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Chao Wang, Haifeng Du, Xuebing Zhao, Chiming Jin, Mingliang Tian, Yuheng Zhang, Renchao Che
Magnetic skyrmion is a topologically stable vortex-like spin texture that offers great promise as information carriers for future spintronic devices. In a two-dimensional chiral magnet, it was generally considered that a tilted magnetic field is harmful to its formation and stability. Here we investigated the angular dependent stability of magnetic skyrmions in FeGe nanosheets by using high-resolution Lorentz transmission electron microscopy (Lorentz TEM). Besides the theoretically predicted destruction of skyrmion lattice state by an oblique magnetic field as temperature close to its magnetic Curie temperature Tc~278 K, we also observed an unexpected reentry-like phenomenon at the moderate temperatures near the border between conical and skyrmion phase,Tt~240 K...
March 28, 2017: Nano Letters
Hannes Kraus, Dmitrij Simin, Christian Kasper, Yoshinori Suda, Shunsuke Kawabata, Wataru Kada, Tomoya Honda, Yasuto Hijikata, Takeshi Ohshima, Vladimir Dyakonov, Georgy V Astakhov
Constructing quantum devices comprises various challenging tasks, especially when concerning their nanoscale geometry. For quantum color centers, the traditional approach is to fabricate the device structure after the non-deterministic placement of the centers. Reversing this approach, we present the controlled generation of quantum centers in silicon carbide (SiC) by focused proton beam in a non-complex manner without need for pre- or post-irradiation treatment. The generation depth and resolution can be predicted by matching the proton energy to the material's stopping power, and the amount of quantum centers at one specific sample volume is tuneable from ensembles of millions to discernible single photon emitters...
March 28, 2017: Nano Letters
Hiroshi Suzuki, Kanako Inabe, Yoshinori Shirakawa, Naoki Umezawa, Nobuki Kato, Tsunehiko Higuchi
The catalytic cycle of cytochrome P450 involves a change from the resting-state, water-bound, six-coordinated form (1, low-spin state) to a five-coordinated form (2, high-spin state) upon binding of a hydrophobic substrate. Here, we used a heme-thiolate model complex (SR complex) with THF as a model of nonionic H2O to address the question of whether or not coordination of nonionic water is sufficient to induce the low-spin state. Measurements of electronic absorption spectra and magnetic properties confirmed that five-coordinated SR complex has a high-spin state, and THF-bound, six-coordinated SR has a low-spin state in dichloromethane at ambient temperature...
March 28, 2017: Inorganic Chemistry
William H Blades, Arthur C Reber, Shiv N Khanna, Luis Lopez-Sosa, Patrizia Calaminici, Andreas M Koster
The atomic structures, bonding characteristics, spin magnetic moments, and stability of VCux(+), VAgx(+), and VAux(+) (x = 3 - 14) clusters have been examined using density functional theory. Our studies indicate that the effective valence of vanadium is size-dependent and at small sizes some of the valence electrons of vanadium are localized on vanadium while at larger sizes the 3d orbitals of the vanadium participate in metallic bonding eventually quenching the spin magnetic moment. The electronic stability of the clusters may be understood through a split-shell model that partitions the valence electrons in either a delocalized shell or localized on the vanadium atom...
March 28, 2017: Journal of Physical Chemistry. A
Will J Hardy, Brandon Isaac, Patrick Marshall, Evgeny Mikheev, Panpan Zhou, Susanne Stemmer, Douglas Natelson
Heterointerfaces of SrTiO3 with other transition metal oxides make up an intriguing family of systems with a bounty of coexisting and competing physical orders. Some examples, such as LaAlO3/SrTiO3, support a high carrier density electron gas at the interface whose electronic properties are determined by a combination of lattice distortions, spin-orbit coupling, defects, and various regimes of magnetic and charge ordering. Here, we study electronic transport in mesoscale devices made with heterostructures of SrTiO3 sandwiched between layers of SmTiO3, in which the transport properties can be tuned from a regime of Fermi-liquid like resistivity (ρ ∝ T(2)) to a non-Fermi liquid (ρ ∝ T(5/3)) by controlling the SrTiO3 thickness...
March 28, 2017: ACS Nano
Lukasz Skorka, Piotr Kurzep, Timothée Chauviré, Lionel Dubois, Jean-Marie Mouesca, Vincent Maurel, Irena Kulszewicz-Bajer
Triarylamines oxidized to radical cations can be used as stable spins sources for the design of high-spin compounds. Here, we present the synthesis of the polyarylamine containing hexaazacyclophanes linked via meta-terphenyl bridges. Spins, created after the oxidation of the polymer, can be coupled magnetically in cyclophane moieties via meta-phenyl and along the polymer chain via meta-terphenyl units. The formation of quintet spin state was evidenced by pulsed-EPR nutation spectroscopy. Two exchange coupling constants via both couplers were determined experimentally and corresponded to J/k = 89 K in cyclophane moiety and j/k = 17 K via meta-terphenyl...
March 27, 2017: Journal of Physical Chemistry. B
Janet E Del Bene, Ibon Alkorta, Jose Elguero
Ab initio MP2/aug'-cc-pVTZ calculations have been performed on the P…C pnicogen-bonded complexes of the singlet carbene molecules C(NH2)2, C(OH)2, and cyclic C(OCH)2 [OHC] with the molecules H2XP for X = F, Cl, NC, OH, CH3, CN, CCH, and H. H2XP:C(NH2)2 and H2XP:C(OH)2 complexes have Cs symmetry and two different structures: one in which the symmetry plane of the complex and the local symmetry plane of the carbene are non-coplanar, and the other in which they are coplanar. The non-coplanar H2XP:C(NH2)2 and H2XP:C(OH)2 complexes arise only when X is one of the more electronegative substituents...
March 27, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Ashish Chhaganlal Gandhi, Rajasree Das, Fang-Cheng Chou, Jauyn Grace Lin
Understanding of magnetocrystalline anisotropy in CaFe2O4 is a matter of importance for its future applications. A high quality single crystal CaFe2O4 sample is studied by using synchrotron x-ray diffraction, a magnetometer and the electron spin resonance (ESR) technique. A broad feature of the susceptibility curve around room temperature is observed, indicating the development of 1D spin interactions above the on-set of antiferromagnetic transition. The angular dependency of ESR reveals an in-plane two-fold symmetry, suggesting a strong correlation between the room temperature spin structure and magnetocrystalline anisotropy...
March 27, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Deborah L Meyer, Florian Lombeck, Sven Huettner, Michael Sommer, Till Biskup
A detailed understanding of the electronic structure of semiconducting polymers and their building blocks is essential to develop efficient materials for organic electronics. (Time-resolved) electron paramagnetic resonance (EPR) is particularly suited to address these questions, allowing to directly detect paramagnetic states and to reveal their spin-multiplicity, besides its clearly superior resolution compared to optical meth- ods. We present here evidence for a direct S0→T optical excitation of distinct triplet states in the repeat unit of a conjugated polymer used in organic photovoltaics...
March 27, 2017: Journal of Physical Chemistry Letters
Kwing To Lai, Alexander Christoph Komarek, Maria Teresa Fernández-Díaz, Pi-Shan Chang, Sungjoon Huh, Helge Rosner, Chang-Yang Kuo, Zhiwei Hu, Tun-Wen Pi, Peter Adler, Vadim Ksenofontov, Liu Hao Tjeng, Martin Valldor
From stoichiometric amounts of CaO, Fe, and Se, pure powders and single crystals of quaternary [Formula: see text] can be obtained by solid-state reaction and self-flux growth, respectively. The as-synthesized compound exhibits a polymorphic crystal structure, where the two modifications have different stacking sequences of [Formula: see text] layers. The two polymorphs have similar unit cells but different crystal symmetries (Cmc21 and Pnma), of which the former is non-centrosymmetric. Fe is divalent (d(6)) and high-spin, as proven by X-ray spectroscopy, Mössbauer spectroscopy, and powder neutron diffraction data...
March 27, 2017: Inorganic Chemistry
Iain McKenzie, Robert Scheuermann, Ian Tucker
Avoided level-crossing muon spin resonance (ALC-μSR) has been used to study the dynamics and local environment of spin probes formed by muonium (Mu) addition to 2-phenylethanol (PEA) and limonene (1-methyl-4-(1-methylethenyl)-cyclohexene) in an aqueous dispersion of the nonionic surfactant C12E4 (tetra(ethylene glycol) n-dodecyl ether). The spin probes derived from both cosurfactants reside within the micelles in the L1 phase and the bilayers in the Lα phase rather than in the aqueous region. The local polarity measured by the different isomers of the Mu adducts of PEA suggests there is a water gradient within the micelles and bilayers...
March 27, 2017: Physical Chemistry Chemical Physics: PCCP
Li Qian Bai, Ning Xue, Xin Rui Wang, Wen Ying Shi, Chao Lu
Obtaining high efficiency room temperature phosphorescence (RTP) by employing non-noble metals poses two challenges: (1) strengthening spin-orbit coupling of excitons to improve the rate of intersystem crossing (ISC) by using non-noble metals with small-atomic-number; (2) employing structural confinement to enhance radiation relaxation because harsh conditions, including carefully selected matrices, rigid solid-state crystalline structure and low temperature, are commonly needed. Here, layered double hydroxides (LDHs) with orderly non-noble metal arrangements were used as an inorganic matrix to activate RTP of carbon dots (CDs)...
March 27, 2017: Nanoscale
P F Yuan, Z H Zhang, Z Q Fan, M Qiu
2D penta-graphene sheets were cut along typical crystallographic orientations in order to construct various penta-graphene nanoribbon (P-GNR) models, and their electronic structures and magnetic properties were systemically investigated. It was demonstrated that P-GNRs are very versatile with rich and unique electronic and magnetic properties. In particular, bipolar magnetic semiconducting features can be achieved in the ferromagnetic state for all magnetic P-GNRs, which makes P-GNRs valuable for developing next-generation information storage devices...
March 27, 2017: Physical Chemistry Chemical Physics: PCCP
Qi Song, Hongrui Zhang, Tang Su, Wei Yuan, Yangyang Chen, Wenyu Xing, Jing Shi, Jirong Sun, Wei Han
The Rashba physics has been intensively studied in the field of spin orbitronics for the purpose of searching novel physical properties and the ferromagnetic (FM) magnetization switching for technological applications. We report our observation of the inverse Edelstein effect up to room temperature in the Rashba-split two-dimensional electron gas (2DEG) between two insulating oxides, SrTiO3 and LaAlO3, with the LaAlO3 layer thickness from 3 to 40 unit cells (UC). We further demonstrate that the spin voltage could be markedly manipulated by electric field effect for the 2DEG between SrTiO3 and 3-UC LaAlO3...
March 2017: Science Advances
Vladimir Tsurkan, Sergei Zherlitsyn, Lilian Prodan, Viorel Felea, Pham Thanh Cong, Yurii Skourski, Zhe Wang, Joachim Deisenhofer, Hans-Albrecht Krug von Nidda, Joahim Wosnitza, Alois Loidl
Frustrated magnets provide a promising avenue for realizing exotic quantum states of matter, such as spin liquids and spin ice or complex spin molecules. Under an external magnetic field, frustrated magnets can exhibit fractional magnetization plateaus related to definite spin patterns stabilized by field-induced lattice distortions. Magnetization and ultrasound experiments in MnCr2S4 up to 60 T reveal two fascinating features: (i) an extremely robust magnetization plateau with an unusual spin structure and (ii) two intermediate phases, indicating possible realizations of supersolid phases...
March 2017: Science Advances
Anne B Stephansen, Theis I Sølling
The competition between ultrafast intersystem crossing and internal conversion in benzene, toluene, and p-xylene is investigated with time-resolved photoelectron spectroscopy and quantum chemical calculations. By exciting to S2 out-of-plane symmetry breaking, distortions are activated at early times whereupon spin-forbidden intersystem crossing becomes (partly) allowed. Natural bond orbital analysis suggests that the pinnacle carbon atoms distorting from the aromatic plane change hybridization between the planar Franck-Condon geometry and the deformed (boat-shaped) S2 equilibrium geometry...
July 2017: Structural Dynamics (Melville, N.Y.)
Mirette Habib, Elijah Mak, Silvy Gabel, Li Su, Guy Williams, Adam Waldman, Katie Wells, Karen Ritchie, Craig Ritchie, John T O'Brien
It is well established that the neurodegenerative process of Alzheimer's disease (AD) begins many years before symptom onset. This preclinical phase provides a crucial time-window for therapeutic intervention, though this requires biomarkers that could evaluate the efficacy of future disease-modification treatments in asymptomatic individuals. The last decade has witnessed a proliferation of studies characterizing the temporal sequence of the earliest functional and structural brain imaging changes in AD. These efforts have focused on studying individuals who are highly vulnerable to develop AD, such as those with familial genetic mutations, susceptibility genes (i...
March 22, 2017: Ageing Research Reviews
Tiago Venâncio, Lyege Magalhaes Oliveira, Javier Ellena, Nubia Boechat, Steven P Brown
Fast magic-angle spinning (MAS) NMR is used to probe intermolecular interactions in a diethylcarbamazine salt, that is widely used as a treatment against adult worms of Wuchereria bancrofti which cause a common disease in tropical countries named filariasis. Specifically, a dihydrogen citrate salt that has improved thermal stability and solubility as compared to the free form is studied. One-dimensional (1)H, (13)C and (15)N and two-dimensional (1)H-(13)C and (14)N-(1)H heteronuclear correlation NMR experiments under moderate and fast MAS together with GIPAW (CASTEP) calculations enable the assignment of the (1)H, (13)C and (14)N/(15)N resonances...
March 2, 2017: Solid State Nuclear Magnetic Resonance
K Seleznyova, N A Sergeev, M Olszewski, P Stępień, S V Yagupov, M B Strugatsky, J Kliava
A comparative analysis of the Czjzek's and Maurer's models of the joint distribution density of NMR quadrupole parameters has been carried out in view of their application to account for spectra broadening induced by local disorder in crystals. As an example of such an application, we have considered Magic Angle Spinning NMR of (11)B and (71)Ga isotopes in polycrystalline gallium borate. Computer simulations carried out using both models unambiguously show that in the case of low local disorder the Maurer's model, in contrast to the Czjzek's model, provides satisfactory fits to experimental NMR spectra...
March 18, 2017: Solid State Nuclear Magnetic Resonance
Shanshan Deng, Shaoguo Kang, Nannan Feng, Jianxin Zhu, Bo Yu, Xiaofeng Xie, Jing Chen
Recent researches indicate that mechanochemical treatment (MCT) is a promising method to degrade the environmental hazards, especially in the area of persistent organic pollutants (POPs) disposal. However, the mechanochemical dechlorination mechanism of POPs still needs to be further verified. In this mechanochemical process, hexachlorobenzene (HCB) was chosen as a model pollutant with aluminum and alumina (Al+Al2O3) powders as the co-milling regents. Both of the intermediate analysis and quantum chemical calculations were adopted to elucidate the free radical dechlorination mechanism of HCB...
March 12, 2017: Journal of Hazardous Materials
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