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Spin filtering

Si-Cong Zhu, Shun-Jin Peng, Kai-Ming Wu, Cho-Tung Yip, Kai-Lun Yao, Chi-Hang Lam
We investigate the electronic and transport properties of vanadium-doped zigzag blue phosphorus nanoribbons by first-principles quantum transport calculations. We study the spin-dependent transport properties and obtain current-voltage curves showing obvious spin polarization and negative differential behaviors. These interesting transport behaviors can be explained by the band structure of the vanadium-doped zigzag blue phosphorus nanoribbons. The tunnel magnetoresistance and spin-filtering effects under different magnetic configurations originate predominately from the symmetry matching between the band structures of the electrodes...
August 3, 2018: Physical Chemistry Chemical Physics: PCCP
Kanghyun Ryu, Jaewook Shin, Hongpyo Lee, Jun-Hyeong Kim, Dong-Hyun Kim
PURPOSE: To obtain in vivo electrical conductivity images from multi-echo gradient-echo (mGRE) sequence using a zero-TE phase extrapolation algorithm based on the Kalman method. METHODS: For estimation of the zero-TE phase from the mGRE data, an iterative algorithm consisting of a combination of the Kalman filter, Kalman smoother, and expectation maximization was implemented and compared with linear extrapolation methods. Simulations were performed for verification, and phantom and in vivo studies were conducted for validation...
July 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Chih-Yu Chen, C D Hu, Yeu-Chung Lin
A gauge invariant effective lagrangian for the fermion axial anomaly is constructed. The dynamical degree of freedom for fermion field is preserved. Using the anomaly lagrangian, the scattering cross section of pair production γγ → e- e+ in Dirac or Weyl semimetal is computed. The result is compared with the corresponding result from Dirac lagrangian. It is found that anomaly lagrangain and Dirac lagrangian exhibit the same E ⋅ B pattern, therefore the E ⋅ B signature may not serve a good indicator of the existence of axial anomaly...
July 26, 2018: Scientific Reports
Sebastian Schmitz, Andrew Kovalchuk, Alejandro Martín-Rodríguez, Jan van Leusen, Natalya V Izarova, Svenja D M Bourone, Yong Ai, Eliseo Ruiz, Ryan C Chiechi, Paul Kögerler, Kirill Yu Monakhov
A series of isostructural dinuclear 3d-4f complexes, isolated as [CuLn(L·SMe)2 (OOCMe)2 (NO3 )]· xMeOH (Ln = Gd 1, Tb 2, Dy 3, and Y 4; x = 0.75-1) and comprising one acetate and two thioether-Schiff base (L·SMe- ) bridging ligands based on 4-(methylthio)aniline and 2-hydroxy-3-methoxybenzaldehyde (HL·SMe = C15 H15 NO2 S), was synthesized and fully characterized. The magnetic properties of the charge-neutral {CuLn} complexes are dominated by ferromagnetic CuII -LnIII exchange interactions. Large-area electron transport studies reveal that the average conductivity of robust, self-assembled {CuLn} monolayers on a gold substrate is significantly lower than that of common alkanethiolates...
August 6, 2018: Inorganic Chemistry
R-Y Yuan, Q-J Yang, Y Guo
Special resonant modes in unique quantum structure can enhance spin and valley filtering effect. Hence we investigated resonant tunneling effect with large incident angles through single electric barrier in monolayer MoS2 junctions consisting of normal/ferromagnetic/normal parts. We found that for large incident angles the spin- and valley-dependent line-type resonances appear in the transmission and conductance spectra, which results in the transmission probabilities of spin-up and spin-down electrons at K and [Formula: see text] valleys being all improved to 100[Formula: see text] but for different special gate voltage...
July 20, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Mustapha Bouhrara, David A Reiter, Michael C Maring, Jean-Marie Bonny, Richard G Spencer
BACKGROUND AND PURPOSE: Myelin water fraction (MWF) mapping permits direct visualization of myelination patterns in the developing brain and in pathology. MWF is conventionally measured through multiexponential T2 analysis which is very sensitive to noise, leading to inaccuracies in derived MWF estimates. Although noise reduction filters may be applied during postprocessing, conventional filtering can introduce bias and obscure small structures and edges. Advanced nonblurring filters, while effective, exhibit a high level of complexity and the requirement for supervised implementation for optimal performance...
July 12, 2018: Journal of Neuroimaging: Official Journal of the American Society of Neuroimaging
Arnab Banerjee, Amlan J Pal
The formation of all-organic dual spin valves (DSVs) with three organic spin-selective layers, that is, spin-injection, spin-detection, and an additional spin-filtering layer at the intermediate, is reported. As spin-selective layers, manganese- and cobalt phthalocyanines, which are well-known single-molecule magnets, are used in their immobilized forms, so that all-organic DSVs can be prefabricated for characterization. The three spin-selective layers have provided four configurations with at most two spin-flip interfaces enforcing spin-flipping at the two nonmagnetic organic spacer layers, for which copper phthalocyanine is used...
July 11, 2018: Small
Zhigang Song, Xiaotian Sun, Jiaxin Zheng, Feng Pan, Yanglong Hou, Man-Hong Yung, Jinbo Yang, Jing Lu
Valleytronics has attracted much attention due to its potential applications in the information processing industry. Creation of permanent valley polarization (PVP), i.e. unbalanced occupation at different valleys, is a vital requirement for practical devices in valleytronics. However, the development of an appropriate material with PVP remains a main challenge. Here we used first-principles calculations to predict that the spin-orbit coupling and magnetic ordering allow spontaneous valley Zeeman-type splitting in the pristine monolayer of VAgP2 Se6 ...
August 7, 2018: Nanoscale
Toshihiko Sugiki, Kyoko Furuita, Toshimichi Fujiwara, Chojiro Kojima
Amino acid selective isotope labeling is an important nuclear magnetic resonance technique, especially for larger proteins, providing strong bases for the unambiguous resonance assignments and information concerning the structure, dynamics, and intermolecular interactions. Amino acid selective 15 N labeling suffers from isotope dilution caused by metabolic interconversion of the amino acids, resulting in isotope scrambling within the target protein. Carbonyl 13 C atoms experience less isotope scrambling than the main-chain 15 N atoms do...
July 3, 2018: Biochemistry
Joel Lapin, Alexander A Nevzorov
An automated technique for the sequential assignment of NMR backbone resonances of oriented protein samples has been developed and tested based on 15 N-15 N homonuclear exchange and spin-exchanged separated local-field spectra. By treating the experimental spectral intensity as a pseudopotential, the Monte-Carlo Simulated Annealing algorithm has been employed to seek lowest-energy assignment solutions over a large sampling space where direct enumeration would be unfeasible. The determined sequential assignments have been scored based on the positions of the crosspeaks resulting from the possible orders for the main peaks...
August 2018: Journal of Magnetic Resonance
Stefan Mattauch, Alexandros Koutsioubas, Ulrich Rücker, Denis Korolkov, Vicenzo Fracassi, Jos Daemen, Ralf Schmitz, Klaus Bussmann, Frank Suxdorf, Michael Wagener, Peter Kämmerling, Harald Kleines, Lydia Fleischhauer-Fuß, Manfred Bednareck, Vladimir Ossoviy, Andreas Nebel, Peter Stronciwilk, Simon Staringer, Marko Gödel, Alfred Richter, Harald Kusche, Thomas Kohnke, Alexander Ioffe, Earl Babcock, Zahir Salhi, Thomas Bruckel
MARIA (magnetism reflectometer with high incident angle) is a world class vertical sample reflectometer dedicated to the investigation of thin films in the fields of magnetism, soft matter and biology. The elliptical vertically focusing guide allows one to measure small samples with a typical size of 1 × 1 cm very efficiently. The double-bounce polarizer and the in situ pumped 3 He SEOP (spin-exchange optical pumping) neutron spin filter cell for analysing the polarization of the reflected neutron beam can be moved into the beam in seconds...
June 1, 2018: Journal of Applied Crystallography
G A Nemnes, T L Mitran, Daniela Dragoman
We investigate the prospects for current modulation in single layer graphene Y-junctions in the ballistic regime, under an external electric field. Overcoming the inability of inducing field effect in graphene nanoribbons by a stacked gate, the proposed in-plane electric field setup enables a controlled current transfer between the branches of the Y-junction. This behavior is further confirmed by changing the angular incidence of the electric field. The ballistic transmission functions are calculated for the three terminal system using the non-equilibrium Green's function formalism, in the framework of density functional theory, under finite bias conditions...
August 31, 2018: Nanotechnology
Soubhik Chakrabarty, A H M Abdul Wasey, Ranjit Thapa, G P Das
To realize a graphene based spintronic device, the prime challenge is to control the electronic structure of edges. In this work we find the origin of the spin filtering property in edge boron doped zigzag graphene nanoribbons (ZGNRs) and provide a guide to preparing a graphene based next-generation spin filter based device. Here, we unveil the role of orbitals (p-electron) to tune the electronic, magnetic and transport properties of edge B doped ZGNRs. When all the edge carbon atoms at one of the edges of ZGNRs are replaced by B (100% edge B doping), the system undergoes a semiconductor to metal transition...
August 24, 2018: Nanotechnology
Sergey Milikisiyants, Maxim A Voinov, Alex I Smirnov
EPR pulsed dipolar spectroscopy (PDS) is indispensable for measurements of nm-scale distances between electronic spins in biological and other systems. While several useful modifications and pulse sequences for PDS have been developed in recent years, DEER experiments utilizing pump and observer pulses at two different frequencies remain the most popular for practical applications. One of the major drawbacks of all the available DEER approaches is the presence of a significant unmodulated fraction in the detected signal that arises from an incomplete inversion of the coupled spins by the pump pulse...
August 2018: Journal of Magnetic Resonance
João Paulo Santos Silva, Luciana da Mata Mônaco, André Monteiro Paschoal, Ícaro Agenor Ferreira de Oliveira, Renata Ferranti Leoni
BACKGROUND: Arterial spin labeling (ASL) is an established magnetic resonance imaging (MRI) technique that is finding broader applications in functional studies of the healthy and diseased brain. To promote improvement in cerebral blood flow (CBF) signal specificity, many algorithms and imaging procedures, such as subtraction methods, were proposed to eliminate or, at least, minimize noise sources. Therefore, this study addressed the main considerations of how CBF functional connectivity (FC) is changed, regarding resting brain network (RBN) identification and correlations between regions of interest (ROI), by different subtraction methods and removal of residual motion artifacts and global signal fluctuations (RMAGSF)...
September 2018: Magnetic Resonance Imaging
Liang Tian, Fei Wang, Yuanda Wu, Yunji Yi, Xiaoqiang Sun, Daming Zhang
A polymer/silica hybrid integration add-drop filter based on a grating-assisted contradirectional coupler fabricated through simple and low-cost contact lithography is proposed. First, the structure pattern of the add-drop filter was formed in the lower silica cladding by contact lithography and inductively coupled plasma (ICP) etching. Then an SU-8 film was fabricated on top of it by a spin-coating method, and an inverted-rib waveguide structure was formed. Next, the slab layer of the inverted-rib waveguide was removed by ICP etching...
May 15, 2018: Optics Letters
Xiang Ni, David Purtseladze, Daria A Smirnova, Alexey Slobozhanyuk, Andrea Alù, Alexander B Khanikaev
Recent advances in condensed matter physics have shown that the spin degree of freedom of electrons can be efficiently exploited in the emergent field of spintronics, offering unique opportunities for efficient data transfer, computing, and storage ( 1 - 3 ). These concepts have been inspiring analogous approaches in photonics, where the manipulation of an artificially engineered pseudospin degree of freedom can be enabled by synthetic gauge fields acting on light ( 4 - 6 ). The ability to control these degrees of freedom significantly expands the landscape of available optical responses, which may revolutionize optical computing and the basic means of controlling light in photonic devices across the entire electromagnetic spectrum...
May 2018: Science Advances
Xing-Kai Hu, Ji-Kai Lyu, Chang-Wen Zhang, Pei-Ji Wang, Wei-Xiao Ji, Ping Li
A large bulk band gap is critical for the application of two-dimensional topological insulators (TIs) in spintronic devices operating at room temperature. On the basis of first-principles calculations, we predict BiXH (X = OH, SH) monolayers as TIs with an extraordinarily large bulk gap of 820 meV for BiOH and 850 meV for BiSH, and propose a tight-binding model considering spin-orbit coupling to describe the electronic properties of BiXH. These large gaps are entirely due to the strong spin-orbit interaction related to the pxy orbitals of the Bi atoms of the honeycomb lattice...
May 16, 2018: Physical Chemistry Chemical Physics: PCCP
Tomasz Slusarski, Tomasz Kostyrko, V M García-Suárez
We propose a molecular switch based on copper dioxolene molecules with valence tautomeric properties. We study the system using density functional theory and a model Hamiltonian that can properly account for electronic correlations in these complex molecular systems. We compute the transport properties of the junction with a Cu-dioxolene unit sandwiched between gold electrodes and analyze its dependence on the valence tautomeric state of the molecule. We also study the effects of doping with ICl2 acceptor molecules on the magnetic and electronic features of the device...
May 16, 2018: Physical Chemistry Chemical Physics: PCCP
Tiancheng Song, Xinghan Cai, Matisse Wei-Yuan Tu, Xiaoou Zhang, Bevin Huang, Nathan P Wilson, Kyle L Seyler, Lin Zhu, Takashi Taniguchi, Kenji Watanabe, Michael A McGuire, David H Cobden, Di Xiao, Wang Yao, Xiaodong Xu
Magnetic multilayer devices that exploit magnetoresistance are the backbone of magnetic sensing and data storage technologies. Here, we report multiple-spin-filter magnetic tunnel junctions (sf-MTJs) based on van der Waals (vdW) heterostructures in which atomically thin chromium triiodide (CrI3 ) acts as a spin-filter tunnel barrier sandwiched between graphene contacts. We demonstrate tunneling magnetoresistance that is drastically enhanced with increasing CrI3 layer thickness, reaching a record 19,000% for magnetic multilayer structures using four-layer sf-MTJs at low temperatures...
June 15, 2018: Science
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