scholarly journals Reversible spin storage in metal oxide—fullerene heterojunctions

2020 ◽  
Vol 6 (12) ◽  
pp. eaax1085 ◽  
Author(s):  
T. Moorsom ◽  
M. Rogers ◽  
I. Scivetti ◽  
S. Bandaru ◽  
G. Teobaldi ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Density Functional ◽  
Muon Spin ◽  
Magnetic Ordering ◽  
Charge Trapping ◽  
Energy Shift ◽  
Storage Device ◽  
Oxide Interface ◽  
Independent Evidence ◽  
Spin Polarized

We show that hybrid MnOx/C60 heterojunctions can be used to design a storage device for spin-polarized charge: a spin capacitor. Hybridization at the carbon-metal oxide interface leads to spin-polarized charge trapping after an applied voltage or photocurrent. Strong electronic structure changes, including a 1-eV energy shift and spin polarization in the C60 lowest unoccupied molecular orbital, are then revealed by x-ray absorption spectroscopy, in agreement with density functional theory simulations. Muon spin spectroscopy measurements give further independent evidence of local spin ordering and magnetic moments optically/electronically stored at the heterojunctions. These spin-polarized states dissipate when shorting the electrodes. The spin storage decay time is controlled by magnetic ordering at the interface, leading to coherence times of seconds to hours even at room temperature.

scholarly journals On-surface Synthesis of [7]triangulene Quantum Ring via Antidot Engineering

2020 ◽  
Author(s):  
Jie Su ◽  
Wei Fan ◽  
Pingo Mutombo ◽  
Xinnan Peng ◽  
Shaotang Song ◽  
...  
Keyword(s):  
High Spin ◽  
Ground State ◽  
Density Functional ◽  
Magnetic Ordering ◽  
Open Shell ◽  
Scanning Tunneling ◽  
Quantum Ring ◽  
Tunneling Microscopy ◽  
Entire Family ◽  
Spin Polarized

The ability to engineer geometrically well-defined antidots in large triangulene homologues allows for creating an entire family of triangulene quantum ring (TQR) structures with tunable high-spin ground state and magnetic ordering, crucial for next-generation molecular spintronic devices. Herein, we report the synthesis of an open-shell [7]triangulene quantum ring ([7]TQR) molecule on Au(111) through the surface-assisted cyclodehydrogenation of a rationally-designed kekulene derivative. Bond-resolved scanning tunneling microscopy (BR-STM) unambiguously imaged the molecular backbone of a single [7]TQR with a triangular zigzag edge topology, which can be viewed as [7]triangulene decorated with a coronene-like antidot in the molecular centre. Additionally, dI/dV mapping reveals that both inner and outer zigzag edges contribute to the edge-localized and spin-polarized electronic states of [7]TQR. Both experimental results and spin-polarized density functional theory calculations indicate that [7]TQR retains its open-shell septuple ground-state (� = 3) on Au(111). This work demonstrates a new route for the design of high-spin graphene quantum rings as the key components for future quantum devices.

Magnetic Properties of Hole-Doped Pyrochlore Iridate (Y1-x-yCuxCay)2Ir2O7

2019 ◽  
Vol 966 ◽  
pp. 269-276
Author(s):  
Julia Angel ◽  
Retno Asih ◽  
Hironori Nomura ◽  
Tomoya Taniguchi ◽  
Kazuyuki Matsuhira ◽  
...  
Keyword(s):  
Density Functional ◽  
Muon Spin ◽  
Quantum Critical Point ◽  
Magnetic Ordering ◽  
Photoemission Spectroscopy ◽  
Metal Insulator Transition ◽  
Functional Theory ◽  
Metal Insulator ◽  
X Ray ◽  
Electronic Ground

We report the results of studies on the electronic state of the hole-doped Y-based pyrochlore iridate, (Y1-x-yCuxCay)2Ir2O7. We carried out the resistivity, Muon Spin Relaxation (μSR), X-ray Photoemission Spectroscopy (XPS) measurements and Density Functional Theory (DFT) calculations on the non-doped (x=y=0) and doped (x=0.05, y=0.15) systems. We found in the non-doped system that the magnetic ordering of Ir spins which was accompanied by the metal-insulator transition (MIT) occurred at around 157 K and disappeared in the doped system in which MIT seems to disappear or smeared out. We suggest from the current study that a quantum critical point which shows a change in the electronic ground state from insulating to metallic to exist between those two systems.

In Situ Observations of Early Stage Oxidation of Ni-Cr and Ni-Cr-Mo Alloys

CORROSION ◽  
10.5006/2807 ◽  
2018 ◽  
Vol 74 (9) ◽  
pp. 939-946 ◽  
Author(s):  
Xiao-xiang Yu ◽  
Ahmet Gulec ◽  
Christopher M. Andolina ◽  
Evan J. Zeitchick ◽  
Kateryna Gusieva ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Rock Salt ◽  
Density Functional ◽  
Early Stage ◽  
Density Functional Theory Calculations ◽  
Layer By Layer ◽  
Oxide Interface ◽  
Corundum Structure ◽  
Kirkendall Voids

Results of in situ transmission electron microscopy experiments on the early stage oxidation of Ni-Cr and Ni-Cr-Mo alloys are reported. An epitaxial rock-salt oxide with compositions outside the conventional solubility limits initiated at the surface of both alloys, progressing by a layer-by-layer mode. Kirkendall voids were found in Ni-Cr alloys near the metal/oxide interface, but were not seen in the Ni-Cr-Mo. The voids initiated in the oxide then diffused to the metal/oxide interface, driven by the misfit stresses in the oxide. A sequential oxide initiation was observed in NiCr alloys: rock-salt → spinel → corundum; however, for NiCrMo alloys, the metastable Ni2-xCrxO3 (corundum structure) phase formed shortly after the growth of the rock-salt phase. Chemical analysis shows that solute atoms were captured in the initial oxide before diffusing and transforming to more thermodynamically stable phases. The results indicate that Mo doping inhibits the formation of Kirkendall voids via an increase in the nucleation rate of corundum, which was verified by density functional theory calculations.

Charge trapping at the polymer-metal oxide interface as a first step in the electroforming of organic-inorganic memory diodes

2015 ◽  
Author(s):  
Benjamin F. Bory ◽  
Paulo Rocha ◽  
Henrique L. Gomes ◽  
Dago M. de Leeuw ◽  
Stefan C. J. Meskers
Keyword(s):  
Metal Oxide ◽  
Charge Trapping ◽  
Oxide Interface ◽  
Polymer Metal

Iron-Water Interface under Electrochemical Condition

2016 ◽  
Vol 879 ◽  
pp. 1399-1403
Author(s):  
Norio Nunomura ◽  
Satoshi Sunada
Keyword(s):  
Density Functional ◽  
Negative Charge ◽  
Positive Charge ◽  
Density Functional Theory Calculations ◽  
Energy Shift ◽  
Contact Layer ◽  
Water Molecules ◽  
Functional Theory ◽  
Electrochemical Condition ◽  
Spin Polarized

Spin polarized density functional theory calculations have been performed to characterize the structure of water molecules on iron surface under applied charges. It is found that water molecules of the contact layer take H-down configuration under the negative charge, on the other hand, under the positive charge, they adsorbed on a top site of iron atom, as the applied charge increases, the dissociation of water molecules proceed. In addition, we found that the energy shift of the Fermi level varies linearly in the range from-e to +e, while beyond this range it tends to saturate.

scholarly journals On-surface Synthesis of [7]triangulene Quantum Ring via Antidot Engineering

2020 ◽  
Author(s):  
Jie Su ◽  
Wei Fan ◽  
Pingo Mutombo ◽  
Xinnan Peng ◽  
Shaotang Song ◽  
...  
Keyword(s):  
High Spin ◽  
Ground State ◽  
Density Functional ◽  
Magnetic Ordering ◽  
Open Shell ◽  
Scanning Tunneling ◽  
Quantum Ring ◽  
Tunneling Microscopy ◽  
Entire Family ◽  
Spin Polarized

The ability to engineer geometrically well-defined antidots in large triangulene homologues allows for creating an entire family of triangulene quantum ring (TQR) structures with tunable high-spin ground state and magnetic ordering, crucial for next-generation molecular spintronic devices. Herein, we report the synthesis of an open-shell [7]triangulene quantum ring ([7]TQR) molecule on Au(111) through the surface-assisted cyclodehydrogenation of a rationally-designed kekulene derivative. Bond-resolved scanning tunneling microscopy (BR-STM) unambiguously imaged the molecular backbone of a single [7]TQR with a triangular zigzag edge topology, which can be viewed as [7]triangulene decorated with a coronene-like antidot in the molecular centre. Additionally, dI/dV mapping reveals that both inner and outer zigzag edges contribute to the edge-localized and spin-polarized electronic states of [7]TQR. Both experimental results and spin-polarized density functional theory calculations indicate that [7]TQR retains its open-shell septuple ground-state (� = 3) on Au(111). This work demonstrates a new route for the design of high-spin graphene quantum rings as the key components for future quantum devices.

Segregation Effects on the Metal-Carbide Interface

2005 ◽  
Vol 475-479 ◽  
pp. 4251-4254 ◽  
Author(s):  
L.M. Liu ◽  
Shao Qing Wang ◽  
Heng Qiang Ye
Keyword(s):  
Electronic Structure ◽  
Transition Metal ◽  
Metal Oxide ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Metal Carbide ◽  
Oxide Interface ◽  
Metal Atoms ◽  
Transition Metal Atoms

We employ density functional calculations to investigate the doped Al/TiC interfaces. The effects of different segregation atoms are discussed. The results show that the different transition metal atoms have different effects on the adhesion. Results of analysis of atom size and electronic structure have shown that both atom size and activity of the doped atom influence on the adhesion. Our results are consistent with other results of doped metal-oxide interface.

CO2 Activation on Heterostructures of Bi2O3-Nanocluster Modified TiO2: Promoting the Critical First Step in CO2 Conversion

2018 ◽  
Author(s):  
Michael Nolan
Keyword(s):  
Metal Oxide ◽  
Density Functional ◽  
Initial Step ◽  
Difficult Problem ◽  
Carbonate Formation ◽  
Structural Distortions ◽  
Strong Adsorption ◽  
Two Factors ◽  
Key Steps ◽  
Recent Experimental Work

The conversion of CO<sub>2</sub> to fuels is of significant importance in enabling the production of sustainable fuels, contributing to alleviating greenhouse gas emissions. While there are a number of key steps required to convert CO<sub>2</sub>, the initial step of adsorption and activation by the catalyst is critical. Well-known metal oxides such as oxidised TiO<sub>2</sub> or CeO<sub>2</sub> are unable to promote this step. In addressing this difficult problem, recent experimental work shows the potential for bismuth-containing materials to activate and convert CO<sub>2</sub>, but the origin of this activity is not yet clear. Additionally, nanostructures can show enhanced activity towards CO<sub>2</sub>. In this paper we present density functional theory (DFT) simulations of CO<sub>2</sub> activation on heterostructured materials composed of extended rutile and anatase TiO<sub>2</sub> surfaces modified with nanoclusters with Bi<sub>2</sub>O<sub>3</sub> stoichiometry. These heterostructures show low coordinated Bi sites in the nanoclusters and a valence band edge that is dominated by Bi-O states. These two factors mean that supported Bi<sub>2</sub>O<sub>3</sub> nanoclusters are able to adsorb and activate CO<sub>2</sub>. Computed adsorption energies lie in the range of -0.54 eV to -1.01 eV. In these strong adsorption modes, CO<sub>2</sub> is activated, in which the molecule bends giving O-C-O angles of 126 - 130<sup>o</sup> and elongation of C-O distances up to 1.28 Å, with no carbonate formation. The electronic properties show a strong CO<sub>2</sub>-Bi-oxygen interaction that drives the interaction of CO<sub>2</sub> to induce the structural distortions. Bi<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> heterostructures can be reduced to form Bi<sup>2+</sup> and Ti<sup>3+</sup> species. The interaction of CO<sub>2</sub> with this electron-rich, reduced system can produce CO directly, reoxidising the heterostructure or form an activated carboxyl species (CO<sub>2</sub><sup>-</sup>) through electron transfer from the heterostructure to CO<sub>2</sub>. These results highlight that a semiconducting metal oxide modified with suitable metal oxide nanoclusters can activate CO<sub>2</sub>, thus overcoming the difficulties associated with the difficult first step in CO<sub>2</sub> conversion.

Surface to bulk charge transfer at an alkali metal/metal oxide interface

2003 ◽  
Vol 547 (1-2) ◽  
pp. L859-L864 ◽  
Author(s):  
R Lindsay ◽  
E Michelangeli ◽  
B.G Daniels ◽  
M Polcik ◽  
A Verdini ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Alkali Metal ◽  
Metal Oxide ◽  
Oxide Interface ◽  
Metal Metal ◽  
Bulk Charge

Magnetic Properties of Embedded Rh Clusters in Ni Matrix

1995 ◽  
Vol 384 ◽  
Author(s):  
Zhi-Qiang Li ◽  
Yuichi Hashi ◽  
Jing-Zhi Yu ◽  
Kaoru Ohno ◽  
Yoshiyuki Kawazoe
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Magnetic Moments ◽  
Functional Formalism ◽  
Rhodium Clusters ◽  
Spin Polarized ◽  
Local Density Functional

ABSTRACTThe electronic structure and magnetic properties of rhodium clusters with sizes of 1 - 43 atoms embedded in the nickel host are studied by the first-principles spin-polarized calculations within the local density functional formalism. Single Rh atom in Ni matrix is found to have magnetic moment of 0.45μB. Rh13 and Rhl 9 clusters in Ni matrix have lower magnetic moments compared with the free ones. The most interesting finding is tha.t Rh43 cluster, which is bulk-like nonmagnetic in vacuum, becomes ferromagnetic when embedded in the nickel host.

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