X-ray detected Ferromagnetic resonance. Indirect measurements of spin transfer using VNA-FMR are unable to provide a conclusive determination of the presence of spin pumping within the heterostructures. XFMR measurements address this limitation, studying the coupled magnetodynamics with a layer-resolved probe, which reveals more information about the nature of the coupling mechanisms. Further, XFMR can determine whether a pumped pure spin current is absorbed by the MgO barrier, or whether some component crosses it, to be absorbed by the spin sink layer. he XFMR measurements were performed on beamline I10 at the Diamond Light Source (UK) and beamline 4.0.2 at the Advanced Light Source (USA). he magnetic samples are excited by microwave radiation, phase-locked to the synchrotron master oscillator, resulting in a steady precession about the efective ield close to the FMR condition. he oscillating magnetization component along the incident x-ray beam direc- tion is probed using x-ray magnetic circular dichroism (XMCD). Element, and consequently layer speciicity, is obtained by tuning the x-ray energy to the Ni and Co L 3 edges. For full details of the XFMR methodology, we refer
We have achieved TMR ratios in excess of 240% at room temperature and 312% at 25 K using EB-MgO barriers grown on amorphous CoFeB electrodes. The 共001兲 texture is obtained by controlling the MgO deposition rate below 5 pm/s. The average calculated barrier height of our EB-MgO is higher than those for previously reported values of rf-MgO with similar TMR ratios, which is thought to be due to a lower defect density in the EB-MgO barrier. This could be advantageous for STT oscillator applications that require high voltage outputs as well as for sensor applications which require a lower low-frequency noise. The asymmetric behav- ior of the TMR drop as a function of bias for the EB-MgO reveals the asymmetry of the top and bottom interfaces, whereas the rf-MgO barrier has a more symmetric structure. Structural differences in the MgO layers are revealed by 2 scans performed on the thick EB and rf-MgO. It was found that the EB-MgO has a d-spacing that matches that of bulk MgO, whereas the rf-MgO shows a slight increase in the d-spacing, which could be attributed to a higher density of oxygen vacancies created during rf sputtering. Further studies are needed to understand the cause of the differences in the d-spacings of both samples. Increases in the resistance
Pannetier et al. 14 developed a yoke-shaped hybrid giant magnetoresistance (GMR)/superconductor sensor devices with a current-in-plane geometry, which detect magnetic fields in the order of fT. The yoke-shaped design provides a stable magnetic domain structure in the long arms of the yoke, which reduces the noise associated with macroscopic domain wall motion. 15,16 However, there are almost no reports of yoke-shaped TMR sensors, because it is hard to obtain the current-perpendicular-to-plane geometry in the MTJ stacks. Here, we report a yoke-shaped TMR sensor de- vice with a MgO barrier. It shows good field sensitivity as well as low detectivity in the low frequency range. By com- paring the magnetic noise for different structures, this type of yoke-shaped TMR sensor design seems to be beneficial for low field detection.
It is interesting to compare these results for DMTJ with studies of crystallization for single CoFeB layers or in MgO based SMTJs. For example, it has been suggested that the MgO barrier acts as a boron sink which promotes the crys- tallization of CoFeB during annealing. 7,23–25 In our case, since the middle CoFeB remains amorphous, it appears that the MgO layers on either side of the middle CoFeB layer must act as barriers to boron diffusion. The free layer is unlike the other two CoFeB pinned layers, where boron can also diffuse into adjacent metallic layers. This situation is unresolved and a nanoscale boron profile is needed before any definitive conclusions can be drawn. Another possibility is that the adjacent Ru layers can initiate the crystallization of two amorphous CoFeB pinned layers during annealing. 26–28 One other factor which would influence the crystallinity of the CoFeB free layer is a lack of coherence of the crystal structures of the two adjacent MgO layers. While both have a 共001兲 texture, they grow independently on amor- phous CoFeB, which would make it difficult for the middle free layer to crystallize quasiepitaxially on both of them.
(Received 24 October 2012; accepted 17 November 2012; published online 19 December 2012) Low frequency 1/f barrier noise has been investigated in sputtered MgO magnetic tunnel junctions (MTJs) with a tunneling magnetoresistance ratio of up to 330% at room temperature. The lowest normalized noise parameter a of the tunnel barrier reaches 2.5 10 12 –2.1 10 11 lm 2 , which is comparable to that found in MTJs with the MgO barrier grown by MBE or electron–beam evaporation. This normalized barrier noise is almost bias independent in the voltage range of up to 61.2 V. The low noise level and high voltage stability may reflect the high quality of the sputtered MgO with a uniform distribution of defects in the MgO layer. V C 2012 American Institute of Physics.
sputtering chambers. All the metal layers are deposited in the main sputtering chamber and the MgO barrier layer was deposited by RF sputtering from a target-facing-target (TFT) gun. In order to establish exchange bias, the wafers were placed in an in-plane magnetic field of 5 mT during the metal deposition. Junctions with the size of 100 X 100 ì m 2 to 20 X 20 ì m 2 were fabricated by UV-lithography and Ar
FIG. 1. Low magnification (a) MAADF and (b) HAADF STEM images of the as- deposited CoFeB/Mg þ MgO/CoFeB MTJ cross section. MgO crystallites with (001) texture are observed throughout the middle of the barrier layer. (c) High magnification HAADF STEM image of a MgO crystallite from the blue rectangle in (b) confirms its (001) orientation and the disorder at the inter- faces above and below it. (d) Oxygen K-edge electron energy-loss-near-edge structure (ELNES) probed at three positions across the MgO barrier marked by the asterisks (the bot- tom CoFeB/MgO interface; in the middle where the MgO fringes are observed; and the top MgO/CoFeB/ interface), ELNES changes (including pre-edge features at 530 eV) at both interfaces suggest the presence of oxy- gen vacancies. These edges are taken from the STEM-EELS line scan across the MgO barrier with all spectra for the O K-edge region shown in (e) and the Fe L 2,3 and Co
The growth of high quality insulating films on graphene is a crucial materials science task for the development of graphene-based spintronics to enhance the efficiency of spin- polarized carrier injection into a graphene sheet. Graphene is expected to suffer from the well known “conductivity mismatch” problem at metal-nonmetal interfaces. The standard approach to mitigating this problem is to grow thin, insulating tunnel barriers between the graphene and the magnetic metallic electrode to provide a spin-dependent resistance via the tunneling magnetoresistance effect. It has been demonstrated by several experiments that direct spin injection from a magnetic electrode to graphene is possible but using aluminum oxide or MgO tunnel barriers to assist injection in graphene spin-valve devices is more efficient if suitable oxide-graphene interfaces can be formed.
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DRG in cervical segments (C4-C8) were isolated and cultured using a previous described protocol . Briefly, after laminectomies on control or diabetic mice, bilateral DRGs were dissected and incubated in dissecting solution with collagenase (1.25mg/ml, Roche, Switzerland)/dispase-II (2.4 units/ml, Roche, Switzerland) for 90 min at 37 °C, then digested with 0.25% trypsin for 8 min at 37 °C, followed by 0.25% trypsin inhibitor. DRGs were mechanically dissociated with a flame polished Pasteur pipette in the presence of 0.05% DNAse I (Cat#ampd1, Sigma-Aldrich, St. Louis, MO, USA). DRG neurons were plated on glass cover slips and grown in a medium (with 2% B27 supplement, Thermo Fisher Scientific) with 5 μM arabinosylcytosine (AraC) and 5% carbondioxide at 36.5 °C. Whole-cell patch clamp recordings were performed at room temperature (22–24 °C) using an Axon 700B amplifier (Molecular Devices, Sunnyvale, CA, USA). The patch pipettes were pulled from borosilicate capillaries (Chase Scientific Glass Inc.). Pipette resistance was 4-6 MΩ. To prevent large current-induced desensitization or tachyphylaxis in the recordings after repeated application of the agonist (AITC, 50 μM) and MGO (1 mM), current amplitudes that were no larger than 1500 pA were used for analysis. The bath solution (in mM) contained: 140 NaCl, 5 KCl, 1 MgCl 2 , 2 CaCl 2 , 5
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that does escape from the scintillation surface. Also we have made attempt to attain reflector which has high ref- lectance and doesn’t depend on the incident angle. This attempt may improve the light collection conditions and result in improving the detection efficiency of the scin- tillation detector. The single layers of Al 2 O 3 and MgO
the Si/MgO-coated. The remarkable enhancement in the corrosion resistance is mainly attributed to the stable and protective Si outer layer, as well as the partially-protective MgO inner layer. In vitro immersion testing in simulated body fluid within seven days of immersion demonstrated that the MgO and Si/MgO coating possesses a good biomineralization performance. With regards the biological tests, cells attach and spread well on the Si/MgO-coated and cells incubated with the extracted medium of the Si/MgO-coated show closer viability to the value obtained from the complete cell culture medium compared to those of the uncoated and MgO-coated. This indicates that the Si/MgO-coated has good biocompatibility in vitro. The improvement in the in vitro biological response cells resulted from the improved corrosion resistance. Si/MgO is a promising method to improve both the corrosion resistance and in vitro biocompatibility of the Mg/HA/TiO 2 bionanocomposite based on our results. Acknowledgments: The authors would like to acknowledge the Universiti Teknologi Malaysia (UTM) and financial support under FRGS GRANT Numbers 4F608, 09H80, 4F648, UTM grant 16H07 and MOHE 4F808. Author Contributions: Shahrouz Zamani Khalajabadi designed and prepared most parts of the experiments and wrote the main part of the manuscript. Aminudin Haji Abu edited the entire manuscript and selected the required experiments. Norhayati Ahmad worked on the XRD, FE-SEM, EDS spectral data together with the measurement of bonding strength of coatings to the substrate. Norizah Bt Hj Redzuan carried out XPS analysis. Mohammad Rafiq Abdul Kadir contributed to the biocorrosion sections (experiments and analysis). The main part of the biological experiments, and the related discussion on biological terms were performed by Rozita Nasiri. Ahmad Fauzi Ismail contributed to the AFM part and to the roughness measurement of sample surfaces. The English of the manuscript was substantially edited by Waseem Haider, who also helped to write and discuss the biological section.
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Effect of MgO on Microstructure Development. The differences in microstructure changes for each sample after sintered at 1600 o C in a closed air system for undoped and doped alumina are shown in Fig.3 and Fig.4. As can be seen in both these figures the addition of MgO can promote the densification and normal grain growth for alumina and results in the stabilization of the microstructure and homogenous densification. As presented proved by previous works  showed that MgO can stabilize the microstructure with homogenous densification. It is due to the its ability to suppress grain growth distribution by allowing the porous region to densify without occurrence
for MgO thin films for different molarity concentrations (0.03, 0.05 and 0.07) M with band gap values (4, 3.6 and 2.8) eV respectively. It's clear that energy gap is narrowing with increasing molarity, namely the energy gap is narrowing when grain size increase, because grain size increasing causes increase in the density of charge atoms and then every electron is effectively surrounded by an exchange and correlation hole that lowers the energy of the electron, and the conduction band is shifted downwards [8, 9].
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and this will form a one-allele barrier effect (Felsenstein 1981). Since Felsenstein ’ s (1981) landmark article, this dis- tinction has been central to the genetics of speciation because there are fewer obstacles to the evolution of one-allele effects, and therefore, they make speciation more likely (e.g., Kirk- patrick and Servedio 2002; Coyne and Orr 2004). It is also critical for our discussion here, and so we expand on it below. A two-allele effect requires divergence in allele frequency between populations at one or more loci or divergence in a trait (Servedio 2000). Traits contributing to local adaptation, loci contributing to Dobzhansky-Muller incompatibilities, and sexual signal traits involved in assortative mating are typical contributors to barriers of this type. The evolution of a two-allele effect can be opposed by gene ﬂ ow, and for loci or traits under indirect selection, it may require the main- tenance of linkage disequilibrium despite recombination (Smadja and Butlin 2011). A one-allele barrier effect does not require divergence between populations and so is not opposed by gene ﬂ ow or recombination, key obstacles to speciation involving two-allele effects. Felsenstein (1981) gave the examples of an allele that reduces migration and an al- lele that enhances mating between similar individuals with respect to a trait under divergent selection. In each case, re- productive isolation is enhanced by the spread of the trait or allele through both populations. Although the one-allele model is most often considered for prezygotic barriers, both types of barrier effect can, in principle, underlie either pre- or postzygotic isolation. One-allele barrier effects are gen- erally considered to arise in response to existing barriers (i.e., as a form of reinforcement [Felsenstein 1981] and usually functioning only to enhance the effects of other barrier loci, i.e., acting as modi ﬁ ers [e.g., Barton and de Cara 2009]). But this need not be the case: they can create barrier effects de novo (cf. Servedio 2000; Bank et al. 2012). For example, an allele that causes a plastic response in ﬂ owering time to varying soil conditions might be advantageous every- where but generate a barrier effect at an environmental boundary (as has been suggested for Howea palms; Savo- lainen et al. 2006). Finally, a one-allele barrier effect will usually have a genome-wide impact on gene ﬂ ow: it in ﬂ u- ences all loci equally because no locus can recombine away from its effect once ﬁ xed, unless it acts as a modi ﬁ er, in which case the barrier effect may be limited to the region around the barrier locus whose effect is being modi ﬁ ed.
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The study on “Preparation of MgO nanoparticles and its characterization”is carried out by a clear study of Nanochemistry and nanoparticles. The unique properties of nanomaterials created an interest among the researchers to devise simple and inexpensive techniques for preparation of nanostructures which have technical importance. The importance of nanoparticles in industrial and environmental fields urges us to prepareand analyseMgO nanoparticles. MgO nanoparticles are synthesized by quick precipitation route and a systematic study of the structural and morphological properties were then carried by using the images from XRD, TEM and SEMtechniques.Further preparation of MgO nanoparticlesby quick precipitation route is concluded as a promising, economic, efficient method.
The foils for transmission electron microscopy (TEM) (Model JEOL 3013, JEOL Ltd., Tokyo, Japan) were prepared via the conventional technique: the sample was taken to the optical thin foils mechanically and ion-beam thinning to electron transparency. Electron diﬀraction (ED) examina- tions were made in carefully thinned foils of MgO-Cr 2 O 3
observed changes in melt composition are related to the aforementioned increase in melt flux linked to the Cobb hotspot (e.g., Carbotte et al., 2008), then the temporal offset between the increase in magma flux (affecting MgO) versus the effects on primary melt chemistry could provide constraints on the dynamics of hotspot/plume migration along MORs (e.g., Ito et al., 2003). The hotspot is currently centered beneath Axial Seamount ~150 km north of the Cleft segment (Fig. 1A) and, although not isotopically distinct, coincides with an along-axis peak in the abundances of alkali and incompatible trace elements (Chadwick et al., 2005; Dreyer et al., 2013). This provides a feasible enriched end-member source component for the higher- K 2 O/TiO 2 melts and is consistent with existing work on the origin of Cleft lavas (Smith et al.,
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tended to follow Coordination barriers with more Diagnosing than females (47.22% vs. 18.75% respectively), whereas females followed them with more Hypothesizing than males (29.17% vs. 8.33%). Essentially, after having trouble coordinating changes to one area of the machine-learned program with other sections of the application, females frequently proposed a generic solution, whereas males tended to fix specific things. This appears to be yet another indication of the comprehensive problem- solving strategy associated with females , providing further evidence of the need to support both comprehensive and non-comprehensive problem-solving strategies. Finally, Use barriers were strongly tied with Diagnosing (44.12%); all the other transitions were below 15%. It seems that when a Use barrier was encountered, our participants' response was to adjust their specific solution, rather than move on to a different problem or generalize a solution. This appeared to be equally the case for males and females.
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A MgO–C refractory brick was crushed to powder (<150 mm),and subjected to the experiments. Composition of the brick is as follows; MgO 76.2 mass%,C 15.5%,Al 3.1%,Si 2.1%. Heating behavior of MgO–C brick powder is shown in Fig. 6. The sample was heated quickly and maximum temperature was higher than any other prepared samples in spite of less carbon content. The size of graphite particles in the MgO–C brick was investigated in C distribution with EPMA. SEM image and X-ray images are shown in Fig. 7. Mapping of carbon (Fig. 7(b)) shows that small graphite particles (<8 mm) existed dispersively. Since the graphite particle size was observed to be smaller size than that of pressed samples,large extent of Joule heating of graphite was indicated.
(3)/MgO (2.5)/CoFeB (3)/Ta (5)/Ru (5) (thicknesses in nm) was also grown as a comparison. Metallic layers were dc- magnetron sputtered, whereas MgO was rf-sputtered from a facing target source. All layers were grown at ambient temper- ature in high vacuum using a Shamrock cluster deposition tool. We grew DB-MTJs with the CoFe thickness t of 0.8, 1.0, or 1.2 nm. MTJ stacks were patterned into 10 10, 10 30, 20 20, 20 60, 50 50, and 50 150 lm 2 junctions using conventional UV lithography and argon ion milling. The