scholarly journals Molecular coupling competing with defects within insulator of the magnetic tunnel junction-based molecular spintronics devices

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pawan Tyagi ◽  
Hayden Brown ◽  
Andrew Grizzle ◽  
Christopher D’Angelo ◽  
Bishnu R. Dahal
Keyword(s):  
Tunnel Junction ◽  
Magnetic Tunnel Junction ◽  
Tunnel Barrier ◽  
Molecular Device ◽  
Molecular Spintronics ◽  
Ferromagnetic Electrodes ◽  
Covalently Bonded ◽  
Wide Range ◽  
Device Properties ◽  
Theoretical Simulations

AbstractNearly 70 years old dream of incorporating molecule as the device element is still challenged by competing defects in almost every experimentally tested molecular device approach. This paper focuses on the magnetic tunnel junction (MTJ) based molecular spintronics device (MTJMSD) method. An MTJMSD utilizes a tunnel barrier to ensure a robust and mass-producible physical gap between two ferromagnetic electrodes. MTJMSD approach may benefit from MTJ's industrial practices; however, the MTJMSD approach still needs to overcome additional challenges arising from the inclusion of magnetic molecules in conjunction with competing defects. Molecular device channels are covalently bonded between two ferromagnets across the insulating barrier. An insulating barrier may possess a variety of potential defects arising during the fabrication or operational phase. This paper describes an experimental and theoretical study of molecular coupling between ferromagnets in the presence of the competing coupling via an insulating tunnel barrier. We discuss the experimental observations of hillocks and pinhole-type defects producing inter-layer coupling that compete with molecular device elements. We performed theoretical simulations to encompass a wide range of competition between molecules and defects. Monte Carlo Simulation (MCS) was used for investigating the defect-induced inter-layer coupling on MTJMSD. Our research may help understand and design molecular spintronics devices utilizing various insulating spacers such as aluminum oxide (AlOx) and magnesium oxide (MgO) on a wide range of metal electrodes. This paper intends to provide practical insights for researchers intending to investigate the molecular device properties via the MTJMSD approach and do not have a background in magnetic tunnel junction fabrication.

scholarly journals Structural Stability of Magnetic Tunnel Junction Based Molecular Spintronics Devices (MTJMSD)

2020 ◽  
Author(s):  
Joshua Dillard ◽  
Uzma Amir ◽  
Pawan Tyagi ◽  
Vincent Lamberti
Keyword(s):  
Thin Films ◽  
Structural Stability ◽  
Tunnel Junction ◽  
Magnetic Tunnel Junction ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Molecular Devices ◽  
Metal Electrodes ◽  
Molecular Spintronics ◽  
Ferromagnetic Electrodes

Abstract Harnessing the exotic properties of molecular level nanostructures to produce novel sensors, metamaterials, and futuristic computer devices can be technologically transformative. In addition, connecting the molecular nanostructures to ferromagnetic electrodes bring the unprecedented opportunity of making spin property based molecular devices. We have demonstrated that magnetic tunnel junction based molecular spintronics device (MTJMSD) approach to address numerous technological hurdles that have been inhibiting this field for decades (P. Tyagi, J. Mater. Chem., Vol. 21, 4733). MTJMSD approach is based on producing a capacitor like a testbed where two metal electrodes are separated by an ultrathin insulator and subsequently bridging the molecule nanostructure across the insulator to transform a capacitor into a molecular device. Our prior work showed that MTJMSDs produced extremely intriguing phenomenon such as room temperature current suppression by six orders, spin photovoltaic effect, and evolution of new forms of magnetic metamaterials arising due to the interaction of the magnetic a molecule with two ferromagnetic thin films. However, making robust and reproducible electrical connections with exotic molecules with ferromagnetic electrodes is full of challenges and requires attention to MTJMSD structural stability. This paper focuses on MTJMSD stability by describing the overall fabrication protocol and the associated potential threat to reliability. MTJMSD is based on microfabrication methods such as (a) photolithography for patterning the ferromagnetic electrodes, (b) sputtering of metallic thin films and insulator, and (c) at the end electrochemical process for bridging the molecules between two ferromagnetic films separated by ∼ 2nm insulating gap. For the successful MTJMSD fabrication, the selection of ferromagnetic metal electrodes and thickness was found to be a deterministic factor in designing the photolithography, thin film deposition strategy, and molecular bridging process. We mainly used isotropic NiFe soft magnetic material and anisotropic Cobalt (Co) with significant magnetic hardness. We found Co was susceptible to chemical etching when directly exposed to photoresist developer and aged molecular solution. However, NiFe was very stable against the chemicals we used in the MTJMSD fabrication. As compared to NiFe, the Co films with > 10nm thickness were susceptible to mechanical stress-induced nanoscale deformities. However, cobalt was essential to produce (a) low leakage current before transforming the capacitor from the magnetic tunnel junction into molecular devices and (b) tailoring the magnetic properties of the ferromagnetic electrodes. This paper describes our overall MTJMSD fabrication scheme and process optimization to overcome various challenges to produce stable and reliable MTJMSDs. We also discuss the role of mechanical stresses arising during the sputtering of the ultrathin insulator and how to overcome that challenge by optimizing the insulator growth process. This paper will benefit researchers striving to make nanoscale spintronics devices for solving grand challenges in developing advanced sensors, magnetic metamaterials, and computer devices.

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

2021 ◽  
Author(s):  
Bishnu R. Dahal ◽  
Marzieh Savadkoohi ◽  
Eva Mutunga ◽  
Andrew Grizzle ◽  
Christopher D'Angelo ◽  
...  
Keyword(s):  
Tunnel Junction ◽  
Magnetic Tunnel Junction ◽  
Molecular Spintronics ◽  
Ferromagnetic Electrodes ◽  
Spintronics Device

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.

scholarly journals Exploring room-temperature transport of single-molecule magnet-based molecular spintronics devices using the magnetic tunnel junction as a device platform

RSC Advances ◽  
2020 ◽  
Vol 10 (22) ◽  
pp. 13006-13015 ◽  
Author(s):  
Pawan Tyagi ◽  
Christopher Riso ◽  
Uzma Amir ◽  
Carlos Rojas-Dotti ◽  
Jose Martínez-Lillo
Keyword(s):  
Single Molecule ◽  
Tunnel Junction ◽  
Room Temperature ◽  
Magnetic Tunnel Junction ◽  
Single Molecule Magnet ◽  
Molecular Spintronics ◽  
Ferromagnetic Electrodes ◽  
Device Architecture

A device architecture utilizing a single-molecule magnet (SMM) as a device element between two ferromagnetic electrodes may open vast opportunities to create novel molecular spintronics devices.

Addressing the Challenges of Using Ferromagnetic Electrodes in Molecular Devices

MRS Advances ◽  
2016 ◽  
Vol 1 (7) ◽  
pp. 483-488
Author(s):  
Pawan Tyagi ◽  
Edward Friebe ◽  
Collin Baker
Keyword(s):  
High Temperature ◽  
Tunnel Junction ◽  
Chemical Bonding ◽  
Chemical Etching ◽  
Magnetic Tunnel Junction ◽  
Device Fabrication ◽  
Molecular Devices ◽  
Molecular Device ◽  
Experimental Development ◽  
Ferromagnetic Electrodes

ABSTRACTFerromagnetic (FM) electrodes chemically anchored with thiol functionalized molecules can yield novel molecular spintronics devices (MSDs). However, significant challenges lie in developing commercially viable MSD fabrication approach utilizing FM electrodes. A practical MSD fabrication approach should consider FM electrodes’ susceptibility to oxidation, chemical etching, and stress induced deformations during fabrication and usage. This paper will discuss NiFe, an alloy used in the present day memory devices and high-temperature engineering applications, as a candidate for FM electrode and for the fabrication of MSDs. Our spectroscopic reflectance studies show that NiFe starts oxidizing aggressively beyond ∼90 ⁰C. The NiFe surfaces, aged for several months or heated for several minutes below ∼90 ⁰C, were suitable for chemical bonding with the thiol-functionalized molecules. NiFe also demonstrated excellent etching resistance in widely used dichloromethane solvent for dissolving molecular device elements. NiFe also reduced the mechanical stress induced deformities in other FM metals like cobalt. This paper also discusses the successful utilization of NiFe electrodes in the magnetic tunnel junction based molecular device fabrication approach. This research is expected to address the knowledge gap blocking the experimental development of FM based MSDs.

scholarly journals Advantages of Prefabricated Tunnel Junction-Based Molecular Spintronics Devices

NANO ◽  
2015 ◽  
Vol 10 (04) ◽  
pp. 1530002 ◽  
Author(s):  
Pawan Tyagi ◽  
Edward Friebe ◽  
Collin Baker
Keyword(s):  
Tunnel Junction ◽  
Magnetic Tunnel Junction ◽  
Device Fabrication ◽  
Molecular Devices ◽  
Memory Devices ◽  
Molecular Device ◽  
Metal Electrodes ◽  
Molecular Spintronics ◽  
Junction Molecules ◽  
Metal Insulator Metal

Molecule-based devices may govern the advancement of the next generation's logic and memory devices. Molecules have the potential to be unmatched device elements as chemists can mass produce an endless variety of molecules with novel optical, magnetic and charge transport characteristics. However, the biggest challenge is to connect two metal leads to a target molecule(s) and develop a robust and versatile device fabrication technology that can be adopted for commercial scale mass production. This paper discusses distinct advantages of utilizing commercially successful tunnel junctions as a vehicle for developing molecular spintronics devices. We describe the use of a prefabricated tunnel junction with the exposed sides as a testbed for molecular device fabrication. On the exposed sides of a tunnel junction molecules are bridged across an insulator by chemically bonding with the two metal electrodes; sequential growth of metal–insulator–metal layers ensures that separation between two metal electrodes is controlled by the insulator thickness to the molecular device length scale. This paper highlights various attributes of tunnel junction-based molecular devices with ferromagnetic electrodes for making molecular spintronics devices. We strongly emphasize a need for close collaboration between chemists and magnetic tunnel junction (MTJ) researchers. Such partnerships will have a strong potential to develop tunnel junction-based molecular devices for futuristic areas such as memory devices, magnetic metamaterials, high sensitivity multi-chemical biosensors, etc.

scholarly journals Bolometric Properties of a Spin-Torque Diode Based on a Magnetic Tunnel Junction

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
G. D. Demin ◽  
K. A. Zvezdin ◽  
A. F. Popkov
Keyword(s):  
Tunnel Junction ◽  
Magnetic Tunnel Junction ◽  
Nonuniform Heating ◽  
Spin Torque ◽  
Rectification Effect ◽  
Wide Range ◽  
Spin Polarized ◽  
Potential Applications ◽  
Dynamic Components ◽  
Bolometric Effect

Spin caloritronics opens up a wide range of potential applications, one of which can be the thermoelectric rectification of a microwave signal by spin-diode structures. The bolometric properties of a spin-torque diode based on a magnetic tunnel junction (MTJ) in the presence of a thermal gradient through a tunnel junction are discussed. Theoretical estimates of the static and dynamic components of the microwave sensitivity of the spin-torque diode, related to thermoelectric tunnel magneto-Seebeck effect and the thermal transfer of spin angular momentum in the MTJ under nonuniform heating, are presented. Despite the fact that the thermal contribution to the microwave sensitivity of the spin-torque diode is found to be relatively small in relation to the rectification effect related to the modulation of the MTJ resistance by a microwave spin-polarized current, nevertheless, the considered bolometric effect can be successfully utilized in some real-world microwave applications.

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