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Magnetization transfer

R John, M Berritta, D Hinzke, C Müller, T Santos, H Ulrichs, P Nieves, J Walowski, R Mondal, O Chubykalo-Fesenko, J McCord, P M Oppeneer, U Nowak, M Münzenberg
Manipulation of magnetisation with ultrashort laser pulses is promising for information storage device applications. The dynamics of the magnetisation response depends on the energy transfer from the photons to the spins during the initial laser excitation. A material of special interest for magnetic storage are FePt nanoparticles, for which switching of the magnetisation with optical angular momentum was demonstrated recently. The mechanism remained unclear. Here we investigate experimentally and theoretically the all-optical switching of FePt nanoparticles...
June 23, 2017: Scientific Reports
P Virtanen, T T Heikkilä
We analyze the statistics of charge and energy currents and spin torque in a metallic nanomagnet coupled to a large magnetic metal via a tunnel contact. We derive a Keldysh action for the tunnel barrier, describing the stochastic currents in the presence of a magnetization precessing with the rate Ω. In contrast to some earlier approaches, our result is valid for an arbitrary ratio of ℏΩ/k_{B}T. We illustrate the use of the action by deriving spintronic fluctuation relations, the quantum limit of pumped current noise, and consider the fluctuations in two specific cases: the situation with a stable precession of magnetization driven by spin transfer torque, and the torque-induced switching between the minima of a magnetic anisotropy...
June 9, 2017: Physical Review Letters
Patrick Back, Meinrad Sidler, Ovidiu Cotlet, Ajit Srivastava, Naotomo Takemura, Martin Kroner, Atac Imamoğlu
For applications exploiting the valley pseudospin degree of freedom in transition metal dichalcogenide monolayers, efficient preparation of electrons or holes in a single valley is essential. Here, we show that a magnetic field of 7 T leads to a near-complete valley polarization of electrons in a MoSe_{2} monolayer with a density 1.6×10^{12}  cm^{-2}; in the absence of exchange interactions favoring single-valley occupancy, a similar degree of valley polarization would have required a pseudospin g factor of 38...
June 9, 2017: Physical Review Letters
Lili Feng, Dan Yang, Fei He, Shili Gai, Chunxia Li, Yunlu Dai, Piaoping Yang
Reactive oxygen species (ROS) produced in the specific tumor site plays the key role in photodynamic therapy (PDT). Herein, a multifunctional nanoplatform is designed by absorbing ultrasmall upconversion nanoparticles (UCNPs) on mesoporous graphitic-phase carbon nitride (g-C3 N4 ) coated superparamagnetic iron oxide nanospheres, then further modified with polyethylene glycol (PEG)molecules (abbreviated as Fe3 O4 @g-C3 N4 -UCNPs-PEG). The inert g-C3 N4 layer between Fe3 O4 core and outer UCNPs can substantially depress the quenching effect of Fe3 O4 on the upconversion emission...
June 23, 2017: Advanced Healthcare Materials
Frédéric Gendron, Valerie E Fleischauer, Thomas J Duignan, Brian L Scott, Matthias W Löble, Samantha K Cary, Stosh A Kozimor, Hélène Bolvin, Michael L Neidig, Jochen Autschbach
We present a combined ab initio theoretical and experimental study of the magnetic circular dichroism (MCD) spectrum of the octahedral UCl6(-) complex ion in the UV-Vis spectral region. The ground state is an orbitally non-degenerate doublet E5/2u and the MCD is a -term spectrum caused by spin-orbit coupling. Calculations of the electronic spectrum at various levels of theory indicate that differential dynamic electron correlation has a strong influence on the energies of the dipole-allowed transitions and the envelope of the MCD spectrum...
June 23, 2017: Physical Chemistry Chemical Physics: PCCP
See-Hun Yang, Stuart Parkin
In this article, we review fascinating new mechanisms on recently observed remarkable current driven domain wall motion in nanowires formed from perpendicularly magnetized synthetic antiferromagnets interfaced with heavy metallic layers, sources of spin-orbit torques. All the associated torques such as volumetric adiabatic and non-adiabatic spin-transfer-torque, spin-orbit torques, shape anisotropy field torques, Dzyaloshinkii-Moriya interaction torques and most importantly a new powerful torque, exchange coupling torque, will be discussed based on an analytical model that provides an intuitive description of domain wall dynamics in synthetic ferromagnets as well as synthetic antiferromagnets...
June 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Qingcai Chen, Fumikazu Ikemori, Yuua Nakamura, Petr Vodicka, Kimitaka Kawamura, Michihiro Mochida
Submicrometer aerosols in the urban atmosphere of Nagoya, Japan, were collected in late winter and early spring, and the water-insoluble organic matter (WISOM) in the samples were fractionated into six subfractions based on their polarities by using solvent and normal-phase solid-phase extractions: non-polar (F1), low-polar (F2 and F3), and medium-polar (F4, F5, and F6) fractions. The overall structural characteristics of these subfractions were then analyzed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and high-resolution aerosol mass spectrometry...
June 22, 2017: Environmental Science & Technology
Lvkang Shen, Liang Wu, Quan Sheng, Chunrui Ma, Yong Zhang, Lu Lu, Ji Ma, Jing Ma, Jihong Bian, Yaodong Yang, Aiping Chen, Xiaoli Lu, Ming Liu, Hong Wang, Chun-Lin Jia
Mechanical flexibility of electronic devices has attracted much attention from research due to the great demand in practical applications and rich commercial value. Integration of functional oxide materials in flexible polymer materials has proven an effective way to achieve flexibility of functional electronic devices. However, the chemical and mechanical incompatibilities at the interfaces of dissimilar materials make it still a big challenge to synthesize high-quality single-crystalline oxide thin film directly on flexible polymer substrates...
June 22, 2017: Advanced Materials
Hye-Young Heo, Yi Zhang, Tina M Burton, Shanshan Jiang, Yansong Zhao, Peter C M van Zijl, Richard Leigh, Jinyuan Zhou
PURPOSE: To quantify amide protein transfer (APT) effects in acidic ischemic lesions and assess the spatial-temporal relationship among diffusion, perfusion, and pH deficits in acute stroke patients. METHODS: Thirty acute stroke patients were scanned at 3 T. Quantitative APT (APT(#) ) effects in acidic ischemic lesions were measured using an extrapolated semisolid magnetization transfer reference signal technique and compared with commonly used MTRasym (3.5ppm) or APT-weighted parameters...
June 21, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Gopikrishna Deshpande, D Rangaprakash, Luke Oeding, Andrzej Cichocki, Xiaoping P Hu
A Brain-Computer Interface (BCI) is a setup permitting the control of external devices by decoding brain activity. Electroencephalography (EEG) has been extensively used for decoding brain activity since it is non-invasive, cheap, portable, and has high temporal resolution to allow real-time operation. Due to its poor spatial specificity, BCIs based on EEG can require extensive training and multiple trials to decode brain activity (consequently slowing down the operation of the BCI). On the other hand, BCIs based on functional magnetic resonance imaging (fMRI) are more accurate owing to its superior spatial resolution and sensitivity to underlying neuronal processes which are functionally localized...
2017: Frontiers in Neuroscience
L Van Damme, D Leiner, P Mardešić, S J Glaser, D Sugny
The design of efficient and robust pulse sequences is a fundamental requirement in quantum control. Numerical methods can be used for this purpose, but with relatively little insight into the control mechanism. Here, we show that the free rotation of a classical rigid body plays a fundamental role in the control of two-level quantum systems by means of external electromagnetic pulses. For a state to state transfer, we derive a family of control fields depending upon two free parameters, which allow us to adjust the efficiency, the time and the robustness of the control process...
June 21, 2017: Scientific Reports
Jacob H Artz, David W Mulder, Michael W Ratzloff, Carolyn E Lubner, Oleg A Zadvornyy, Axl X LeVan, S Garrett Williams, Michael W W Adams, Anne K Jones, Paul W King, John W Peters
An [FeFe]-hydrogenase from Clostridium pasteurianum, CpI, is a model system for biological H2 activation. In addition to the catalytic H-cluster, CpI contains four accessory iron-sulfur [FeS] clusters in a branched series that transfer electrons to and from the active site. In this work, potentiometric titrations have been employed in combination with electron paramagnetic resonance (EPR) spectroscopy at defined electrochemical potentials to gain insights into the role of the accessory clusters in catalysis...
June 21, 2017: Journal of the American Chemical Society
Shengfeng Huang, Ning Gan, Haibo Liu, You Zhou, Yinji Chen, Yuting Cao
In this work, a novel aptamer functionalized magnetic adsorbent was developed and combined with magnetic dispersive solid phase extraction (MDSPE) for selective enrichment of several amphenicol antibiotics residues (chloramphenicol(CAP), thiamphenicol(TAP) and florphenicol(FF)) in foodstuff then determined by High Performance Liquid Chromatography (HPLC)-Diode array detector(DAD). Firstly, a magnetic silica-coated Fe3O4 microsphere(Fe3O4@SiO2) was synthetized by sol-gel method, then it was functionalized by amino groups through 3-Aminopropyltriethoxysilane (APTES) reagent to form Fe3O4@SiO2-NH2; Thirdly, the amino group on Fe3O4@SiO2-NH2 was transferred to carboxylic group via the succinic anhydride to form Fe3O4@SiO2-COOH...
June 12, 2017: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
Roman Michez, Thomas Doneux, Claudine Buess-Herman, Michel Luhmer
Potential controlled electrolyses of [BMIm][NTf2 ] ionic liquid were performed at a gold cathode under nitrogen atmosphere. The structures of the major conversion products of the BMIm(+) cation were elucidated on the basis of 1D and 2D nuclear magnetic resonance (NMR) analyses and gas chromatography (GC) analysis of the volatile compounds. Recombination of the imidazol-2-yl radicals, generated at the electrode by single electron transfer, leads to neutral diastereomeric dimers in equal proportions, with a faradaic efficiency of 80 %, while disproportionation of these radicals and/or reaction with hydrogen atoms adsorbed at the electrode generates a neutral monomer with 20 % faradaic efficiency...
June 20, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Zeynab Mousavikhamene, Mohammad J Abdekhodaie, Hamid Ahmadieh
A unique method was used to facilitate ocular drug delivery from periocular route by drug loaded magnetic sensitive particles. Injection of particles in periocular space along the eye axis followed by application of magnetic field in front of the eye would trigger the magnetic polymeric particles to move along the direction of magnetic force and reside against the outer surface of the sclera. This technique prevents removal of drug in the periocular space, observed in conventional transscleral drug delivery systems and hence higher amount of drug can enter the eye in a longer period of time...
October 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Gahyun Baek, Heejung Jung, Jaai Kim, Changsoo Lee
Promotion of direct interspecies electron transfer (DIET) between exoelectrogenic bacteria and electron-utilizing methanogens has recently been discussed as a new method for enhanced biomethanation. This study evaluated the effect of magnetite-promoted DIET in continuous anaerobic digestion of dairy effluent and tested the magnetic separation and recycling of magnetite to avoid continuous magnetite addition. The applied magnetite recycling method effectively supported enhanced DIET activity and biomethanation performance over a long period (>250days) without adding extra magnetite...
June 14, 2017: Bioresource Technology
David Ryoo, Xiang Xu, Yuguo Li, Joel Tang, Jia Zhang, Peter C M van Zijl, Guanshu Liu
The development of new analytical methods to accurately quantify hydrogen peroxide is of great interest. In the current study, we developed a new magnetic resonance (MR) method for noninvasively quantifying hydrogen peroxide (H2O2) in aqueous solutions based on chemical exchange saturation transfer (CEST), an emerging MRI contrast mechanism. Our method can detect H2O2 by its specific CEST signal at ~6.2 ppm downfield from water resonance, with more than 1000 times signal amplification compared to the direct NMR detection...
June 19, 2017: Analytical Chemistry
Er-Jia Guo, Jonathan R Petrie, Manuel A Roldan, Qian Li, Ryan D Desautels, Timothy Charlton, Andreas Herklotz, John Nichols, Johan van Lierop, John W Freeland, Sergei V Kalinin, Ho Nyung Lee, Michael R Fitzsimmons
Here, a quantitative magnetic depth profile across the planar interfaces in BiFeO3 /La0.7 Sr0.3 MnO3 (BFO/LSMO) superlattices using polarized neutron reflectometry is obtained. An enhanced magnetization of 1.83 ± 0.16 μB /Fe in BFO layers is observed when they are interleaved between two manganite layers. The enhanced magnetic order in BFO persists up to 200 K. The depth dependence of magnetic moments in BFO/LSMO superlattices as a function of the BFO layer thickness is also explored. The results show the enhanced net magnetic moment in BFO from the LSMO/BFO interface extends 3-4 unit cells into BFO...
June 19, 2017: Advanced Materials
Daniel Nohr, Bernd Paulus, Ryan Rodriguez, Asako Okafuji, Robert Bittl, Erik Schleicher, Stefan Weber
Light-generated short-lived radial pairs have been suggested to play pivotal roles in cryptochromes and photolyases. Chryptochromes are very probably involved in magnetic compass sensing in migratory birds and the magnetic-field-dependent behavior of insects. We examined photo-generated transient states in the cryptochrome of Drosophila melanogaster and in the structurally related DNA-repair enzyme Escherichia coli DNA photolyase. Using pulsed EPR spectroscopy, the exchange and dipolar contributions to the electron spin-spin interaction were determined in a straightforward and direct way...
June 19, 2017: Angewandte Chemie
R Kovrlija, C Rondeau-Mouro
This review deals with the use of Nuclear Magnetic Resonance techniques to monitor the behavior of starch as well as the migration and distribution of water during the processing or storage of starchy matrices. The aim is to emphasize the potentials of NMR techniques for the quantitative characterization of water transfers in starch-water systems on different length scales. Relaxation and self-diffusion experiments using low-field NMR spectrometry provided important information on the relationship between water dynamics and the microscopic organization of starch granules at various temperatures and water contents...
December 1, 2017: Food Chemistry
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