# L. Gozzelino's research while affiliated with INFN - Istituto Nazionale di Fisica Nucleare and other places

## Publications (190)

Article
The analysis of the radiation damage associated with energetic neutrons is a key factor for the application of glass-ceramics as joining materials in nuclear fusion plants. Triple ion beam irradiation is, currently, the only way to emulate the displacement damage and the effects of transmutation products induced by high energy neutrons at elevated...
Article
Full-text available
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
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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We report on ion irradiation experiments performed on compounds belonging to the BaFe2As2 family, each one involving the partial substitution of an atom of the parent compound (K for Ba, Co for Fe, and P for As), with an optimal composition to maximize the superconducting critical temperature Tc. Employed ion beams were 3.5-MeV protons, 250-MeV Au...
Article
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We report on the Eliashberg analysis of the electrodynamic response of Ba(Fe1−xRhx)2As2 single crystals across the disorder-induced s± to s++ transition. We previously experimentally identified the transition by its signature in the low temperature value of the penetration depth and observed a peculiar dependency of the critical temperature on diso...
Article
We report on the anisotropy of the London penetration depth of CaKFe4As4, discussing how it relates to its electronic structure and how it modifies under introduction of disorder, both chemically induced (by Ni substitution) and irradiation induced (by 3.5-MeV protons). Indeed, CaKFe4As4 is particularly suitable for the study of fundamental superco...
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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Irradiation effects are often used to improve the effective pinning in superconductors, but sometimes they can reveal detrimental for superconducting properties. Fe(Se,Te) has been proven to be a very robust material against irradiation, in particular proton irradiation, thus configuring as an ideal material to work in harsh environments such as pa...
Article
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We report on the microwave analysis of the interplay between magnetism and superconductivity in single crystals of EuFe2(As1−xPx)2, accomplished by means of a coplanar waveguide resonator technique. The bulk complex magnetic susceptibility χm extracted through a cavity perturbation approach is demonstrated to be highly sensitive to the magnetic str...
Article
Most iron-based superconductors are characterized by the s± symmetry of their order parameter, and are expected to go through a transition to the s++ state if enough disorder is introduced. We previously reported the observation of this transition in Ba(Fe1−xRhx)2As2 through a study of the disorder dependence of the critical temperature and low-tem...
Preprint
Most iron-based superconductors are characterized by the s+- symmetry of their order parameter, and are expected to go through a transition to the s++ state if enough disorder is introduced. We previously reported the observation of this transition in Ba(Fe1-xRhx)2As2 through a study of the disorder dependence of the critical temperature and low-te...
Article
Full-text available
We report on the combined experimental and theoretical analysis of the microwave-frequency electromagnetic response of BaFe2As2 single crystals with different substitutions: K in the Ba site (hole doping), Co in the Fe site (electron doping), and P in the As site (isovalent substitution). Measurements using a coplanar resonator technique lead to th...
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
Full-text available
Microwave measurements of the London penetration depth and critical temperature Tc were used to show evidence of a disordered-driven transition from s± to s++ order parameter symmetry in optimally doped Ba(Fe1−xRhx)2As2 single crystals, where disorder was induced by means of 3.5 MeV proton irradiation. Signatures of such a transition, as theoretica...
Article
IR pulsed laser radiation in air was applied to Si3N4 and Invar to obtain reliable Si3N4/Si3N4 and Si3N4/Invar adhesive bonded components. The laser pre-treatment produced a homogeneous nanostructured oxide layer on the surfaces, which effectively increased the adhesion at the adhesive/adherends interface and led to cohesive failure in the joining...
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...
Article
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In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out a systematic experimental investigation with different irradiation fluences up to 7.30x10^16 cm^-2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enha...
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
We investigate the penetration depth of high-quality Ba1−xKxFe2As2 single crystals by a planar waveguide resonator technique, in a cavity perturbation approach. The experimental λL is compared to calculations based on the three-band Eliashberg equations within the s± wave model. To this end, the anisotropy of the penetration depth is taken into acc...
Article
We present a \asnmr Nuclear Magnetic Resonance (NMR) and resistivity study of the effect of 5.5 MeV proton irradiation on the optimal electron doped ($x=$ 0.068) and overdoped ($x=$ 0.107) Ba(Fe$_{1-x}$Rh$_x$)$_2$As$_2$ iron based superconductors. While the proton induced defects only mildly suppress the critical temperature and increase residual r...
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
MgB2 bulk superconductors were shaped by Spark Plasma Sintering (SPS) process and the superconducting properties were measured. The obtained materials were 98% dense. Trapped field higher than 1.4 T was measured at 20 K. Otherwise, the possibility to use MgB2 for magnetic levitation has been investigated. The levitation force was investigated below...
Article
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We have irradiated epitaxial thin films of BaFe2(As1-xPx)2 with x ≃0.2 (optimal doping) with Au ions having an energy of 250MeV. We have used two different fluences, Φ 1 =2.4×10¹¹ cm⁻² and Φ 2 =7.3×10¹¹ cm⁻², and we have studied the effects of irradiation on the surface morphology, on the resistivity and on the critical temperature. We have found t...
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
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
CaO–Al2O3 (CA) and SiO2–Al2O3–Y2O3 (SAY) glass-ceramics are promising candidates for SiC/SiC indirect joints. In view of their use in locations where high radiation level is expected (i.e. fusion plants) it is important to investigate how radiation-induced damage can modify the material microstructure. To this aim, pellets of both types were irradi...
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
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
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
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
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
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
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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
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
Surface columnar defects, SCDs, are produced in high quality (Bi,Pb)2Sr2Ca2Cu3Oy/Ag tapes by irradiating them with 0.25 GeV gold ions only on a top layer up to ≈15% of the full volume. The ion beam is orthogonal to the tape plane. In this paper we report experimental results of the surface implantation of columnar defects both in the high-current a...
Article
The dominating pinning mechanism in YBa2Cu3O7-x thin film has been investigated by means of resistivity and ac susceptibility measurements and by structural characterizations. The aim of the work is to determine optimal pinning conditions in order to prevent the field-induced drop of the critical current density. The Clem and Sanchez model is used...
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
The aim of the present work is the optimization of the Si /buffer-layer/YBCO multilayer deposition process so as to grow superconducting films of quality suitable for device applications. The structural properties of the Si/CeO 2 system, obtained by RF magnetron sputtering of CeO 2 targets in Ar atmosphere, have been studied. More than 50 films hav...
Article
In the framework of a research aimed to superconductor/semiconductor integrated electronics, we have grown a-axis oriented YBa2Cu3O7-δ (YBCO) thin films on silicon (100) substrates with (111) oriented insulating buffer layers of cerium dioxide (CeO2), using magnetron sputtering deposition techniques. The properties of the cerium dioxide layer have...
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
We describe a method to produce MgB2 bulk via a microwave processing, which has not been reported yet for this material. We used two experimental arrangements, which were different in the form of the graphite thermal activator responsible for the microwave absorption. The reaction products have been analyzed from the morphological, structural and e...
Article
The possibility to enhance in a predictable way the superconducting properties behavior of a bulk material by introducing linearly correlated defects within a surface layer has been demonstrated. Ag/BSCCO-2223 tapes were irradiated by means of 0.25 GeV Au ions at different fluences, with a dose equivalent field Bϕ ranging from 1 T to 5 T. The impla...
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 present measurements of the magnetic field dependent microwave dissipation in a heavy-ion irradiated thin YBa2Cu3O7-δ film, in order to study the effects of columnar defects on the pinning of vortices. Columnar defects were produced at 45° with respect to the c axis. Measurements of the microwave dissipation at 48 GHz were taken as a function of...
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
The critical current Jc of superconducting films is about two order of magnitude larger than that of single crystals. The dependence of such Jc on field depends on the presence and distribution of defects. We speculate that High Temperature Superconducting (HTS) films can be modeled as an agglomeration of islands coupled via Josephson contacts and...
Article
This paper studies the striking correlation between nanosized structural patterns in YBCO films and macroscopic transport current. A nanosized network of parallel Josephson junctions laced by insulating dislocations is almost mimicking the grain boundary structural network. It contributes to the macroscopic properties and accounts for the strong in...
Article
This paper investigates the possibility of using superconductive elements as passive magnetic shields, in order to mitigate the magnetic field in limited regions around magnetic resonance scanners where medical staff could operate. The analysis is performed through the Finite Element Method by assuming a relative permeability close to zero to simul...
Article
The thin-shell formulation is applied to a combined finite element-boundary element technique to study the magnetic shielding efficiency of superconducting layers and hybrid superconducting-ferromagnetic sandwich structures in 3-D domains. The behavior of the superconducting material, assumed to be in a Meissner-like state, is here described by the...
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
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
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
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...