Day 2 :
Keynote Forum
Michael W Roth
Northern Kentucky University, USA
Keynote: Exploration of intermediate phases of matter on surfaces
Time : 08:45-09:15
Biography:
Michael W Roth is a Computational Physicist, Professor and Chair at Northern Kentucky University’s Department of Physics, Geology and Engineering Technology. He has numerous publications and presentations in the field of dynamics and surface phase transitions of atomic and molecular systems adsorbed onto graphene and graphite. Other interests include classical astrophysical simulations of planetary formation as well as material point method simulations of impact, and material stress and failure.
Abstract:
As computing power has advanced over the last 20 years, we have been able to use molecular dynamics computer simulations to better understand the phase transitions exhibited by various molecules adsorbed onto surfaces. In particular, great advances have been made in understanding the nematic and smectic crystal phases that exist in between solid and liquid phases of organic layers. The means of characterizing these fascinating phases of matter and the mechanisms that drive associated phase transitions will be discussed, followed by extensions to current work on more complex organic layers. Finally, the current trajectory of large scale computing along with a computational wish list will be discussed. Throughout the talk there will be anecdotes from our research group that will give context to various elements of the work presented here.
Keynote Forum
C S Ting
University of Houston, USA
Keynote: Topological phase transitions and a two-dimensional Weyl superconductor in a superconductor/half-metal heterostructure
Time : 09:15-09:45
Biography:
C S Ting is a Professor of Physics at the University of Houston, USA. His major research area has been on theoretical condensed matter physics including transport theories in various solid state systems, superconductivity in copper oxide materials and iron pnictides, magnetism, metal-insulator transition, electronic property of graphene, solids with the spin-orbit couplings and strongly correlated electron systems. He is the Principal Investigator of Theory at the Texas Center for Superconductivity at the University of Houston, and a Fellow of APS in the Division of Condensed Matter Physics.
Abstract:
We find a series of topological phase transitions in s-wave superconductor/half-metal thin-film heterostructure, by tuning the direction of the magnetization of the half-metal film. The heterostructure is grown on top of a semiconductor. The function of the semiconductor surface is to provide a Rashba spin-orbit coupling to charge carriers in the half-metal film where the superconductivity could be induced via the proximity effect from the superconducting film. Employing numerical and analytic methods, we explore the novel physics in the half-metal film and its edge states, these include transitions from a topological superconducting phase with a bulk gap to another phase without a bulk gap, but has a ubiquitous local gap which implies only parts of the Fermi surface being gaped. At the same time, the edge states change from counter-propagating Majorana edge modes to unidirectional Majorana edge modes. In addition, we find transitions between the second phase and a nodal phase which turns out to be a two-dimensional Weyl superconductor with Fermi line edge states. We identify the topological invariants relevant to each phase and the symmetry that protects the Weyl superconductivity. Experiments to detect these phases are going to be proposed. The physics with a d-wave superconducting film in the heterostructure will also be discussed.
- Nano and Mesoscopic Scale
Chair
Elie A Moujaes
Federal University of Rondonia, Brazil
Co-Chair
Yuko Ichiyanagi
Yokohama National University, Japan
Session Introduction
Nathan Newman
Arizona State University, USA
Title: Fundamental mechanisms that determine the loss tangent and temperature coefficient of resonant frequency (Ï„f) in modern microwave ceramic dielectrics
Time : 09:45-10:05
Biography:
Nathan Newman is a Professor of Solid State Sciences and is a faculty member in the Materials Program at Arizona State University. His research interests focus on the investigation of novel solid-state materials for microwave, photonic and high-speed applications. His current work involves synthesis, characterization and modeling of novel superconductor junctions and materials, III-N semiconductors, low loss dielectrics for microwave communication, and novel photovoltaic material. He is an author and co-author of over 200 technical papers, has 12 patents, has an h-index over 40 and his papers have been cited over 5,000 times. He has received the IEEE Van Duzer Award, is a Fellow of the IEEE and the American Physical Society, and has won Faculty Teaching Awards at Northwestern University and Arizona State University. He also serves as an Associate Editor for Materials in the IEEE Transactions of Applied Superconductivity and has served as the Chair of the US Committee on Superconductor Electronics and ASU’s LeRoy Eyring Center for Solid State Sciences.
Abstract:
Despite the practical importance of achieving a small loss tangent (tan δ) and near-zero temperature coefficient of resonant frequency (τF) for microwave communication systems, a fundamental understanding of which mechanism determine these important parameters had not been firmly established. In this talk, I will focus on my group’s work using modern experimental and theoretical condensed matter methods to identify the responsible mechanisms. We will focus our discussions on results from Ni-doped BaZn‑Ta2/3O3 (BZT), since it is the highest performer at room temperature. We will also show that the conclusions are general for other commonly-used materials. Ba(Zn1/3Ta2/3)O3 exhibits the unusual combination of a large dielectric constant, εr, and a small loss tangent at microwave frequencies. Using ab-initio electronic structure calculations, we show that d-electron bonding in BZT and related materials is responsible for producing a more rigid lattice with higher melting points, enhanced phonon energies than comparable ionic materials and thus inherently less microwave loss. The properties of commercial materials are optimized by adding dopants or alloying agents, such as Ni or Co to adjust the temperature coefficient, tF to zero. This occurs as a result of the temperature dependence of ε offsetting the thermal expansion. At low temperatures, we show that the dominant loss mechanism in these commercial materials comes from spin excitations of unpaired transition-metal d electrons in isolated atoms (light doping) or exchange coupled clusters (moderate to high doping), a mechanism differing from the usual suspects. At high temperatures, we give evidence that loss also arises and may be dominated by localized hopping transport. The temperature coefficient of resonant frequency (τf) of a microwave resonator is determined by three materials parameters according to the following equation: τf = - (½τε+½τμ+αL), where αL, τε and τμ are defined as the linear temperature coefficients of the lattice constant, dielectric constant, and magnetic permeability, respectively. We have experimentally determined each of these parameters for undoped and Ni-doped Ba(Zn1/3Ta2/3)O3 materials. These results, in combination with density functional theory (DFT) calculations, have allowed us to develop a nearly complete understanding of the fundamental mechanisms responsible for τf.
Kirstin Alberi
National Renewable Energy Laboratory, USA
Title: Strongly localized isoelectronic impurities for synthesizing novel semiconductor alloys
Time : 10:05-10:25
Biography:
Kirstin Alberi received a B.S. in Materials Science and Engineering from the Massachusetts Institute of Technology in 2003 and a PhD in Materials Science and Engineering from the University of California, Berkeley in 2008. She is currently a Senior Staff Scientist at the National Renewable Energy Laboratory, where she conducts basic research on the epitaxy of novel semiconductors and heterostructures and studies the optical and electronic properties of semiconductor alloys for photovoltaic and solid-state lighting applications. She also serves as a member of the Editorial Board of Journal of Physics D: Applied Physics.
Abstract:
Isoelectronic impurities whose electronegativity and size are very different than the host atom the substitute can introduce resonant states in either the conduction or valence band that induce substantial changes in the electronic bandstructure. Nitrogen is well known to create a resonant state above the conduction band minimum that causes band mixing and a 180 meV/% N drop in the bandgap energy. Bismuth also produces a similar effect in the valence band of GaAs that leads to a bandgap reduction of 88 meV/% Bi. This strong dependence of the bandgap energy on the alloy composition makes both GaAs1-xNx and GaAs1-xBix alloys potentially important materials for high efficiency multijunction solar cells, infrared lasers, LEDs and detectors. Moreover, they provide rich systems for exploring the interaction of localized states dispersed throughout a host matrix. Statistically occurring N pairs and clusters strongly localize electrons in the bandgap, while analogous Bi-related states localize holes. These states can then be made to interact by increasing their concentration. For example, wavefunction overlap between localized N pair states creates delocalized superclusters that further perturb the host GaAs electronic structure. Application of a magnetic field can then be used to reduce the Bohr radius of excitons bound at these states, fragmenting the superclusters. The investigation of such phenomena provide insight into the evolution of localized impurity states into delocalized alloy states and shed light on the birth of novel semiconductor alloys.
Yuko Ichiyanagi
Yokohama National University, Japan
Title: Local structure analysis and biomedical applications of multifunctional magnetic nanoparticles
Time : 10:25-10:45
Biography:
Yuko Ichiyanagi has completed her PhD from Yokohama National University, Japan. She is an Associate Professor of Yokoham National University since 2009. She has published more than 30 papers in reputed journals and has been serving as an international advisory committee member of some reputed conferences.
Abstract:
Magnetic nanoparticles (MNPs) encapsulated with amorphous SiO2 ranging several nm were prepared by our original wet chemical method. Local structure of magnetic cluster was analyzed by X-ray absorption fine structure (XAFS). MNPs prepared by this method, Si ions are located on the surface, and this characteristic structure enables amino-silane coupling and functionalization is made easier. We have established the way of functionalization of these magnetic nanoparticles in order to conjugate other molecules. We have confirmed that our particles were introduced into the living cells, and these particles were localized by the external magnetic field. Then cancer cell selective NPs were further developed by attaching folic acid. Mn-Zn ferrite nanoparticles were prepared and optimized in composition and particle size. To estimate heating effect of magnetic nanoparticles for an application of hyperthermia treatment, ac magnetic susceptibilities were measured and analyzed. Samples were examined for heating agent from the result of frequency dependence and particle size dependence of imaginary part of ac
magnetic susceptibilities χ”. A temperature increase of approximately 18 K was observed in a 192-Oe, 15-kHz field for Mn-Zn ferrite NPs. Increase rate of temperature was found to be high enough to suppress cancer cells. In vitro experiment showed an extensive hyperthermia effect. In addition, we have suggested out NPs as an agent of MR imaging, CT imaging, magnetic particle imaging (MPI) and mass spectrometric imaging for diagnostics. Our magnetic nanoparticles are expected to develop theranostics system.
Elie A Moujaes
Federal University of Rôndonia, Brazil
Title: Magnetization of ultrathin [Fe1-cNic]n alloy nanojunctions between Fe or Co leads using an EFTMFT model
Time : 11:05-11:25
Biography:
Elie A Moujaes completed his PhD in theoretical condensed matter physics at the age of 28 from the University of ottingham, UK (2007). He has two postdoctoral xperiences: One at the University of ottingham and the other at the Federal University of Minas Gerais (UFMG). He has more than 10 publications in well respected journals and is currently an adjoint professor at the Federal University of Rôndonia. His research involves magnetism and magnetic materials as well as DFT calculations associated with electron phonon coupling for various bi-dimensional exotic materials.
Abstract:
The Fe and Ni sublattice magnetizations of ultrathin iron-nickel alloy nanonjunctions [Fe1-cNic] between Fe and Co leads are inspected. For c ≤ 0.4, the alloy has a bcc structure and becomes fcc otherwise. A combined EFT and MFT treatment is used to obtain the sublattice magnetizations of Fe and Ni in the individual layers as a function of temperature and concentration. This is achieved by calculating single site spin correlations within EFT and making use of reliable experimental data such as lattice parameters a, stiffness spin constants D, and Curie temperatures Tc leading to reasonable values of the exchange parameters J. According to our model, the alloys forming the bcc nanojunctions we examine (c = 0.0841; 0.204; 0.268) are ferrimagnetic with the absence of a compensation temperature while those for the fcc structures (c = 0.5; 0.81) are ferromagnetic. These EFT results feed the MFT calculations for the nanojunction from the interface inwards. The effect of adding several alloy layers to both bcc and fcc types is also considered. The sublattice magnetizations are necessary elementsfor certain spin dynamic computations, such as ballistic magnon transport across embedded nanojunctions in magnonics.
Jan Smotlacha
Joint Institute for Nuclear Research, Russia
Title: Electronic structure of graphene wormhole and graphitic nanocone
Time : 11:25-11:45
Biography:
Jan Smotlacha has completed his Ph.D at the age of 33 years from Czech Technical University. Now he works as the senior research scientist in the Bogoliubov Laboratory of Theoretical Physics in the Joint Institute for Nuclear Research in Dubna. He has published about 13 papers in reputed jounals or conference proceedings.
Abstract:
The graphene nanostructures are the materials derived from the hexagonal carbon lattice. In our research of the graphene nanoparticles we are concerned with two kinds of them: the graphene wormhole and the graphitic nanocone. Due to extremely curved geometry of the graphene wormhole, the relativistic effects could be observed here: the mass of the electrons appearing close to the wormhole center can be much higher than the invariant mass. This fact together with the effect of the spin-orbit interaction can cause the appearance of the chiral massive fermions. The calculations show that on the wormhole bridge the density of the corresponding zero states should be very high, so it could be used to detect the wormhole centers during the production. The geometric structure we acquire by the connection of 2 graphene sheets with the help of 12 heptagonal defects. In addition to the theoretical calculations, we carried out the numerical simulations. The graphitic nanocone is the structure which arises by the addition of one or more pentagonal defects into the original graphene structure. In the numerical simulations, the calculations of the electronic structure are based on the exact atomic structure, in the continuum approximation we work with different approximations: either we suppose the pure conical geometry or we simulate the smooth geometry close to the tip by different supplementary effects like the placement of the charge into the place of the tip. Next significant effect influencing the electronic structure of the nanocone is the spin-orbit interaction.
Mukhtar Ahmad
COMSATS Institute of Information Technology, Pakistan
Title: Synthesis and characterization of Zn-substituted lithium cobalt ferrite using sol-gel autocombustion for a cathode material in lithium ion batteries
Time : 11:45-12:05
Biography:
Mukhtar Ahmad is a assosate professor in university of Cosmsats, Pakistan. He is published so many papers.He is research interestes are M-type hexagonal ferritesGd-substitutionSEM analysisDC resistivityM–H loops.
Abstract:
Li-ferrites are scientifically advanced smart materials and their structural and magnetic properties can be modified for a particular application by controlling the synthesis conditions and better choice of metal ions. In the present work, single phase samples of lithium zinc ferrites with general formula LiCo0.5-xZnxFe2O4 (where 0≤x≤0.5) were synthesized by sol gel auto combustion method. To study the mass loss (%) and endothermic and exothermic reactions as a function of temperature, thermal analyses (TGA/DTA) were carried out for a selected sample. The structure and morphology for all the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns confirm that all the samples retain phase purity of spinel structure when substituted with Zn contents in place of Co ions. However, the structural parameters such as lattice constant, cell volume and X-ray density were altered after Zn-substitution into the spinel lattice. The SEM images show that the grain size estimated by line intercept method was found to be unchanged by substituting Zn ions because the values of ionic radii of Zn and Co are almost equal. The M-H loops for all the samples show a low value of coercivity (a few hundred oersteds) which confirms the soft magnetic nature of these ferrites. Moreover, the values of saturation magnetization and remenance are in good agreement with earlier reported values for this structure. The observed parameters suggest that these ferrites may be potential candidates for a cathode material in Li-ion batteries, core materials and microwave devices.
M Kofoworola Awodele
Ladoke Akintola University, Nigeria.
Title: Transport properties of “man-made†crystalline: semiconductor superlattice
Time : 12:05-12:25
Biography:
M Kofoworola Awodele received MSc in Physics from University of Ibadan, Nigeria in 2002 and a PhD in Physics from Loughborough University, Loughborough UK in 2015. She is working at Ladoke Akintola University of Technology, Ogbomoso. Her research interest is theoretically investigating novel mechanism for electron and spin transport in nanostructures looking at electron transport in semiconductor superlattices.
Abstract:
The electron transport in semiconductor superlattices exhibits interesting phenomena, which are quite different from those that occurred in a bulk material. This depends on the electronic band structures in the semiconductor superlattices. The energy band gaps of the superlattices are aligned, but the magnitudes of the band gaps are different. The difference in the width of the energy gap in different semiconductors forms the boundary of the conductivity band for perfect semiconductor superlattices that is modulated periodically and leads to the formation of energy minibands.
Tonezzer Matteo
University of Trento, Italy
Title: Nanosensors based on single and multiple metal oxide nanostructures
Time : 12:25-12:45
Biography:
Matteo Tonezzer received his PhD degree “cum laude” in Physics at the University of Trento (Italy) in 2011. He won the Young Scientist Award from the European Materials Research Society (EMRS) and worked in research centers in France (ESRF), Brazil (UFMG), Vietnam (HUST), Italy (INFM) and USA (GeorgiaTech). He currently works for IMEM in the Italian National Research Council, authored more than twenty papers on international journals, is reviewer for 25 international peer-review journals, editor of international peer-review journals, organizer and chairman of international conferences. His main area of interest concerns the sensing properties of nanostructured organic and inorganic materials.
Abstract:
Nanostructured metal oxides are nowadays attracting more and more interest in several fields due to their unique properties. Binary n-type semiconducting oxides (SnO2 and ZnO principally) are known as excellent gas-sensing materials, whereas p-type oxides (mainly NiO) are only recently being investigated, because they are more difficult to grow in a controlled way. In this presentation we show both n- and p-type metal oxide nanowires grown by different methods, studying their sensing properties in multi- and single-nanowire devices. Single SnO2 nanowires are grown by CVD and used to experimentally study the depletion layer modulation model that is at the basis of such sensing devices. The mechanism is confirmed, with a depletion layer experimental value of 14 nm. Furthermore, stable and very fast (few seconds) response and recovery are found, proving that these sensors are good for real-time applications. NiO polycrystalline nanowires grown via a simple hydrothermal method are used as sensors with tuneable selectivity in different practical applications related to clean energy: their response to different gases can be enhanced in order to optimize their use with different steam reforming fuel cells, and demonstrating that post-processing of the nanosensors outputs can be a valuable tool to overcome metal oxide weaknesses. At the end of this contribution we will show how metal oxide micro- and nanostructures can be functionalized with organic molecules to greatly decrease the working temperature of hybrid sensors close to room temperature. The metal oxide – organics interface seems to be crucial to achieve the best performance.
Anshul Kumar Sharma
Guru Nanak Dev University, India
Title: Enhancement of sensitivity in gas chemiresistors based on carbon nanotube surface functionalized with substituted phthalocyanines
Time : 12:45-13:05
Biography:
Anshul Kumar Sharma received his M.Sc. degree in Physics from Department of Physics, Himachal Pradesh University Shimla, India in the year 2009 and he did M.Phil. degree in Physics in the year 2011 from Department of Physics, Guru Nanak Dev University, Amritsar, India. Presently, he is working towards his Ph.D. degree in the same department. His research interests are preparation and characterization of carbon nanotubes based functional hybrid materials and their application as gas sensors.
Abstract:
Carbon nanotubes (CNTs) possessing unique structure and properties are attractive building blocks for novel materials and devices of important practical interest. Particularly, Multi wall carbon nanotubes (MWCNTs) have attracted extensive attention in sensing application owing to their unique one-dimensional carbon nanostructure and electrical properties. However, the insolubility or poor dispersibility of pristine CNTs in common solvents poses a serious obstacle to their further development. Various attempts have been made to obtain homogeneous CNT dispersions in both aqueous and organic media. Among those approaches, chemical modification of side walls, defect sites, and open ends are often found to result in changes of the structural, mechanical, and electronic properties of CNTs. Generally, carbon nanotubes are very sensitive to many types of target molecules showing an apparent lack of selectivity. This drawback of carbon nanotube sensors can be overcome through functionalization of nanotube surface in order to provide molecular specificity or unbalanced promoted sensitivity to a class of chemical species. Introduction of functional groups, such as carboxyl and amino groups, not only can improve CNTs solubility in various solvents, but also are useful for the further chemical link with other compounds. Recently, in order to improve the sensing performance of these MWCNTs based sensors, many sensing materials such as conducting polymers metals and metal oxides have been anchored on the surface of MWCNTs and play important roles in the improvement of the sensitivity and selectivity of the resultant gas sensors. Phthalocyanine (Pc), as an excellent sensing material, has been extensively studied based on its high sensitivities, excellent thermal and chemical stability. Substituting functional groups on phthalocyanine molecules make them soluble in various organic solvents and thus enable them for low cost solution processing techniques such as spin coating and self-assembly etc Therefore, we expect that combining the nanoscale CNTs with gas sensing active Pc would feature not only the intrinsic properties of CNTs and Pc arising from the mutual interaction between CNTs and Pc but also enhance the gas sensing behaviour of CNTs. In this work, we have prepared a hybrid material of MWCNTs-COOH and Hexa-fluorinated copper phthalocyanine (F16CuPc). The formation of F16CuPc/MWCNTs-COOH hybrid was confirmed by UV-Visible, Raman and FT-IR spectroscopy. SEM, TEM and AFM studies revealed that F16CuPc8 molecules were successfully anchored on the surface of MWCNTs-COOH through π-π stacking interaction. Subsequently, a chemi-resistive sensor have been fabricated by drop casting F16CuPc/MWCNTs-COOH hybrid onto alumina substrate. The gas sensing potential of the fabricated hybrid materials has been tested upon exposure to different hazardous gases like NO2, NO, Cl2 and NH3 at different operating temperatures. It has been demonstrated that F16CuPc/MWCNTs-COOH hybrid is highly selective towards Cl2 with minimum detection limit of 100 ppb. The response of sensor increases linearly with increase in Cl2 concentration. The results obtained emphasize on the application of F16CuPc/MWCNTs-COOH hybrid material in Cl2 sensing applications.
Himanshu Verma
University of South Florida, USA
Title: AFM controlled studies of nanoscale polymeric spheres on a Si substrate
Time : 14:00-14:20
Biography:
Himanshu Verma has done Masters in Physics from Michigan Technological University, Houghton, MI in 2006 and Ph.D. in Applied Physics from University of South Florida, Tampa, FL in 2015. Dr. Verma served as Assistant Professor of Physics in Southern Chicago with a community college for 1 year and about to begin investigation on Novel Magnetic Materials as Research Associate at Morgan State University in Baltimore, Maryland.
Abstract:
The understanding of physical motions such as rolling, sliding, stick-slip, and spinning is of great importance, since the energy loss and wear between the contacting surfaces is determined by the mode of motion of these particles. When a lateral force is applied onto a nano size particle lying on a surface, what happens to its translational motion? Does it roll, does it slide, or both? How can the force required be predicted from the particle’s properties? These questions have relevance in technological applications where nano size particles are used in lubricating mixtures and in nano-electromechanical devices, where they are used as building blocks. Using Lateral Force Microscopy to provide the forces required to produce translational motion of nano-sized particles across a planar substrate will help understand the tribological properties that inform their use in such applications. Such knowledge will help in designing new lubricants, hard disk storage technology, new materials for post chemical mechanical polishing (CMP), and generally in the reliable, repeatable and controllable manipulation of nano-size particles on substrates. We have utilized Atomic Force Microscopy and Force Spectroscopy to study the tribological properties of nanoscale polymeric particles to explore how the friction between these nanoscale spherical objects translating over planar substrates is related to interfacial energy and the mechanical properties for these particles. A technique for modifying the mechanical properties was developed and used to provide a set of samples over which we had control of the elastic modulus without corresponding changes in the chemical bonds. Lateral force microscopy was used to measure the force required to translate asymmetric, nanoscale particles of controlled size, surface chemistry and moduli. The effects of work of elastic modulus of polystyrene microspheres, contact radius between particle and substrate have been studied for the different modes of particle translation under an external force.
T V Torchynska
Instituto Politécnico Nacional, México
Title: Emission, structure and aging of silver doped ZnO nanorod films
Time : 14:20-14:40
Biography:
T V Torchynska is Professor of Physics at National Polytechnic Institute of Mexico. She obtained MS (1973) in Solid State Physics at National Technical University of Ukraine, PhD (1978) and Habilitation (1991) degrees in Physics and Mathematics at Institute of Semiconductor Physics at National Academy of Sciences of Ukraine. She is the author of over 350 articles published in prestige journals, the monographs “Mechanisms of Degradation of III-V Semiconductor Light-Emitting Diodes and Lasers”, “Harwood Academic Publisher”, 1997, and “Nanocrystals and Quantum Dots of Group IV Semiconductors” American Scientific Publisher, 2010, 18 book chapters and 14 patents.
Abstract:
ZnO has attracted scientific attention during the last decade owing to its potential application in short-wavelength and hightemperature optoelectronics, such as short-wavelength light emitting diodes, photodetectors, ultraviolet lasers, etc. To fabricate the optoelectronics devices n- and p-type ZnO NC layers are required. As in any II-VI semiconductors, the preparation of p-type ZnO NC layers is the difficult task owing to the high concentration of native shallow donors. It was shown recently that Ag is a most promising element from the group IB atoms for p-type ZnO doping. Additionally, Ag-doping stimulates the near band edge (NBE) emission in ZnO NCs that is interesting for optoelectronics. The emission, structure and the aging process have been studied in the silver doped ZnO nanorods (NRs) obtained by ultrasound spray pyrolysis with different Ag concentrations within of 1-4 at%. Electronic scanning microscopy (SEM), X ray diffraction (XRD), photoluminescence (PL)
spectroscopy and its temperature dependences have been applied. It is revealed that at low Ag content (1-2 at%), the doping improves essentially the structure and emission of ZnO Ag NRs. Simultaneously, the inter-planar distances in ZnO NR crystal lattice decreases and the new Ag related PL band with the peak at 2.87-2.95 eV at 10 K appears in PL spectra. At higher Ag content (3-4%) the PL intensity of majority PL bands falls down together with the stimulation of orange PL band intensity, the inter-planar distances in ZnO NR crystal lattice increase and the formation of metallic Ag nanocrystals have been detected by
XRD. The aging process is accompanied by the new Pl band (2.87-2.95 eV) falls down as well and intensity raising the orange PL band. The PL temperature dependence study permits to analyze the nature of defects responsible for the new Ag-related PL band (2.87-2.95 eV) and for the orange PL band. The optimized concentrations for the Ag doping of ZnO NRs have been revealed.
L. N. Singh
Dr. Babasaheb Ambedkar Technological University, India
Title: Transport mechanism in solgel prepared Nd0.7Sr0.3-xBaxMnO3 (0≤x≤0.3) nanomanganite
Biography:
Dr. L. N. Singh has completed Ph. D. in Experimental Solid State Physics in 1992 at IIT, Bombay. He is the Head, Department of Physics, Dr. B. A. Technological University, Maharashtra, India. He was also worked as Dean, Faculty of Science, Gombe State University and Head, Department of Physics, Gombe State University. He has 20 years of teaching and research experience. He has published more than 20 papers in reputed journals presented more than 50 papers in conference/seminar. He supervised 5 PhD students successfully till this date.
Abstract:
Transport behavior and magnetoresistance in solgel prepared Nd0.7Sr0.3-xBaxMnO3 (0≤x≤0.3) nanomanganite system have been investigated in temperature range 10 -330 K. The composition and structural properties were studied at various concentrations by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). X-ray diffraction (XRD) pattern confirms the single phase nature of the samples with orthorhombic crystal symmetry. The average A-site ionic radii which is directly related to tolerance factor and size variance, plays a vital role in magnetotransport properties. The metal-insulator transition temperature, TMI, shifts toward low temperature with increasing Ba substitution from 205 to 95 K and shows semiconducting like behavior at low temperature. It is shown that the correlated polaron model accounts for the temperature dependence resistivity and magnetoresistance in the entire temperature range. The number of charge carriers, n decreases as Ba2+ ion concentration increases. The small polaron binding energy, ep, is found to decrease as Ba2+ ion concentration increases. The increase in the thermally assisted activation energy, U0, is observed as the system varies from Sr- to Ba- substitution. The number of charge carriers, n, is decreases as Sr2+ ion concentration decreases which is responsible for the increase in resistivity values.
L. N. Singh
Dr. Babasaheb Ambedkar Technological University, India
Title: Transport mechanism in solgel prepared Nd0.7Sr0.3-xBaxMnO3 (0≤x≤0.3) nanomanganite
Biography:
Dr. L. N. Singh has completed Ph. D. in Experimental Solid State Physics in 1992 at IIT, Bombay. He is the Head, Department of Physics, Dr. B. A. Technological University, Maharashtra, India. He was also worked as Dean, Faculty of Science, Gombe State University and Head, Department of Physics, Gombe State University. He has 20 years of teaching and research experience. He has published more than 20 papers in reputed journals presented more than 50 papers in conference/seminar. He supervised 5 PhD students successfully till this date.
Abstract:
Transport behavior and magnetoresistance in solgel prepared Nd0.7Sr0.3-xBaxMnO3 (0≤x≤0.3) nanomanganite system have been investigated in temperature range 10 -330 K. The composition and structural properties were studied at various concentrations by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). X-ray diffraction (XRD) pattern confirms the single phase nature of the samples with orthorhombic crystal symmetry. The average A-site ionic radii which is directly related to tolerance factor and size variance, plays a vital role in magnetotransport properties. The metal-insulator transition temperature, TMI, shifts toward low temperature with increasing Ba substitution from 205 to 95 K and shows semiconducting like behavior at low temperature. It is shown that the correlated polaron model accounts for the temperature dependence resistivity and magnetoresistance in the entire temperature range. The number of charge carriers, n decreases as Ba2+ ion concentration increases. The small polaron binding energy, ep, is found to decrease as Ba2+ ion concentration increases. The increase in the thermally assisted activation energy, U0, is observed as the system varies from Sr- to Ba- substitution. The number of charge carriers, n, is decreases as Sr2+ ion concentration decreases which is responsible for the increase in resistivity values.
Elie A Moujaes
Federal University of Rôndonia, Brazil
Title: Determination of the magnetization of ultrathin [Fe1-cNic]n alloy nanojunctions between Fe and co leads within the realms of MFT and EFT.
Biography:
Elie A Moujaes completed his PhD in theoretical condensed matter physics at the age of 28 from the University of ottingham, , UK (2007). He has two postdoctoral xperiences: One at the University of ottingham and the other at the Federal University of Minas Gerais (UFMG). He has more than 10 publications in well respected journals and is currently an adjoint professor at the Federal University of Rôndonia. His research involves magnetism and magnetic materials as well as DFT calculations associated with electron phonon coupling for various bi-dimensional exotic materials.
Abstract:
The Ising effective field theory (EFT) method has proved to be a successful tool providing the appropriate exchange constants of basic ferromagnetic materials. In this work, Fe and Ni sublattice magnetizations of n-layered ultrathin iron-nickel alloy nanonjunctions [Fe1-cNic]n between Fe and Co leads, c being the Ni concentration inside the alloy, are inspected using a combination of EFT and mean field theory (MFT). Our EFT+MFT cocktail is believed to provide a simple yet accurate picture about the magnetizations, in complex ferromagnetic systems, through the calculation of parameters without the need to complicated theoretical models and in the absence of DFT results. For c < 0.4, the alloy has a bcc structure and becomes fcc otherwise. In the former case, the n layers of the alloy are connected to bcc Fe leads, whereas in the latter case, fcc Co leads are used instead. The exchange constants J and sublattice magnetizations σ calculated through EFT alone, are considered basic ingredients for quantum transport properties across the nanojunctions; total magnetizations within each layer are also exploited. Such EFT-based results then feed MFT calculations for the nanojunction from the interface inwards. Interestingly, it was observed that for bcc nanojunctions, the shape of all magnetization curves is unique for all c and for any value of n. This completely changes for fcc nanojunctions where differences are spotted for various concentrations. Special attention is given to the invar (c=0.5) and permalloy (c=0.81) alloys where some kind of saturation occurs when layers n ≥2 are constructed.
- Meta materials and Magnetic Materials
Chair
Roberto Zivieri
University of Ferrara, Italy
Co-Chair
Rikio Konno
Kindai University Technical College, Japan
Session Introduction
Roberto Zivieri
University of Ferrara, Italy
Title: 2D ferromagnetic nanostructures:a new class of metamaterials
Time : 14:40-15:00
Biography:
Roberto Zivieri is a theoretical condensed matter physicist. He got the Master Degree in Medicine and Surgery and the Master Degree in Physics with honors and the PhD in Physics (grade excellent) from the University of Modena, Italy. He is author of about 200 scientific contributions including 70 articles in international and reputed journals. He has been serving as an editorial board of repute. He is member by invitation of the American Physical Society, of the American Chemical Society and of the Italian Society of Mathematical Physics. He is winner of the APS Award “Outstanding Referees 2016”.
Abstract:
In recent years the study of low-dimensional magnetic systems has become topical for its several technological applications but also for a complete understanding of the underlying physics of magnetic nanostructures. Very recently, for their challenging features, great attention has been given to the investigation of the static and dynamical properties of magnetic nanostructures with special regard to magnonic crystals, a class of periodic magnetic systems characterized by modulated properties. As shown by several theoretical approaches, the ferromagnetic materials composing periodic magnetic systems can be described as metamaterials since they exhibit effective properties. For instance, it is possible to define an effective magnetization and an effective permeability both in a lossless and in a lossy ferromagnetic medium, an effective wavelength and an effective wave vector for collective excitations and, under some conditions, an effective diamagnetic behavior of ferromagnetic periodic systems. Moreover, the band structure of different kinds of magnonic crystals can be determined. The aim of this talk is to give an overview of the recent results obtained on the study of metamaterial and effective properties of two-dimensional ferromagnetic nanostructures. Micromagnetic simulations and simple analytical calculations first applied to thin ferromagnetic films and then to differen kinds of two-dimensional periodic magnetic systems allow to extract the above described metamaterial properties. Some possible applications based on the effective properties for tailoring new magnetic devices are suggested.
Rikio Konno
Kindai University Technical College, Japan
Title: Theory of thermal expansion of heavy fermion systems
Time : 15:00-15:20
Biography:
Rikio Konno has completed his PhD at the age of 28 years from University of Tokyo and postdoctoral studies from Tsukuba University. He is the Science Section Head of Kindai University Technical College, a famous college based on Kindai University in Japan. He has published more than 25 papers in reputed journals.
Abstract:
We investigated the temperature dependence of thermal expansion of heavy fermion systems based on the Coqblin-Schrieffer model (the Kondo lattice model) theoretically. Thermal expansion of heavy ferimon systems has been unresolved based on the microscopic model. In order to study thermal expansion, we use Takahashi’s method that is based on the Landau expansion of the free energy about the small volume. Takahashi’s method was applied to the free energy derived by Hanzawa and Ohara based on the Coqblin-Schrieffer model. We found that thermal expansion at low temperatures showed an exponential behavior. Near the Kondo temperature, thermal expansion showed T-linear dependence. We also discussed thermal expansion of the localized paramagnon that was valid in one of heavy fermion compounds.
Paweł Zięba
University of Rzeszow, Poland
Title: New Types of composite metamaterials
Time : 15:20-15:40
Biography:
PaweÅ‚ ZiÄ™ba is an Assistant Professor in University of Rzeszow, Poland. He has completed MSc in Physics, Pedagogical University in Rzeszów and PhD in Physics from University of Rzeszów. His research interests are methods for terahertz radiation generation, analysis and design of met materials, optical processing of information and holography.
Abstract:
All the proposed designs of metamaterials are characterized by ever-increasing sophistication of fabrication methods. We propose a comparatively simple recipe for the fabrication of a metamaterial, which is both gyrotropic and of the simultaneously negative permittivity and permeability. The idea is to make a mixture of three ingredients, where one of them would be responsible for the negativity of μ, while the other two would be responsible for the negativity of ε. The first component of the mixture is the “swarm” of single-domain ferromagnetic nanoparticles, immersed in a mixture of other two, silver and mercury cadmium telluride (MCT). The choice of silver is determined by the fact, that as it was shown, the permittivity of a mixture of silver and a dielectric material can be negative in some frequency domain. In addition, silver is that it is a diamagnetic material. It means that considering the “swarm” of single – domain ferromagnetic nanoparticles suspended in a mixture containing silver, we can neglect the interaction between their magnetic moments and treat the whole mixture as superparamagnetic. The choice of MCT is determined by the remarkable dependence of its energy gap on the fraction of cadmium in the compound. In its turn, it leads to the strong dependence of the electron concentration on this fraction as well as on the temperature. It enables to adjust each of the two frequency domains, where ε <0 and μ <0 and makes them simultaneously negative. Similar dependence on the electron concentration exhibits Pb1-xSnxTe. By carrying out the computer simulations, the domains where metamaterial to exist, relative to all parameters characterizing the model, that is, the temperature, external magnetic field, parameters of nanoparticles, and the fraction of cadmium in MCT as well as the fraction of tin in Pb1-xSnxTe and relative concentrations of the mixture components are established.
Majid Niaz Akhtar
COMSATS Institute of Information Technology, Pakistan
Title: Impact of CuZn on structural, morphological and magnetic properties of spinel nanocrystalline ferrites for variety of applications
Time : 16:00-16:20
Biography:
Majid Niaz Akhtar completed his PhD studies in the field of nanotechnology from Universiti Teknologi PETRONAS (UTP), Malaysia. He has expertise in the field of electromagnetics, material science (Adanced magnetic materials) and RF microwave devices (EM Antenna, Nanodevices). He completed his Masters of Philosophy and Masters of Science in (Applied Physics specialization with industrial Electronics) from Bahauddin Zakariya University, Multan, Pakistan. He has got gold medal awards in his M.Phil and Masters from Bahauddin Zakariya University, Multan. On completion of his Masters studies he has worked as a lecturer in Army Public Degree College, Multan. During his M.Phil studies, he worked as visiting lecturer in Govt. College of Technology, Multan and Bahauddin Zakariya University (BZU), Multan. Working at Bahauddin Zakariya University, he has been involved in conducting basic research in the fields of advanced material science for micrwave absorption and memory storage devices. Currently, he is working in Comsats institute of Technology (CIIT), Lahore as Assistant Professor in Department of Physics.
Abstract:
The influence of Cu-Zn substitution on the structural and morphological characteristics of Ni nanocrystalline ferrites have been discussed in this work. The detailed and systematic magnetic characterizations were also done for Cu-Zn substituted Ni nanoferrites. The nanocrystalline ferrites of Cu-Zn with different compositions were synthesized using sol gel self combustion hybrid method. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM) were used to find out the properties of CuZn substituted nanocrystalline ferrites. Single phase structure of CuZn substituted in Ni nanocrystalline ferrites were investigated for all the samples. Crystallite size, lattice constant and volume of the cell were found to be increased by increasing Cu contents in spinel structure. The better morphology with well organized nanocrystals of CuZn ferrites at x=0 and 1.0 were observed from both FESEM and TEM analysis. The average grain size was 35-46 nm for all prepared nanocrystalline samples. Magnetic properties such as coercivity, saturation, remanence, magnetic squareness, magneto crystalline anisotropy constant (K) and Bohr magneton were measured from the recorded hysterises MH loops. The magnetic saturation and remanence were increased as Cu contents increased. However, coercivity follow the Stoner-Wolforth model except for x=0.6 which may be due to the site occupancy and replacement of Cu contents from octahedral site. The squareness ratio confirms the superparamgentic behaviour of the CuZn substituted in Ni nanocrystalline ferrites. Furthermore, CuZn substituted Ni nanocrystalline ferrites may be suitable for many industrial and domestic applications such as component of transformers, core, switching, and MLCI's due to variety of the soft magnetic characteristics.
Muhammad Maqbool
Ball State University, USA
Title: Titanium doped semiconductor microRing laser on optical fibers
Time : 16:20-16:40
Biography:
Muhammad Maqbool works as an Associate Professor of Physics at Ball State University. He has obtained his Ph.D. degree in experimental condensed matter physics from Ohio University, USA, in 2005. He has obtained his Master of Science degree in Medical & Radiation Physics from the University of Birmingham, UK, in 1998. His area of research is experimental condensed matter and surface physics. He has published over 60 research papers and book chapters in peer reviewed journals. Dr. Maqbool has presented his work in several international meetings, conferences and workshops. He has also worked as an organizing chair of the American Physical Society Ohio Region Fall-2011 meeting. Dr. Maqbool has obtained over half a million dollars in grant from various organizations like National Science Foundation, Indiana Academy of Science and Ball State University.
Abstract:
Microlaser plays an important role in laser technology and applications due to its smaller size. When a lasing material is deposited around an optical fiber, the cylindrical shape of the fiber acts as cavity for laser production. Transition metals and rare-earth elements are good candidates to produce such kind of laser due to their characteristic light emission in all UV, visible and IR regions of the spectrum. In this talk, an infrared laser made out of titanium doped aluminum nitride (AlN:Ti) deposited around an optical fiber will be discussed. Optical fibers of 12 μm diameter were coated with a sputter-deposited layer (4 μm thick) of titanium (1 at: %)-doped amorphous aluminum nitride. When optically pumped by an Nd:YAG green laser at 532 nm, laser action was observed in whispering gallery modes around the fiber (in a ring shape) at 780:5 nm with a quality factor Q > 1500. Other modes were also observed between 775 and 800 nm. The primary and secondary modes give a mode separation of 4:6 nm. No waveguide modes were observed in the cavity