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Papers by Dr. Pawan Tyagi

Research paper thumbnail of Sulfide and Fluoride Ions Based Passivation of GaAs(100) Surface and Concept of Combining Surface Passivation with Tunnel Junction Based Molecular Devices

Research paper thumbnail of Molecular electronics and spintronics devices produced by the plasma oxidation of photolithographically defined metal electrode

Applied Physics A, Jun 16, 2012

Research paper thumbnail of Fabrication of tunnel junction-based molecular electronics and spintronics devices

Journal of Nanoparticle Research, Sep 22, 2012

Research paper thumbnail of Molecular spintronics devices exhibiting properties of a solar cell

Nanotechnology, Sep 19, 2019

Research paper thumbnail of Advantages of Prefabricated Tunnel Junction-Based Molecular Spintronics Devices

Research paper thumbnail of Study of Anisotropy on Ferromagnetic Electrodes of a Magnetic Tunnel Junction (MTJ)-Based Molecular Spintronics Device (MTJMSD)

arXiv (Cornell University), May 24, 2021

Research paper thumbnail of Spin State of Single Molecular Magnet (SMM) Creating Long Range Ordering on Ferromagnetic Layers of Magnetic Tunnel Junction -A Monte Carlo Study

arXiv (Cornell University), May 25, 2021

Single molecular magnet (SMM) like paramagnetic molecules interacting with the ferromagnetic elec... more Single molecular magnet (SMM) like paramagnetic molecules interacting with the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) produce a new system that differs dramatically from the properties of isolated molecules and ferromagnets. However, it is unknown how far deep in the ferromagnetic electrode the impact of the paramagnetic molecule and ferromagnet interactions can travel for various levels of molecular spin states. Our prior experimental studies showed two types of paramagnetic SMMs, the hexanuclear Mn6 and octanuclear Fe-Ni molecular complexes, covalently bonded to ferromagnets produced unprecedented strong antiferromagnetic coupling between two ferromagnets at room temperature leading to a number of intriguing observations. In this paper, we report Monte Carlo Simulations (MCS) study focusing on the impact of the molecular spin state on cross junction shaped MTJ based molecular spintronics device (MTJMSD). Our MCS study focused on the Heisenberg model of MTJMSD and investigated the impact of various molecular coupling strengths, thermal energy, and molecular spin states. To gauge the impact of the molecular spin state on the region of ferromagnetic electrodes, we examined the spatial distribution of molecule-ferromagnet correlated phases. Our MCS study shows that under a strong coupling regime molecular spin state should be ~30% of the ferromagnetic electrode's atomic spins to create long-range correlated phases.

Research paper thumbnail of Review of Sulphur Interaction based GaAs Surface Passivation and Its Potential Application in Magnetic Tunnel Junction (MTJ) based Molecular Spintronics Devices (MTJMSD)

arXiv (Cornell University), May 25, 2021

GaAs surface is characterized by a high density of surface states, which preclude the utilization... more GaAs surface is characterized by a high density of surface states, which preclude the utilization of this semiconducting material for the realization of several advanced devices. Sulphur-based passivation has been found significantly useful in reducing the effect of dangling bonds. In this article first, the problem associated with GaAs surface has been discussed in a tutorial form. Secondly, the brief introduction of a wide variety of surface passivation methods was introduced. Sulphur passivation, the most effective surface state quenching method, has been elaborated. Thirdly, current trends in the field of surface passivation of GaAs surface has been discussed. Our discussion also focusses on utilizing GaAs and alloys for the molecular electronics and molecular spintronics and based on our insights in the GaAs (P.

Research paper thumbnail of Nanoscale Tantalum Layer Controlling the Magnetic Coupling between Two Ferromagnetic Electrodes via Insulator of a Magnetic Tunnel Junction

arXiv (Cornell University), Dec 3, 2019

Research paper thumbnail of Fabrication and characterization of molecular spintronics devices

Research paper thumbnail of Photovoltaic Effect on Molecule Coupled Ferromagnetic Films of a Magnetic Tunnel Junction

arXiv (Cornell University), Dec 8, 2011

Research paper thumbnail of Reliable and Versatile Molecular Electrodes

Bulletin of the American Physical Society, Mar 6, 2007

Research paper thumbnail of Electrodes for Molecular Spin-Valves

Bulletin of the American Physical Society, Mar 6, 2007

Research paper thumbnail of Monte Carlo and Experimental Magnetic Studies of Molecular Spintronics Devices

NANO, Jun 1, 2015

Molecular spintronics devices (MSDs) are highly promising candidates for enabling quantum computa... more Molecular spintronics devices (MSDs) are highly promising candidates for enabling quantum computation and revolutionizing computer logic and memory. An advanced MSD will require the placement of magnetic molecules between the two ferromagnetic (FM) electrodes. Recent experimental studies showed that some magnetic molecules produced unprecedented strong exchange couplings between the two FM 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 switchability, functional temperature range, and stability. However, the large size of MSD systems and fragile device fabrication scheme continue to limit the theoretical and experimental studies of magnetic attributes produced by molecules in a MSD. This paper theoretically studies the MSD by performing Monte Carlo simulations (MCS). Our MCS encompasses the full range of MSDs that can be realized by establishing different kinds of magnetic interaction between magnetic molecules and FM electrodes. Our MSDs are represented by a 2D Ising model. We studied the effect of a wide range of molecule-FM electrode couplings on the basic properties of MSDs. This wide range covered (i) molecule possessing ferromagnetic coupling with both FM electrodes, (ii) molecule possessing antiferromagnetic coupling with both FM electrodes, and (iii) molecule possessing ferromagnetic coupling with one electrode and antiferromagnetic coupling with another FM electrode. Our MCS will enable the fundamental understanding and designing of a wide range of novel MSDs utilizing a variety of molecules and FM electrodes; these studies will also benefits nanomaterials based spintronics devices employing nanoclusters and quantum dots as the device elements.

Research paper thumbnail of Molecule Induced Strong Coupling between Ferromagnetic Electrodes of a Molecular Spintronics Device

Materials Science Forum, Dec 1, 2012

Research paper thumbnail of Nanoscale Tantalum layer impacting magnetic properties of tunnel junction-based molecular devices

MRS Communications, Jul 23, 2018

Research paper thumbnail of Magnetic molecules lose identity when connected to different combinations of magnetic metal electrodes in MTJ-based molecular spintronics devices (MTJMSD)

Scientific Reports

Understanding the magnetic molecules’ interaction with different combinations of metal electrodes... more Understanding the magnetic molecules’ interaction with different combinations of metal electrodes is vital to advancing the molecular spintronics field. This paper describes experimental and theoretical understanding showing how paramagnetic single-molecule magnet (SMM) catalyzes long-range effects on metal electrodes and, in that process, loses its basic magnetic properties. For the first time, our Monte Carlo simulations, verified for consistency with regards to experimental studies, discuss the properties of the whole device and a generic paramagnetic molecule analog (GPMA) connected to the combinations of ferromagnet-ferromagnet, ferromagnet-paramagnet, and ferromagnet-antiferromagnet metal electrodes. We studied the magnetic moment vs. magnetic field of GPMA exchange coupled between two metal electrodes along the exposed side edge of cross junction-shaped magnetic tunnel junction (MTJ). We also studied GPMA-metal electrode interfaces’ magnetic moment vs. magnetic field response...

Research paper thumbnail of Transactional Analysis Training for Improving Engineering Graduate Students’ Abilities to Understand Different Personalities

Volume 9: Mechanics of Solids, Structures, and Fluids; Micro- and Nano-Systems Engineering and Packaging; Safety Engineering, Risk, and Reliability Analysis; Research Posters

Aspiring graduate students in science and technology generally lack formal training in understand... more Aspiring graduate students in science and technology generally lack formal training in understanding human behavior and traits that can adversely impact their ability to perform and innovate at the highest level. Positive intelligence (PI) and Transactional Analysis are two practical methods in human psychology that millions of people have tested for self-growth. The author previously published the application of PI for enhancing engineering students (Tyagi, P., Positive Intelligence Education for Unleashing Student Potential. ASME 2019 International Mechanical Engineering Congress and Exposition 2019, Volume 5: Engineering Education, V005T07A009). This paper focuses on training graduate students about the popular and practical transactional analysis science and assessing their competence in utilizing this knowledge to decipher their own and other people’s. Transactional analysis was taught to students via Student presentation-based effective teaching (SPET) methodology developed by...

Research paper thumbnail of Assessing Undergraduate Students’ Level of Awareness of Commercialization of Engineering Research Innovation at a Historically Black College and University

Volume 7: Engineering Education

Engineering Research Innovation Commercialization (ERIC) seeks to translate products or services ... more Engineering Research Innovation Commercialization (ERIC) seeks to translate products or services from the research laboratory to the marketplace or the end-user for societal benefit. Research indicates that universities have distinctive capabilities that allow them to play an important role in the process of research innovation commercialization. Historically Black Colleges and Universities (HBCUs), though originally established mainly as teaching and blue-collar trade institutions to educate African Americans, have been gradually commercializing several research innovations through patenting. However, this is significantly lower compared to that of their counterparts (specifically, Predominately White Institutions – PWIs). This according to available research is mainly because HBCUs have been traditionally under-served and under-resourced. Currently several programs such as the National Science Foundation (NSF) I-Corps and National Science Foundation Center of Research Excellence i...

Research paper thumbnail of Alternating Chempolishing and Electropolishing for Interior and Exterior Surface Finishing of Additively Manufactured(AM) Metal components

Additively Manufactured (AM) components' surface finishing is crucial in adopting them for in... more Additively Manufactured (AM) components' surface finishing is crucial in adopting them for intended applications in challenging environments involving fatigue, corrosion, high temperature, and nuclear radiation. In our prior research, chempolishing(C) was utilized as an electroless etching process that uniformly smoothens complex AM components' accessible interior and exterior surfaces(Tyagi et al., Additive Manufacturing, Vol.25 pp.32). A wide range of electropolishing(E) has been demonstrated for AM surface finishing. However, electropolishing can impact a surface that can be juxtaposed to counter electrode and can a very smooth surface to sub-micrometer level roughness. However, a knowledge gap exists about the impact of applying both approaches on the same surface one after another and what new advantages may arise because of combining two methods. This paper uses dual-stage liquid-based surface finishing strategies produced by alternating the chempolishing(C) and electr...

Research paper thumbnail of Sulfide and Fluoride Ions Based Passivation of GaAs(100) Surface and Concept of Combining Surface Passivation with Tunnel Junction Based Molecular Devices

Research paper thumbnail of Molecular electronics and spintronics devices produced by the plasma oxidation of photolithographically defined metal electrode

Applied Physics A, Jun 16, 2012

Research paper thumbnail of Fabrication of tunnel junction-based molecular electronics and spintronics devices

Journal of Nanoparticle Research, Sep 22, 2012

Research paper thumbnail of Molecular spintronics devices exhibiting properties of a solar cell

Nanotechnology, Sep 19, 2019

Research paper thumbnail of Advantages of Prefabricated Tunnel Junction-Based Molecular Spintronics Devices

Research paper thumbnail of Study of Anisotropy on Ferromagnetic Electrodes of a Magnetic Tunnel Junction (MTJ)-Based Molecular Spintronics Device (MTJMSD)

arXiv (Cornell University), May 24, 2021

Research paper thumbnail of Spin State of Single Molecular Magnet (SMM) Creating Long Range Ordering on Ferromagnetic Layers of Magnetic Tunnel Junction -A Monte Carlo Study

arXiv (Cornell University), May 25, 2021

Single molecular magnet (SMM) like paramagnetic molecules interacting with the ferromagnetic elec... more Single molecular magnet (SMM) like paramagnetic molecules interacting with the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) produce a new system that differs dramatically from the properties of isolated molecules and ferromagnets. However, it is unknown how far deep in the ferromagnetic electrode the impact of the paramagnetic molecule and ferromagnet interactions can travel for various levels of molecular spin states. Our prior experimental studies showed two types of paramagnetic SMMs, the hexanuclear Mn6 and octanuclear Fe-Ni molecular complexes, covalently bonded to ferromagnets produced unprecedented strong antiferromagnetic coupling between two ferromagnets at room temperature leading to a number of intriguing observations. In this paper, we report Monte Carlo Simulations (MCS) study focusing on the impact of the molecular spin state on cross junction shaped MTJ based molecular spintronics device (MTJMSD). Our MCS study focused on the Heisenberg model of MTJMSD and investigated the impact of various molecular coupling strengths, thermal energy, and molecular spin states. To gauge the impact of the molecular spin state on the region of ferromagnetic electrodes, we examined the spatial distribution of molecule-ferromagnet correlated phases. Our MCS study shows that under a strong coupling regime molecular spin state should be ~30% of the ferromagnetic electrode's atomic spins to create long-range correlated phases.

Research paper thumbnail of Review of Sulphur Interaction based GaAs Surface Passivation and Its Potential Application in Magnetic Tunnel Junction (MTJ) based Molecular Spintronics Devices (MTJMSD)

arXiv (Cornell University), May 25, 2021

GaAs surface is characterized by a high density of surface states, which preclude the utilization... more GaAs surface is characterized by a high density of surface states, which preclude the utilization of this semiconducting material for the realization of several advanced devices. Sulphur-based passivation has been found significantly useful in reducing the effect of dangling bonds. In this article first, the problem associated with GaAs surface has been discussed in a tutorial form. Secondly, the brief introduction of a wide variety of surface passivation methods was introduced. Sulphur passivation, the most effective surface state quenching method, has been elaborated. Thirdly, current trends in the field of surface passivation of GaAs surface has been discussed. Our discussion also focusses on utilizing GaAs and alloys for the molecular electronics and molecular spintronics and based on our insights in the GaAs (P.

Research paper thumbnail of Nanoscale Tantalum Layer Controlling the Magnetic Coupling between Two Ferromagnetic Electrodes via Insulator of a Magnetic Tunnel Junction

arXiv (Cornell University), Dec 3, 2019

Research paper thumbnail of Fabrication and characterization of molecular spintronics devices

Research paper thumbnail of Photovoltaic Effect on Molecule Coupled Ferromagnetic Films of a Magnetic Tunnel Junction

arXiv (Cornell University), Dec 8, 2011

Research paper thumbnail of Reliable and Versatile Molecular Electrodes

Bulletin of the American Physical Society, Mar 6, 2007

Research paper thumbnail of Electrodes for Molecular Spin-Valves

Bulletin of the American Physical Society, Mar 6, 2007

Research paper thumbnail of Monte Carlo and Experimental Magnetic Studies of Molecular Spintronics Devices

NANO, Jun 1, 2015

Molecular spintronics devices (MSDs) are highly promising candidates for enabling quantum computa... more Molecular spintronics devices (MSDs) are highly promising candidates for enabling quantum computation and revolutionizing computer logic and memory. An advanced MSD will require the placement of magnetic molecules between the two ferromagnetic (FM) electrodes. Recent experimental studies showed that some magnetic molecules produced unprecedented strong exchange couplings between the two FM 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 switchability, functional temperature range, and stability. However, the large size of MSD systems and fragile device fabrication scheme continue to limit the theoretical and experimental studies of magnetic attributes produced by molecules in a MSD. This paper theoretically studies the MSD by performing Monte Carlo simulations (MCS). Our MCS encompasses the full range of MSDs that can be realized by establishing different kinds of magnetic interaction between magnetic molecules and FM electrodes. Our MSDs are represented by a 2D Ising model. We studied the effect of a wide range of molecule-FM electrode couplings on the basic properties of MSDs. This wide range covered (i) molecule possessing ferromagnetic coupling with both FM electrodes, (ii) molecule possessing antiferromagnetic coupling with both FM electrodes, and (iii) molecule possessing ferromagnetic coupling with one electrode and antiferromagnetic coupling with another FM electrode. Our MCS will enable the fundamental understanding and designing of a wide range of novel MSDs utilizing a variety of molecules and FM electrodes; these studies will also benefits nanomaterials based spintronics devices employing nanoclusters and quantum dots as the device elements.

Research paper thumbnail of Molecule Induced Strong Coupling between Ferromagnetic Electrodes of a Molecular Spintronics Device

Materials Science Forum, Dec 1, 2012

Research paper thumbnail of Nanoscale Tantalum layer impacting magnetic properties of tunnel junction-based molecular devices

MRS Communications, Jul 23, 2018

Research paper thumbnail of Magnetic molecules lose identity when connected to different combinations of magnetic metal electrodes in MTJ-based molecular spintronics devices (MTJMSD)

Scientific Reports

Understanding the magnetic molecules’ interaction with different combinations of metal electrodes... more Understanding the magnetic molecules’ interaction with different combinations of metal electrodes is vital to advancing the molecular spintronics field. This paper describes experimental and theoretical understanding showing how paramagnetic single-molecule magnet (SMM) catalyzes long-range effects on metal electrodes and, in that process, loses its basic magnetic properties. For the first time, our Monte Carlo simulations, verified for consistency with regards to experimental studies, discuss the properties of the whole device and a generic paramagnetic molecule analog (GPMA) connected to the combinations of ferromagnet-ferromagnet, ferromagnet-paramagnet, and ferromagnet-antiferromagnet metal electrodes. We studied the magnetic moment vs. magnetic field of GPMA exchange coupled between two metal electrodes along the exposed side edge of cross junction-shaped magnetic tunnel junction (MTJ). We also studied GPMA-metal electrode interfaces’ magnetic moment vs. magnetic field response...

Research paper thumbnail of Transactional Analysis Training for Improving Engineering Graduate Students’ Abilities to Understand Different Personalities

Volume 9: Mechanics of Solids, Structures, and Fluids; Micro- and Nano-Systems Engineering and Packaging; Safety Engineering, Risk, and Reliability Analysis; Research Posters

Aspiring graduate students in science and technology generally lack formal training in understand... more Aspiring graduate students in science and technology generally lack formal training in understanding human behavior and traits that can adversely impact their ability to perform and innovate at the highest level. Positive intelligence (PI) and Transactional Analysis are two practical methods in human psychology that millions of people have tested for self-growth. The author previously published the application of PI for enhancing engineering students (Tyagi, P., Positive Intelligence Education for Unleashing Student Potential. ASME 2019 International Mechanical Engineering Congress and Exposition 2019, Volume 5: Engineering Education, V005T07A009). This paper focuses on training graduate students about the popular and practical transactional analysis science and assessing their competence in utilizing this knowledge to decipher their own and other people’s. Transactional analysis was taught to students via Student presentation-based effective teaching (SPET) methodology developed by...

Research paper thumbnail of Assessing Undergraduate Students’ Level of Awareness of Commercialization of Engineering Research Innovation at a Historically Black College and University

Volume 7: Engineering Education

Engineering Research Innovation Commercialization (ERIC) seeks to translate products or services ... more Engineering Research Innovation Commercialization (ERIC) seeks to translate products or services from the research laboratory to the marketplace or the end-user for societal benefit. Research indicates that universities have distinctive capabilities that allow them to play an important role in the process of research innovation commercialization. Historically Black Colleges and Universities (HBCUs), though originally established mainly as teaching and blue-collar trade institutions to educate African Americans, have been gradually commercializing several research innovations through patenting. However, this is significantly lower compared to that of their counterparts (specifically, Predominately White Institutions – PWIs). This according to available research is mainly because HBCUs have been traditionally under-served and under-resourced. Currently several programs such as the National Science Foundation (NSF) I-Corps and National Science Foundation Center of Research Excellence i...

Research paper thumbnail of Alternating Chempolishing and Electropolishing for Interior and Exterior Surface Finishing of Additively Manufactured(AM) Metal components

Additively Manufactured (AM) components' surface finishing is crucial in adopting them for in... more Additively Manufactured (AM) components' surface finishing is crucial in adopting them for intended applications in challenging environments involving fatigue, corrosion, high temperature, and nuclear radiation. In our prior research, chempolishing(C) was utilized as an electroless etching process that uniformly smoothens complex AM components' accessible interior and exterior surfaces(Tyagi et al., Additive Manufacturing, Vol.25 pp.32). A wide range of electropolishing(E) has been demonstrated for AM surface finishing. However, electropolishing can impact a surface that can be juxtaposed to counter electrode and can a very smooth surface to sub-micrometer level roughness. However, a knowledge gap exists about the impact of applying both approaches on the same surface one after another and what new advantages may arise because of combining two methods. This paper uses dual-stage liquid-based surface finishing strategies produced by alternating the chempolishing(C) and electr...