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Sheng-Shi Li, Wei-Xiao Ji, Ping Li, Shu-Jun Hu, Tie Zhou, Chang-Wen Zhang, Shi-Shen Yan
Adequately understanding band inversion mechanism, one of the significant representations of topological phase, has substantial implications for design and regulation of topological insulators (TIs). Here, by identifying an unconventional band inversion, we propose an intrinsic quantum spin Hall (QSH) effect in iodinated group-V binary (ABI2) monolayers with a bulk gap as large as 0.409 eV, guaranteeing its viable application at room temperature. The nontrivial topological characters, which can be established by explicit demonstration of Z2 invariant and gapless helical edge states, are derived from the band inversion of antibonding states of p x,y orbitals at the K point...
July 21, 2017: Scientific Reports
Alexandr Alekhin, Ilya Razdolski, Nikita Ilin, Jan P Meyburg, Detlef Diesing, Vladimir Roddatis, Ivan Rungger, Maria Stamenova, Stefano Sanvito, Uwe Bovensiepen, Alexey Melnikov
Using the sensitivity of optical second harmonic generation to currents, we demonstrate the generation of 250-fs long spin current pulses in Fe/Au/Fe/MgO(001) spin valves. The temporal profile of these pulses indicates ballistic transport of hot electrons across a sub-100 nm Au layer. The pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Considering the calculated spin-dependent Fe/Au interface transmittance we conclude that a nonthermal spin-dependent Seebeck effect is responsible for the generation of ultrashort spin current pulses...
July 7, 2017: Physical Review Letters
Yalong Jiao, Fengxian Ma, Chunmei Zhang, John Bell, Stefano Sanvito, Aijun Du
Spin-polarized materials with Dirac features have sparked great scientific interest due to their potential applications in spintronics. But such a type of structure is very rare and none has been fabricated. Here, we investigate the already experimentally synthesized manganese fluoride (MnF_{3}) as a novel spin-polarized Dirac material by using first-principles calculations. MnF_{3} exhibits multiple Dirac cones in one spin orientation, while it behaves like a large gap semiconductor in the other spin channel...
July 7, 2017: Physical Review Letters
Naihua Miao, Bin Xu, Nicholas C Bristowe, Jian Zhou, Zhimei Sun
Atomically thin two-dimensional (2D) materials have received considerable research interest due to their extraordinary properties and promising applications. Here we predict the mono-layered indium triphosphide (InP3) as a new semiconducting 2D material with a range of favourable functional properties by means of ab initio calculations. The 2D InP3 crystal shows high stability and promise of experimental synthesis. It possesses an indirect band-gap of 1.14 eV and a high electron mobility of 1919 cm(2)V(-1)s(-1), which can be strongly manipulated with applied strain...
July 21, 2017: Journal of the American Chemical Society
Minwoong Joe, Hosik Lee, Mustafa Menderes Alyoruk, Jinhwan Lee, Sung Youb Kim, Changgu Lee, Jun Hee Lee
We performed first-principles calculations to investigate the magnetic, mechanical and electronic properties of the tetrachalcogenide CrPS4. Although bulk CrPS4 has been shown to exhibit a low-dimensional antiferromagnetic (AFM) ground state where ferromagnetic (FM) Cr-chains are coupled antiferromagnetically, our calculations indicated that the monolayer can be transformed to an FM material by applying a uniaxial tensile strain of ≥4% along the FM Cr-chain direction. The AFM-to-FM transition is explained to be driven by an increase of the exchange interaction induced by a decrease in the distance between the FM Cr-chains...
July 19, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Kuppusamy Senthil Kumar, Ivan Šalitroš, Eufemio Moreno-Pineda, Mario Ruben
A simple "isomer-like" variation of the spacer group in a set of Fe(ii) spin crossover (SCO) complexes designed to probe spin state dependence of electrical conductivity in graphene-based molecular spintronic junctions led to the observation of remarkable variations in the thermal- and light-induced magnetic characteristics, paving a simple route for the design of functional SCO complexes with different temperature switching regimes based on a 2,6-bis(pyrazol-1-yl)pyridine ligand skeleton.
July 19, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Arnab Pal, C Dhana Sekhar, Adyam Venimadhav, Pattukkannu Murugavel
The evolution of various magnetic ordering has been studied for orthorhombic perovskite GdMn<sub>1-<i>x</i></sub>Fe<sub><i>x</i></sub>O<sub>3</sub> (0 ≤ <i>x</i> ≤ 0.7) system to get its comprehensive magnetic phase diagram. We observed that the substitution of Fe in GdMnO<sub>3</sub> increases the antiferromagnetic Neel temperature (T<sub>N</sub>) from 40 K to above 400 K and importantly induces a spin-reorientation transition (T<sub>SR</sub>) for <i>x</i> ≥ 0...
July 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Hiroshi Terada, Shinobu Ohya, Le Duc Anh, Yoshihiro Iwasa, Masaaki Tanaka
Reducing the power consumption necessary for magnetization reversal is one of the most crucial issues facing spintronics devices. Electric field control of the magnetic anisotropy of ferromagnetic thin films is a promising method to solve this problem. However, the electric field is believed to be effective only within several nanometres of the surface in ferromagnetic metals because of its short Thomas-Fermi screening length, which prevents its practical application to devices. Herein, we successfully modulate the magnetic anisotropy of the entire region of the ferromagnetic layers in the elongated mesas of vertical spin field-effect transistors with widths as large as ~500 nm by applying an electric field to the side surface of the metallic GaMnAs-based mesas through an electric double layer...
July 17, 2017: Scientific Reports
Jose Hugo Garcia Aguilar, Aron W Cummings, Stephan Roche
We report on a theoretical study of the spin Hall Effect (SHE) and weak antilocalization (WAL) in graphene/transition metal dichalcogenide (TMDC) heterostructures, computed through efficient real-space quantum transport methods, and using realistic tight-binding models parametrized from ab initio calculations. The graphene/WS2 system is found to maximize spin proximity effects compared to graphene on MoS2, WSe2, or MoSe2, with a crucial role played by disorder, given the disappearance of SHE signals in the presence of strong intervalley scattering...
July 17, 2017: Nano Letters
Jie Pan, Stephan Lany, Yue Qi
Two-dimensional (2D) materials offer many key advantages to innovative applications, such as spintronics and quantum information processing. Theoretical computations have accelerated 2D materials design. In this issue of ACS Nano, Kumar et al. report that ferromagnetism can be achieved in functionalized nitride MXene based on first-principles calculations. Their computational results shed light on a potentially vast group of materials for the realization of 2D magnets. In this Perspective, we briefly summarize the promising properties of 2D materials and the role theory has played in predicting these properties...
July 17, 2017: ACS Nano
T Pincelli, V Lollobrigida, F Borgatti, A Regoutz, B Gobaut, C Schlueter, T-L Lee, D J Payne, M Oura, K Tamasaku, A Y Petrov, P Graziosi, F Miletto Granozio, M Cavallini, G Vinai, R Ciprian, C H Back, G Rossi, M Taguchi, H Daimon, G van der Laan, G Panaccione
In the rapidly growing field of spintronics, simultaneous control of electronic and magnetic properties is essential, and the perspective of building novel phases is directly linked to the control of tuning parameters, for example, thickness and doping. Looking at the relevant effects in interface-driven spintronics, the reduced symmetry at a surface and interface corresponds to a severe modification of the overlap of electron orbitals, that is, to a change of electron hybridization. Here we report a chemically and magnetically sensitive depth-dependent analysis of two paradigmatic systems, namely La1-xSrxMnO3 and (Ga,Mn)As...
July 17, 2017: Nature Communications
Sarmita Majumder, Karalee Jarvis, Sanjay K Banerjee, Karen L Kavanagh
The authors study the composition and abruptness of the interfacial layers that form during deposition and patterning of a ferromagnet, Fe on a topological insulator (TI), Bi2Se3, Bi2Te3, and SiOx/Bi2Te3. Such structures are potentially useful for spintronics. Cross-sectional transmission electron microscopy, including interfacial elemental mapping, confirms that Fe reacts with Bi2Se3 near room temperature, forming an abrupt 5 nm thick FeSe0.92 single crystalline binary phase, predominantly (001) oriented, with lattice fringe spacing of 0...
July 2017: Journal of Vacuum Science and Technology. B, Nanotechnology & Microelectronics: Materials, Processing, Measurement, & Phenomena: JVST B
Martin Stier, Wolfgang Häusler, Thore Posske, Gregor Gurski, Michael Thorwart
Magnetic Skyrmions can be considered as localized vortexlike spin textures which are topologically protected in continuous systems. Because of their stability, their small size, and the possibility to move them by low electric currents, they are promising candidates for spintronic devices. Without changing the topological charge, it is possible to create Skyrmion-anti-Skyrmion pairs. We derive a Skyrmion equation of motion which reveals how spin-polarized charge currents create Skyrmion-anti-Skyrmion pairs...
June 30, 2017: Physical Review Letters
Peng Gou, Jie Qian, Fuchun Xi, Yuexin Zou, Jun Cao, Haochi Yu, Ziyi Zhao, Le Yang, Jie Xu, Hengliang Wang, Lijian Zhang, Zhenghua An
The applications of spin dynamos, which could potentially power complex nanoscopic devices, have so far been limited owing to their extremely low energy conversion efficiencies. Here, we present a unique plasmonic diabolo cavity (PDC) that dramatically improves the spin rectification signal (enhancement of more than three orders of magnitude) under microwave excitation; further, it enables an energy conversion efficiency of up to ~0.69 mV/mW, compared with ~0.27 μV/mW without a PDC. This remarkable improvement arises from the simultaneous enhancement of the microwave electric field (~13-fold) and the magnetic field (~195-fold), which cooperate in the spin precession process generates photovoltage (PV) efficiently under ferromagnetic resonance (FMR) conditions...
July 13, 2017: Scientific Reports
Y Shiomi, J Lustikova, E Saitoh
Although magnetism and superconductivity hardly coexist in a single material, recent advances in nanotechnology and spintronics have brought to light their interplay in magnetotransport in thin-film heterostructures. Here, we found a periodic oscillation of Nernst voltage with respect to magnetic fields in Pt|LiFe5O8 (Pt|LFO) bilayers grown on a cuprate superconductor YBa2Cu3O7-x (YBCO). At high temperatures above the superconducting transition temperature (T C ) of YBCO, spin Seebeck voltages originating in Pt|LFO layers are observed...
July 13, 2017: Scientific Reports
Chunhui Du, Toeno van der Sar, Tony X Zhou, Pramey Upadhyaya, Francesco Casola, Huiliang Zhang, Mehmet C Onbasli, Caroline A Ross, Ronald L Walsworth, Yaroslav Tserkovnyak, Amir Yacoby
The spin chemical potential characterizes the tendency of spins to diffuse. Probing this quantity could provide insight into materials such as magnetic insulators and spin liquids and aid optimization of spintronic devices. Here we introduce single-spin magnetometry as a generic platform for nonperturbative, nanoscale characterization of spin chemical potentials. We experimentally realize this platform using diamond nitrogen-vacancy centers and use it to investigate magnons in a magnetic insulator, finding that the magnon chemical potential can be controlled by driving the system's ferromagnetic resonance...
July 14, 2017: Science
N Jedrecy, M Hamieh, C Hebert, J Perriere
The solid phase growth of self-assembled nanocrystals embedded in a crystalline host matrix opens up wide perspectives for the coupling of different physical properties, such as magnetic and semiconducting. In this work, we report the pulsed laser growth at room temperature of thin films composed of a dispersed array of ferromagnetic Co (0001) nanoclusters with an in-plane mono-size width of 1.3 nm, embedded in a ZnO (0001) crystalline matrix. The as-grown films lead to very high values of magnetoresistance, ranging at 9 T from -11% at 300 K to -19% at 50 K, with a steep decrease of the magnetoresistance at low magnetic fields...
July 13, 2017: Nanoscale
Alexander J Grutter, Kathryn L Krycka, Elena V Tartakovskaya, Julie A Borchers, K Sai Madhukar Reddy, Eduardo Ortega, Arturo Ponce, Bethanie J H Stadler
A comprehensive three-dimensional picture of magnetic ordering in high-density arrays of segmented FeGa/Cu nanowires is experimentally realized through the application of polarized small-angle neutron scattering. The competing energetics of dipolar interactions, shape anisotropy, and Zeeman energy in concert stabilize a highly tunable spin structure that depends heavily on the applied field and sample geometry. Consequently, we observe ferromagnetic and antiferromagnetic interactions both among wires and between segments within individual wires...
July 20, 2017: ACS Nano
Lars Bocklage
The generation of short spin current pulses is the basis for fast spintronic devices. In thin bilayer systems consisting of a nonmagnetic metal and a ferromagnet, a pure spin current is induced by a precessing magnetization into the nonmagnetic layer by spin pumping. This effect has been experimentally demonstrated at ferromagnetic resonance at GHz frequencies. Here, it is theoretically shown that transient magnetization dynamics efficiently generates short spin current pulses that exhibit two transient contributions...
June 23, 2017: Physical Review Letters
Shun-Tsung Lo, Chin-Hung Chen, Ju-Chun Fan, L W Smith, G L Creeth, Che-Wei Chang, M Pepper, J P Griffiths, I Farrer, H E Beere, G A C Jones, D A Ritchie, Tse-Ming Chen
The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin-orbit interaction in semiconductor nanostructures...
July 10, 2017: Nature Communications
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