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David L Cortie, Yury Khaydukov, Thomas Keller, David John Sprouster, Jacob S Hughes, James P Sullivan, Xiaolin Wang, Anton P Le Brun, Joel Bertinshaw, Sara J Callori, Robert D Aughterson, Michael James, Peter J Evans, Gerry Triani, Frank Klose
High magnetizations are desirable for spintronic devices that operate by manipulating electronic states using built-in magnetic fields. However, the magnetic moment in promising dilute magnetic oxide nanocomposites is very low, typically corresponding to only fractions of a Bohr magneton for each dopant atom. In this study we report a large magnetization formed by ion implantation of Co into amorphous TiO2-δ films producing an inhomogenous magnetic moment, with certain regions producing over 2.5 µB per Co, depending on the local dopant concentration...
February 23, 2017: ACS Applied Materials & Interfaces
Jörg Wunderlich
No abstract text is available yet for this article.
February 22, 2017: Nature Materials
Ji Ma, Kezheng Chen
The steadfast rule of a ferromagnetic hysteresis loop claims its saturation positioned within the first and third quadrants, whereas its saturation positioned in the second and fourth quadrants (named as self-reversed magnetic hysteresis) is usually taken as an experimental artifact and is always intentionally ignored. In this report, a new insight in this unique hysteresis phenomenon and its modulation were discussed in depth. Different iron oxides (magnetite, maghemite and hematite) with varying dimensions were soaked in FeCl3 aqueous solution and absorbed Fe(3+) cations due to their negative enough surface zeta potentials...
February 21, 2017: Scientific Reports
Jiří Tuček, Kateřina Holá, Athanasios B Bourlinos, Piotr Błoński, Aristides Bakandritsos, Juri Ugolotti, Matúš Dubecký, František Karlický, Václav Ranc, Klára Čépe, Michal Otyepka, Radek Zbořil
Materials based on metallic elements that have d orbitals and exhibit room temperature magnetism have been known for centuries and applied in a huge range of technologies. Development of room temperature carbon magnets containing exclusively sp orbitals is viewed as great challenge in chemistry, physics, spintronics and materials science. Here we describe a series of room temperature organic magnets prepared by a simple and controllable route based on the substitution of fluorine atoms in fluorographene with hydroxyl groups...
February 20, 2017: Nature Communications
Grant M Rotskoff, Gavin E Crooks, Eric Vanden-Eijnden
Optimal control of nanomagnets has become an urgent problem for the field of spintronics as technological tools approach thermodynamically determined limits of efficiency. In complex, fluctuating systems, such as nanomagnetic bits, finding optimal protocols is challenging, requiring detailed information about the dynamical fluctuations of the controlled system. We provide a physically transparent derivation of a metric tensor for which the length of a protocol is proportional to its dissipation. This perspective simplifies nonequilibrium optimization problems by recasting them in a geometric language...
January 2017: Physical Review. E
Sergi Vela, Martin Verot, Emmanuel Fromager, Vincent Robert
The present paper reports the application of a computational framework, based on the quantum master equation, the Fermi's golden Rule, and conventional wavefunction-based methods, to describe electron transport through a spin crossover molecular junction (Fe(bapbpy) (NCS)2, 1, bapbpy = N-(6-(6-(Pyridin-2-ylamino)pyridin-2-yl)pyridin-2-yl)-pyridin-2-amine). This scheme is an alternative to the standard approaches based on the relative position and nature of the frontier orbitals, as it evaluates the junction's Green's function by means of accurate state energies and wavefunctions...
February 14, 2017: Journal of Chemical Physics
Giulia Capuzzo, Dmytro Kysylychyn, Rajdeep Adhikari, Tian Li, Bogdan Faina, Aitana Tarazaga Martín-Luengo, Alberta Bonanni
Since the technological breakthrough prompted by the inception of light emitting diodes based on III-nitrides, these material systems have emerged as strategic semiconductors not only for the lighting of the future, but also for the new generation of high-power electronic and spintronic devices. While III-nitride optoelectronics in the visible and ultraviolet spectral range is widely established, all-nitride efficient devices in the near-infrared (NIR) are still wanted. Here, through a comprehensive protocol of design, modeling, epitaxial growth and in-depth characterization, we develop AlxGa1-xN:Mn/GaN NIR distributed Bragg reflectors and we show their efficiency in combination with GaN:(Mn,Mg) layers containing Mn-Mgk complexes optically active in the near-infrared range of wavelengths...
February 15, 2017: Scientific Reports
Han-Chun Wu, Alexander N Chaika, Ming-Chien Hsu, Tsung-Wei Huang, Mourad Abid, Mohamed Abid, Victor Yu Aristov, Olga V Molodtsova, Sergey V Babenkov, Yuran Niu, Barry E Murphy, Sergey A Krasnikov, Olaf Lübben, Huajun Liu, Byong Sun Chun, Yahya T Janabi, Sergei N Molotkov, Igor V Shvets, Alexander I Lichtenstein, Mikhail I Katsnelson, Ching-Ray Chang
Graphene supports long spin lifetimes and long diffusion lengths at room temperature, making it highly promising for spintronics. However, making graphene magnetic remains a principal challenge despite the many proposed solutions. Among these, graphene with zig-zag edges and ripples are the most promising candidates, as zig-zag edges are predicted to host spin-polarized electronic states, and spin-orbit coupling can be induced by ripples. Here we investigate the magnetoresistance of graphene grown on technologically relevant SiC/Si(001) wafers, where inherent nanodomain boundaries sandwich zig-zag structures between adjacent ripples of large curvature...
February 15, 2017: Nature Communications
Tianxiao Nie, Xufeng Kou, Jianshi Tang, Yabin Fan, Shengwei Lee, Qinglin He, Li-Te Chang, Koichi Murata, Yin Gen, Kang L Wang
The realization and application of spintronic devices would be dramatically advanced if room-temperature ferromagnetism could be integrated into semiconductor nanostructures, especially when compatible with mature silicon technology. Herein, we report the observation of such a system - an Si/MnGe superlattice with quantum dots well aligned in the vertical direction successfully grown by molecular beam epitaxy. Such a unique system could take full advantage of the type-II energy band structure of the Si/Ge heterostructure, which could trap the holes inside MnGe QDs, significantly enhancing the hole-mediated ferromagnetism...
February 14, 2017: Nanoscale
Zhifeng Chen, Yong Yan, Shufa Li, Xiaoguang Xu, Yong Jiang, Tianshu Lai
Spin-wave dynamics in full-Heusler Co2FeAl0.5Si0.5 films are studied using all-optical pump-probe magneto-optical polar Kerr spectroscopy. Backward volume magnetostatic spin-wave (BVMSW) mode is observed in films with thickness ranging from 20 to 100 nm besides perpendicular standing spin-wave (PSSW) mode, and found to be excited more efficiently than the PSSW mode. The field dependence of the effective Gilbert damping parameter appears especial extrinsic origin. The relationship between the lifetime and the group velocity of BVMSW mode is revealed...
February 14, 2017: Scientific Reports
Yilei Wu, Matthew D Krzyaniak, J Fraser Stoddart, Michael R Wasielewski
Crystalline supramolecular frameworks consisting of charged molecules, held together by hydrogen bonds and Coulomb interactions, have attracted great interest because of their unusual structural, chemical, electronic and magnetic properties. Herein, we report the preparation, structure and magnetic properties of the triradical trianion of a shape-persistent chiral equilateral molecular triangle having three naphthalene-1,4:5,8-bis(dicarboximide)s ((+)-NDI-(Δ3(-•))). Single-crystal X-ray diffraction of its tris(cobaltocenium) salt ([(+)-NDI--(Δ3(-•))(CoCp2(+))(3)]) reveals accessible one-dimensional tubular cavities, and variable-temperature electron paramagnetic resonance (EPR) spectroscopy shows that a dilute solution of [(+)-NDI--(Δ3(-•))(CoCp2(+))(3)] in an organic glass has a spin-frustrated doublet ground state and a thermally accessible quartet state...
February 14, 2017: Journal of the American Chemical Society
Myung-Geun Han, Joseph A Garlow, Matthew S J Marshall, Amanda L Tiano, Stanislaus S Wong, Sang-Wook Cheong, Frederick J Walker, Charles H Ahn, Yimei Zhu
The ability to map out electrostatic potentials in materials is critical for the development and the design of nanoscale electronic and spintronic devices in modern industry. Electron holography has been an important tool for revealing electric and magnetic field distributions in microelectronics and magnetic-based memory devices, however, its utility is hindered by several practical constraints, such as charging artifacts and limitations in sensitivity and in field of view. In this article, we report electron-beam-induced-current (EBIC) and secondary-electron voltage-contrast (SE-VC) with an aberration-corrected electron probe in a transmission electron microscope (TEM), as complementary techniques to electron holography, to measure electric fields and surface potentials, respectively...
February 6, 2017: Ultramicroscopy
Niko Pavliček, Anish Mistry, Zsolt Majzik, Nikolaj Moll, Gerhard Meyer, David J Fox, Leo Gross
Triangulene, the smallest triplet-ground-state polybenzenoid (also known as Clar's hydrocarbon), has been an enigmatic molecule ever since its existence was first hypothesized. Despite containing an even number of carbons (22, in six fused benzene rings), it is not possible to draw Kekulé-style resonant structures for the whole molecule: any attempt results in two unpaired valence electrons. Synthesis and characterization of unsubstituted triangulene has not been achieved because of its extreme reactivity, although the addition of substituents has allowed the stabilization and synthesis of the triangulene core and verification of the triplet ground state via electron paramagnetic resonance measurements...
February 13, 2017: Nature Nanotechnology
Ryo Ohshima, Yuichiro Ando, Kosuke Matsuzaki, Tomofumi Susaki, Mathias Weiler, Stefan Klingler, Hans Huebl, Eiji Shikoh, Teruya Shinjo, Sebastian T B Goennenwein, Masashi Shiraishi
A d-orbital electron has an anisotropic electron orbital and is a source of magnetism. The realization of a two-dimensional electron gas (2DEG) embedded at a LaAlO3/SrTiO3 interface surprised researchers in materials and physical sciences because the 2DEG consists of 3d-electrons of Ti with extraordinarily large carrier mobility, even in the insulating oxide heterostructure. To date, a wide variety of physical phenomena, such as ferromagnetism and the quantum Hall effect, have been discovered in this 2DEG system, demonstrating the ability of d-electron 2DEG systems to provide a material platform for the study of interesting physics...
February 13, 2017: Nature Materials
Xiaozhe Zhang, Yuewei Yin, Sen Yang, Zhimao Yang, Xiaoshan Xu
We have carried out the growth of h-RFeO3 (001) (R=Lu, Yb) thin films on Fe3O4 (111)/Al2O3 (001) substrates, and studied the effect of the h-RFeO3 (001)/Fe3O4 (111) interfaces on the epitaxy and magnetism. The observed epitaxial relations between h-RFeO3 and Fe3O4 indicates an unusual matching of Fe sub-lattices rather than a matching of O sub-lattices. The out-of-plane direction was found to be the easy magnetic axis for h-YbFeO3 (001) but the hard axis for Fe3O4 (111) in the h-YbFeO3 (001)/Fe3O4 (111)/Al2O3 (001) films, suggesting a perpendicular magnetic alignment at the h-YbFeO3 (001)/Fe3O4 (111) interface...
February 10, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
R P Beardsley, D E Parkes, J Zemen, S Bowe, K W Edmonds, C Reardon, F Maccherozzi, I Isakov, P A Warburton, R P Campion, B L Gallagher, S A Cavill, A W Rushforth
We investigate the role of lithographically-induced strain relaxation in a micron-scaled device fabricated from epitaxial thin films of the magnetostrictive alloy Fe81Ga19. The strain relaxation due to lithographic patterning induces a magnetic anisotropy that competes with the magnetocrystalline and shape induced anisotropies to play a crucial role in stabilising a flux-closing domain pattern. We use magnetic imaging, micromagnetic calculations and linear elastic modelling to investigate a region close to the edges of an etched structure...
February 10, 2017: Scientific Reports
Melinda J Shearer, Leith Samad, Yi Zhang, Yuzhou Zhao, Alexander A Puretzky, Kevin W Eliceiri, John C Wright, Robert J Hamers, Song Jin
The interesting and tunable properties of layered metal dichalcogenides heavily depend on their phase and layer stacking. Here, we show and explain how the layer stacking and physical properties of WSe2 are influenced by screw dislocations. A one-to-one correlation of atomic force microscopy and high- and low-frequency Raman spectroscopy of many dislocated WSe2 nanoplates reveals variations in the number and shapes of dislocation spirals and different layer stackings that are determined by the number, rotation, and location of the dislocations...
February 8, 2017: Journal of the American Chemical Society
Biplab Bhattacharyya, Alka Sharma, V P S Awana, A K Srivastava, T D Senguttuvan, Sudhir Husale
In the last few years, research based on topological insulators (TIs) has been of great interest due to their intrinsic exotic fundamental properties and potential applications such as quantum computers or spintronics. The fabrication of TI nanodevices and the study of their transport properties has mostly focused on high quality crystalline nanowires or nanoribbons. Here, we report a robust approach to Bi2Se3 nanowire formation from deposited flakes using an ion beam milling method. Fabricated Bi2Se3 nanowire devices were employed to investigate the robustness of the topological surface state (TSS) to gallium ion doping and any deformation in the material due to the fabrication tools...
March 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Jun-Yang Chen, Yong-Chang Lau, J M D Coey, Mo Li, Jian-Ping Wang
The magnetic tunnel junction (MTJ) using MgO barrier is one of most important building blocks for spintronic devices and has been widely utilized as miniaturized magentic sensors. It could play an important role in wearable medical devices if they can be fabricated on flexible substrates. The required stringent fabrication processes to obtain high quality MgO-barrier MTJs, however, limit its integration with flexible electronics devices. In this work, we have developed a method to fabricate high-performance MgO-barrier MTJs directly onto ultrathin flexible silicon membrane with a thickness of 14 μm and then transfer-and-bond to plastic substrates...
February 2, 2017: Scientific Reports
V Lavrentiev, A Stupakov, I Lavrentieva, M Motylenko, M Barchuk, D Rafaja
We report on the establishing of an exclusive magnetic effect in air-exposed CoxC60 nanocomposites (x > 2) created through self-assembling in the depositing mixture. In order to verify the influence of ambient air on the CoxC60 mixture film, we have studied in detail the film magnetization at rather low temperatures, which provides their ferromagnetic behavior. Tracing the possible exchange bias effect, we distinguished a clear vertical shift of the hysteresis loops recorded for the air-exposed CoxC60 films in the field cooling (FC) regime...
March 24, 2017: Nanotechnology
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