scholarly journals Monte Carlo and Experimental Magnetic Studies of Molecular Spintronics Devices

NANO ◽  
2015 ◽  
Vol 10 (04) ◽  
pp. 1550056 ◽  
Author(s):  
Pawan Tyagi ◽  
Christopher D'Angelo ◽  
Collin Baker
Keyword(s):  
Monte Carlo ◽  
Magnetic Properties ◽  
Coupling Effect ◽  
Experimental Studies ◽  
Magnetic Tunnel Junction ◽  
Magnetic Interactions ◽  
Magnetic Studies ◽  
Magnetic Molecules ◽  
Wide Range ◽  
Different Temperatures

Molecule-based spintronics devices (MSDs) are highly promising candidates for discovering advanced logic and memory computer units. An advanced MSD will require the placement of paramagnetic molecules between the two ferromagnetic (FM) electrodes. Due to extreme fabrication challenges, only a couple of experimental studies could be performed to understand the effect of magnetic molecules on the overall magnetic and transport properties of MSDs. To date, theoretical studies mainly focused on charge and spin transport aspects of MSDs; there is a dearth of knowledge about the effect of magnetic molecules on the magnetic properties of MSDs. This paper investigates the effect of magnetic molecules, with a net spin, on the magnetic properties of 2D MSDs via Monte Carlo (MC) simulations. Our MC simulations encompass a wide range of MSDs that can be realized by establishing different kinds of magnetic interactions between molecules and FM electrodes at different temperatures. The MC simulations show that ambient thermal energy strongly influenced the molecular coupling effect on the MSD. We studied the nature and strength of molecule couplings (FM and antiferromagnetic) with the two electrodes on the magnetization, specific heat and magnetic susceptibility of MSDs. For the case when the nature of molecule interaction was FM with one electrode and antiferromagnetic with another electrode the overall magnetization shifted toward zero. In this case, the effect of molecules was also a strong function of the nature and strength of direct coupling between FM electrodes. In the case when molecules make opposite magnetic couplings with the two FM electrodes, the MSD model used for MC studies resembled with the magnetic tunnel junction based MSD. The experimental magnetic studies on these devices are in agreement with our theoretical MC simulations results. Our MC simulations will enable the fundamental understanding and designing of a wide range of novel spintronics devices utilizing a variety of molecules, nanoclusters and quantum dots as the device elements.

A Monte Carlo Study of Molecular Spintronics Devices

2013 ◽  
Author(s):  
Pawan Tyagi ◽  
Christopher D’Angelo
Keyword(s):  
Monte Carlo ◽  
Magnetic Properties ◽  
Exchange Coupling ◽  
Coupling Effect ◽  
Experimental Studies ◽  
Magnetic Molecules ◽  
Molecular Spintronics ◽  
Ferromagnetic Electrodes ◽  
Wide Range ◽  
And Control

Molecular spintronics devices (MSDs) are capable of harnessing the controllable transport and magnetic properties of molecular device elements and are highly promising candidates for revolutionizing computer logic and memory. These advanced MSD can enable the next generation of instrumentation and control devices for the wide range of mechanical engineering systems. A MSD is typically produced by placing magnetic molecule(s) between the two ferromagnetic electrodes. Recent experimental studies show that some magnetic molecules produced unprecedented strong exchange couplings between the two ferromagnetic electrodes, leading to intriguing magnetic and transport properties in a MSD. Future development of MSDs will critically depend on obtaining an in-depth understanding of the molecule induced exchange coupling, and its impact on MSD’s switchability, functional temperature range, stability etc. However, the large size of MSD systems and unsuitable device designs are the two biggest hurdles in theoretical and experimental studies of magnetic attributes produced by molecules in a MSD. This research theoretically studies the MSD by performing Monte Carlo simulations (MCS). The effect of magnetic molecule induced exchange coupling was studied at different temperature and for different device sizes — represented by a 2D Ising model. Our MCS shows that thermal energy of the MSD strongly influenced the molecular coupling effect. We studied the effect of a wide range of molecule-metal electrode couplings on the fundamental properties of MSDs. If molecules induced exchange coupling increased beyond a threshold limit a MSD acquired dramatically new attributes. Our MCS exhibited that the transition points in MSD’s magnetic properties was the interplay of temperature and molecular coupling strength. These simulations will allow the understanding of fundamental device mechanisms behind the functioning of novel MSDs. Our MSD model represents a myriad of magnetic molecules and ferromagnets combinations promising for realizing experimental MSDs. These MCS will also assist in designing new class of MSDs with desired attributes for advanced computers and control systems.

scholarly journals A comprehensive Monte Carlo study to design a novel multi-nanoparticle loaded nanocomposites for augmentation of attenuation coefficient in the energy range of diagnostic X-rays

2021 ◽  
Vol 27 (4) ◽  
pp. 279-289
Author(s):  
Elahe Sayyadi ◽  
Asghar Mesbahi ◽  
Reza Eghdam Zamiri ◽  
Farshad Seyyed Nejad
Keyword(s):  
Monte Carlo ◽  
Energy Range ◽  
Radiation Protection ◽  
Experimental Studies ◽  
Rubber Matrix ◽  
Photon Flux ◽  
Monte Carlo Code ◽  
X Rays ◽  
Wide Range ◽  
Shielding Properties

Abstract Introduction: The present study aimed to investigate the radiation protection properties of silicon-based composites doped with nano-sized Bi2O3, PbO, Sm2O3, Gd2O3, WO3, and IrO2 particles. Radiation shielding properties of Sm2O3 and IrO2 nanoparticles were investigated for the first time in the current study. Material and methods: The MCNPX (2.7.0) Monte Carlo code was utilized to calculate the linear attenuation coefficients of single and multi-nano structured composites over the X-ray energy range of 10–140 keV. Homogenous distribution of spherical nanoparticles with a diameter of 100 nm in a silicon rubber matrix was simulated. The narrow beam geometry was used to calculate the photon flux after attenuation by designed nanocomposites. Results: Based on results obtained for single nanoparticle composites, three combinations of different nano-sized fillers Sm2O3+WO3+Bi2O3, Gd2O3+WO3+Bi2O3, and Sm2O3+WO3+PbO were selected, and their shielding properties were estimated. In the energy range of 20-60 keV Sm2O3 and Gd2O3 nanoparticles, in 70-100 keV energy range WO3 and for photons energy higher than 90 keV, PbO and Bi2O3 nanoparticles showed higher attenuation. Despite its higher density, IrO2 had lower attenuation compared to other nanocomposites. The results showed that the nanocomposite containing Sm2O3, WO3, and Bi2O3 nanoparticles provided better shielding among the studied samples. Conclusions: All studied multi-nanoparticle nanocomposites provided optimum shielding properties and almost 8% higher attenuation relative to single nano-based composites over a wide range of photon energy used in diagnostic radiology. Application of these new composites is recommended in radiation protection. Further experimental studies are suggested to validate our findings.

Magnetic Studies of Layered Cathode Materials for Lithium Ion Batteries

2006 ◽  
Vol 972 ◽  
Author(s):  
Natasha A. Chernova ◽  
Miaomiao Ma ◽  
Jie Xiao ◽  
M. Stanley Whittingham ◽  
Jordi Cabana Jiménez ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Ion Exchange ◽  
Cathode Materials ◽  
Ac Susceptibility ◽  
Exchange Process ◽  
Lithium Ion ◽  
Magnetic Ordering ◽  
Magnetic Interactions ◽  
Magnetic Studies ◽  
Ion Exchange Process

AbstractThe magnetic properties of layered LiNi0.5Mn0.5O2 and NaNi0.5Mn0.5O2 cathode materials are studied using AC susceptibility and DC magnetization techniques in order to elucidate magnetic interactions within transition metal (TM) layers and between them in samples with various TM distributions. In NaNi0.5Mn0.5O2 antiferromagnetic (AF) ordering transition is found at 60 K and a spin-flop transition at high magnetic field. In LiNi0.5Mn0.5O2 obtained by ion exchange from NaNi0.5Mn0.5O2 ferrimagnetic ordering is found at around 100 K. The saturation magnetization and the hysteresis loop size of ion-exchanged compounds vary from sample to sample, which implies that the Ni2+ ions migrate upon ion exchange process. Magnetic properties of high-temperature and ion-exchanged LiNi0.5Mn0.5O2 are compared; magnetic ordering models for all compounds are proposed based on experimental results and Goodenough-Kanamori rules.

Magnetic properties of Exchange-spring DyFe2/YFe2 Superlattices by Monte Carlo Simulations

2012 ◽  
Vol 1471 ◽  
Author(s):  
Pierre-Emmanuel Berche ◽  
Saoussen Djedai ◽  
Etienne Talbot
Keyword(s):  
Monte Carlo ◽  
Magnetic Properties ◽  
Monte Carlo Simulations ◽  
Field Dependence ◽  
Hysteresis Loops ◽  
Atomic Scale ◽  
Exchange Spring ◽  
Scale Modelling ◽  
Different Temperatures

ABSTRACTMonte Carlo simulations are used to perform an atomic scale modelling of the magnetic properties of epitaxial exchange-coupled DyFe2/YFe2 superlattices. These samples, extremely well-researched experimentally, are constituted by a hard ferrimagnet DyFe2 and a soft ferrimagnet YFe2 antiferromagnetically coupled. Depending on the layers and on the temperature, the field dependence of the magnetization depth profile is complex. In this work, we reproduce by Monte Carlo simulations hysteresis loops for the net and compound-specific magnetizations at different temperatures, and assess the quality of the results by a direct comparison to experimental hysteresis loops.

Modeling of Size Effects in Diffusion Driven Processes at Nanoscale - Large Atomic and Mesoscale Methods

2017 ◽  
Vol 12 ◽  
pp. 38-73
Author(s):  
Tomasz Wejrzanowski ◽  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Free Surface ◽  
Size Effects ◽  
Experimental Studies ◽  
High Energy ◽  
Intergranular Phase ◽  
Wide Range ◽  
Microstructure Effect

The results of the studies presented here are devoted to understanding of microstructure effect on the processes and properties driven by diffusion. The role of various interfaces (intergranular, phase, free surface), as the high-energy defects, is underlined and investigated with special attention. The methodology relevant to analyses of the microstructural processes is first briefly presented. The capability and limitations of classical molecular dynamics, mesoscale Monte Carlo and cellular automaton techniques are described. Two examples of the diffusion driven processes analyzed at various length and time scale are shown: namely, grain growth in nanometallic materials and melting of thin embedded films. The modeling results are also accompanied with experimental studies. Thanks to application of numerical methods, models of relevant processes were proposed, which enabled to provide quantitative relationships between microstructure and the process kinetics. Such relationships can be later used for design of optimized materials for wide range of applications.

Synchrotron Moessbauer Spectroscopy and Resistivity Studies of Iron Oxide Under High Pressure

2006 ◽  
Vol 987 ◽  
Author(s):  
Viktor V. Struzhkin ◽  
Mikhail I. Eremets ◽  
Ivan M. Eremets ◽  
Jung-Fu Lin ◽  
Wolfgang Sturhahn ◽  
...  
Keyword(s):  
High Pressure ◽  
Magnetic Properties ◽  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
High Pressures ◽  
Structural Phase ◽  
Experimental Studies ◽  
Magnetic Interactions ◽  
Diamond Anvil

AbstractThe strong electron correlations play a crucial role in the formation of a variety of electronic and magnetic properties of the transition metal oxides. In strongly correlated electronic materials many theoretical predictions exist on pressure-induced insulator-metal transitions, which are followed by a collapse of localized magnetic moments and by structural phase transitions [1]. The high-pressure studies provide additional degree of freedom to control the structural, electronic, optical, and magnetic properties of transition metal oxides. With the development of the high-pressure diamond-anvil-cell technique the experimental studies of such transitions are now possible with the advanced synchrotron techniques. In our studies, the iron monooxide Fe0.94O was studied under high pressures up to 200 GPa in diamond anvil cells. The single crystals enriched with Fe57 isotopes have been prepared for nuclear resonance measurements. The results of synchrotron Mössbauer spectroscopy (nuclear forward scattering -NFS), and electro-resistivity measurements suggest a complicated scenario of magnetic interactions governed by band-broadening effects.

Molecular Magnet Induced Transformative Effects in Molecular Spintronics Devices: A Monte Carlo Study

2013 ◽  
Vol 1508 ◽  
Author(s):  
Christopher D’Angelo ◽  
Pawan Tyagi
Keyword(s):  
Monte Carlo ◽  
Experimental Studies ◽  
Magnetic Tunnel Junction ◽  
Temperature Stability ◽  
Monte Carlo Study ◽  
Molecular Magnet ◽  
Test Bed ◽  
Molecular Spintronics ◽  
Before And After ◽  
Computer Logic

ABSTRACTMolecular spintronics devices (MSDs) are capable of harnessing the controllable transport and magnetic properties of molecular device elements and are highly promising candidates for revolutionizing computer logic and memory. A MSD is typically produced by placing magnetic molecule(s) between the two ferromagnetic electrodes. Recent experimental studies show that the molecules produced unprecedented strong exchange couplings between the two ferromagnets, leading to intriguing magnetic and transport properties in a MSD. Future development of MSDs will critically depend on obtaining an in-depth understanding of the molecule induced exchange coupling and its impact on MSD’s switchability and temperature stability. However, the large size of MSD systems and unsuitable device designs are the two biggest hurdles in theoretical and experimental studies of magnetic attributes produced by molecules in a MSD. This research theoretically studies the MSD by performing Monte Carlo Simulation (MCS) studies, which have the capacity to tackle large systems- such as MSD based on magnetic tunnel junction (MTJ) test bed. The MTJ based MSD has the distinctive advantage that MTJ test bed can be subjected to experimental magnetic characterizations before and after transforming it into a MSD by bridging the molecules of interest between the two metal electrodes of a MTJ. Hence the result of our MCS can be verified experimentally.

scholarly journals High Temperature Magnetic Properties of Indirect Exchange Spring FePt/M(Cu,C)/Fe Trilayer Thin Films

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Anabil Gayen ◽  
Barnali Biswas ◽  
Akhilesh Kumar Singh ◽  
Padmanapan Saravanan ◽  
Alagarsamy Perumal
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
High Temperature ◽  
Exchange Coupling ◽  
High Performance ◽  
Interlayer Exchange Coupling ◽  
Magnetic Studies ◽  
Different Temperatures ◽  
Interlayer Exchange ◽  
Hard Magnetic Properties

We report the investigation of temperature dependent magnetic properties of FePt and FePt(30)/M(Cu,C)/Fe(5) trilayer thin films prepared by using magnetron sputtering technique at ambient temperature and postannealed at different temperatures.L10ordering, hard magnetic properties, and thermal stability of FePt films are improved with increasing postannealing temperature. In FePt/M/Fe trilayer, the formation of interlayer exchange coupling between magnetic layers depends on interlayer materials and interface morphology. In FePt/C/Fe trilayer, when the C interlayer thickness was about 0.5 nm, a strong interlayer exchange coupling between hard and soft layers was achieved, and saturation magnetization was enhanced considerably after using interlayer exchange coupling with Fe. In addition, incoherent magnetization reversal process observed in FePt/Fe films changes into coherent switching process in FePt/C/Fe films giving rise to a single hysteresis loop. High temperature magnetic studies up to 573 K reveal that the effective reduction in the coercivity decreases largely from 34 Oe/K for FePt/Fe film to 13 Oe/K for FePt/C(0.5)/Fe film demonstrating that the interlayer exchange coupling seems to be a promising approach to improve the stability of hard magnetic properties at high temperatures, which is suitable for high-performance magnets and thermally assisted magnetic recording media.

scholarly journals Linking ab initio Energetics to Experiment: Kinetic Monte Carlo Simulation of Transient Enhanced Diffusion of B in Si

1998 ◽  
Vol 538 ◽  
Author(s):  
Silva K. Theiss ◽  
M.-J. Caturla ◽  
T. Diaz de la Rubia ◽  
M.C. Johnson ◽  
Ant Uralt ◽  
...  
Keyword(s):  
Experimental Data ◽  
Monte Carlo ◽  
Ab Initio ◽  
Time Scales ◽  
First Principles ◽  
Kinetic Monte Carlo ◽  
Experimental Studies ◽  
Enhanced Diffusion ◽  
Transient Enhanced Diffusion ◽  
Wide Range

AbstractWe have developed a kinetic Monte Carlo (kMC) simulator that links atomic migration and binding energies determined primarily from first principles calculations to macroscopic phenomena and laboratory time scales. Input for the kMC simulation is obtained from a combination of ab initio planewave pseudopotential calculations, molecular dynamics simulations, and experimental data. The simulator is validated against an extensive series of experimental studies of the diffusion of B spikes in self-implanted Si. The implant energy, dose, and dose rate, as well as the detailed thermal history of the sample, are included. Good agreement is obtained with the experimental data for temperatures between 750 and 950°C and times from 15 to 255 s. At 1050°C we predict too little diffusion after 105 s compared to experiment: apparently, some mechanism which is not adequately represented by our model becomes important at this temperature. Below 1050°C, the kMC simulation produces a complete description over macroscopic time scales of the atomic level diffusion and defect reaction phenomena that operate during the anneals. This simulator provides a practical method for predicting technologically interesting phenomena, such as transient enhanced diffusion of B, over a wide range of conditions, using energetics determined from first-principles approaches.

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