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 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.

Room Temperature Current Suppression on Magnetic Tunnel Junction Based Molecular Spintronics Devices

2013 ◽  
Vol 1507 ◽  
Author(s):  
Pawan Tyagi
Keyword(s):  
Tunnel Junction ◽  
Exchange Coupling ◽  
Room Temperature ◽  
Spin Transport ◽  
Magnetic Tunnel Junction ◽  
Test Bed ◽  
Force Microscopy ◽  
Molecular Spintronics ◽  
Ferromagnetic Electrodes ◽  
Strong Exchange

ABSTRACTMolecular conduction channels between two ferromagnetic electrodes can produce strong exchange coupling and dramatic effect on the spin transport, thus enabling the realization of novel logic and memory devices. To realize such device, we produced Multilayer Edge Molecular Spintronics Devices (MEMSDs) by bridging the organometallic molecular clusters (OMCs) across a ∼2 nm thick insulator of a magnetic tunnel junction (MTJ), along its exposed side edges. These MEMSDs exhibited unprecedented increase in exchange coupling between ferromagnetic films and dramatic changes in the spin transport. This paper focuses on the dramatic current suppression phenomenon exhibited by MEMSDs at room temperature. In the event of current suppression, the effective MEMESDs’ current reduced by as much as six orders in magnitude as compared to the leakage current level of a MTJ test bed. Current suppression phenomenon was found to be associated with the equally dramatic changes in the MTJ test beds due to OMCs. Role of OMC in changing MTJ test bed properties was determined by the three different types of magnetic characterizations: SQUID Magnetometer, Ferromagnetic Resonance, and Magnetic Force Microscopy. Observation of current suppression by independent research groups and supporting studies on similar systems will be crucially important to unequivocally establish the utility of MEMSD approach.

scholarly journals Molecule Induced Strong Coupling between Ferromagnetic Electrodes of a Molecular Spintronics Device

2012 ◽  
Vol 736 ◽  
pp. 32-54 ◽  
Author(s):  
Pawan Tyagi
Keyword(s):  
Tunnel Junction ◽  
Magnetic Tunnel Junction ◽  
Molecular Complexes ◽  
Ferromagnetic Material ◽  
Molecular Magnet ◽  
Force Microscopy ◽  
Molecular Spintronics ◽  
Ferromagnetic Electrodes ◽  
Spintronics Device ◽  
Magnetic Hardness

Utilizing molecules for tailoring the exchange coupling strength between ferromagnetic electrodes can produce novel metamaterials and molecular spintronics devices (MSD). A practical way to produce such MSD is to connect the molecular channels to the electrodes of a magnetic tunnel junction (MTJ). This paper discusses the dramatic changes in the properties of MTJ testbed of a MSD due to molecular device elements with a net spin state. When organometallic molecular complexes (OMCs) were bridged across the insulator along the exposed side edges, a MTJ testbed exhibited entirely different magnetic response in magnetization, ferromagnetic resonance and magnetic force microscopy studies. OMCs only affected the ferromagnetic material when it was serving as the electrode of a tunnel junction. Molecule produced the strongest effect on the MTJ with electrodes of dissimilar magnetic hardness. This study encourages the validation of this work and exploration of similar observations with the other combinations MTJs and molecules, like single molecular magnet, porphyrin, and molecular clusters.

Analyzing Observed Composite Differences Across Groups

Methodology ◽  
2013 ◽  
Vol 9 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Holger Steinmetz
Keyword(s):  
Monte Carlo ◽  
Structural Equation Modeling ◽  
Measurement Invariance ◽  
Structural Equation ◽  
Monte Carlo Study ◽  
Equation Modeling ◽  
Factor Loadings ◽  
Latent Mean Differences ◽  
Partial Invariance ◽  
Mean Differences

Although the use of structural equation modeling has increased during the last decades, the typical procedure to investigate mean differences across groups is still to create an observed composite score from several indicators and to compare the composite’s mean across the groups. Whereas the structural equation modeling literature has emphasized that a comparison of latent means presupposes equal factor loadings and indicator intercepts for most of the indicators (i.e., partial invariance), it is still unknown if partial invariance is sufficient when relying on observed composites. This Monte-Carlo study investigated whether one or two unequal factor loadings and indicator intercepts in a composite can lead to wrong conclusions regarding latent mean differences. Results show that unequal indicator intercepts substantially affect the composite mean difference and the probability of a significant composite difference. In contrast, unequal factor loadings demonstrate only small effects. It is concluded that analyses of composite differences are only warranted in conditions of full measurement invariance, and the author recommends the analyses of latent mean differences with structural equation modeling instead.

Detecting Between-Groups Heteroscedasticity in MMR: A Monte Carlo Study

2011 ◽  
Author(s):  
Patrick J. Rosopa ◽  
Amber N. Schroeder ◽  
Jessica Doll
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Study

Monte Carlo study of 50 nm-long single and dual-gate MODFETs: suppression of short-channel effects

1993 ◽  
Vol 3 (9) ◽  
pp. 1719-1728
Author(s):  
P. Dollfus ◽  
P. Hesto ◽  
S. Galdin ◽  
C. Brisset
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Study ◽  
Short Channel Effects ◽  
Short Channel ◽  
Channel Effects ◽  
Dual Gate
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