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Zhida Zheng, Xiaocha Wang, Wenbo Mi
The strain and electric-field effects on the electronic structure of MoTe2/WTe2 van der Waals heterostructures are investigated by first-principles calculations. The MoTe2/WTe2 heterostructures are indirect band gap semiconductors under different strains except for 2%. At a strain from  -6% to 6% under a zero electric field, the band gap is 0.56, 0.62, 0.69, 0.62, 0.46, 0.37 and 0.29 eV, respectively. Meanwhile, spin splitting at the conduction band minimum (CBM) decreases monotonically from 76-1 meV, and that at the valance band maximum (VBM) is 232, 266, 292, 307, 319, 302 and 283 meV...
October 26, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Matthias Götte, Michael Joppe, Thomas Dahm
Two-dimensional topological insulators possess two counter propagating edge channels with opposite spin direction. Recent experimental progress allowed to create ferromagnetic topological insulators realizing a quantum anomalous Hall (QAH) state. In the QAH state one of the two edge channels disappears due to the strong ferromagnetic exchange field. We investigate heterostructures of topological insulators and ferromagnetic topological insulators by means of numerical transport calculations. We show that spin current flow in such heterostructures can be controlled with high fidelity...
October 26, 2016: Scientific Reports
M S Anwar, S R Lee, R Ishiguro, Y Sugimoto, Y Tano, S J Kang, Y J Shin, S Yonezawa, D Manske, H Takayanagi, T W Noh, Y Maeno
Efforts have been ongoing to establish superconducting spintronics utilizing ferromagnet/superconductor heterostructures. Previously reported devices are based on spin-singlet superconductors (SSCs), where the spin degree of freedom is lost. Spin-polarized supercurrent induction in ferromagnetic metals (FMs) is achieved even with SSCs, but only with the aid of interfacial complex magnetic structures, which severely affect information imprinted to the electron spin. Use of spin-triplet superconductors (TSCs) with spin-polarizable Cooper pairs potentially overcomes this difficulty and further leads to novel functionalities...
October 26, 2016: Nature Communications
Vandrangi Suresh, Jheng-Cyuan Lin, Heng-Jui Liu, Zaoli Zhang, Ping-Chih Chiang, Yu-Ching Hsun, Yi-Chun Chen, Jiunn-Yuan Lin, Ying-Hao Chu
The competition between superconductivity and ferromagnetism poses great challenges and has attracted renewed interest for applications in novel spintronic devices. In order to emphasize their interactions, we fabricated a heterostructure composed of superconducting YBa2Cu3O7-δ (YBCO) film embedded with itinerant ferromagnetic SrRuO3 (SRO) mesocrystals. Starting from a doping concentration of 10 vol% of SRO mesocrystal in a YBCO matrix, corresponding to the density of SRO nanocrystals ∼5 × 10(9) cm(-2), which exhibits the typical characteristic of a metal-superconductor transition, and then increasing the magnetic interactions as a function of SRO embedment, the electronic correlation and the interplay between superconductivity and magnetism throughout the temperature regime were investigated...
October 25, 2016: Nanoscale
J R Yuan, X H Yan, Y Xiao, Y D Guo, C J Dai
Motivated by recent measurement of the magnetism and conductance of the oxygen-assisted Pt nanojunctions, we performed first principle calculations of the magnetic order and electronic transport by explicitly including fully relativistic effects. Our results show that the spin alignment is a cycloidal spiral feature attributed to the Dzyaloshinskii-Moriya interaction, which indicates that the observed magnetism in experiments is of noncollinear nature. The oxygen concentration is the responsible for the switching of the rotational sense of the spiral magnetic order found in oxygen-assisted Pt nanojunctions...
October 24, 2016: Nanotechnology
Emily S Walker, Seung Ryul Na, Daehwan Jung, Stephen D March, Joon-Seok Kim, Tanuj Trivedi, Wei Li, Li Tao, Minjoo L Lee, Kenneth M Liechti, Deji Akinwande, Seth R Bank
We report the first direct dry transfer of a single-crystalline thin film grown by molecular beam epitaxy. A double cantilever beam fracture technique was used to transfer epitaxial bismuth thin films grown on silicon (111) to silicon strips coated with epoxy. The transferred bismuth films retained electrical, optical, and structural properties comparable to the as-grown epitaxial films. Additionally, we isolated the bismuth thin films on freestanding flexible cured-epoxy post-transfer. The adhesion energy at the bismuth/silicon interface was measured to be ∼1 J/m(2), comparable to that of exfoliated and wet transferred graphene...
October 24, 2016: Nano Letters
Søren Ulstrup, Jyoti Katoch, Roland J Koch, Daniel Schwarz, Simranjeet Singh, Kathleen M McCreary, Hyang Keun Yoo, Jinsong Xu, Berend T Jonker, Roland K Kawakami, Aaron Bostwick, Eli Rotenberg, Chris Jozwiak
There is a substantial interest in the heterostructures of semiconducting transition metal dichalcogenides (TMDCs) amongst each other or with arbitrary materials, through which the control of the chemical, structural, electronic, spintronic, and optical properties can lead to a change in device paradigms. A critical need is to understand the interface between TMDCs and insulating substrates, for example high-κ dielectrics, which can strongly impact the electronic properties such as the optical gap. Here we show that the chemical and electronic properties of the single-layer (SL) TMDC, WS2, can be transferred onto high-κ transition metal oxide substrates TiO2 and SrTiO3...
October 21, 2016: ACS Nano
Yin-Shan Meng, Shang-Da Jiang, Bing-Wu Wang, Song Gao
Single-molecule magnets (SMMs) can retain their magnetization status preferentially after removal of the magnetic field below a certain temperature. The unique property, magnetic bistable status, enables the molecule-scale SMM to become the next-generation high-density information storage medium. SMMs' new applications are also involved in high-speed quantum computation and molecular spintronics. The development of coordination chemistry, especially in transition metal (3d) and lanthanide (4f) complexes, diversifies SMMs by introducing new ones...
October 21, 2016: Accounts of Chemical Research
J Krempaský, S Muff, F Bisti, M Fanciulli, H Volfová, A P Weber, N Pilet, P Warnicke, H Ebert, J Braun, F Bertran, V V Volobuev, J Minár, G Springholz, J H Dil, V N Strocov
Entanglement of the spin-orbit and magnetic order in multiferroic materials bears a strong potential for engineering novel electronic and spintronic devices. Here, we explore the electron and spin structure of ferroelectric α-GeTe thin films doped with ferromagnetic Mn impurities to achieve its multiferroic functionality. We use bulk-sensitive soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES) to follow hybridization of the GeTe valence band with the Mn dopants. We observe a gradual opening of the Zeeman gap in the bulk Rashba bands around the Dirac point with increase of the Mn concentration, indicative of the ferromagnetic order, at persistent Rashba splitting...
October 21, 2016: Nature Communications
Daqiang Gao, Yonggang Liu, Peitao Liu, Mingsu Si, Desheng Xue
Since the graphitic carbon nitride (g-C4N3), which can be seen as C-doped graphitic-C3N4 (g-C3N4), was reported to display ferromagnetic ground state and intrinsic half-metallicity (Du et al., PRL,108,197207,2012), it has attracted numerous research interest to tune the electronic structure and magnetic properties of g-C3N4 due to their potential applications in spintronic devices. In this paper, we reported the experimentally achieving of high temperature ferromagnetism in metal-free ultrathin g-C3N4 nanosheets by introducing of B atoms...
October 20, 2016: Scientific Reports
Tianxiao Nie, Jianshi Tang, Xufeng Kou, Yin Gen, Shengwei Lee, Xiaodan Zhu, Qinglin He, Li-Te Chang, Koichi Murata, Yabin Fan, Kang L Wang
Voltage control of magnetism in ferromagnetic semiconductor has emerged as an appealing solution to significantly reduce the power dissipation and variability beyond current CMOS technology. However, it has been proven to be very challenging to achieve a candidate with high Curie temperature (Tc), controllable ferromagnetism and easy integration with current Si technology. Here we report the effective electric-field control of both ferromagnetism and magnetoresistance in unique MnxGe1-x nanomeshes fabricated by nanosphere lithography, in which a Tc above 400 K is demonstrated as a result of size/quantum confinement...
October 20, 2016: Nature Communications
R Galceran, I Fina, J Cisneros-Fernández, B Bozzo, C Frontera, L López-Mir, H Deniz, K-W Park, B-G Park, Ll Balcells, X Martí, T Jungwirth, B Martínez
Antiferromagnetic spintronics is an emerging field; antiferromagnets can improve the functionalities of ferromagnets with higher response times, and having the information shielded against external magnetic field. Moreover, a large list of aniferromagnetic semiconductors and metals with Néel temperatures above room temperature exists. In the present manuscript, we persevere in the quest for the limits of how large can anisotropic magnetoresistance be in antiferromagnetic materials with very large spin-orbit coupling...
October 20, 2016: Scientific Reports
Q Mahmood, M Hassan, N A Noor
The structural, magnetic and optical characteristics of Zn1-x TM x S/Se (TM  =  Mn, Fe, Co, Ni and x  =  6.25%) have been investigated through the full-potential linearized augmented plane wave method within the framework of density functional theory. The optimized structures have been used to calculate the ferromagnetic and the antiferromagnetic ground-state energies. The stability of the ferromagnetic phase has been confirmed from the formation and the cohesive energies. The Heisenberg model is used to elucidate the Curie temperature (T c) of these alloys...
October 19, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Suman Chowdhury, Debnarayan Jana
Inspired by the success of graphene, various two dimensional (2D) structures in free standing (FS) (hypothetical) form and on different substrates have been proposed recently. Silicene, a silicon counterpart of graphene, is predicted to possess massless Dirac fermions and to exhibit an experimentally accessible quantum spin Hall effect. Since the effective spin-orbit interaction is quite significant compared to graphene, buckling in silicene opens a gap of 1.55 meV at the Dirac point. This band gap can be further tailored by applying in plane stress, an external electric field, chemical functionalization and defects...
October 18, 2016: Reports on Progress in Physics
E Coronado, M Yamashita
No abstract text is available yet for this article.
October 17, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Yan Sun, Yang Zhang, Claudia Felser, Binghai Yan
Since their discovery, topological insulators are expected to be ideal spintronic materials owing to the spin currents carried by surface states with spin-momentum locking. However, the bulk doping problem remains an obstacle that hinders such an application. In this work, we predict that a newly discovered family of topological materials, the Weyl semimetals, exhibits a large intrinsic spin Hall effect that can be utilized to generate and detect spin currents. Our ab initio calculations reveal a large spin Hall conductivity in the TaAs family of Weyl materials...
September 30, 2016: Physical Review Letters
Keshab R Sapkota, Weimin Chen, F Scott Maloney, Uma Poudyal, Wenyong Wang
We report magnetoresistance (MR) manipulation and sign reversal induced by carrier concentration modulation in Mn-doped ZnO nanowires. At low temperatures positive magnetoresistance was initially observed. When the carrier concentration was increased through the application of a gate voltage, the magnetoresistance also increased and reached a maximum value. However, further increasing the carrier concentration caused the MR to decrease, and eventually an MR sign reversal from positive to negative was observed...
October 14, 2016: Scientific Reports
Hongmei Liu, Hisashi Kondo, Takahisa Ohno
Utilizing first-principles theory, we demonstrate that half-metallicity can be realized in a junction composed of non-magnetic armchair graphene nanoribbon (AGNR) and ferromagnetic Ni electrodes. The half-metallic property originates from the AGNR energy gap of the up spin located at the Fermi energy, while large electronic states are generated for the down spin. By altering the interlayer distance and the contact area, namely, the strength of AGNR-Ni interaction, the efficiency of the spin filter becomes lower, since the energy gap moves away from the Fermi energy with the variation of charge transfer intensity...
December 2016: Nanoscale Research Letters
Simone Marocchi, Andrea Candini, David Klar, Willem Van den Heuvel, Haibei Huang, Filippo Troiani, Valdis Corradini, Roberto Biagi, Valentina De Renzi, Svetlana Klyatskaya, Kurt Kummer, Nicholas B Brookes, Mario Ruben, Heiko Wende, Umberto Del Pennino, Alessandro Soncini, Marco Affronte, Valerio Bellini
We investigate the electronic and magnetic properties of \ce{TbPc2} single ion magnets adsorbed on a graphene/Ni(111) substrate, by density-functional theory (DFT), ab-initio complete active space self-consistent field calculations, and x-ray magnetic circular dichroism (XMCD) experiments. Despite the presence of the graphene decoupling layer a sizable antiferromagnetic coupling between Tb and Ni is observed in the XMCD experiments. The molecule-surface interaction is rationalized by the DFT analysis and is found to follow a relay-like communication pathway, where the radical spin on the organic Pc ligands mediates the interaction between Tb ion and Ni substrate spins...
October 11, 2016: ACS Nano
Hongyu An, Yuito Kageyama, Yusuke Kanno, Nagisa Enishi, Kazuya Ando
The spin Hall effect is a spin-orbit coupling phenomenon, which enables electric generation and detection of spin currents. This relativistic effect provides a way for realizing efficient spintronic devices based on electric manipulation of magnetization through spin torque. However, it has been believed that heavy metals are indispensable for the spin-torque generation. Here we show that the spin Hall effect in Cu, a light metal with weak spin-orbit coupling, is significantly enhanced through natural oxidation...
October 11, 2016: Nature Communications
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