scholarly journals Real-space observation of ferroelectrically induced magnetic spin crystal in SrRuO3

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
S. D. Seddon ◽  
D. E. Dogaru ◽  
S. J. R. Holt ◽  
D. Rusu ◽  
J. J. P. Peters ◽  
...  
Keyword(s):  
Hall Effect ◽  
Density Functional ◽  
Hysteresis Loops ◽  
Real Space ◽  
Zero Field ◽  
Force Microscopy ◽  
Switching Regime ◽  
Conflicting Evidence ◽  
Magnetic Spin

AbstractUnusual features in the Hall Resistivity of thin film systems are frequently associated with whirling spin textures such as Skyrmions. A host of recent investigations of Hall Hysteresis loops in SrRuO3 heterostructures have provided conflicting evidence for different causes for such features. We have constructed an SrRuO3-PbTiO3 (Ferromagnetic – Ferroelectric) bilayer that exhibits features in the Hall Hysteresis previously attributed to a Topological Hall Effect, and Skyrmions. Here we show field dependent Magnetic Force Microscopy measurements throughout the key fields where the ‘THE’ presents, revealing the emergence to two periodic, chiral spin textures. The zero-field cycloidal phase, which then transforms into a ‘double-q’ incommensurate spin crystal appears over the appearance of the ‘Topological-like’ Hall effect region, and develop into a ferromagnetic switching regime as the sample reaches saturation, and the ‘Topological-like’ response diminishes. Scanning Tunnelling Electron Microscopy and Density Functional Theory is used to observe and analyse surface inversion symmetry breaking and confirm the role of an interfacial Dzyaloshinskii–Moriya interaction at the heart of the system.

scholarly journals Colossal topological Hall effect at the transition between isolated and lattice-phase interfacial skyrmions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
M. Raju ◽  
A. P. Petrović ◽  
A. Yagil ◽  
K. S. Denisov ◽  
N. K. Duong ◽  
...  
Keyword(s):  
Thin Films ◽  
Hall Effect ◽  
Variable Temperature ◽  
Dominant Role ◽  
Real Space ◽  
Spin Fluctuations ◽  
Magnetic Imaging ◽  
Topological Hall Effect ◽  
Lattice Result

AbstractThe topological Hall effect is used extensively to study chiral spin textures in various materials. However, the factors controlling its magnitude in technologically-relevant thin films remain uncertain. Using variable-temperature magnetotransport and real-space magnetic imaging in a series of Ir/Fe/Co/Pt heterostructures, here we report that the chiral spin fluctuations at the phase boundary between isolated skyrmions and a disordered skyrmion lattice result in a power-law enhancement of the topological Hall resistivity by up to three orders of magnitude. Our work reveals the dominant role of skyrmion stability and configuration in determining the magnitude of the topological Hall effect.

Some methods to regulate low-bias negative differential resistance in σ barrier separating nanoscale molecular transport systems

2016 ◽  
Vol 30 (02) ◽  
pp. 1550256 ◽  
Author(s):  
Ji-Mei Shen ◽  
Jing Liu ◽  
Yi Min ◽  
Li-Ping Zhou
Keyword(s):  
Negative Differential Resistance ◽  
Density Functional ◽  
Molecular Transport ◽  
Differential Resistance ◽  
Real Space ◽  
Peak Position ◽  
Transport Systems ◽  
Orbital Interaction ◽  
Potential Applications

Using the first-principles method which combines the nonequilibrium Green’s function (NEGF) with density functional theory (DFT), the role of defect, dopant, barrier length and geometric deformation for low-bias negative differential resistance (NDR) in two capped armchair carbon nanotubes (CNTs) sandwiching [Formula: see text] barrier are systematically analyzed. We found that this method can regulate the negative differential resistance (NDR) effects such as current peak and peak position. The adjusting mechanism may originate from orbital interaction and orbital reconstruction. Our calculations try to manipulate the transport characteristics in energy space by simply manipulating the structure in real space, which may promise the potential applications in nanomolecular-electronics in the future.

Development of the UHV-STM

1990 ◽  
Vol 48 (1) ◽  
pp. 322-323
Author(s):  
M. Iwatsuki ◽  
S. Kitamura ◽  
A. Mogami
Keyword(s):  
Surface Science ◽  
Real Space ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Great Promise ◽  
Force Microscopy ◽  
Atomic Force ◽  
Stm Image ◽  
Surface Construction ◽  
Very High

Since Binnig, Rohrer and associates observed real-space topographic images of Si(111)-7×7 and invented the scanning tunneling microscope (STM),1) the STM has been accepted as a powerful surface science instrument.Recently, many application areas for the STM have been opened up, such as atomic force microscopy (AFM), magnetic force microscopy (MFM) and others. So, the STM technology holds a great promise for the future.The great advantages of the STM are its high spatial resolution in the lateral and vertical directions on the atomic scale. However, the STM has difficulty in identifying atomic images in a desired area because it uses piezoelectric (PZT) elements as a scanner.On the other hand, the demand to observe specimens under UHV condition has grown, along with the advent of the STM technology. The requirment of UHV-STM is especially very high in to study of surface construction of semiconductors and superconducting materials on the atomic scale. In order to improve the STM image quality by keeping the specimen and tip surfaces clean, we have built a new UHV-STM (JSTM-4000XV) system which is provided with other surface analysis capability.

The Nature of S-N Bonding in Sulfonamides and Related Compounds: Insights into π-Bonding Contributions from Sulfur K-Edge XAS

2020 ◽  
Author(s):  
Tulin Okbinoglu ◽  
Pierre Kennepohl
Keyword(s):  
Density Functional ◽  
Chemical Properties ◽  
Functional Theory ◽  
Rotational Barriers ◽  
Td Dft ◽  
Nitrogen Bonds ◽  
X Ray Absorption ◽  
Related Compounds ◽  
And Chemical Properties

Molecules containing sulfur-nitrogen bonds, like sulfonamides, have long been of interest due to their many uses and chemical properties. Understanding the factors that cause sulfonamide reactivity is important, yet their continues to be controversy regarding the relevance of S-N π bonding in describing these species. In this paper, we use sulfur K-edge x-ray absorption spectroscopy (XAS) in conjunction with density functional theory (DFT) to explore the role of S<sub>3p</sub> contributions to π-bonding in sulfonamides, sulfinamides and sulfenamides. We explore the nature of electron distribution of the sulfur atom and its nearest neighbors and extend the scope to explore the effects on rotational barriers along the sulfur-nitrogen axis. The experimental XAS data together with TD-DFT calculations confirm that sulfonamides, and the other sulfinated amides in this series, have essentially no S-N π bonding involving S<sub>3p</sub> contributions and that electron repulsion and is the dominant force that affect rotational barriers.

Isolation of Natural Compounds from Syzygium densiflorum Fruits and Exploring its Chemical Property, Therapeutic Role in Diabetic Management

2020 ◽  
Vol 10 (2) ◽  
pp. 168-176
Author(s):  
Krishnasamy Gopinath ◽  
Nagarajan Subbiah ◽  
Muthusamy Karthikeyan
Keyword(s):  
Density Functional ◽  
Chemical Reactivity ◽  
Natural Compounds ◽  
Structure Activity Relationship ◽  
Activity Relationship ◽  
Computational Studies ◽  
Therapeutic Role ◽  
Relationship Analysis ◽  
Structure Activity

Background: Syzygium densiflorum Wall. ex Wight & Arn (Myrtaceae) has been traditionally used by the local tribes of the Nilgiris, Tamil Nadu, India, for the treatment of diabetes. Objective: This study aimed to isolate the major phytoconstituents from the S. densiflorum fruits and to perform computational studies for chemical reactivity and biological activity of the isolated compound. Materials and Methods: Two different compounds were isolated from ethanolic extract of S. densiflorum fruits and purified using HPLC. The structures of the compounds were elucidated on the basis of their 1H NMR, 13C NMR, 1H-1H COSY, HMBC, HRESIMS, and FT-IR data. Further, the chemical reactivity of the compounds was analyzed by density functional theory calculations and its therapeutic role in diabetic management was examined by comparing the structure of isolated compounds with previously reported bioactive compounds. Results: Of the two compounds ((6,6 & 1-kestopentaose (1) and 6-(hydroxymethyl)-3-[3,4,5- trihydroxy- 6-[(3,4,5-trihydroxyoxan-2-yl)oxymethyl]oxan-2-yl]oxyoxane-2,4,5-triol)(2)). β-glucosidase, β-galactosidase, α-glucosidase and β-amylase inhibition activity of the compounds were predicted by structure activity relationship. Conclusion: Structure-activity relationship analysis was performed to predict the therapeutic role of isolated compounds. These computational studies may be performed to minimize the efforts to determine the therapeutic role of natural compounds.

The role of zero-field splitting and π-stacking interaction of different nitrogen-donor ligands on the optical properties of luminescent rhenium tricarbonyl complexes

2021 ◽  
Author(s):  
Plinio Cantero-López ◽  
Yoan Hidalgo-Rosa ◽  
Zoraida Sandoval-Olivares ◽  
Julián Santoyo-Flores ◽  
Pablo Mella ◽  
...  
Keyword(s):  
Excited States ◽  
Coordination Compounds ◽  
Donor Ligands ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Nitrogen Donor Ligands ◽  
Nitrogen Donor ◽  
Π Stacking Interaction ◽  
Rhenium Tricarbonyl

Rhenium tricarbonyl complexes are one of the most important classes of coordination compounds in inorganic chemistry. Exploring their luminescent excited states, lowest singlet (S1), and the lowest triplet (T1), is...

scholarly journals Tensor-structured algorithm for reduced-order scaling large-scale Kohn–Sham density functional theory calculations

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Chih-Chuen Lin ◽  
Phani Motamarri ◽  
Vikram Gavini
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Density Functional Theory Calculations ◽  
System Size ◽  
Real Space ◽  
Functional Theory ◽  
Reduced Order ◽  
Separable Approximation ◽  
Tensor Basis

AbstractWe present a tensor-structured algorithm for efficient large-scale density functional theory (DFT) calculations by constructing a Tucker tensor basis that is adapted to the Kohn–Sham Hamiltonian and localized in real-space. The proposed approach uses an additive separable approximation to the Kohn–Sham Hamiltonian and an L1 localization technique to generate the 1-D localized functions that constitute the Tucker tensor basis. Numerical results show that the resulting Tucker tensor basis exhibits exponential convergence in the ground-state energy with increasing Tucker rank. Further, the proposed tensor-structured algorithm demonstrated sub-quadratic scaling with system-size for both systems with and without a gap, and involving many thousands of atoms. This reduced-order scaling has also resulted in the proposed approach outperforming plane-wave DFT implementation for systems beyond 2000 electrons.

scholarly journals Anomalous transport due to Weyl fermions in the chiral antiferromagnets Mn3X, X = Sn, Ge

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Taishi Chen ◽  
Takahiro Tomita ◽  
Susumu Minami ◽  
Mingxuan Fu ◽  
Takashi Koretsune ◽  
...  
Keyword(s):  
Technological Innovation ◽  
Essential Role ◽  
Condensed Matter ◽  
Zero Field ◽  
Theoretical Studies ◽  
Planar Hall Effect ◽  
Topological States ◽  
Experimental And Theoretical Studies ◽  
Weyl Fermions

AbstractThe recent discoveries of strikingly large zero-field Hall and Nernst effects in antiferromagnets Mn3X (X = Sn, Ge) have brought the study of magnetic topological states to the forefront of condensed matter research and technological innovation. These effects are considered fingerprints of Weyl nodes residing near the Fermi energy, promoting Mn3X (X = Sn, Ge) as a fascinating platform to explore the elusive magnetic Weyl fermions. In this review, we provide recent updates on the insights drawn from experimental and theoretical studies of Mn3X (X = Sn, Ge) by combining previous reports with our new, comprehensive set of transport measurements of high-quality Mn3Sn and Mn3Ge single crystals. In particular, we report magnetotransport signatures specific to chiral anomalies in Mn3Ge and planar Hall effect in Mn3Sn, which have not yet been found in earlier studies. The results summarized here indicate the essential role of magnetic Weyl fermions in producing the large transverse responses in the absence of magnetization.

γ-Valerolactone-Introduced Controlled-Isomerization of Glucose for Lactic Acid Production over Sn-Beta Catalyst

2021 ◽  
Author(s):  
Xinpeng Zhao ◽  
Zhimin Zhou ◽  
hu luo ◽  
Yanfei Zhang ◽  
Wang Liu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Lactic Acid ◽  
Dft Calculations ◽  
Acid Production ◽  
Density Functional ◽  
Lactic Acid Production ◽  
Hydrothermal Conversion ◽  
Functional Theory ◽  
Environment Friendly

Combined experiments and density functional theory (DFT) calculations provided insights into the role of the environment-friendly γ-valerolactone (GVL) as a solvent in the hydrothermal conversion of glucose into lactic acid...

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