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High-quality titanium nitride (TiN) films with different crystal orientations (001, 110, and 111) obtained under the same growth conditions are systematically investigated by both ultra-low temperature scanning tunneling microscope/spectroscopy and transport experiments. Our results reveal that all of them are conventional type-II superconductors, which exhibit spatially homogeneous superconducting properties. The superconductivity is uniform between surface and bulk. Intriguingly, the TiN (111) film has the highest transition temperature (Tc) but the lowest upper critical field (Hc2). This crystal orientation-dependent superconductivity could be explained by the fact that TiN (001) and TiN (110) films are dirtier than TiN (111). Our results suggest that (111)-oriented TiN is superior to design certain superconducting devices, including Josephson junction devices. The crystallographic orientation could offer an effective controlling parameter for designing TiN-based superconducting devices. [ABSTRACT FROM AUTHOR]

Coaxial cavities are the main interaction structures of high-power high-frequency gyrotrons at present. With the increase of operating frequency and output power, ohmic loss becomes to be a vital issue needed to be analyzed compulsorily for coaxial-cavity gyrotron. It would lead to operating frequency shift and efficiency decline. In addition, the long pulse operation would be deteriorated to a large extent as a consequence of rather severe ohmic losses. Therefore, it is of great meaning to analyze the ohmic losses of coaxial cavity more accurately. In this paper, a new method is introduced to analyze the influence of the ohmic losses on coaxial cavities and TE34,11 mode operating at 170 GHz is taken as an example to compare this method with other two methods. The results show that this method can be used to analyze the coaxial cavity with higher accuracy and fewer restrictions. [ABSTRACT FROM AUTHOR]

The temperature dependence of the dielectric and ferroelectric properties of lead-free piezoceramics of the composition (1-x-y)Bi0.5Na0.5TiO3–xBaTiO3–yK0.5Na0.5NbO3 (0.05≤x≤0.07, 0.01≤y≤0.03) was investigated. Measurements of the polarization and strain hystereses indicate a transition to predominantly antiferroelectric order when heating from room temperature to 150 °C, while for 150

Lead-free piezoelectric ceramics, (1-x-y)Bi0.5Na0.5TiO3–xBaTiO3–yK0.5Na0.5NbO3 (0.05≤x≤0.07 and 0.01≤y≤0.03), have been synthesized by a conventional solid state sintering method. The room temperature ferroelectric and piezoelectric properties of these ceramics were studied. Based on the measured properties, the ceramics were categorized into two groups: group I compositions having dominant ferroelectric order and group II compositions displaying mixed ferroelectric and antiferroelectric properties at room temperature. A composition from group II near the boundary between these two groups exhibited a strain as large as ∼0.45% at an electric field of 8 kV/mm. Polarization in this composition was not stable in that the piezoelectric coefficient d33 at zero electric field was only about 30 pm/V. The converse piezoelectric response becomes weaker when the composition deviated from the boundary between the groups toward either the ferroelectric or antiferroelectric compositions. These results were rationalized based on a field induced antiferroelectric-ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

A simple and effective method that solid state reaction followed by quenching process is developed to prepare multiferroic La-substituted BiFeO3 (Bi1-xLaxFeO3 (BLFOx) with x=0–0.40) ceramics. X-ray diffraction, x-ray photoelectron spectroscopy, and inductively coupled plasma studies show that the ceramics prepared under the optimized conditions are single phase. A phase transition from rhombohedral to orthorhombic phase is observed near x=0.30. This transition has great effects on the multiferroic properties. Magnetic and electric measurements reveal that the BLFO0.30 has enhanced multiferroic properties with two times remnant magnetization and polarization of 0.041 emu/g and 22.4 μC/cm2, respectively. The enhanced multiferroic properties are attributed to the enhanced magnetoelectric interaction, which results from the La substitution-induced destruction of the spin cycloid. These results show that BiFeO3-based perovskite solid solution with no other ferroelectric end member can have improved multiferroic properties via enhancing magnetoelectric interaction. This work may provide some guidelines for further study on BiFeO3 and BiFeO3-based solid solutions. [ABSTRACT FROM AUTHOR]

Polycrystalline ferroelectric SrBi[sub 4]Ti[sub 4]O[sub 15] thin films were prepared on Pt-coated silicon substrates by pulsed laser deposition. Structures of the films were analyzed by x-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy. At an applied field of 275 kV/cm, the films showed good hysteresis loops with remnant polarization (P[sub r]), saturated polarization (P[sub s]) and coercive field (E[sub c]) of 3.11 µC/cm[sup 2], 7.81 µC/cm[sup 2] and 68 kV/cm, respectively. At 120 kV/cm switching pulse field, fatigue tests were carried out systematically by varying the switching pulsewidth with a fixed duty cycle and with a fixed switching period, respectively. A gradual increase followed by an abrupt increase of the fatigue rate was observed with the increase of the switching pulsewidth. Field-induced defect diffusion was used to explain the results. [ABSTRACT FROM AUTHOR]

Ceramic-based capacitors with excellent recoverable energy storage density (Wrec) and efficiency (η) are greatly desired for pulsed capacitors but challenge as well. In this work, the high energy storage performance with an Wrec of 5.1 J/cm3, an η of 93.4%, and an ultrafast discharge–charge speed t0.9 of 72 ns is achieved in unusual interstitial and substitutional hybrid solid solution of Sr0.64Bi0.18Na0.18TiO3-ZnO (SBNT-Zn), in which two Zn2+ ions occupy one A-site, while one Zn2+ ion occupies one B-site of ABO3 perovskite lattice simultaneously. The addition of Zn2+ increases lattice distortion and breaks long-range ferroelectric order, resulting in more highly dynamic polar nanoregions, higher relaxation behaviors as well as larger polarization (ΔP). Moreover, the extraordinary hybrid solid solution configuration enhances the bandgap of SBNT-Zn and ZnO as a sintering aid refines grain size, both help to enhance electric breakdown strength. This work affirms the feasibility and reliability of forming a hybrid solid solution to develop high-performance ferroelectric materials. [ABSTRACT FROM AUTHOR]

The propagation of a Gaussian laser pulse in a preformed plasma channel is investigated. The conditions for the existence of electromagnetic solitary waves are obtained theoretically by analyzing the differential equation of the pulse spot size including the effects of relativistic self-focusing, ponderomotive self-channeling, and preformed channel focusing. Some solitarylike wave solutions are presented numerically and their possible implications on laser-plasma acceleration are discussed briefly. [ABSTRACT FROM AUTHOR]

The observation of the anomalous Hall effect (AHE) in 5d perovskite oxides has been challenging due to their lack or weak ferromagnetic order, which is necessary for breaking time-reversal symmetry. Here, we present compelling evidence of ferromagnetism and consequent AHE in a series of carefully designed and fabricated 5d/5d SrTaO3/SrIrO3 (STO/SIO) superlattices. The coexistence of Ta5+ and Ta4+ chemical states induces ferromagnetism in the STO layer, while the interfacial magnetic proximity effect further enhances it in the SIO layer, resulting in both ferromagnetism and AHE within the STO/SIO superlattice. Additionally, the strong spin–orbit coupling between Ta and Ir elements positively contributes to enhancing the AHE. This work offers an alternative approach for designing artificial materials with AHE and holds potential for advancing spintronics. [ABSTRACT FROM AUTHOR]

Phase diagram of Bi0.5Na0.5TiO3-BaTiO3-K0.5Na0.5NbO3 ternary system has been analyzed and (0.94-x)BNT-0.06BT-xKNN (0.15≤x≤0.30) ceramics have been prepared and investigated. Pseudocubic structures were confirmed by x-ray diffractions and its preliminary Rietveld refinements. P-E, S-E, and S-P2 profiles (where P, E, and S denote polarization, electric field, and strain, respectively) indicate electrostrictive behavior of all ceramics. The compositions with x=0.20 and 0.25 show pure electrostrictive characteristics. The dissipation energy, electrostrictive strain, and electrostrictive coefficient have been determined and compared with other lead-free and lead-containing electrostrictors. The electrostrictive coefficient can reach as high as 0.026 m4/C2, about 1.5 times of the value of traditional Pb-based electrostrictors. [ABSTRACT FROM AUTHOR]

Piezoelectric actuators convert electrical into mechanical energy and are implemented for many large-scale applications such as piezoinjectors and ink jet printers. The performance of these devices is governed by the electric-field-induced strain. Here, the authors describe the development of a class of lead-free (0.94-x)Bi0.5Na0.5TiO3–0.06BaTiO3–xK0.5Na0.5NbO3 ceramics. These can deliver a giant strain (0.45%) under both unipolar and bipolar field loadings, which is even higher than the strain obtained with established ferroelectric Pb(Zr,Ti)O3 ceramics and is comparable to strains obtained in Pb-based antiferroelectrics. [ABSTRACT FROM AUTHOR]

B-site Ti-substituted Bi1.5Zn1.0Nb1.5O7 (Bi1.5Zn1.0Nb1.5-xTixO7, x=0, 0.05, and 0.10) thin films have been fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. The x-ray diffraction and scanning electron microscopy measurements show that the films have a single phase and are well crystallized and homogeneous. Dielectric properties are investigated as function of temperature and frequency. It is found that the Ti substitution increases the dielectric constant. At 10 kHz, the room temperature dielectric constant and loss tangent ([variant_greek_epsilon], tan δ) are (163, 0.006), (182, 0.014), (197, 0.010) for the films with x=0, 0.05, and 0.10, respectively. In a wide temperature and frequency range (-100 °C∼50 °C, 1 kHz∼1 MHz), the dielectric constant is almost constant. However, below -100 °C, a dielectric relaxation depending on Ti content is observed. The relationship between structure and property of this thin film system is discussed. [ABSTRACT FROM AUTHOR]

The weak light absorption and zero-bandgap properties of two-dimensional graphene negatively affect electron–hole recombination and quantum yield, restricting its usefulness in practical optoelectronic applications. In this work, plasma-assisted chemical vapor deposition is used to synthesize three-dimensional graphene (3D-graphene) in situ on the surface of silicon-on-insulator (SOI) wafers, thereby creating high-performance broadband photodetectors. The nanocavity structure of the 3D-graphene integrates with the optical cavity structure of the SOI to enhance the interaction that occurs between the 3D-graphene and incident light. The resulting device has excellent performance in the near-infrared (NIR). The mechanism by which the light absorption of the photodetector is enhanced is explored in detail via experimental analysis and theoretical calculation. Photodetectors based on the 3D-graphene/SOI Schottky heterojunction exhibit a broad detection range (from 440 to 1550 nm), ultrahigh responsivity (27.4 A/W), and excellent detectivity (1.37 × 1011 Jones) at a wavelength of 1550 nm. The Schottky heterojunctions combine two structures (nanocavity and optical cavity) that enhance light absorption. They are also compatible with complementary metal-oxide-semiconductor technology, providing a strategy for manufacturing high-performance NIR photodetectors. [ABSTRACT FROM AUTHOR]

This paper presents the simulation results of a multistage depressed collector for a MW-class gyrotron. The energy distribution of spent electrons is obtained by a beam–wave interaction code. By increasing the number of depressed electrodes, the maximum collection efficiency can be increased to 81% with a low percentage of backstreaming 0.04% with regard to a four-stage depressed collector. By considering the secondary electron emission, the effects of different kinds of secondary electrons are simulated in the CST software, which is developed by Computer Simulation Technology Company in Germany. In order to reduce bad effects of secondary electrons, the structure of the fourth depressed electrode has been adjusted to form a slope. The axial length and slant angle of the slope have been optimized. The results indicate that the collection efficiency can exceed 70% and the percentage of backstreaming is less than 1%. Besides, in view of the limited power capacity of the collector wall, a magnetic field sweeping system has been introduced. The maximum power density is reduced to 392 W/cm2, and the deposited length of the electron beam trajectory is 470 mm. [ABSTRACT FROM AUTHOR]

Lead-free (1-x)Bi0.5Na0.5TiO3-xBiCoO3 (x = 0, 0.015, 0.025, 0.03, 0.035, 0.04, and 0.06) piezoelectric ceramics have been synthesized and their structure and electric properties have been investigated systemically. The rhombohedral-tetragonal morphotropic phase boundary (MPB) locates near x = 0.025-0.035. For the ceramics with x = 0.025, the saturated polarization (Ps), remnant polarization (Pr), coercive field (Ec), strain(S), piezoelectric constant (d33), and thickness electromechanical coupling factor (kt) are 40.6 μC/cm2, 35.4 μC/cm2, 5.25 kV/mm, 0.11%, 107pC/N, and 0.45, respectively. The low temperature humps of relative dielectric constant, which is indicative of TR-T, are becoming inconspicuous gradually with the increasing x and almost disappear at x = 0.04. The depolarization temperature Td decreases first and then increases with the increasing x. Our results may be helpful for further work on Bi0.5Na0.5TiO3-based lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Unusual substitutional and interstitial solid solutions were observed in (1−x)Ba(Zr0.35Ti0.65)O3-xZnO thin films, where one Zn2+ cation substituted one B-site Zr4+/Ti4+ site and two Zn2+ cations substituted one A-site Ba2+ site simultaneously. Such a hybrid solid solution with an appropriate ZnO content remarkably increases both the electric breakdown strength (Eb) by widening the bandgap and the energy storage efficiency (η) by suppressing the hysteresis of the ferroelectric loop. As a result, the films with x = 0.2 show superior energy storage performance with a recoverable energy storage density (Wrec) of 130.3 J/cm3 and η of 89.1%. This work confirms the feasibility of forming an unconventional hybrid solid solution, which may shed light on further work on perovskite oxides with improved ferroic functionalities. [ABSTRACT FROM AUTHOR]

Medium-power gyrotron operating in high frequency usually operates in harmonics to reduce the required guiding magnetic field strength. Low guiding magnetic field is in favor of compact gyrotron, which makes it easier to apply the gyrotron to large scale devices and to extend the applications of gyrotron to wider fields. However, high harmonic modes suffer from low intensity of cyclotron radiation and additional competition with neighboring fundamental modes. As we all know, single mode operation can be realized by using a special startup scenario and a positive magnetic field taper can increase output efficiency. The influence of magnetic field taper on gyrotron operation is studied by generalizing the well-known η ⊥ μ , F plot, which just discussed the transverse efficiency using Gaussian field profile and not took the self-consistent non-stationary codes or ohmic dissipation into consideration. In this paper, linear and self-consistent nonlinear codes are used to investigate influences of magnetic field taper on start current and output parameters of a 394 GHz gyrotron, which is designed for enhancement of Nuclear Magnetic Resonance spectroscopy through Dynamic Nuclear Polarization. Simulation results show that when the magnetic field taper is +0.04 T the maximum output power is obtained and the maximum value is 3% larger than that corresponding to uniform magnetic field. Appropriate startup scenario is designed for single mode operation and multimode simulation is carried out to demonstrate that mode TE261+ dose dominate in mode competition in the designed startup path. [ABSTRACT FROM AUTHOR]

(Na0.5Bi0.5)0.93Ba0.07Ti1 − x(Mn1/3Nb2/3)xO3 ceramics (x = 0–0.02) were prepared, and their structure and property were investigated systematically. (Mn1/3Nb2/3)4+ doping shifts ferroelectric–relaxor transition temperature (TF–R) toward low temperature. Thus, ferroelectric order is suppressed and relaxor behavior is enhanced monotonously, as further evidenced by composition-dependent electrical properties and domain evolution from labyrinthian to nanodomain. As a result, the x = 0.010 ceramic yields a large room temperature field-induced strain of 0.37%, especially the strain is temperature- and frequency-insensitive with a variety of 4.3% and 4.1% in the ranges of 25–125 °C and 0.5–10 Hz, respectively. This work suggests that the low content (Mn1/3Nb2/3)4+ complex cation doping is an alternative method to effectively tune the electrical properties of Na0.5Bi0.5TiO3-based ferroelectrics. [ABSTRACT FROM AUTHOR]

While the unique geometrical frustration of pyrochlore Yb2Ti2O7 has attracted attention, the dielectric and other properties of this pyrochlore beyond frustrated magnetism are not well understood. Here, we report on the fascinating low-temperature dielectric relaxation of Yb2-xBaxTi2O7-δ (x = 0–0.20) and demonstrate that this phenomenon is related to structural distortion. A-site Ba substitution, which increases the density of point defects and introduces a different atomic radius, enhances the chemical disorder and structural distortion. As a result, the increases in oxygen vacancies and nonmagnetic Ba2+ and Yb2+ ions dilute the ferromagnetic Yb3+–Yb3+ interactions, as indicated by the decrease in effective magnetic moment. On the other hand, the distorted octahedra facilitate the hopping of Yb ions, and the random distribution of Ba2+ ions at the Yb3+ sites gives rise to additional random fields, leading to significantly increased dielectric relaxation. The room-temperature dielectric constant is improved to ∼170, twice that of pristine Yb2Ti2O7. This work provides a comprehensive view of the structural, magnetic, and dielectric properties of Yb2Ti2O7 and lays the foundation for additional research into pyrochlore compounds. [ABSTRACT FROM AUTHOR]

(1−x)Sr0.75Ba0.25Nb2O6–xNaNbO3 (x = 0–0.8) ceramics were prepared by the traditional solid-state reaction method. The x = 0–0.4 ceramics preserve the tungsten bronze phase with a gradually unfilled–filled structure evolution accompanying a relaxor-normal ferroelectric transition. This transition process is accompanied by an increase in the maximum dielectric constant temperature or Curie temperature (Tc), enhancement of room temperature ferroelectric and piezoelectric properties, and appearance of the stripe domain. On the other hand, ceramics with x > 0.4 consist of coexisting tungsten bronze and perovskite phases, for which Tc slightly fluctuates, and the ferroelectric and piezoelectric properties decrease with increasing x. This work provides a feasible way to manipulate the relaxor-normal ferroelectric transition and the electrical properties of the tungsten bronze family. [ABSTRACT FROM AUTHOR]

In the presence of relativistic and channel-coupling nonlinearity and wakefield effects, the propagation characteristics and solitary waves of an intense short laser pulse in a preformed plasma channel are investigated. The evolution equation of the laser spot size is derived by using variational technique, the initial laser and plasma parameters for propagation with constant spot size, periodic defocusing and focusing oscillations, and solitary waves are identified. For illustration, some numerical results are also presented. It is found that the laser focusing is enhanced by the wakefield effects that result in a significant reduced focusing power. [ABSTRACT FROM AUTHOR]

Bubble core field modification due to the nondepleted electrons present inside the bubble is investigated theoretically. These residual electrons induce charge and current densities that can induce the bubble core field modification as well as the bubble shape change. It is found that the electrons entering into the bubble move backward at almost light speed and would weaken the transverse bubble fields. This reduces the ratio of longitudinal to transverse radius of the bubble. For the longitudinal bubble field, two effects compensate with each other because of their competition between the enhancement by the shortening of bubble shape and the reduction by the residual electrons. Therefore the longitudinal field is hardly changeable. As a comparison we perform particle-in-cell simulations and it is found that the results from theoretical consideration are consistent with simulation results. Implication of the modification of fields on bubble electron acceleration is also discussed briefly. [ABSTRACT FROM AUTHOR]

The ion acceleration from a double-layer target irradiated by a transversely Gaussian laser pulse is investigated by theoretical analysis and particle-in-cell simulations. The main idea of the double-layer target is to match the transverse areal mass density of the target with the laser intensity profile by single ion specie with two densities or by two ion species. Two-dimensional particle-in-cell simulations show that the target deformation and the transverse instability are efficiently suppressed in the double-layer scheme, ions within the laser spot are uniformly accelerated and are well collimated in the forward direction, GeV/u monoenergetic ion beams with very low divergency are observed. [ABSTRACT FROM AUTHOR]

Recently, a large amount of effort has been devoted to bringing p- and n-type two-dimensional (2D) materials in close contact to promise a p–n junction for photodetectors and photovoltaic devices. However, all solar cells based on 2D materials are single p–n junctions so far, where the open circuit voltage is usually limited by the bandgap of semiconductor materials. Here, by using a scanning-probe domain patterning method to polarize the ferroelectric film, we demonstrate a series connected MoTe2 photovoltaic cell with an additive open circuit voltage and output electrical power. The nonvolatile MoTe2 p–n diodes exhibit a rectification ratio of 100. As a photodetector, the device presents a responsivity of 220 mA/W and an external quantum efficiency of 41% without any gate or bias voltages. The open circuit voltage increases linearly with the number of series connected p–n junctions and can be beyond the bandgap of the multilayer MoTe2. [ABSTRACT FROM AUTHOR]

Magnetic compounds with significant and temperature-insensitive magnetoresistance are quite promising for device applications. Here, we intentionally doped different amounts (0.025-0.1) of Co into epitaxial (La0.7Sr0.3)MnO3 thin films. The evolution of electrical, magnetic, magneto-transport, and valence state of this series of Co-doped (La0.7Sr0.3)MnO3 have been systematically characterized. Remarkably, the magnetoresistance in 0.1Co-doped (La0.7Sr0.3)MnO3 can reach significantly 35% within an extremely large temperature window (from 40 to 200 K). Other Co-doped epitaxial (La0.7Sr0.3)MnO3 thin films show similar sharp MR-peaks around Curie temperature as that in (La0.7Sr0.3)MnO3. The evolution of magnetic and magneto-transport properties of Co-(La0.7Sr0.3)MnO3 films can be explained by antiferromagnetic coupling induced by paramagnetic/low-spin Co3+(Co2+) ions in (La0.7Sr0.3)MnO3. Our work demonstrates that doping paramagnetic/low-spin Co into manganites is an effective way to optimize their magneto-transport properties. [ABSTRACT FROM AUTHOR]

We synthesized the copper foam sustained silica aerogel (CFSA) by sol-gel transition followed by CO2 supercritical drying. The as-prepared CFSA exhibits excellent sound absorption capability and favorable compressive properties. Incorporation of epoxy resin during sol-gel process can improve the combination between silica aerogel and copper foam framework, which helps to significantly increase the average sound absorption from ∼36% to ∼55% (200-3900 Hz) and the maximum sound absorption coefficient from 0.78 to 0.99. A high Young's modulus of ∼11.01 MPa and compression strength of ∼0.30 MPa were demonstrated for CFSA as well. The fabricated CFSA also shows some advantages, e.g., lightweight (density of 0.28 g/cm3) and hydrophobic. Such fascinating artificial composite may provide new insights into the development of strong and effective aerogel sound-absorbing materials for various applications. [ABSTRACT FROM AUTHOR]

Monolayer molybdenum disulfide (m-MoS2) has attracted significant interest owing to its unique electronic and optical properties. Chemical vapor deposition has been well recognized as one of the preferred methods to prepare MoS2 film. Little is known, however, about the effect of the temperature gradient from MoO3 powder to growth substrate on shape, size evolution and growth mechanism. Herein, by controlling the temperature gradient from the pre-vaporization temperature of MoO3 powder to the pre-nucleation temperature of growth substrate at nucleation stage, the inversive, equal, positive temperature gradient (ITG, ETG and PTG) are originally designed. Additionally, we investigate the morphology variation from monolayer to multilayer domains with the change in the temperature gradient on the basis of classical crystal growth theory and the Antonie equation. Also, the IGT could effectively suppress the nuclei density and facilitate the growth of m-MoS2 domains. The results suggest introducing temperature gradient is a significant way for tuning the morphological evolution and achieving the controllable shape of monolayer MoS2 film. And thus, the conclusion will further lay the foundation for expanding the process window of m-MoS2 growth. [ABSTRACT FROM AUTHOR]

We experimentally studied unidirectional perfect absorbers with asymmetric sandwich structures composed of two thick metallic films with different thicknesses and a truncated symmetric photonic crystal (PC). Single-channel and multichannel near-perfect absorbers were obtained by adjusting period number of the PC. According to electromagnetic field intensity distributions at absorption wavelengths, the physical mechanism of near-perfect absorption derived from the coupling effect between optical Tamm state and Fabry-Pérot resonance. The unidirectional absorption phenomena were attributed to weak electric field distributions at absorption wavelengths for opposing directions of light incidence. The experimental values showed good agreement with theoretical results. [ABSTRACT FROM AUTHOR]

A series of LaFeO3/YMnO3 superlattices with various thicknesses are synthesized epitaxially on (001) and (111) SrTiO3 substrates. X-ray diffraction, high-resolution cross-sectional transmission electron microscopy, and sub-nanometer-scale resolved electron energy loss spectroscopy characterizations prove that grown superlattices have designed layer-by-layer structures, and there is atomically sharp interface between two successive constituent layers. Temperature-dependent magnetization and magnetic hysteresis loop measurements substantiate that there is significant ferrimagnetism generated at LaFeO3/YMnO3 interfaces. The generated ferrimagnetism is discussed by considering the magnetic structures in each constituent layer. [ABSTRACT FROM AUTHOR]

An optimizing and alternative scheme for electron injection and acceleration in the wake bubble driven by an ultraintense laser pulse is presented. In this scheme, the dense-plasma wall with an inner diameter matching the expected bubble size is placed along laser propagation direction. Meanwhile, a dense-plasma block dense-plasma is adhered inward transversely at some certain position of the wall. Particle-in-cell simulations are performed, which demonstrate that the block plays an important role in the first electron injection and acceleration. The result shows that a collimated electron bunch with a total number of about 4.04×108μm-1 can be generated and accelerated stably to 1.61 GeV peak energy with 2.6% energy spread. The block contributes about 50% to the accelerated electron injection bunch by tracing and sorting statistically the source. [ABSTRACT FROM AUTHOR]