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S L Zuo, Y Zhang, L C Peng, X Zhao, R Li, H Li, J F Xiong, M He, T Y Zhao, J R Sun, F X Hu, B G Shen
The evolution of topological magnetic domains microscopically correlates the dynamic behavior of memory units in spintronic application. Nanometric bubbles with variation of spin configurations have been directly observed in a centrosymmetric hexagonal magnet (Mn0.5Ni0.5)65(Ga1-yYy)35 (y = 0.01) using Lorentz transmission electron microscopy. Magnetic bubbles instead of biskyrmions are generated due to the enhancement of quality factor Q caused by the substitution of rare-earth element Y. Furthermore, the bubble density and diversified spin configurations are systematically manipulated via combining the electric current with perpendicular magnetic fields...
January 19, 2018: Nanoscale
Jing Zeng, Ke-Qiu Chen
Although a lot of theoretical studies have designed perfect spin filters using inorganic/organic/organometallic materials, their fabrication methods are not experimentally feasible. This dilemma could be solved by a recent experiment, where porphyrins have been covalently coupled to graphene edges in a precise manner (Y. He et al., Nat. Chem., 2017, 9, 33-38). In particular, experimental results confirmed that the intrinsic features of porphyrins for metallation are preserved after dehydrogenative coupling to graphene edges, paving the way for realizing synthesizable spintronic devices...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Mustafa Mert Torunbalci, Tanay Arun Gosavi, Kerem Yunus Camsari, Sunil Ashok Bhave
This paper introduces a novel oscillator that combines the tunability of spin Hall-driven nano oscillators with the high quality factor (Q) of high overtone bulk acoustic wave resonators (HBAR), integrating both reference and tunable oscillators on the same chip with CMOS. In such magneto acoustic spin Hall (MASH) oscillators, voltage oscillations across the magnetic tunnel junction (MTJ) that arise from a spin-orbit torque (SOT) are shaped by the transmission response of the HBAR that acts as a multiple peak-bandpass filter and a delay element due to its large time constant, providing delayed feedback...
January 18, 2018: Scientific Reports
Michihiro Yamada, Yuichi Fujita, Shinya Yamada, Kentarou Sawano, Kohei Hamaya
We study the influence of the junction size in ferromagnet (FM)/semiconductor (SC) contacts on four-terminal nonlocal spin signals in SC-based lateral spin-valve (LSV) structures. When we use FM/Ge Schottky-tunnel junctions with relatively low resistance-area products, the magnitude of the nonlocal spin signal depends clearly on the junction size, indicating the presence of the spin absorption effect at the spin-injector contact. The temperature-dependent spin signal can also be affected by the spin absorption effect...
January 17, 2018: Materials
Licong Peng, Ying Zhang, Min He, Bei Ding, Wenhong Wang, Jianqi Li, Jianwang Cai, Shouguo Wang, Guangheng Wu, Baogen Shen
Magnetic skyrmions are topologically protected spin configurations and have recently received growingly attention in magnetic materials. The existence of biskyrmions within a broad temperature range has been identified in our newly-discovered MnNiGa material, promising for potential application in physics and technological study. Here, the biskyrmion microscopic origination from the spin configuration evolution of stripe ground state is experimentally identified. The biskyrmion manipulations based on the influences of the basic microstructures and external factors such as grain boundary confinement, sample thickness, electric current, magnetic field and temperature have been systematically studied by using real-space Lorentz transmission electron microscopy...
January 17, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Jan Müller, Jayaraman Rajeswari, Ping Huang, Yoshie Murooka, Henrik M Rønnow, Fabrizio Carbone, Achim Rosch
Skyrmions are nanometric spin whirls that can be stabilized in magnets lacking inversion symmetry. The properties of isolated Skyrmions embedded in a ferromagnetic background have been intensively studied. We show that single Skyrmions and clusters of Skyrmions can also form in the helical phase and investigate theoretically their energetics and dynamics. The helical background provides natural one-dimensional channels along which a Skyrmion can move rapidly. In contrast to Skyrmions in ferromagnets, the Skyrmion-Skyrmion interaction has a strong attractive component and thus Skyrmions tend to form clusters with characteristic shapes...
September 29, 2017: Physical Review Letters
K Yasuda, A Tsukazaki, R Yoshimi, K Kondou, K S Takahashi, Y Otani, M Kawasaki, Y Tokura
The current-nonlinear Hall effect or second harmonic Hall voltage is widely used as one of the methods for estimating charge-spin conversion efficiency, which is attributed to the magnetization oscillation by spin-orbit torque (SOT). Here, we argue the second harmonic Hall voltage under a large in-plane magnetic field with an in-plane magnetization configuration in magnetic-nonmagnetic topological insulator (TI) heterostructures, Cr_{x}(Bi_{1-y}Sb_{y})_{2-x}Te_{3}/(Bi_{1-y}Sb_{y})_{2}Te_{3}, where it is clearly shown that the large second harmonic voltage is governed not by SOT but mainly by asymmetric magnon scattering without macroscopic magnetization oscillation...
September 29, 2017: Physical Review Letters
Jun-Wei Luo, Shu-Shen Li, Alex Zunger
The electric field manipulation of the Rashba spin-orbit coupling effects provides a route to electrically control spins, constituting the foundation of the field of semiconductor spintronics. In general, the strength of the Rashba effects depends linearly on the applied electric field and is significant only for heavy-atom materials with large intrinsic spin-orbit interaction under high electric fields. Here, we illustrate in 1D semiconductor nanowires an anomalous field dependence of the hole (but not electron) Rashba effect (HRE)...
September 22, 2017: Physical Review Letters
L Lόpez-Mir, C Frontera, H Aramberri, K Bouzehouane, J Cisneros-Fernández, B Bozzo, L Balcells, B Martínez
Multiple spin functionalities are probed on Pt/La2Co0.8Mn1.2O6/Nb:SrTiO3, a device composed by a ferromagnetic insulating barrier sandwiched between non-magnetic electrodes. Uniquely, La2Co0.8Mn1.2O6 thin films present strong perpendicular magnetic anisotropy of magnetocrystalline origin, property of major interest for spintronics. The junction has an estimated spin-filtering efficiency of 99.7% and tunneling anisotropic magnetoresistance (TAMR) values up to 30% at low temperatures. This remarkable angular dependence of the magnetoresistance is associated with the magnetic anisotropy whose origin lies in the large spin-orbit interaction of Co2+ which is additionally tuned by the strain of the crystal lattice...
January 16, 2018: Scientific Reports
Oleksii M Volkov, Denis D Sheka, Yuri Gaididei, Volodymyr P Kravchuk, Ulrich K Rößler, Jürgen Fassbender, Denys Makarov
Crystals with broken inversion symmetry can host fundamentally appealing and technologically relevant periodical or localized chiral magnetic textures. The type of the texture as well as its magnetochiral properties are determined by the intrinsic Dzyaloshinskii-Moriya interaction (DMI), which is a material property and can hardly be changed. Here we put forth a method to create new artificial chiral nanoscale objects with tunable magnetochiral properties from standard magnetic materials by using geometrical manipulations...
January 16, 2018: Scientific Reports
Cheng Song, Yunfeng You, Xianzhe Chen, Xiaofeng Zhou, Yuyan Wang, Feng Pan
Antiferromagnetic materials, which have drawn considerable attention recently, have fascinating features: they are robust against perturbation, produce no stray fields, and exhibit ultrafast dynamics. Discerning how to efficiently manipulate the magnetic state of an antiferromagnet is key to the development of antiferromagnetic spintronics. In this review, we introduce four main methods (magnetic, strain, electrical, and optical) to mediate the magnetic states and elaborate on intrinsic origins of different antiferromagnetic materials...
January 16, 2018: Nanotechnology
Guang Yang, Yanmin Yang, Hongran Ma, Xiujuan Mao, Congcong Li, Jie Li, Qiang Zhang, Zhidong Zhang, Fuxing Yin, Jia Li
The structural, electronic and magnetic properties of Cr, Mn, Fe, Co and Ni-doped bilayer WSe2 are predicted by using first principles calculations. The doped transition-metal atoms show a covalent-binding with the nearest Se atoms. The calculated electronic structures reveal that the transition metal Cr, Mn, Fe and Co-doped bilayer WSe2 exhibit the half-metallic character with a 100% spin polarization at the Fermi level, and the reason is ascribed to the strong hybridization peak between the transition metals and parent W and Se atoms...
January 16, 2018: Nanotechnology
Y T Fanchiang, K H M Chen, C C Tseng, C C Chen, C K Cheng, S R Yang, C N Wu, S F Lee, M Hong, J Kwo
Harnessing the spin-momentum locking of topological surface states in conjunction with magnetic materials is the first step to realize novel topological insulator-based devices. Here, we report strong interfacial coupling in Bi2Se3/yttrium iron garnet (YIG) bilayers manifested as large interfacial in-plane magnetic anisotropy (IMA) and enhancement of damping probed by ferromagnetic resonance. The interfacial IMA and damping enhancement reaches a maximum when the Bi2Se3 film approaches its two-dimensional limit, indicating that topological surface states play an important role in the magnetization dynamics of YIG...
January 15, 2018: Nature Communications
Yuki Ohuchi, Jobu Matsuno, Naoki Ogawa, Yusuke Kozuka, Masaki Uchida, Yoshinori Tokura, Masashi Kawasaki
One of the key goals in spintronics is to tame the spin-orbit coupling (SOC) that links spin and motion of electrons, giving rise to intriguing magneto-transport properties in itinerant magnets. Prominent examples of such SOC-based phenomena are the anomalous and topological Hall effects. However, controlling them with electric fields has remained unachieved since an electric field tends to be screened in itinerant magnets. Here we demonstrate that both anomalous and topological Hall effects can be modulated by electric fields in oxide heterostructures consisting of ferromagnetic SrRuO3 and nonmagnetic SrIrO3...
January 15, 2018: Nature Communications
Daniel Thuberg, Enrique Muñoz, Sebastian Eggert, Sebastián A Reyes
We consider the problem of particle tunneling through a periodically driven ferromagnetic quantum barrier connected to two leads. The barrier is modeled by an impurity site representing a ferromagnetic layer or a quantum dot in a tight-binding Hamiltonian with a local magnetic field and an ac-driven potential, which is solved using the Floquet formalism. The repulsive interactions in the quantum barrier are also taken into account. Our results show that the time-periodic potential causes sharp resonances of perfect transmission and reflection, which can be tuned by the frequency, the driving strength, and the magnetic field...
December 29, 2017: Physical Review Letters
Takahiro Moriyama, Michinari Kamiya, Kent Oda, Kensho Tanaka, Kab-Jin Kim, Teruo Ono
Spin interaction in antiferromagnetic materials is of central interest in the recently emerging antiferromagnetic spintronics. In this Letter, we explore the spin current interaction in antiferromagnetic FeMn by the spin pumping effect. Exchange biased FeNi/FeMn films, in which the Néel vector can be presumably controlled via the exchange spring effect, are employed to investigate the damping enhancement depending on the relative orientation between the Néel vector and the polarization of the pumped spin current...
December 29, 2017: Physical Review Letters
Minghong Tang, Bingcheng Zhao, Weihua Zhu, Zhendong Zhu, Qingyuan Jin, Zongzhi Zhang
Dynamic magnetic properties in perpendicularly exchange-coupled [Co/Ni]5/Cu(tCu=0-2 nm)/TbCo structures show strong dependences on the interfacial AFM strength Jex controlled by the Cu interlayer thickness. The precession frequency f and effective damping constant αeff of [Co/Ni]5 multilayer differs distinctly for parallel (P) and antiparallel (AP) magnetization orientation states. For samples with a thin tCu, f of AP state is apparently higher while αeff is lower than in P state, owing to the unidirectional exchange bias effect (HEB) from the TbCo layer...
January 12, 2018: ACS Applied Materials & Interfaces
Zongmin Ma, Shaowen Zhang, Yueping Fu, Hua Yuan, Yunbo Shi, Jian Gao, Li Qin, Jun Tang, Jun Liu, Yanjun Li
Sensitivity of magnetometers that use color centers is limited by poor photon-collection and detection efficiency. In this paper, we present the details of a newly developed all-optical collection combined frequency-modulated microwave method. The proposed method achieves a high sensitivity in static magnetic-field detection both theoretically and experimentally. First, we demonstrate that this collection technique enables both a fluorescence collection as high as 40% and an efficient pump absorption. Subsequently, we exploit the optically detected magnetic resonance (ODMR) signal and quantitative magnetic detection of an ensemble of nitrogen vacancy (NV) centers, by applying a frequency-modulated (FM) microwave method followed by a lock-in technique on the resonance frequency point...
January 8, 2018: Optics Express
Keshab Bashyal, Christopher K Pyles, Sajjad Afroosheh, Aneer Lamichhane, Alexey T Zayak
ZnO is a well-known wide band gap semiconductor with promising potential for applications in optoelectronics, transparent electronics, and spintronics. Computational simulations based on the density functional theory (DFT) play an important role in the research of ZnO, but the standard functionals, like Perdew-Burke-Erzenhof, result in largely underestimated values of the band gap and the binding energies of the Zn3d electrons. Methods like DFT  +  U and hybrid functionals are meant to remedy the weaknesses of plain DFT...
January 12, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Atsufumi Hirohata, William Frost, Marjan Samiepour, Jun-Young Kim
For the sustainable development of spintronic devices, a half-metallic ferromagnetic film needs to be developed as a spin source with exhibiting 100% spin polarisation at its Fermi level at room temperature. One of the most promising candidates for such a film is a Heusler-alloy film, which has already been proven to achieve the half-metallicity in the bulk region of the film. The Heusler alloys have predominantly cubic crystalline structures with small magnetocrystalline anisotropy. In order to use these alloys in perpendicularly magnetised devices, which are advantageous over in-plane devices due to their scalability, lattice distortion is required by introducing atomic substitution and interfacial lattice mismatch...
January 11, 2018: Materials
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