3^rd International Conference on Magnetism and Magnetic Materials October 22-23, 2018 Rome, Italy

Chair

Consiglia Mocerino

Sapienza University of Rome-MIUR, Italy

Co-Chair

Dmytro A Bozhko

Universität Kaiserslautern, Germany

Session Introduction

Fedor Pudonin

P.N. Lebedev Physical Institute of RAS, Russia

Title: Nanoisland magnetic films: Technology and possible applications

Biography:

Fedor Pudonin is the Head of Laboratory in P.N.Lebedev Physical Institute Russian Academy of Science, Russia. He is the chief researcher in the Laboratory of Heterogeneous Systems Physics.

Abstract:

Now there has been a significant interest in the technology of obtaining and studying magnetic nanoisland films. This is due both to the enormous applied potential of these objects. We used the RF-sputtering method to obtain nanoisland films of magnetic materials such as FeNi, Co, Ni, etc. In this report we will present the results of our work on obtaining magnetic nanoisland films and some applied aspects of these structures. Since the deposition rate is a stable value at constant technological parameters, we deposit thin films whose effective thickness was determined by the time of deposition. There is a critical thickness d*(percolation threshold) below which the films are nanoisland, and films with effective thickness d>d* become continuous. To determine the d* value, we have grown several series of FeNi films with effective thicknesses from 0.5 to 3.0 nm with thickness steps Δ~0.07 nm. The standard polished ceramic plates (sitall), crystalline silicon, silicon nitride, glass, as well as thin Al₂O₃ layers deposited on silicon were used as substrates. Figure 1 shows an image of some island FeNi films. To determine d*, the dependences of the permittivity e(w) and conductivity s on the thickness were studied. It was found that Re e(w) and δ=[σ (T=300 K) - σ(T=77 K) simultaneously change sign at d~1.6-1.8 nm, which indicates the presence of a percolation transition at d*~1.6-1.8 nm. Thus, FeNi films with an effective thickness d<1.6 nm are island. We have shown that photoconductivity in the range 500-1500 nm, anomalous conductivity in weak electric fields, giant dielectric constant, and other unusual properties are observed in nanoisland films of FeNi and other metals. We proposed to use nanoisland FeNi films in which the effect of anomalous conductivity is observed as labels that can serve as a protection for various documents and securities and other products. Nanoisland films can also be used to create sensors of superweak magnetic fields at room temperature. For this, we fabricated multilayer island structures such as [FeNi/Co]_N in figure 2. With the help of X-ray studies it was shown that in such systems the island layers do not mix and they really are periodic structures. It was found that these structures are capable of detecting (changing their resistance) magnetic fields H<10^-11 T. This is a great result and we hope to improve it.

Consiglia Mocerino

Sapienza University of Rome—MIUR, Italy

Title: Efficiency of nanotechnologies in the high performance of buildings

Biography:

Consiglia Mocerino, graduated cum laude with a Master of Science degree in Architecture, Ph.D. in Urban Recovery and Regeneration and specialist in Restoration of monuments, has held at the Faculty of Architecture, Sapienza University of Rome, teaching and research collaboration and teaching assignments, as a contract professor, in Architectural Technology. In the same Faculty she obtained the nomination of subject expert in the discipline of Technology of Architecture and Industrial Design. She is an expert in research on issues related to innovation and technological experimentation of systems and products in efficient, intelligent, low impact, environmentally friendly architectures, innovative materials and the application of third generation nanotechnologies.

Abstract:

New research in the field of technological innovation, with nanotechnologies and nano-structured eco-active materials, smart materials that change according to meteorological and atmospheric flows, with new adaptive and smart models, etc. identify new processes in the efficient building of infrastructures in cities and territories, with low environmental impact and reduction of CO₂. Objectives of innovation and sustainability with use of functional materials that mainly focus on optical, magnetic, electrical properties, such as those of semiconductor, magnetic materials, etc. with the dematerialized technologies and high performance in the building and use of sustainable materials with high solar transmittance, lightness, air quality and low thermal conductivity. So methodologies with the application of efficient nanostructured materials including silica aerogels, the doped materials by epoxy resins with carbon nanotubes (CNT), much stronger than steel, intelligent bio phase change materials (PCM), bioplastics, etc. Application of advanced materials such as aerographite, based on carbon nanotubes, with characteristics of resilience, strength, flexibility and durability, aimed at different uses in the building sector of the construction industry, for super-light energy accumulators, for purification devices of air and water. Distinguishing materials by environmental quality since recyclable, renewable and biodegradable, linked to chemical/physical, mechanical and technological, while denouncing criticality and application limits for the protection of human health. High performance requirements of architectural beauty even through transparency and surface gloss, with nanostructured materials ecoactive high performance, glassy and light-sensitive materials, iridescent and translucent colors, from thermal comfort with use of minimum thickness. The challenge is in the application of advanced materials in the emerging areas of digital fabrication for environmental sustainability and in the efficient, intelligent and sustainable building sector.

Victor V Sokolov

MIREA— Russian Technological University, Russia

Title: Macroscopic dynamics of ferrofluids

Biography:

Victor V Sokolov is a Professor at MIREA-Russian Technological University, Russia. His activities and awards include the Russian Government Premium in Education (2013), Honoured Worker of Higher Education of the Russian Federation (2003), Certificate of Soros's Associate Professor of Physics (1998). He is a Member of the Russian National Committee on Theoretical and Applied Mechanics. His research interests lie in macroscopic theory of continuum with frozen-in magnetization and Hamiltonian dynamics of complex fluids.

Abstract:

Ferrofluids (magnetic fluids, magnetic nanofluids) are ultrastable colloidal suspensions of magnetic nanoparticles in non-polar and polar carrier liquids. The most striking feature of a ferrofluid is that it is a liquid with strong magnetic properties. The macroscopic dynamics of ferrofluids remains a subject of interest. Here we concentrate mainly on the two limiting cases. One corresponds to the assumption about equilibrium magnetization of ferrofluids i.e., under dynamic perturbations of the ferrofluids, the relaxation time of a magnetic field strength to its equilibrium value is infinitely small. Another limiting case corresponds to the assumption of frozen-in magnetization. The relaxation time of a magnetic field strength to its equilibrium value is infinitely large. The physical grounds for introducing this limiting case were descriptions of dynamic processes, in particular, ultrasound propagation in ferrofluids. The obtained expression for the velocity of fast magnetosonic waves describes the existing experimental data on the anisotropy of ultrasound wave propagation in ferrofluids. The previous theories could not describe the propagation of ultrasound waves in magnetic fluid under external magnetic field. The prediction concerning the existence of new waves, namely slow magnetosonic wave and Alfvén-type wave in ferrofluids seems very important and requires an experimental verification. We believe these waves would prove a most prolific area of experimental research.

Vladyslav O Cheranovskii

V.N. Karazin Kharkiv National University, Ukraine

Title: The electron correlation effect on the magnetic properties of quasi-one dimensionalmaterials on the base of graphitic nanoclusters with embedded transition metals

Biography:

Vladyslav O Cheranovskii has completed his Doctor of Sciences in the year 1994 from Institute for Single Crystal. He is the Professor of V.N.Karazin Kharkiv National University, Department of Chemistry. He has published 49 papers recognized by Scopus and Web of Science databases. He is working in field of Solid State Physics and Quantum Chemistry. His main subject of interests includes strongly correlated electron system quantum theoretical simulation of electron structure and thermodynamics of nanomagnets.

Abstract:

It is well known, the phase diagrams of the nanostructured magnetic materials demonstrate a variety of low-spin and high-spin states. The switch ability of these states is the central point to potential applications in molecular spintronics and high-density magnetic data storage. In this work, we studied the energy spectrum and thermodynamics of quantum Heisenberg spin model for graphitic nanoribbons with periodically embedded heteroatoms and model chain magnets formed by triangular graphitic clusters. The exact diagonalization study, density matrix renormalization group and Quantum Monte-Carlo method based on stochastic series expansion approach were used for this purpose. We found that clusters with frustrated interactions could exhibit spin switching when the corresponding coupling parameters are changed. For several carbon nanoribbons, we found macroscopic ground state spin and intermediate magnetization plateau. We also studied the exact thermodynamics of infinite distorted nanoribbons described by the special case of Heisenberg-Ising model. Special attention was given to the doped systems described by single-band Hubbard model with strong electron repulsion at partial electron filling. Here we used cyclic spin permutation formalism to derive the corresponding low-energy lattice Hamiltonians. We found numerically the possibility of the spin switching with the change of model parameters. We also demonstrated that the correlated hopping terms, which are present in our Hamiltonians, may change significantly the lowest energy spectra of the corresponding magnets in comparison with the similar description within the framework of the t-J model.

Victor Pavlov

Ioffe Institute of Russian Academy of Sciences, Russia

Title: Photo-induced magneto-optical phenomena in magnetic semiconductors: europium chalcogenides

Biography:

Victor Pavlov has completed his PhD in the year 1993 and second PhD in the year 2007 at the Ioffe Institute, St Petersburg, Russia He is the laboratory head of optical phenomena in magnetic and semiconductor crystals He has published more than 80 papers on linear and nonlinear magneto-optical phenomena in bulk magnetically ordered materials and nanostructures.

Abstract:

Europium chalcogenides EuX (X = O, S, Se, Te) are a compact group of magnetic semiconductors with unique electronic, magnetic, optical and magneto-optical properties. The physical properties of the europium chalcogenides EuX are determined by the electronic structure of the Eu²⁺ ions, which have strongly localized 4f⁷ electrons with a large spin S = 7/2. A photo-induced Faraday effect (FE) was studied in the chalcogenides EuTe and EuSe by the optical pump-probe technique using continuous lasers and a broadband light source. The photo-induced FE was investigated as a function of the intensity of light, magnetic field, and temperature. Figure 1 shows field dependences of the photo-induced FE in EuTe at various optical pumping intensities. It has been established that resonant excitation of the 4f⁷5d⁰ → 4f⁶5d¹ optical electric-dipole transition in EuTe produces magnetic polarons with a quantum efficiency of about 10% and a magnetic moment exceeding 600 μB for EuTe and 6000 μB EuSe at low temperatures. A quantum mechanical model has been developed for calculating the photoinduced FE associated with the formation of giant magnetic polarons in EuTe. The developed theory describes well the experimentally observed dependencies. The optical pump-probe technique with a femtosecond time resolution was used to study ultrafast dynamics in EuTe near the absorption band gap. A magnetic-field-induced crossover from the inverse FE to the optical orientation was observed. In conclusion, a number of new photo-induced optical effects in magnetic semiconductors EuX were observed.

Adil Guler

Marmara University, Turkey

Title: Process, characterization and physical properties of 3d transition ion doped-tetrahedrite compounds

Biography:

Adil Guler, Lecturer, now is a Researcher in Marmara University, Ataturk Faculty of Education, Department of Computer and Instructive Technology Teacher. He completed his BSc degree in Physics and Specialist in Magnetic and Superconductive materials. He got his PhD at Marmara University, Department of Physics. He works in the research group of Prof. Dr. Arunava Gupta as a Research Scientist in Alabama State University. He also makes projects with Assist. Prof. Dr. Cihat Boyraz on superconductivity and magnetism. His magnetic superconductivity group has been working on Fe-based superconductors for 5 years.

Abstract:

The demand on new and waste energy potential increases with decreasing energy sources in the world. This situation brings new attitudes globally on using waste energy and discovering new energy sources. Among the main types of waste renewable energy, thermoelectricity which is converted electric energy from waste heat play a very important role on science and with its applications on industry. Among the many sulphate salts, the group of tetrahedrite/tennantite has potential interest in physics in many ways are widely used in thermoelectric and photovoltaic applications. The importance of the thermoelectric researches is coming from neglecting the high material costs and long-termed synthesizing procedures. On the other hand, the properties of cheapness, accesibility, minimized risk factor in the usage of thermoelectric materials make important for technological applications in scientific studies. Recently, tetrahedrite Cu₁₂Sb₄S₁₃ material doped with different dopant elements exhibits important thermoelectric properties. Tetrahedrite, Cu₁₂Sb₄S₁₃, is emerging as a promising phase in thermoelectrics. It exhibits an intrinsically low lattice thermal conductivity (κL = 0.4W m−1 K−1 at 700 K) due to unique features in its crystal structure. At the same time, the defect zinc-blende lattice ensures a good crystalline pathway for electron transport. At the same time, tetrahedrites are one of the most abundant TE minerals on Earth. In this study, main material Cu₁₂Sb₄S₁₃ tetrahedrite doped with 3d ions such as Sb and As were synthesized using solid state reaction method. The annealing procedure was optimized for Sb and As doped -Cu₁₂Sb₄S₁₃ tetrahedrite samples. Structural characterization was done by X-ray diffraction method (XRD). Scanning electron microscope (SEM) and an in-situ electron dispersive spectroscopy (EDS) were used for particle size and elemental compositions respectively. The compositions were also analyzed by electron spin resonance (EPR) and vibrating sample magnetometer (VSM) tools as shown in images.