We investigate the generation of the frequency components at the second-order sidebands based on a spinning resonator containing a degenerate optical parametric amplifier (OPA). We show that an OPA driven by different pumping frequencies inside a cavity can enhance and modulate the amplitude of the second-order sideband with different influences. We find that both the second-order sideband amplitude and its associated group delay sensitively depend on the nonlinear gain of the OPA, the phase of the field driving the OPA, the rotation speed of the resonator, and the incident direction of the input fields. Tuning the pumping frequency of the OPA can remain the localization of the maximum value of the sideband efficiency and nonreciprocal behavior due to the optical Sagnac effect, which also can adjust the linewidth of the suppressive window of the second-order sideband. Furthermore, we extend the study of the second-order sideband to the non-Markovian bath, which consists of a collection of infinite oscillators (bosonic photonic modes). We illustrate that the second-order sidebands in a spinning resonator exhibit a transition from the non-Markovian to the Markovian regime by controlling the environmental spectral width. We also study the influences of the decay from the non-Markovian environment coupling to an external reservoir on the efficiency of second-order upper sidebands. This indicates a promising way to enhance or steer optomechanically induced transparency devices in nonlinear optical cavities and provides potential applications for precision measurement, optical communications, and quantum sensing.

采用高温固相反应法,在空气气氛中制备了纯LaAlO3和Ca2+–Cr3+共掺杂LaAlO3陶瓷材料,对其在近红外的发射率以及热导率进行了研究比较.结果表明:20％Ca2+(摩尔分数)和20％Cr3+掺杂后的La0.8Ca0.2Al0.8Cr0.2O3在0.76～2.50μm的红外发射率达0.92,比纯LaAlO3提高了300％;Ca2+和Cr3+的掺杂降低了陶瓷材料的热导率,在1200℃时LaAlO3和La0.8Ca0.2Al0.8Cr0.2O3的热导率最低,La0.8Ca0.2Al0.8Cr0.2O3的热导率最低值为2.602 W·m–1·K–1,较纯LaAlO3降低了38％.

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to Tunable Transport Gap in PhosphoreneSaptarshi Das*, Wei Zhang, Marcel Demarteau, Axel Hoffmann, Madan Dubey, and Andreas RoelofsCite this: Nano Lett. 2016, 16, 3, 2122Publication Date (Web):February 2, 2016Publication History Published online2 February 2016Published inissue 9 March 2016https://pubs.acs.org/doi/10.1021/acs.nanolett.6b00357https://doi.org/10.1021/acs.nanolett.6b00357correctionACS PublicationsCopyright © 2016 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views1317Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (510 KB) Get e-Alertsclose Get e-Alerts

A heterogeneous, inexpensive, and environmentally friendly graphene oxide catalytic system for the C-H bond arylation of benzene enables the formation of biaryl compounds in the presence of aryl iodides. The oxygen functional groups in these graphene oxide sheets and the addition of KOtBu are essential for the observed catalytic activity. Reactions with various model compounds and DFT calculations confirmed that these negatively charged oxygen atoms promote the overall transformation by stabilizing and activating K(+) ions, which in turns facilitates the activation of the C-I bond. However, the graphene π system also greatly facilitates the overall reaction as the aromatic coupling partners are easily adsorbed.

Bit-patterned media, a promising candidate for next generation high density magnetic recording, requires sub-100 nm dots array on a wafer scale, a high degree of patterning control of the size distribution, and a material with high perpendicular anisotropy. In this work, large area (0.75 cm × 0.75 cm) dots array was achieved by nanoimprint lithography and ion milling from L10 FePt thin films that are pre-sputtered at 450 °C with both high crystalline quality and good chemical order. The sub-100 nm dots are decoupled from each other and show both narrow size distributions and high coercivity values on the order of 11 kOe. Our work would cast light for the application of bit-patterned media.

Thin-film based novel magnetic and electronic devices have entered a new era in which the film crystallography, structural coherence, and epitaxy play important roles in determining their functional properties. The capabilities of controlling such structural and functional properties are being continuously developed by various physical deposition technologies. Epitaxial patterning strategies further allow the miniaturization of such novel devices, which incorporates thin-film components into nanoscale architectures while keeping their functional properties unmodified from their ideal single-crystal values. In the past decade, epitaxial patterning methods on the laboratory scale have been reported to meet distinct scientific inquires, in which the techniques and processes used differ from one to the other. In this review we summarize many of these pioneering endeavors in epitaxial patterning of thin-film devices that use both conventional and novel lithography techniques. These methods demonstrate epitaxial patterning for a broad range of materials (metals, oxides, and semiconductors) and cover common device length scales from micrometer to sub-hundred nanometer. Whilst we have been motivated by magnetic materials and devices, we present our outlook on developing systematic-strategies for epitaxial patterning of functional materials which will pave the road for the design, discovery and industrialization of next-generation advanced magnetic and electronic nano-devices.

A modified effective field model was developed to quantitatively interpret the angular dependent magnetization reversal processes in exchange biased Fe/IrMn bilayers. Several kinds of multi-step loops with distinct magnetization reversal routes were observed for the samples measured at various field orientations. Two types of angular dependent switching fields are observed and their transitions are investigated, which are found to be driven by both Fe and IrMn layer thicknesses. Our modified effective field model can nicely describe all the switching field behaviors including the critical effects of the exchange bias induced uniaxial anisotropy on the magnetization reversal processes.

We report an investigation on the antiferromagnetic layer thickness dependence of magnetization reversal in c-axis oriented MnPd/Fe epitaxial exchange biased bilayers. Several kinds of multistep loops were observed for different samples measured at various field orientation. The evolution of the angular dependent magnetic behavior evolving from a representative Fe film to the exchange biased bilayers was revealed. With increase of the thickness of the antiferromagnetic layers, asymmetrically shaped loops and biased two-step loops are induced by exchange bias. Including the unidirectional anisotropy, a model based on the domain nucleation and propagation was developed, which can nicely describe the evolution of the magnetic behaviors for MnPd/Fe bilayers and correctly predicts the critical angles separating the occurrence of different magnetic switching processes. For fields applied along the bias direction, the 180 degrees magnetic reversal changes from two successive 90 degrees domain wall nucleations to a single 180 degrees domain wall nucleation at the critical thickness of the MnPd layer.

We demonstrate how a mechanical point-contact technique can provide information on the wavenumber of spin waves excited by high-density electrical current in magnetic multilayers. By varying the size of point-contacts, we have been able to control the size of the excitation volume and therefore the wavelength of current-induced spin waves. This leads to a technique with in situ sensitivity to wavenumbers of current-induced excitations. Our detailed size-dependent measurements support the prediction that the excited wavelength is determined by the contact size.

A convenient and inexpensive approach to producing carbonaceous field emitters has been developed. Combined structures of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) were grown on graphitic substrates with an improved chemical vapor deposition (CVD) method. The fabrication featured a high reaction temperature and a rapid temperature rising. In each combined structure, a CNT with good crystallinity was surrounded by a cone-shaped CNF. The CNTs and the bases of the CNFs were less than 0.1 and 10μm in diameter, respectively. These combined CNT/CNF structures, several ten microns in length, had an upward orientation from the substrate and an appropriate separation between each other, which are believed to be two favorable factors to the field emission. Electron current was readily extracted from them. Current densities of 10μA/cm2 and 1mA/cm2 were obtained when the average fields between the anode and the cathode were 2.3 and 3.9V/μm, respectively.

This Article focuses on the fabrication of highly ordered nanotubes and some novel nanostructures of titania (TiO2) with a two-step anodization method. The first-step anodization was actually a pretreatment of the Ti foil surface and provided well-ordered imprints that served as a template for the further growth of nanotubes. As a result, the TiO2 nanotubes growing in the second-step anodization appreciably outperformed those fabricated with the conventional one-step Ti anodization in terms of size uniformity and arrangement orderliness. The parameters of the anodization were then modulated to obtain more complex structures. When the voltage in the second-step anodization was lower than that in the first-step anodization, a lotus root-shaped TiO2 nanostructure, in which each imprint contained several smaller nanopores, was achieved. When the second anodization was further divided into two stages, double-layered nanotube arrays were synthesized. They contained two distinctly separated parts, i.e., the bamboo-shaped upper one and the smooth-walled lower one. These results have demonstrated the effectiveness and controllability of the two-step anodization method in producing high-quality TiO2 nanotubes, which are believed to have potential applications in such fields as solar cells, photonic crystals, and hydrogen storage.

In this paper, continuous wavelet transform has been applied to inclusion detection in cantilever beams. By means of FEM, a cantilever beam with an inclusion is subjected to an impact on its free end, and its stress wave propagation process is calculated. Here, two kinds of inclusions which are distinct in material behavior have been discussed. And we change the inclusion's sizes in the beam and set it in three different positions to Simulate some complicated situations. For soft inclusion, the results show that the arrival times of incident and reflective wave are distinguishable by performing Gabor wavelet transform and extracting a proper frequency component from the strain data of two certain points on beam edge. Consequently, the position of inclusion is identified and the size of it is investigated quantitatively by the reflection and transmission ratio. For hard inclusion, an improved method is adopted to amplify the signal-to-noise ratio. The inclusion is located by analysis of the difference between an intact beam and a beam with inclusion. In addition, the corresponding dynamic experiments for both kinds of inclusions are carried out to verify the detection method. The experimental results show that Gabor wavelet transform precisely estimates the location and size of inclusions, and is proved to be an effective method to quantify the inhomogeneity in a beam.

Spintronics in ferromagnetic systems is built on a complementary set of phenomena in which the magnetic configuration of the system influences its transport properties and vice versa. Giant magnetoresistance (GMR) and spin transfer phenomena are typical examples of such interconnections found in ferromagnetic (F) multilayers. Recently, MacDonald and co-workers predicted that corresponding effects ought to occur in antiferromagnetic (AFM) multilayers where F components are replaced by AFMs. First, it was predicted that resistance of an AFM spin valve-here two AFM layers are separated by a nonmagnetic (N) spacer-could depend upon the relative orientations of magnetic moments in the two AFM layers (antiferromagnetic GMR). Second, injection of a strong enough current density into an antiferromagnet was predicted to affect its magnetic state; in particular, they predicted current-driven variations in exchange bias in F/AFM metal pairs. These new AFM effects may potentially lead to a new all-antiferromagnetic spintronics where antiferromagnets are used in place of ferromagnets. We and others have recently provided experimental evidence of current-driven effects on exchange bias at F/AFM interfaces. This talk will focus upon our experiments which demonstrated for the first time that the exchange bias is affected by an electrical current of high density (~10 12 A/m 2 ) flowing across the F/AFM interface. We find that, depending on the polarity of the current, the strength of the exchange bias can either increase or decrease. To explain our findings we exploit the theoretical prediction that the current mediates the transfer of spin angular momentum to AFM metal and generates a torque on its magnetic moments. Such a current-mediated variation of exchange bias could be used to control the magnetic state of spin-valve devices, e.g., in magnetic memory applications. I will also discuss our search for antiferromagnetic GMR in systems containing two AFMs separated by a non-magnetic (N) metal spacer.

Field emission from zinc oxide (ZnO) nanowires grown by directly heating brass substrate in air was systematically studied. The turn-on electric field was measured to be 3.3V/μm and the field emission came uniformly from the entire array. The emission stability was also tested over a period of time of 9 days. The degradation of the field emission was found to have arisen from the breaking of the nanowires. Compared with similar structures grown on Si substrate by thermal evaporation, which were made as a reference, the brass-based ZnO nanowire array appeared to be superior in field emission performance; thus, the importance of the substrate has been confirmed. At the brass–ZnO interface, the downward bending of the energy band of ZnO resulted in a low-resistance Ohmic contact. As a contrast, a large number of nanowires fell off from the Si substrate during the stability test, indicating the difficulty in the electron injection from the substrate to the nanowires. These findings have enhanced the understanding of the failure mechanism of ZnO nanowire emitters and also highlighted the essential importance of the substrate in the field emission from nanomaterials.

MacDonald and co-workers recently predicted that high current densities could affect the magnetic order of antiferromagnetic (AFM) multilayers, in ways similar to those that occur in ferromagnetic (F) multilayers, and that changes in AFM magnetic order can produce an antiferromagnetic Giant Magnetoresistance (AGMR). Four groups have now studied current-driven effects on exchange bias at F/AFM interfaces. In this paper, we first briefly review the main predictions by MacDonald and co-workers, and then the results of experiments on exchange bias that these predictions stimulated.

In this paper, continuous wavelet transform has been performed to extract the inner crack information from the guided waves in cantilever beams, and the location and size of crack can be detected exactly. Considering its best time-frequency property, Gabor continuous wavelet transform is employed to analyze the complicated flexible wave signals in cantilever beam, which is inspirited by an impact on the free end. Otherwise, in order to enhance the sensitivity of detection for some small cracks, an improved method is discussed. Here, both computational and experimental methods are carried out for comparing the influence of different crack location in beam. Therefore, the method proposed can be expected to expand to a powerful damage detection method in a broad engineering application.

We show that a high-density electric current, injected from a point contact into an exchange-biased spin valve, systematically changes the exchange bias. The bias can either increase or decrease depending upon the current direction. This observation is not readily explained by the well-known spin-transfer torque effect in ferromagnetic metal circuits, but could be evidence for the recently predicted current-induced torques in antiferromagnetic metals.

An electrical current can transfer spin angular momentum to a ferromagnet. This novel physical phenomenon, called spin transfer, offers unprecedented spatial and temporal control over the magnetic state of a ferromagnet and has tremendous potential in a broad range of technologies, including magnetic memory and recording. Recently, it has been predicted that spin transfer is not limited to ferromagnets, but can also occur in antiferromagnetic materials and even be stronger under some conditions. In this paper we demonstrate transfer of spin angular momentum across an interface between ferromagnetic and antiferromagnetic metals. The spin transfer is mediated by an electrical current of high density (~10^12 A/m^2) and revealed by variation in the exchange bias at the ferromagnet/antiferromagnet interface. We find that, depending on the polarity of the electrical current flowing across the interface, the strength of the exchange bias can either increase or decrease. This finding is explained by the theoretical prediction that a spin polarized current generates a torque on magnetic moments in the antiferromagnet. Current-mediated variation of exchange bias can be used to control the magnetic state of spin-valve devices, e.g., in magnetic memory applications.

Mg65Cu25Y10 amorphous ribbons obtained by melt-spinning method were aged at temperatures nearby the glass transition one.Mg65Cu25Y10 alloy ribbons contain different phases after aging at different temperatures for different times.Meanwhile,the room temperature plasticity of the aged Mg65Cu25Y10 alloy ribbon degrades.According to the XRD and SEM images of different specimens,the crystallization mechanism of Mg65Cu25Y10 amorphous ribbon is briefly analyzed.