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Junke Jiang, Qiuhua Liang, Ruishen Meng, Qun Yang, Chunjian Tan, Xiang Sun, Xianping Chen
Ferromagnetic character and biocompatible properties have become key factors for developing next-generation spintronic devices and show potential in biomedical applications. Unfortunately, the Mn-containing monolayer is not biocompatible though it has been extensively studied, and the Cr-containing monolayer is not environmental friendly, although these monolayers are ferromagnetic. Herein, we systematically investigated new types of 2D ferromagnetic monolayers Nb3X8 (X = Cl, Br or I) by means of first principles calculations together with mean field approximation based on the classical Heisenberg model...
January 18, 2017: Nanoscale
Hui Li, Wei Chen, Xiaopeng Shen, Jingwei Liu, Xuri Huang, Guangtao Yu
On the basis of first-principles computations, we propose a simple and effective strategy through surface-adsorbing 3d-transition metal (TM) atoms, including Ti, Cr, Mn, Fe and Co, to modulate the electronic and magnetic behaviors of zigzag SiC nanoribbons (zSiCNRs), in view of the unique d electronic structures and intrinsic magnetic moments of TM atoms. It is revealed that like applying an electric field, the adsorption of these transition metal atoms can induce an evident change in the electrostatic potential of the substrate zSiCNRs owing to the electron transfer from the TM atom to the substrate...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Kwan Lee, Jung-Tak Jang, Hiroshi Nakano, Shigeki Nakagawa, Sun Ha Paek, Seongtae Bae
Although the blocking temperature of superparamagnetic nanoparticles (SPNPs) is crucial for various spintronics and biomedical applications, the precise determination of the blocking temperature is still not clear. Here, we present 'intrinsic' and 'extrinsic' characteristics of the blocking temperature in SPNP systems. In zero-field-cooled/field-cooled (ZFC-FC) curves, there was no shift of 'intrinsic blocking temperature' at different applied external (excitation) magnetic fields. However, 'extrinsic blocking temperature' shift is clearly dependent on the external (excitation) magnetic field...
February 17, 2017: Nanotechnology
Alessandro Molle, Joshua Goldberger, Michel Houssa, Yong Xu, Shou-Cheng Zhang, Deji Akinwande
Silicene, germanene and stanene are part of a monoelemental class of two-dimensional (2D) crystals termed 2D-Xenes (X = Si, Ge, Sn and so on) which, together with their ligand-functionalized derivatives referred to as Xanes, are comprised of group IVA atoms arranged in a honeycomb lattice - similar to graphene but with varying degrees of buckling. Their electronic structure ranges from trivial insulators, to semiconductors with tunable gaps, to semi-metallic, depending on the substrate, chemical functionalization and strain...
January 16, 2017: Nature Materials
Zheng-Zhe Lin
Ferromagnetism in half-metallic two-dimensional (2D) materials can lead to unique spintronics applications. In this paper, we report first-principle calculations that predict 2D single-layer C12Mn2 as a ferromagnetic half metal, and 2D single-layer C12Cr2 as an antiferromagnetic semiconductor. A systematic study is carried out to demonstrate the reliability of our research. We employ a bottom-up method to investigate the structural and magnetic stability of single, two and more Cr or Mn atoms on graphyne at room temperature...
January 16, 2017: Physical Chemistry Chemical Physics: PCCP
Z C Wang, X Y Zhong, L Jin, X F Chen, Y Moritomo, J Mayer
Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr2FeMoO6, we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations...
December 30, 2016: Ultramicroscopy
Ricardo Pablo-Pedro, Hector Lopez-Rios, Serguei Fomine, Mildred S Dresselhaus
Utilizing density functional theory (DFT) and a complete active space self-consistent field (CASSCF) approach, we study the electronic properties of rectangle silicene nano clusters with hydrogen passivated edges denoted by H-SiNRs(nz,na), with nz and na representing the zigzag and armchair directions, respectively. The results show that in the nz direction, the H-SiNRs prefer to be in a singlet (S=0) ground state for nz > na. However, a transition from a singlet to a triplet (S=1) ground state is revealed for na> nz...
January 16, 2017: Journal of Physical Chemistry Letters
Sungwoo Lee, Dongwook Kim, Alex W Robertson, Euijoon Yoon, Suklyun Hong, Jisoon Ihm, Jaejun Yu, Jamie H Warner, Gun-Do Lee
Metal-doped graphene produces magnetic moments that have potential application in spintronics. Here we use density function theory computational methods to show how the magnetic interaction between metal atoms doped in graphene can be controlled by the degree of flexure in a graphene membrane. Bending graphene by flexing causes the distance between two substitutional Fe atoms covalently bonded in graphene to gradually increase and these results in the magnetic moment disappearing at a critical strain value...
January 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Lipeng Hou, Weichang Zhou, Bingsuo Zou, Yu Zhang, Junbo Han, Xinxin Yang, Zhihong Gong, Jingbo Li, Sishen Xie, Lijie Shi
For their spintronic applications the magnetic and optical properties of diluted magnetic semiconductors (DMS) have been studied widely. However, the exact relationships between their magnetic interactions and optical emission behaviors in DMS are not well understood yet due to their complicated microstructural and compositional characters from different growth and preparation techniques. Manganese (Mn) doped ZnSe nanoribbons with high quality were obtained by using the chemical vapor deposition (CVD) method...
January 12, 2017: Nanotechnology
Alexander A Tulub, Vassily E Stefanov
Despite the fact that DNA molecule is studied up and down, we know very little about the role of DNA triplets in coding amino acids and stop-codons. The paper aims to fill this gap through attracting spintronic ideas and carrying out QM/MM computations on a full-turn DNA fragment. The computations reveal two hidden symmetries: the spin splitting (the Rashba effect), confined within each triplet, and the quantum "phase" link between the triplet nature (in total, 64 triplets) and the corresponding amino acid and three stop-codons...
January 7, 2017: Journal of Theoretical Biology
Xue-Jun Qiu, Zhen-Zhou Cao, Yan-Fu Cheng, Chaochao Qin
We theoretically study ballistic transport of Dirac fermions in MoS<sub>2</sub> junction through arrays of barriers, of width L , in the presence of a tunable potential of height U and an exchange field h .The charge conductance as functions of U and h , exhibits more conspicuous and sharpened oscillation as the number of barriers increase, due to the contribution of evanescent modes near the edges of the extremum conductance which are exponentially suppressed or enhanced. Furthermore, we found the valley-resolved conductance exhibits a similar oscillating behavior as the charge conductance for multiple barriers, but with inverse oscillatory phases for G<sub>K</sub> and G<sub>K'</sub>, accordingly, a high-efficiency fully valley polarized device is proposed in our system...
January 11, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Paul Avramov, Alexander A Kuzubov, Artem V Kuklin, Hyosun Lee, Evgenia A Kovaleva, Seiji Sakai, Shiro Entani, Hiroshi Naramoto, Pavel B Sorokin
The structure of the interfaces and the mechanisms of induced spin polarization of 1D infinite and finite narrow graphene- and h-BN zigzag nanoribbons placed on a SrO-terminated La1-xSrxMnO3 (LSMO) (001) surface were studied using density functional theory (DFT) electronic structure calculations. It was found that the π-conjugated nanofragments are bonded to the LSMO(001) surface by weak disperse interactions. The types of coordination of the fragments, the strength of bonding, and the rate of spin polarization depend upon the nature of the fragments...
January 11, 2017: Journal of Physical Chemistry. A
Jewook Park, Changwon Park, Mina Yoon, An-Ping Li
Controlling the spin states of the surface and interface is key to spintronic applications of magnetic materials. Here, we report the evolution of surface magnetism of Co nanoislands on Cu(111) upon hydrogen adsorption and desorption with the hope of realizing reversible control of spin-dependent tunneling. Spin-polarized scanning tunneling microscopy reveals three types of hydrogen-induced surface superstructures, 1H-(2 × 2), 2H-(2 × 2), and 6H-(3 × 3), with increasing H coverage. The prominent magnetic surface states of Co, while being preserved at low H coverage, become suppressed as the H coverage level increases, which can then be recovered by H desorption...
January 11, 2017: Nano Letters
Matthias B Jungfleisch, Junjia Ding, Wei Zhang, Wanjun Jiang, John E Pearson, Valentine Novosad, Axel Hoffmann
Magnetic insulators, such as yttrium iron garnet (Y3Fe5O12), are ideal materials for ultralow power spintronics applications due to their low energy dissipation and efficient spin current generation and transmission. Recently, it has been realized that spin dynamics can be driven very effectively in micrometer-sized Y3Fe5O12/Pt heterostructures by spin-Hall effects. We demonstrate here the excitation and detection of spin dynamics in Y3Fe5O12/Pt nanowires by spin-torque ferromagnetic resonance. The nanowires defined via electron-beam lithography are fabricated by conventional room temperature sputtering deposition on Gd3Ga5O12 substrates and lift-off...
January 11, 2017: Nano Letters
Yinghui Yu, Huixia Fu, Limin She, Shuangzan Lu, Qinmin Guo, Hui Li, Sheng Meng, Gengyu Cao
It is highly desirable to fabricate two-dimensional ferromagnetic membranes on basis of orthodox magnetic elements due to their inherent magnetic properties. In this work, we report on two superstructures including a honeycomb-like lattice and identical nanocluster arrays formed by depositing Fe on Sb(111). Combined with first-principles calculations, both detailed atomic structures have been clarified. The honeycomb structure consists of a single layered Fe-Sb phase and the cluster phase is assigned as a (3×3) Fe3Sb7 superlattice...
January 10, 2017: ACS Nano
Leena Aggarwal, Sirshendu Gayen, Shekhar Das, Ritesh Kumar, Vicky Süß, Claudia Felser, Chandra Shekhar, Goutam Sheet
A Weyl semimetal is a topologically non-trivial phase of matter that hosts mass-less Weyl fermions, the particles that remained elusive for more than 80 years since their theoretical discovery. The Weyl semimetals exhibit unique transport properties and remarkably high surface spin polarization. Here we show that a mesoscopic superconducting phase with critical temperature Tc=7 K can be realized by forming metallic point contacts with silver (Ag) on single crystals of TaAs, while neither Ag nor TaAs are superconductors...
January 10, 2017: Nature Communications
Enric Menéndez, Hiwa Modarresi, Claire Petermann, Josep Nogués, Neus Domingo, Haoliang Liu, Brian J Kirby, Amir Syed Mohd, Zahir Salhi, Earl Babcock, Stefan Mattauch, Chris Van Haesendonck, André Vantomme, Kristiaan Temst
The combination of lithography and ion implantation is demonstrated to be a suitable method to prepare lateral multilayers. A laterally, compositionally, and magnetically modulated microscale pattern consisting of alternating Co (1.6 µm wide) and Co-CoO (2.4 µm wide) lines has been obtained by oxygen ion implantation into a lithographically masked Au-sandwiched Co thin film. Magnetoresistance along the lines (i.e., current and applied magnetic field are parallel to the lines) reveals an effective positive giant magnetoresistance (GMR) behavior at room temperature...
January 9, 2017: Small
Xiao-Fei Li, Lingling Liu, Qing Yan, Qin-Kun Li, Yunxiang Wang, Mingsen Deng, Qi Qiu
Ferromagnetic devices have special significance in spintronics. Here, we investigate the electronic structures and transport properties of the experimentally achievable FeN4-embedded armchair and zigzag graphene nanoribbons (FeN4-AGNR and FeN4-ZGNR). The first principles results show that FeN4 induces room-temperature stable ferromagnetic ground states in both AGNRs and ZGNRs, but only significant changes in the band structure of the latter, inducing strong current polarization (nearly 100%) and spin-dependent negative differential resistance (NDR) in the FeN4-ZGNR based devices...
January 9, 2017: Physical Chemistry Chemical Physics: PCCP
Xi Chen, Tengfei Yan, Bairen Zhu, Siyuan Yang, Xiaodong Cui
Optical excitation could generate electrons' spin polarization in some semiconductors with the control of the field polarization. In this article, we report a series of spin-resolved photocurrent experiments on monolayer tungsten disulfide. The experiments demonstrate that the optical excitations with the same helicity could generate opposite spin polarization around the Fermi level by tuning the excitation energy. The mechanism lies in the valley-dependent optical selection rules, the giant spin-orbit coupling, and spin-valley locking in monolayer transition metal dichalcogenides (TMDs)...
January 13, 2017: ACS Nano
Bin Pang, Lunyong Zhang, Y B Chen, Jian Zhou, Shuhua Yao, Shantao Zhang, Yanfeng Chen
The heterostructure interface provides a powerful platform for exploring rich emergent phenomena, such as interfacial superconductivity and nontrivial topological surface states. Here, SrRuO3/SrIrO3 superlattices were epitaxially synthesized. The magnetic and magneto-transport properties of these superlattices were characterized. A broad cusp-type splitting in the zero-field-cooling/field-cooling temperature-dependent magnetization and magnetization relaxation, which follows the modified stretched function model, accompanied by double hysteresis magnetization loops were demonstrated...
January 13, 2017: ACS Applied Materials & Interfaces
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