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Il Tempo della Scienza

Seminari tecnici 2016

Sala Conferenze (Edificio M)
Strada delle Cacce 91, Torino

Data Relatore Titolo
15 dicembre
ore 14:30
Ed. D
Arianna Casiraghi
Aalto University and ISI Foundation

Ferromagnetic-ferroelectric domain coupling in multiferroic heterostructures

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Spintronics relies on the spin of electrons rather than their charge to perform common tasks including store information, sense magnetic fields, or perform logic operations. With the commercialization of several devices such as read heads of computer hard-disk drives and magnetic random access memory (MRAM), spintronics is arguably the most successful field of nanotechnology yet. Due to their potential for spintronics application, multiferroic heterostructures composed of ferromagnetic and ferroelectric layers have recently attracted an ever-increasing level of interest.

Following a brief introduction discussing the state of the field, I will present some of our recent results on strain-coupled multiferroic hetersotructures composed of a magnetic thin film and a BaTiO3 ferroelectric substrate. These systems exhibit a one-to-one correspondence between ferroelectric and ferromagnetic domain patterns. Furthermore, magnetic domain walls are strongly pinned on top of the corresponding ferroelectric domain boundaries. Pinning of magnetic domain walls has a profound influence on the magnetization reversal process in the multiferroic heterostructure. I will first show how this unique switching process can be exploited to implement the concept of a magnetic logic cell. Depending on the applied bias field, non-volatile NAND, NOR, AND and OR logic gates can be realized in the same device. Finally, I will also show how the coupling between the ferroic domains in these heterostructures can be exploited for electric-field switching of perpendicularly magnetised multilayers and pure electric-field driven magnetic domain wall motion.

1 dicembre
ore 14:30
Ed. D
Samridh Jaiswal
Institute of Physics, Johannes Gutenberg-University Mainz, Germany
Singulus Technologies AG, Kahl am Main, Germany

Investigation of Dzyaloshinskii-Moriya Interaction in novel room temperature skyrmion systems

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The need to produce low cost, high density magnetic data storage devices requires a core understanding of the magnetic spin textures and their underlying mechanisms. Ferromagnets (FM) sandwiched between Heavy Metal (HM) and oxide thin films have shown novel spin textures such as spin spirals and skyrmions arising from an interfacial Dzyaloshinskii-Moriya interaction (DMI). This DMI manifests due to the high spin-orbit coupling of the HM and the structural inversion asymmetry at the HM/FM interface. Due to the various novel interface related phenomenon, there has been in recent times a growing interest to study physics at these interfaces.

Therefore it is crucial to engineer material thin films of high quality which allows the study of interfacial Anisotropic-Magnetoresistance, DMI, Spin-Orbit torques, interfacial SOC, spin mixing conductance, and interfacial perpendicular anisotropy, etc. Therefore, I will provide a brief overview as too the different deposition techniques/requirements for the production of such ultra-smooth interfaces and elaborate on the different interfacial characterization methods.

In this work, we will focus on the study of the DMI and the skyrmion motion in continuous thin films of perpendicularly magnetised W/CoFeB/MgO. The DMI leads to an asymmetric expansion of magnetic bubble domains in the presence of an in-plane applied field. Full field Kerr microscopy was used to observe magnetic bubble domains and on application of an in-plane field the asymmetric expansion of each domain wall was measured. The degree of the asymmetric expansion of the bubble domain was used to estimate the value for DMI energy which was found to be 20.68±0.01 mJ/m for a single repetition of the stack. Scanning Transmission X-ray Microscopy (STXM) was used to image the magnetic spin texture in such films grown on SiN substrates with multiple stack repetitions. We observe stable room temperature magnetic skyrmions in patterned nanowires and study their current induced motion. Additionally, magnetic stripe domains in the nanowires and their expansion due to the applied magnetic field were used to calculate the DMI value of 0.78±0.5 mJ/m2. The two techniques in obtaining the DMI are discussed in this talk and their differing values may be attributed to stray field coupling in multiple stack repetitions.

27 ottobre
ore 11
Giovanni Daniele Rovera
Paris Observatory

UTC(OP) realization based on atomic fountain

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UTC(OP), the French national realization of the international Coordinated Universal Time, was redesigned and rebuilt. The first step was the implementation in October 2012 of a new algorithm based on a H-maser and on atomic fountain data. Thanks to the new implementation, the stability of UTC(OP) was dramatically improved and UTC(OP) competes with the best time scales available today.
Then the hardware generating and distributing the UTC(OP) physical signals was replaced. Part of the new hardware is composed of commercial devices, but the key elements were specifically developed. One of them is a special switch that allows the UTC(OP) signals be derived from one of two time scales, based on two different H-masers, which are generated simultaneously. This insures the continuity of the UTC(OP) signal even when a change of the reference H-maser is required. With the new hardware implementation, UTC(OP) is made available through three coherent signals: 100 MHz, 10 MHz and 1 PPS.
For more than 3 years, UTC(OP) remained well below 10 ns close to UTC, with a difference even less than 5 ns if we except a short period around MJD 56650.

14 ottobre
ore 11
Ed. D
Galina Kurlyandskaya
Departamento de Electricidad y Electrónica
Universidad del País Vasco (UPV/EHU)
Bilbao, Spain

Nanoparticles for Magnetic Biosensing Systems

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Magnetic biosensors development requires better understanding the interaction between living system and magnetic nanoparticles (MNPs). We describe our experience in fabrication of stable ferrofluids (FF) using electrostatic or steric stabilization of iron oxide MNPs obtained by the laser target evaporation. Controlled amounts of FF were used for in vitro experiments with human mesenchymal stem cells. Their morphofunctional response in the Fe concentration range 2-1000 maximum tolerated dose revealed no cytotoxicity.

22 settembre
ore 11
Vincenzo Lippolis
Istituto di Scienze delle Produzioni Alimentari (ISPA) del CNR

Metodi di analisi per la sicurezza e tracciabilità dei prodotti agroalimentari

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La rilevanza della problematica connessa alla sicurezza e tracciabilità degli alimenti ha indotto negli ultimi anni un crescente impiego di tecnologie innovative, finalizzato al miglioramento della fase di determinazione analitica. Sarà presentata una panoramica dei principali metodi innovativi sviluppati negli ultimi anni presso l'ISPA-CNR di Bari per la sicurezza e tracciabilità dei prodotti agroalimentari, basati principalmente sull'impiego di tecniche immunometriche, nasi elettronici, spettroscopia del vicino infrarosso, spettrometria di massa e risonanza magnetica nucleare.

10 agosto
ore 10:30
Liisa Kuhn
Department of Reconstructive Sciences
Center for Regenerative Medicine and Skeletal Development
University of Connecticut

Enabling sequential delivery of growth factors from layer-by-layer films with a nanoCaP barrier layer

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Part I. Tissue regeneration involves a cascade of cellular events including infection control, progenitor cell recruitment, proliferation and differentiation. Various designs of biomaterial delivery systems are being investigated as a means to sequentially deliver multiple growth factors in order to trigger a recapitulation of the multiple steps of tissue regeneration. In most delivery systems, diffusion of growth factors through the multiple biomaterial phases or layers prevents true sequential delivery. The focus of the Kuhn lab is on delivery of multiple growth factors to stimulate bone regeneration. Layer-by-layer deposition of polyelectrolyte multilayer (PEM) coatings that have been modified with a nanocrystalline calcium phosphate barrier (bCaP) layer can block diffusion and enable sequential delivery of multiple growth factors. Measurements of MC3T3-E1 viability over time were used to evaluate kinetics of active biomolecule delivery and demonstrate that bCaP-PEM enables sequential delivery of a proliferative factor (fibroblast growth factor -2 (FGF-2) followed by a cytotoxic factor (antimycin A, AntiA). Sequential drug delivery systems are anticipated to play a large role in stem cell-based therapies that may require reprogramming, proliferation, differentiation and apoptosis cues to accomplish tissue regeneration. In related work, the effects of FGF-2 delivered in combination with BMP-2 on healing of bone in old mice demonstrates the need for age specific therapies that address the reduced number and activity of osteoprogenitor stem cells.
Part II. The American Society of Testing and Materials International (ASTM) is a premier developer and provider of voluntary consensus standards, related technical information, and services that contribute to the reliability of biomaterial devices and tissue engineered medical products. Over 250 published standards have been written by technical committee F04 on Medical and Surgical Materials and Devices since its establishment in 1962 and are available on the ASTM website (www.astm.org). These standards play a critical role in regulation and commerce. Approximately 30% of these standards have been recognized by the US FDA, Center for Devices and Radiological Health and using those standards accelerates new product approval. Dr. Kuhn has served as a task force chair for five medical product standards and is F04.42 Biomaterials and Biomolecules subcommittee chair. This presentation will describe the ASTM standards development process for biomaterials and biologics using case studies. Standards development activities are valuable because they can streamline your research, increase your global visibility and help get medical devices and regenerative medicine/tissue engineering products into patients faster.
4 maggio
ore 11
Ed. 7
Alessandro Balsamo

Riferibilità delle misurazioni a coordinate: principi adottati all'INRIM

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Le CMM (Coordinate Measuring Machines) sono strumenti flessibili e riprogrammabili, in grado di misurare qualsiasi geometria, anche molto complessa; questo ne costituisce il pregio principale. Dall'altra parte la garanzia della riferibilità è difficile da ottenere: ogni misurazione fa storia a sé. È storia complessa: per calcoli essenziali (ad esempio l'approssimazione di una circonferenza a partire dalle coordinate dei punti misurati) non sono disponibili formule chiuse ma solo algoritmi iterativi; le grandezze d'ingresso per il calcolo dell'incertezza sono alcune centinaia con significative correlazioni; il mal condizionamento numerico spesso intrinseco ad una misurazione amplifica l'influenza di alcune grandezze d'ingresso.
Nel seminario si affronteranno i principi generali che sono stati messi a punto all'INRIM, per garantire la riferibilità di categorie di tarature, basati essenzialmente sul confronto con opportuni campioni tarati di geometria più semplice.

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21 aprile
ore 11
Ed. D
Arash Hadadian
Politecnico di Torino

Energy harvesting based on magnetostrictive materials

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Energy harvesting is the conversion of energy present in the environment into electrical energy. It is identical in principle to large-scale renewable energy generation (e.g. solar, wind power, thermal), but very different in scale. In the last decades, many researches have been focused on sensor networks, especially with the help of new technologies like GPS, GSM and, in general, wireless communications. To make these systems autonomous a power supply is needed, but batteries require at least an annual maintenance and the periodic replacement makes such systems less autonomous. Energy harvesters, having a lifespan of 10 or 20 years, are an interesting alternative to batteries because they do not need human intervention and are environmentally friendly. During my speech three different type of harvesters will be discussed and analyzed.
20 aprile
ore 10:30
Ed. D
Davide Peddis
Istituto di Struttura della Materia (ISM-CNR)

Design of magnetic nano-architecture

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A physical property depends on the size of an object, if its size is comparable to a dimension relevant to that property. In magnetism, typical sizes are in the nanometer range, leading to a drastic change of magnetic properties at the nanoscale. In particular, magnetic nanoparticles have generated much interest because of their possible applications in high density data storage, ferrofluid technology, catalysis and biomedicine (drug delivery, contrast enhanced MRI). In addition NPs play an important role in nature, as they are commonly found in soils, sediments and rocks and may store information on the past Earth’s magnetic field as well as environmental conditions at the time of sediment deposition.
In the last two decades, great attention has been directed towards these materials, mainly discussing physical properties in term of their dependence on particle size. Recent studies have demonstrated that besides the particle size, other factors such as, chemical composition, magnetic structure, and magnetic interactions strongly influence magnetic features of nanocrystals. On the other hand, changing the physical properties without significant variation of the particle size is not trivial and for this reason few examples of comprehensive studies are present in literature. In this view, this contribution focuses on the design of magnetic nanostructured in order to govern the magnetic properties beyond the effect of particle size. Particular attention will be devoted to discuss interparticle magnetic interactions and magnetic structure (e.g. cationic distribution and spin canting) as a tool to modify magnetic properties of nanoparticle based materials.
18 aprile
ore 10
Giuseppe Tettamanzi
School of Physics and CQC2T,
University of New South Wales, Sydney, Australia

Precise GHz single-electron pumping with silicon quantum nano-structures

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On-demand transfer of single electrons at sub-nanosecond timescales with semiconductor nanostructures has attracted great interest in quantum technologies since the early 90s. The technique has been developed to enable a quantum realization of the ampere, fermionic quantum optics, quantum computers.
Silicon implementation promise to simplify the operation of single electronics in light of the mature single dopant and MOS technologies, offering good control of the electrostatic confinement.
The talk will introduce a model for single-dopant devices, and experimental results on MOS quantum dots. Precise single-electron transfer at temperatures as high as 4 K and frequencies in excess of 3.5 GHz has been achieved.
6 aprile
ore 11
Giovanni Borasi
Università degli Studi di Milano-Bicocca,
Istituto di Bioimmagini e Fisiologia Molecolare (IBFM-CNR)

Ultrasuoni focalizzati: aspetti tecnologici, dosimetria MR ed US in campo clinico ed applicazioni terapeutiche

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La prima parte del seminario prenderà in esame le più avanzate tecniche per le terapie tumorali basate su HIFU (High Intensity Focused Ultrasound) evidenziando le necessità metrologiche in ambito clinico e pre-clinico.
La seconda parte analizzerà lo stato dell'arte relativo alla dosimetria elettromagnetica e ultrasonora, connesso con i possibili sviluppi delle tecniche diagnostiche e terapeutiche.
2 febbraio
ore 11
Bruno Desruelle
Institut d'Optique d'Aquitaine

A new generation of ultra-high performance instruments based on laser-cooled atoms

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After 30 years of academic research, intensive developments are being conducted to improve the compactness and the reliability of quantum physics experimental set-ups in order to transfer such devices from laboratory-based research to an operational utilization.
This seminar will be dedicated to the presentation of the Absolute Quantum Gravimeter and the atomic clock that are being developed by Muquans. We will present in detail the principles of operation and the main features of our instruments. Their performances in terms of sensitivity, stability and accuracy and the latest results they achieved will be reviewed. We will then discuss their use to support other research activities.
Muquans is a French SME specialized in high-precision measurements based on laser-cooled atoms. Muquans is a spin-off from Institut d’Optique (LP2N) and Observatoire de Paris (LNE-SYRTE), where the core of our products has been developed for more than 15 years. After 4 years of activity, Muquans has built a highly-experienced team of 20 scientists and engineers gathering a deep expertise in various technological domains.

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