3^rd International Conference on Theoretical and Condensed Matter Physics October 19-21, 2017 New York, USA

Biography:

Sergey V Kravchenko has completed his PhD in 1988 from Institute of Solid State Physics, Russia. Since 1998, he is a Professor of Physics at Northeastern University, Boston, USA. His discovery of the metallic state in 2D was listed among 50 main discoveries of the last century in the field of mesoscopic physics.

Abstract:

In two-dimensional (2D) electron system, electrons can move in two dimensions but are confined in the third, pretty much like billiard balls. Low-disorder 2D electron systems are currently the focus of a great deal of attention, particularly for low electron densities, where the interactions between them dominate their behavior, theoretical methods are still poorly developed, and new experimental results are of great interest. Consistent with Fermi liquid theory at high electron densities, these 2D systems are expected to freeze into a Wigner crystal in the dilute, strongly-interacting limit. In the intermediate regime, where interactions are not yet strong enough to cause crystallization, the electrons behave like a strongly-correlated liquid. Our recent data show that the low-temperature (fractions of 1 kelvin) properties of this strongly correlated electron liquid are unusual and very interesting. For example, the spin susceptibility grows and seemingly diverges as the electrons become more dilute, which indicates transition to a new state of matter (Wigner crystal or a precursor). Moreover, I will report the observation of strongly nonlinear voltage-current characteristics that display two distinct thresholds and a dramatic increase in noise at the breakdown of the insulating state. With the roles of voltage and current interchanged, this behavior is strikingly like that observed for the depinning of the vortex lattice in Type-II superconductors. Adapting the model used for vortexes to the case of an electron solid yields good agreement with our experimental results. This strongly favors the formation of the electron solid in the insulating phase as the double threshold behavior cannot be described within existing alternative models.

Biography:

Gennadiy Filippov has his expertise in particle-solid interaction physics. He has completed his PhD from Tomsk State University (Russia). He is the Head of the Laboratory of Biophysics and Bio-Nanotechnology in the Chuvash State Agricultural Academy and Professor in the Chuvash State Pedagogical University in Cheboksary, Russian Federation.

Abstract:

Calculation and further analysis of density matrix (DM) for projectile which collides with a solid film reveals some new representations which hard to be anticipated without the calculation. Namely: 1) The coherence properties in the projectile’s wave field are describing through the special function of coherence. 2) The collision with the solid leads to a significant decrease in the total coherence length of the projectile’s wave field. The coherence length can become much smaller than the initial size of a wave packet of a particle passing through the film. 3) During the collision with solid, the number of different spatial areas where the mutual coherence in the projectile’s wave field is supported, can be multiplied. 4) Every part of projectile’s wave field can be individualizing as the separate particle having own property in its inner quantum state. 5) The procedure which has a responsibility for such a transformation can be characterized as a spontaneous breaking of symmetry. The process described in the point three can be considered as a special form of breaking in quantum mechanics. 6) Knowing the wave packet evolution during the passage through the solid film allows one to explain experimental results on the pore formation during the passage of high charged atomic ions through the thin carbon nano-membranes. 7) The parts of the wave field considered above can be stabilized in its quantum state after been captured in its own polarization well.

Biography:

Ming B Yu has graduated from Jilin University, 1961. Before retiring, he worked as a Lecturer in Zhengzhou Coal Manage College, China, and a Visiting Adjunct Lecturer in University of Georgia, USA. Currently he is still active in studies in theoretical condensed matter physics and nonequilibrium statistical theory of closed and open systems.

Abstract:

It has a long history to study monatomic and diatomic chains with or without impurity as models for dynamics of lattices. By means of recurrence relations method, a diatomic chain with an impurity is studied. The Laplace transform of the momentum autocorrelation function of the impurity is derived. It has two pairs of resonant pole and three separated branch cuts. The poles lead to cosine function(s) and the cuts result in acoustic and optical branches. A frequency theorem is derived governing the upper and lower frequencies of the two branches; Criteria for resonant poles are established; general expres-sions for frequency and amplitude of cosine(s) are derived. The acoustic and optical branches can be expressed as inverse Laplace trans-forms which are not easy to be carried out in general. By means of convolu-tion theorem, analytical expressions for acoustic and optical branches are derived as expansions of even-order Bessel functions. The expansion coeffi-cients of the acoustic branch are integrals of real Jacobin elliptic functions. However, coefficients of the optical branch are integrals of complex elliptical functions. By addition theorem, the expansion coefficients for the optical branch are obtained as integrals of elliptic function along a contour parallel to the imaginary axis in a complex plane. A modulus theorem is derived relating the modulus of elliptic functions in the acoustic and optical branches.

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. He won the International Plato Award for the Educational Achievement, the Order of International Fellowship Golden Peace Prize, and Ultimate Achiever Award for Science-Certificate in 2009. He is a member of Physical Society Japan, a Life member of American Physical Society, and a member of Institute of Physics, U.K.

Abstract:

We have investigated the thermal expansion of localized paramagnets, with almost negligible wave-vector dependence of their dumping constant of spin fluctuations. By assuming the Lorentzian form of the dynamical susceptibility, we have found that the thermal expansion coefficient has the T-linear dependence at low temperatures. The volume dependence of the spectral width of spin fluctuations is included accoding to the theory of magneto-volume effects by Takahashi. This dependence is equivalent to that of the specific heat, and both of their T-linear coefficients are related with the magnetic Gruneisen parameters. Our localized paramagnon model will be well applicable to almost localized 5f electron system, UPt3.

Biography:

Luxmi Rani has completed her PhD (Theoretical condensed matter physics: Superconductivity) from IIT Roorkee India in 2015 and received degree in 2016. She has worked as a Post-Doctoral Fellow in Theoretical Physics Division, Physical Research Laboratory Ahmedabad during 2015-2017. She has published over eight research papers in peer reviewed journals.

Abstract:

The discovery of high -Tc superconductivity in cuprates by Bednorz and Müller and the recent finding of the high -Tc iron based superconductors by Kamihara group in 2008 changed the traditional concept and clearly indicated that BCS theory based on the electron-phonon interaction may not be able to explain such high Tc’s and spin fluctuation since antiferromagnetic background can also contribute to the pairing mechanism, and still a debatable issue from the theoretical point of view. The isotope effect coefficients show a deviation (above and below the BCS limit) in Fe based high-Tc superconductors and need careful attention in any theoretical analysis. Motivated from the fact, the present work is devoted to a theoretical analysis of isotope effect coefficient as a function of transition temperature in two orbital per site model hamiltonian in Fe based superconducting system. The expression of isotope effect coefficient has been computed numerically and self-consistently by employing green’s function technique within the BCS- mean-field approximation. It is observed that the isotope effect coefficient increases with the increase of the hybridization while with the increase in coulomb interaction it starts decreasing. On increasing the carrier density per site in two orbital per site iron pnictide system, isotope effect coefficient (α) exhibits large values (much higher than BCS limit) at lower temperatures, while in the under doped case, isotope effect coefficient shows minimum value in superconducting states of the iron based systems. Furthermore, it has been found that the large value of the isotope effect coefficient is the indication of the fact that the contribution of phonon alone is inadequate as the origin of superconductivity in these systems. Finally, the obtained theoretical results have been compared with experimental and existing theoretical observations in iron based superconductors.

Biography:

Rita John is Professor and Head, Department of Theoretical Physics, University of Madras, Chennai, India. She is fulbright Visiting Professor at the Department of Physics and Astronomy, Texas Christian University, Fort Worth, Texas, USA (2014). She has been teaching condensed matter physics for graduate students over 18 years. The book, ‘Solid State Physics’ authored by her and published by Tata McGraw Hill publisher (2014) is used globally by graduate students. She guides PhD, MPhil, MSc and MTech projects. She has over 50 international publications. She is the recipient of various awards and prizes for her academic and research contributions.

Abstract:

Shape memory alloys are intermetallic compounds that have the ability to recover their original shape upon appropriate thermomechanical loading. TiPd, a prominent high temperature shape memory alloy (HTSMA) undergoes martensitic transformation (MT) from the parent B2 (cubic) phase to the product B19 (orthorhombic) phase. We have studied the effect of addition of X (Co, Rh, Ir) on the structural and electronic properties of TiPd shape memory alloys. The site preference of ternary additions X are determined from the calculated formation energy. It was found that X has strong preference for Ti sublattice for the composition considered. The cubic structure of B2 phase is maintained for the substitutional alloying of 6.25% of Ti/Pd sites with X. The density of states (total, site and angular momentum decomposed) are plotted for both Ti43.75Pd50X6.25 and Ti50Pd43.75X6.25 series. Higher stability of Ti43.75Pd50X6.25 is due to the decrease of d states of Ti and X at fermi level with increasing atomic number of X impurities. Though localization effect is more pronounced in Ti50Pd43.75X6.25 series with increasing atomic number of X, the number of d states of Ti remains same. It is Tid states at fermi level that determines the phase stability of these alloys. Also, we have investigated the impact of addition of varying concentration of magnetic impurity Co (6.25, 12.5, 25%) on B2 and B19 phases of TiPd. Band Jahn Teller broadening is observed in Ti25Pd50Co25 which is one of the accompanying features of MT. Band structure calculations are consistent with the results of density of states. Hole and electron pockets observed in the band structure are endorsed in fermi surfaces. Charge density contours are plotted which give an idea about electron charge distribution and nature of bonding.

Biography:

Valentiyn A Nastasenko, the Kherson State Maritime Academy Ukraine, faculties Electrical engineering and electronics, the department of transport technologies. Sphere of scientific interests includes quantum physics, the theory of gravitation, fundamentals of the material world and the birth of the Universe, the author of 50 scientific works in these spheres.

Abstract:

Currently gravitational constant G is defined up to 5 characters, that is 2 or 3 orders of magnitude less than the accuracy of other fundamental physical constants – the speed c of light in vacuum and Planck’s constant h. However in the Earth conditions the possibility of increasing the accuracy of defining G experimentally has reached its technical limit, which requires the search of new fundamental approaches. For this purpose the original approach is suggested and the system of calculated dependences resulted from fundamental physical constants c, G, h, as well as from Planck’s values of length l_p, time t_p and mass m_p, is obtained allowing to refine the presently known value of the gravitational constant G by 3 orders. Scientific discoveries are put of the solution this problem:

1) The possibility of expressing the fundamental physical constants in the framework of their dimension in terms of their Planck’s values l_p, t_p, m_p [1] found in which for the gravitational constant G amounts to (1) [2]:

2) Next transformed constant G of this basis

3) this allowed on a strict basis to determine the wave parameters of the gravitational field:

4) 1-th work hypnotize of this: paper ν_p – is quantum parameter of time 1 second [3] and can be expressed by an exact number of ν_p =7.4∙10⁴²(s^-1)Of this basis gravitational constant, at the strict physical (3) and mathematical level, amounts the value with the accuracy of up to 9 characters (4) [4]:

Taking into account the obtained wave characteristics [5] it can be strictly maintained that gravitational field can only by unified with electromagnetic field having the same wave characteristics. Thus, It can be summed up that unification of given fields is possible only on Plank’s level. This conclusion is confirmed number physical and mathematical level [5].

Biography:

Yoshihito Kuno is Postdoctoral Fellow of Japan Society for the Promotion of Science (JSPS), and a Member of Quantum Optics Group of Kyoto University, Japan. He got his PhD at Nagoya Institute of Technology.

Abstract:

Recently atomic quantum simulation for high-energy physics comes to become an active field in cold-atom physics society. In particular there are a plethora of proposals to build up a quantum simulator for lattice gauge theory by using cold atoms in an optical lattice. To realize the quantum simulator for lattice gauge theory, theoretical proposal for future experiment is important. In this talk, we show theoretically an atomic quantum simulator of U lattice gauge-Higgs model based on an extended Bose-Hubbard model in one dimensional (1D) optical lattice. This quantum simulator of the lattice gauge theory is directly connected towards the Bose-Hubbard model with nearest-neighbor (NN) interactions. In the 1D system the most important ingredient, i.e., Gauss’ law can be implemented in a much simple way, i.e., only controlling the NN interactions. Furthermore we show a global phase diagram. Also by using the correspondence between the Bose Hubbard model and the lattice gauge theory we interpret these phases from the view of the lattice gauge theory. In addition, it is important and interesting to detect the non-equilibrium properties of the quantum simulator. We focus on simulating the dynamics of an electric flux (confinement string) in both Higgs and confinement phase. To study this subject we use the Gross-Pitaevskii equation for the Higgs (superfluid) regime and the semi-truncated Wigner method for shallow confinement regime. We certify that the electric flux spontaneously breaks in the Higgs phase on the other hand in the shallow confinement regime the electric flux is dynamically stable. These results are expected to be measured in future real experiments. Moreover our numerical simulations find that the Schwinger-like mechanism which can be observed. Electric fields oscillate via a Higgs and anti-Higgs pair creation.

Biography:

Azher M Siddiqui is an Associate Professor in the Department of Physics, Faculty of Natural Sciences, Jamia Millia Islamia (Central University), India. He has completed his PhD at School of Physics, University of Hyderabad, India, under the supervision of Professor Anand P Pathak. He has worked as a Research Associate with Dr. D K Avasthi in the Materials Science Group at the Inter University Accelerator Centre (IUAC) (formerly known as: Nuclear Science Centre, NSC,), New Delhi, India. He has over 50 papers to his account in International Journals of repute. He has Supervised two students so far for their PhD and 5 students are currently registered with him to carry out their PhD. He has presented his papers in about 20 conferences and has also taken up 3 major research projects from various sponsoring agencies like UGC and IUAC.

Abstract:

In this work, we report the effects of 100 MeV Ag9+ and O7+ ions irradiation on the structural, optical and gas sensing properties of thermally oxidized thin films of tin and indium. XRD, SEM and RBS techniques have been employed to study the structural, modifications induced in the films because of irradiation. It was observed that, irradiation with 100 MeV Ag9+ and O7+ ions resulted in a decrease in the crystallinity of the films along with a decrease in the grain size due to increase in the lattice strain. The structural modifications induced have been correlated with the simulations based on the thermal spike model. The optical properties of the pristine and SHI irradiated films was examined using UV-Vis spectroscopy. It was noticed that the optical band gap of the films increased upon irradiation with 100 MeV Ag9+ and O7+ ions. The changes in the response characteristics of indium oxide and tin oxide films towards methane and hydrogen respectively due to SHI irradiation are extensively discussed.

Biography:

Georges Bouzerar is a Research Director at Centre National de la Recherche Scientifique (CNRS). He is an expert in quantum and classical magnetism (itinerant and localized) and in quantum transport. He has completed his PhD in mesoscopic physics (interplay between electron-electron interaction and disorder) in 1996 from Paris XI (Orsay) University. He has spent several years as a Postdoc in Germany (Koeln University, Berlin University, Max Planck Institute) and in France (Laue Langevin Institute in Grenoble). He got a Senior Scientist permanent position at CNRS in 2004 and became research director in 2011. Over the past 10 years he has focused attention on spintronics, in particular on magnetism and transport in diluted magnetic semiconductors and non-magnetic impurity induced ferromagnetism. He has contributed by about 25-30 papers to this research area and received a prize in 2014 from the French Academy of Science for his achievements in this field.

Abstract:

The nature of carrier-induced ferromagnetism in both Mn doped III-V compounds GaAs and InP is investigated. Although, direct band gap and effective masses are very close in both InP and GaAs, we demonstrate that the magnetic properties change drastically. The influence of the acceptor level position on magnetic properties will prove to be crucial. Because of both dilution effects (percolation) and short-range nature of the carrier induced Mn-Mn magnetic couplings (calculated), thermal/transverse spin fluctuations and disorder effects (localization) have to be properly treated (beyond effective medium or perturbation approach). To tackle efficiently this issue, different large-scale theoretical approaches are combined: Kernel Polynomial Method (KPM) for the accurate calculation of Mn-Mn couplings, Monte Carlo (MC) and Local Random Phase approximation (L-RPA) for the magnetic properties (TC, T- dependent magnetization, and magnetic excitation spectrum and spin stiffness). TC in (In, Mn)P is found much smaller than that of Mn doped GaAs and scales linearly with Mn concentration in contrast to the square root behavior found in (Ga, Mn)As. Moreover, we find that the magnetization behave almost linearly with the temperature in contrast to the standard mean field Brillouin shape. These findings are in quantitative agreement with the experimental data and reveal that magnetic and transport properties are extremely sensitive to the position of the Mn acceptor level. We finally discuss the transport properties in both compounds and demonstrate that our non-perturbative theory is able to capture not only qualitatively but quantitatively as well the transport properties in these materials such as the Infrared optical conductivity, the carrier and Mn concentration dependent Drude weight, the effects of sample annealing, and also the Metal-Insulator-Transition as observed experimentally in Mn doped GaAs, whilst (In,Mn)P remains an insulating compound.

Biography:

Juan-Luis Domenech-Garret is currently an Associate Professor (Permanent Staff) at the Technical University of Madrid. He is a Member of the Spanish Royal Society of Physics. He obtained his European-PhD from Valencia University (Spain) and CERN (Geneva-Switzerland) with a CERN-PhD thesis. He is a Member of the Plasma Laboratory of the Aeronautics and Space School–Technical University of Madrid. In previous years, he achieved academic positions in: Avila C University–Spain (Lecturer and Associate Professor), Lleida University–Spain (Lecturer and Associate Professor), and Technical University of Madrid (Lecturer).

Abstract:

This talk is focused on the discussion about the role of the generalized Fermi–Dirac Kappa Distribution which describes the electron population in pure metals. First, we present some experimental evidences and phenomenological facts – in such metals the Kappa parameter, which governs the distribution function, appears to vary linearly with the temperature. Taking this relationship into account, we reviewed the derivation of the generalized electrical conductivity. The relationship between the melting point of several pure metals and a material-dependent coefficient which can be obtained by analyzing the material’s thermionic emission is shown. Also, we presented the transport coefficients for non-equilibrium hot metals, i.e., a new generalized thermal conductivity and a generalized Wiedemann-Franz Law, which are compared with experimental results. As a new property, these transport coefficients droped when the metals achieved the solid–liquid phase transition. In addition, we also showed the impact of the temperaturedependent Kappa parameter on the thermionic emission law in metals. Moreover, we compared the Kappa distribution with the wellknown expanded non-equilibrium function. This study leads to an analytical form of the Kappa parameter. The obtained expression shows the connection between the Kappa parameter and the factors causing the departure from equilibrium. We analyzed the behavior of this obtained equation and compared with the experimental one.

Biography:

Jose Alberto Perez Benitez has completed his PhD at the age of 33 years from University of Oriente in Cuba and postdoctoral studies from University of Sao Paulo and University of Aveiro. He is professor of postgraduation of Electronic Engineering at the Instituto Politécnico Nacional in Mexico. He has published more than 30 papers in reputed journals in the area of electromagnetic nondestructive methods and machine learning.

Abstract:

The Magnetic Barkhausen Noise (MBN) results from the discontinuous motion of magnetic domain walls in magnetic materials under the effect of a variable magnetic field. The MBN signal contains information of several materials features. It has been shown that the MBN is sensible to changes in steel properties such as grain size, carbon content and plastic deformation. Also, the MBN allows detecting the presence of applied or residual stress. Recently, was demonstrated that the MBN signal also contains information about the magnetos-crystalline anisotropy energy of the material. This fact represents an important step in the consolidation of the MBN as a method for magnetic material characterization. The study of the correlation between the MBN and the magneto-crystalline anisotropy energy was possible due to the analysis of the MBN signal by time-bands (or applied field-bands). The time-band method also allows indentifying the presence of magnetization stages using the MBN raw signal. However, although the MBN presents a high potential as a method for extracting different material characteristics, it is worth noting that some of these features vary simultaneously, which make difficult to establish correlations between a specific feature of the material and the MBN parameters. In order to solve this problem several approaches have been proposed, most of them concerning the use of pattern recognition and artificial intelligence algorithms. In particular, it have been demonstrated that it is possible to separated the influence of carbon content and plastic deformation on MBN signal using Feature Extraction algorithms and Self-Organizing Maps artificial networks. These algorithms have proven to be successful for separating the influence of two simultaneously varying materials properties on MBN. Additionally, to the aforementioned progress, the comprehension of how to obtain material features using MBN have been also improved, recently, with new models for the simulation of domain wall dynamics using an assembly of micro-mesoscopic model and Maxwell equation solved using Finite Difference method and computed using parallel programming methods.

Biography:

Yuko Ichiyanagi has completed her PhD from Yokohama National University, Japan. She is the 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:

Mn-Zn ferrite nanoparticles (NPs) and Co ion doped pluralistic ferrite NPs encapsulated with amorphous SiO2 ranging several nm were prepared by our original wet chemical method. 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. Characterization of obtained ferrite NPs were performed by X-ray diffraction measurements, chemical analysis. Local structure of magnetic cluster was analyzed by X-ray absorption fine structure (XAFS). DC and AC magnetization measurements were performed using SQUID magnetometer. Composition and particle size were optimized for Mn-Zn ferrite nanoparticles. Samples were examined for heating agent from the result of frequency dependence and particle size dependence of imaginary part of AC magnetic susceptibilities χ”. In order to estimate heating effect of magnetic nanoparticles for an application of hyperthermia treatment, increase in temperature of the samples in AC field was observed. Increase rate of temperature was found to be high enough to suppress cancer cells. Finally, in vitro experiment for hyperthermia treatment was carried out for the cultured cancer cells using our pluralistic ferrite samples. Human prostate cancer cells and human breast cancer cells were cultured in a dish and were exposed to an AC magnetic field. As the result, an extensive hyperthermia effect was observed. Using these NPs, MR relaxation curves were investigated. It was found that super paramagnetic behavior and smaller particles were effective for MRI contrast.

Biography:

Feroz A Khan has completed his PhD degree from the Bangladesh University of Engineering and Technology (BUET) and his Postdoctoral research at the University of Delaware, USA, University of Uppsala, Sweden, and the University of Tsukuba, Japan. He is a Professor in Physics at the Bangladesh University of Engineering and Technology (BUET). He is a Leader of a research group called Dhaka Materials Science Group under scientific research collaboration with the International Science Programs (ISP), Uppsala University, Sweden. He has supervised more than 25 Postgraduate degrees that includes Masters, MPhil, and PhD degrees. He has to his credit more than 50 research publications. He is involved in promoting the basic science research through establishment of regional research collaborations with the south-east Asian Universities under the umbrella of International Science Programs.

Abstract:

The structural, magnetic and electrical properties of Mn doped cobalt ferrites Co1-xMnxFe2O4 have been investigated. The samples are found to be of spiel structure. The DC and AC magnetic properties have been measured at different temperatures. A significant change in the electrical and magnetic properties has been observed with increasing Mn content in the sample. It is observed that the ferri-ferromagnetic Curie temperature is tunable by changing the Mn content in the sample. The optimum point is yet to be determined as the research work is in progress. However primary investigation shows that for transition from ferri-to-ferro and ferrito-para the bifurcation point shifts towards the low temperature side. The ac electrical properties have also shown strong frequency dependence. The variation of real part of the dielectric constant ε’ with frequency at room temperature for all samples of composition Co0.75Mn0.25Fe2O4(CMF2),Co1Mn0.25Fe1.750O4(CFM2), Co1.25Mn0.25Fe1.75O4 (CMFZ2), CoFe2O4 (parent) and also of a bi-layer sample CMF-2+CFM-2. It is observed that the dielectric constants of all the investigated samples have gone through a maximum at two different frequency bands 1 MHz- 4.5 MHz and 7.5 MHz.-10.5 MHz. This is attributed to the electronic, ionic, dipolar and interfacial polarizations that occur at the tetrahedral and octahedral sites.

Biography:

Elie A Moujaes has done BA in Physics from the Lebanese University in 1999, MSc in Theoretical Physics from the American University of Beirut in 2003 and PhD in Theoretical Condensed Matter Physics from Nottingham University (2007). At the end of 2009, he has moved to Brazil where he worked on several projects in graphene, including calculations of electronic structure of grain boundaries and molecular dynamics of carbon nanotubes with polymers in the groups of Marcos A Pimenta and Ricardo W Nunes from the Federal University of Minas Gerais (UFMG), in Belo Horizonte, Brazil. He is currently an Adjoint Professor at the Department of Physics/UNIR- Brazil. My general research areas involve electron-phonon interactions, electronic structure calculations of two-dimensional materials, and phase transitions in magnetism.

Abstract:

Transition metal (TM) multilayers, such as those involving Fe and Ni, hold great expectations underpinning the next generation of magneto-electronic devices. Previously, we used a combination of effective field theory (EFT) and mean field theory (MFT) to calculate single site spin correlations in multiple layered disordered Fe1-cNic nanojunctions with Co leads, c being the concentration of Ni in the Fe-Ni alloy. In this work, calculations are presented for the spin wave scattering and ballistic transport for ferromagnetic iron-nickel nanojunctions between Co leads with Ni concentrations c =0.5 and 0.81. The [Fe1-cNic]n alloys themselves are randomly disordered forming n hcp lattice planes between hcp planes of Co leads. To study the spin dynamics for 1≤ n≤ 7, the sublattice magnetizations were previously evaluated on each layer with the help of a virtual crystal approximation (VCA) particularly valid at the length scale of the nanojunctions at submicroscopic spin wave (SW) wavelengths. Localized and propagating magnon modes in the nanojunction are examined within the phase field matching technique (PFMT). These magnonic modes propagate in the symmetry plane of the nanojunction with spin precession amplitudes decaying or matching the SW states of the semi-infinite Co leads. Eigenvectors corresponding to such amplitudes and illustrating some of the cases encountered are given. This same approach is used, together with the Landauer-Büttiker formalism to determine the reflectance and transmittance for the SW incident from the Co leads onto the multilayered nanojunctions. Our results show Fabry-Perot type resonance assisted maxima for the SW transmission spectra of all layered nanojunctions and for both values of the Ni concentration, due to the interactions between the incident modes coming from the Co leads and the nanojunction magnon modes. As the Ni concentration is changed and the thickness of the nanojunction increases, by adding more layers, the positions of such maxima are modified.