modelling can be exploited to guide the shield...
Article
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This work deals with the synthesis and characterization of novel Fe-containing sol-gel materials obtained by modifying the composition of a binary SiO₂-CaO parent glass with the addition of Fe₂O₃. The effect of different processing conditions (calcination in air vs. argon flowing) on the formation of magnetic crystalline phases was investigated. Th...
Article
The electrodynamic response of Ba1-xKxFe2As2 single crystals at the microwave frequencies has been investigated by means of a coplanar resonator technique, at different values of non-magnetic disorder introduced into the samples by heavy-ion irradiation. The surface impedance Z s = R s + iX s conforms to the classical skin effect above the critical...
Conference Paper
We investigate the effects of pure charge doping (obtained by using the so-called electric-double layer gating technique) in thin films of the metallic superconductor NbN. Despite the electrostatic screening due to the large intrinsic carrier density of this material, we observe measurable, ambipolar modulations of the superconducting critical temp...
Article
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One of the open issues concerning iron-based superconductors is whether the s± wave model is able to account for the overall effects of impurity scattering, including the low rate of decrease of the critical temperature with the impurity concentration. Here we investigate Ba1−xKxFe2As2 crystals where disorder is introduced by Au-ion irradiation. Cr...
Article
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Silver-containing ferrimagnetic glass–ceramic (Ag-SC45) was synthesized by means of melt and quenching technique. Samples were subjected to morphological, compositional, structural analyses, ability to generate heat, magnetic measurements at high and low magnetic field and antibacterial test using S. aureus strain. The influence of silver introduct...
Chapter
The vortex diffusion in Type II superconductors is the dominant dissipative mechanism both in transport and in magnetization properties. The strong nonlinear relation between the current density and the electric field, along with nonlocal interactions, determines the complex behavior of the vortex matter, which also includes “catastrophic” phenomen...
Article
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The electrochemical gating technique is a powerful tool to tune the surface electronic conduction properties of various materials by means of pure charge doping, but its efficiency is thought to be hampered in materials with a good electronic screening. We show that, if applied to a metallic superconductor (NbN thin films), this approach allows obs...
Article
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This paper compares the shielding properties of superconducting (SC) and superimposed superconducting/ferromagnetic (SC/FM) systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. Both bilayer structures, with the SC cup placed inside the FM one, and multilayer structures, made up of two SC and two FM alternati...
Article
Composite bone cements, based on commercial polymethylmethacrylate, loaded with ferrimagnetic and bioactive glass-ceramic particles, were prepared and characterized. The characterization included: the evaluation of hysteresis losses in quasi static conditions, the quantification of specific power losses by calorimetric tests, optimization of experi...
Article
In this work, we present an approach towards achieving a detailed knowledge on the effects of irradiation in iron-based superconductors with high-energy heavy ions. Ba1−x K x Fe2As2 single crystals (x = 0.42) were irradiated with 250 MeV Au-ions. The crystals were shaped to be thin plates with thickness lower than the ion implantation depth and bas...
Article
Current transport in high-temperature superconductors is strongly affected by the presence of grain boundaries (GBs). Thin epitaxial films of high-temperature superconducting YBa2Cu3O7-δ containing low-angle GBs with fixed angles of 5° have been prepared on bicrystalline substrates. The current-carrying capability of these GBs is investigated by qu...
Article
In this work, an experimental approach toward reaching new insights into the mechanism of superconductivity in the iron-based compounds is presented. The temperature dependence of the penetration depth and of the microwave conductivity of high-quality Ba(Fe1-xCox)2As2 and (Ba1-xKx)Fe2As2 single crystals have been obtained by a 7.97-GHz superconduct...
Article
In this paper we investigate and compare the shielding properties of superconducting and hybrid superconducting/ferromagnetic systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. First, we reproduced, by finite-element calculations, the induction magnetic field values measured along the symmetry axis in a su...
Article
Full-text available
We perform electric double-layer gating experiments on thin films of niobium nitride. Thanks to a cross-linked polymer electrolyte system of improved efficiency, we induce surface charge densities as high as ≈ 2.8 × 1015cm−2 in the active channel of the devices. We report a reversible modulation of the superconducting transition temperature (either...
Article
We visualize, with a magneto optical imaging technique with indicator film, the local magnetic response of the compound La(Fe0.9Co0.015Si0.085)13 during its first order magneto structural transition. The technique allowed us by comparing the stray fields of the main magneto caloric phase and of secondary phases present in the sample to obtain the m...
Article
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A systematic characterization of Co-doped BaFe 2 As 2 (Ba-122) thin films has been carried out. Two samples were available, one grown on CaF 2 substrate and the other on MgO with an Fe buffer layer. The goal was to investigate films’ magnetic and superconducting properties, their reciprocal interplay, and the role played by the Fe buffer layer in m...
Article
Magneto-optical imaging with an indicator film is used for investigating the magnetic pattern in ferromagnetic material specimens whose optical properties do not allow the direct visualization of their magnetic pattern. The magneto-optical indicator is a ferromagnetic film with low coercitivity that detects the magnetic field from a magnetic source...
Article
Full-text available
Multiple versions can be downloaded from this site. The version available from www.hope.edu is the current version. Micro-channels of nanosized columnar tracks were planted by heavy-ion irradiation into superconducting microwave microstrip resonators that were patterned from YBa2Cu3O7-x thin films on LaAlO3 substrates. Three different ion fluences...
Article
We report on the systematic characterization of Ba(Fe0.92Co0.08)(2)As-2 epitaxial thin films on CaF2 substrate in view of their possible use for superconducting electronic applications. By using different and complementary techniques we studied the morphological characteristics of the surface, the structural properties, the magnetic response, and t...
Article
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Femtosecond spectroscopy has been used to investigate the quasi-particle relaxation times in nearly optimally doped Fe-based superconductors FeSe0.5Te0.5 and optimally doped Ba-122 thin films growth on a Fe buffer layer. Experimental results concerning the temperature dependence of the relaxation time of such pnictides both in the superconducting s...
Article
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We investigate the temperature induced ferromagnetic to paramagnetic phase transition in Co substituted La(FexCoySi1−x−y)13 with x = 0.9 and low Co content of y = 0.015 (Tc≃200 K) by means of magneto-optical imaging with indicator film and by calorimetry at very low temperature rates. We were able to visualize the motion of the ferromagnetic (FM)/p...
Article
Here we present a study of the pinning properties of high-quality single crystals of Ba(Fe1−xCox)2As2 (x = 0.07) by means of the quantitative magneto-optical imaging (MOI). This technique allows us to measure the magnetic field and supercurrent distribution as a function of the applied magnetic field and temperature, thus extracting the local param...
Article
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Hyperthermia is a technique for destroying cancer cells which involves the exposition of body's tissue to a controlled heat, normally between 41℃ and 46℃. It has been reported that ferro- or ferrimagnetic materials can heat locally, if they are placed (after being implanted) under an alternating magnetic field, damaging only tumoral cells and not t...
Article
We introduce a simple approach to evaluate the magnetic field distribution around superconducting samples, based on the London equations; the elementary variable is the vector potential. This procedure has no adjustable parameters, only the sample geometry and the London length, $\lambda$, determine the solution. The calculated field reproduces qua...
Article
The paper deals with nanostructuring of superconducting materials by means of swift heavy ion beams. The aim is to modify their structural, optical and electromagnetic properties in a controlled way, to provide possibility of making them functional for specific applications. Results are presented concerning flux pinning effects (implantation of co...
Article
We investigated the efficiency in magnetic field mitigation of superimposed MgB2/Fe coaxial cups with cylindrical symmetry, subjected to an applied magnetic field parallel to their axis. The MgB2 cup was grown by a microwave-assisted Mg-liquid infiltration technique in a boron preform. This technique allows obtaining samples with a reduced amount o...
Article
Microcollimated swift heavy-ion irradiation has been employed to carve channels with micron-sized width in YBa2Cu3O7-x(YBCO) superconducting coplanar microwave resonators. Comparative analysis of the first two resonant modes as a function of temperature, magnetic field, and input power was used to characterize the properties of the microchannels. A...
Article
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We studied the magnetic shielding properties of a MgB2/Fe hybrid structure consisting of two coaxial cups subjected to a magnetic field applied parallel to their axis. This study was performed to analyze the magnetic shield properties of a system contemporary exploiting the opposite magnetic properties of superconducting/ferromagnetic materials. Th...
Article
Spatial distributions of magnetic field and of current density in superconductors are obtained, in real-time, by the magneto-optical imaging technique with an indicator film. Quantitative values of the local magnetic field and then of the local current density were achieved by a careful optical calibration and custom algorithms for the inversion of...
Article
We report effects of particle energy on physical properties of Co-doped BaFe2As2 in the case of Xe and Au irradiations. The irradiation-induced suppression of Tc is found to be related with several factors, such as defect structures and the thickness of the crystal. Heavy-ion irradiation induces enhancement of critical current density Jc, and a wea...
Article
We studied magnetic flux penetration in a hybrid MgB2/Fe structure consisting of two coaxial cups in a magnetic field applied parallel to their axis. This analysis was performed to investigate the potential of magnetic shielding of systems with a reduced length/radius aspect ratio exploiting the opposite magnetic properties of superconducting and f...
Article
Channels with micron-size width have been carved in Y Ba2Cu3O7−x (YBCO) coplanar microwave resonators by micro-collimated swift heavy-ion irradiation at high fluences. The response of the resonators as a function of temperature, magnetic field and input power as well as magneto-optical imaging was used to characterize the properties of such micro-c...
Article
Radiation-hard sensors are at present time highly requested for applications in environments with potential radiation hazard such as space, accelerators and fusion machines. We developed device prototypes for magnetic field and THz photon detection, both based on YBa2Cu3O7−x (YBCO) superconducting films locally nanostructured by means of 0.25GeV Au...
Article
We report about the functional exploiting of the High-Energy Heavy-Ion (HEHI) lithography aimed at modulating in confined regions both structural and electrical properties of high temperature superconducting YBa2Cu3O7−x (YBCO) films. We discuss the physical behaviors related to the HEHI modification of such films by means of 3D columnar defects, ex...
Article
Full-text available
By using ac susceptibility measurements at different frequencies and dc fields we investigated the creep properties of MgB2 bulk samples. Two independent analysis have been used in order to determine the behavior of the pinning energy in the whole investigated temperature and field ranges. The main result of the first analysis (χ′′-peak analysis) i...
Article
We performed magneto-optical analysis on slightly overdoped Bi2Sr2CaCu2O8+x single crystals, looking for the second peak effect. On the basis of a method suitably developed to extract from the magneto-optical images the main electrodynamic quantities (magnetic induction field, Bz, and current density, J), the local magnetisation, Ms and the local J...
Article
A magneto-optical equipment has been set up and carefully calibrated. In this paper, we shortly review the main characteristic of this equipment, then we focus on the analysis to be performed in order to extract from magneto-optical images the local values of magnetic induction and electrical current density along the superconducting sample. This i...
Article
An irradiation facility to irradiate "long" stripe-shaped high-Tc superconductors by means of GeV heavy ions is described. This facility was designed and installed at INFN - Laboratori Nazionali del Sud (LNS), Catania, Italy. It consists into a moving apparatus automatically driven at a given velocity in order to obtain the in-vacuum exposure of co...
Article
An experimental set-up for magneto-optical analysis equipped with a new low- temperature controlling system is described. Magneto-optical investigations of the magnetic flux distribution are performed on as-grown as well as Au-on ion-irradiated Bi-2122 single crystals. The comparative analysis of as-grown and irradiated specimens shows that the mag...
Article
Magnetic shielding properties of MgB2 bulk samples synthesized by the SPS (Spark–Plasma–Sintering) technique were characterized in low applied magnetic fields at temperatures ranging from 20 to 37 K. The used growth technique allows one to produce this compound in different shapes and sizes required for shielding applications. In this framework, sh...
Article
Broadband electromagnetic characterization of hot plasmas and electron beams requires real-time, direct detection of high flux of electromagnetic radiation. We report about a project aimed at creating robust THz detectors based on YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> (YBCO) films, working around liquid nitrogen temperature and in a regime o...
Article
A local magnetic characterization of disk-shaped MgB<sub>2</sub> bulk samples synthesized by the Spark-Plasma-Sintering technique was carried out aimed at studying the material magnetic shielding properties. This growth technique allows one to produce samples in different shapes and sizes as required for shielding applications. The analysis employe...
Article
We investigate the nonlinear behavior of magnesium diboride coplanar waveguide resonators in order to iden- tify the basic mechanisms limiting the performance of polycrys- talline films in microwave applications. In particular, we focus on several kinds of switching response. Switching is observed due to increase of rf currents above a given thresh...
Article
Quantitative imaging of the local magnetic field and of current density distribution in superconductors (with microscopic resolution over macroscopic length scales) is achieved by means of the Magneto-Optical Imaging technique with an indicator film. We exploit this technique to study the vortex arrangement and the corresponding supercurrent distri...
Article
Broadband electromagnetic characterization of hot plasmas, such as in nuclear fusion reactors and related experiments, requires detecting systems that must withstand high flux of particles and electromagnetic radiations. We propose a rugged layout of a high temperature superconducting detector aimed at 3 THz collective Thomson scattering (CTS) spec...
Article
High energy heavy ion lithography was used for modulating through implanted nanostructures the local structural and electrical properties of high temperature superconducting YBa2Cu3O7 films. The controlled reduction of the critical temperature of irradiated films results in a localization into heavy ion patterned micro-regions of the electrical dis...
Article
High-energy heavy-ion lithography is a powerful tool for tuning both structural and electromagnetic properties of high temperature superconductors by inducing nanometer scale defects confined in micron scale patterns. We show how the vortex dynamics in YBCO thin films patterned by heavy-ion lithography can be controlled and potentially exploited fo...
Article
Measurements of the photoresponse of superconducting YBa2Cu3O7-x film devices to THz radiation are reported. The properties of the films were modulated in a functional way by High-Energy-Heavy-Ion lithography, an effective tool to locally enhance the response of the sensor to the infrared spectrum.
Article
We investigated the switching response of MgB2 coplanar waveguide resonators to increase of rf currents. A model based on the heat balance equation is able to account for the observed behaviors, including the presence of a thermal bistability regime. The model also reproduces the temperature dependence of the limiting currents. Results are consiste...