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

D’Angelo

Baker

2015

NANO

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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 e®ect 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 e®ect of magnetic molecules on the magnetic properties of MSDs. This paper investigates the e®ect 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 di®erent kinds of magnetic interactions between molecules and FM electrodes at di®erent temperatures. The MC simulations show that ambient thermal energy strongly in°uenced the molecular coupling e®ect on the MSD. We studied the nature and strength of molecule couplings (FM and antiferromagnetic) with the two electrodes on the magnetization, speci¯c 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 e®ect 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 1550056-1 NANO: Brief Reports and Reviews Vol. 10, No. 4 (2015) designing of a wide range of novel spintronics devices utilizing a variety of molecules, nanoclusters and quantum dots as the device elements.

Section: Resultsmentioning

confidence: 99%

“…16 The magnetic tunnel junction (MTJ) based molecular spintronics devices (MTJMSDs) were found to be a close representation of 2D models used in the MC simulations. A MTJ represents two physically separated FM electrodes that can only be coupled by molecules along the edges.…”

Section: Experimental Con¯rmationmentioning

confidence: 99%

Monte Carlo and Experimental Magnetic Studies of Molecular Spintronics Devices

D’Angelo

Baker

2015

NANO

Self Cite

“…2(c)] the e®ective length of molecular channels to demonstrate that only intended molecular bridges play the role in enhancing conduction 23 or a®ecting the overall device behavior. 32 …”

Section: Molecules Serve As a Device Element Not As A Physical Barriermentioning

confidence: 99%

“…33 Tyagi et al 23,33 produced TJMDs with a typical tunnel junction of $ 25 m 2 area; overall $ 10 m length was available for posting molecular bridges along the tunnel junction edges. 23,32 For instance, reducing the width of the top metal electrode to 1 m or less will reduce the tunnel junction leakage current by a factor of¯ve, making the molecule e®ect more prominent. Reduction in tunnel junction area will also prolong the TJMD's stability and lifetime.…”

Section: 2mentioning

confidence: 99%

“…4,32,33 A TJMD fabrication protocol involves two key steps: (i) fabrication of a tunnel junction with exposed side edges where the maximum distance between two metal electrodes is equal to the thickness of tunnel barrier [ Fig. 1(d)] 3 and (ii) chemically bonding the molecule(s) of interests across the insulator gap [ Fig.…”

Section: Tunnel Junction-based Molecular Devicesmentioning

confidence: 99%

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Advantages of Prefabricated Tunnel Junction-Based Molecular Spintronics Devices

Friebe

Baker

2015

NANO

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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.

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

2012

Appl. Phys. A

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A multilayer edge molecular electronics device (MEMED), which utilize the two metal electrodes of a metal-insulator-metal tunnel junction as the two electrical leads to molecular channels, can overcome the long standing fabrication challenges for developing futuristic molecular devices. However, producing ultrathin insulator is the most challenging step in MEMED fabrication. A simplified molecular device approach was developed by avoiding the need of depositing a new materiel on the bottom electrode for growing ultrathin insulator. This paper discuss the approach for MEMED's insulator growth by one-step oxidation of a tantalum (Ta) bottom electrode, in the pholithographically defined region; i.e. ultrathin tantalum oxide (TaOx) insulator was grown by oxidizing bottom metal electrode itself. Organometallic molecular clusters (OMCs) were bridged across 1-3 nm TaOx along the perimeter of a tunnel junction to establish the highly efficient molecular conduction channels. OMC transformed the asymmetric transport profile of TaOx based tunnel junction into symmetric one. A TaOx based tunnel junction with top ferromagnetic (NiFe) electrode exhibited the transient current suppression by several orders. Further studies will be needed to strengthen the current suppression phenomenon, and to realize the full potential of TaOx based multilayer edge molecular spintronics devices.Introduction: Molecule based electronics and spin devices are highly promising to give novel computational strategies and ultimate device miniaturization. Molecular devices have been produced by various methods [1]. The common approaches are: (a) sandwiching selfassembled molecular monolayer between two metal electrodes, (b) bridging nm gap of the metal break-junction with molecule(s), and (c) bridging the molecular conduction channels across a tunnel junction's insulator [1,2]. The last approach is based on utilizing a prefabricated multilayer tunnel junction's edges as a test bed, and hence can be justifiably termed as multilayer edge molecular electronics device (MEMED) [2]. MEMED approach has several