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When it comes to simulate or calculate an optoelectronic tweezer (OET) response for a microparticle suspended in a given medium, a precise electrical conductivity (later referred to as conductivity) value for the microparticle is critical. However, there are not well-established measurements or well-referenced values for microparticle conductivities in the OET realm. Thus, we report a method based on measuring the escape velocity of a microparticle with a standard OET system to calculate its conductivity. A widely used 6 μm polystyrene bead (PSB) is used for the study. The conductivity values are found to be invariant around 2×10-3 S/m across multiple different aqueous media, which helps clarify the ambiguity in the usage of PSB conductivity. Our convenient approach could principally be applied for the measurement of multiple unknown OET-relevant material properties of microparticle-medium systems with various OET responses, which can be beneficial to carry out more accurate characterization in relevant fields. [ABSTRACT FROM AUTHOR]

Environment-friendly lead-free potassium sodium niobate-based piezoelectric materials have been widely used in acoustic device applications because of its high piezoelectric response, high Curie temperature, and low acoustic impedance. In our previous works, samarium modified 0.915(K0.45Na0.5Li0.05)NbO3–0.075BaZrO3–0.01(Bi0.5Na0.5)TiO3 (Sm–KNLN–BZ–BNT) ceramics have achieved high piezoelectric properties with good thermal stability. To further improve its properties and thermal stability, grain orientation-controlled methods have been introduced to Sm–KNLN–BZ–BNT ceramics. In this work, textured Sm–KNLN–BZ–BNT ceramics with a 93% ⟨001⟩c-oriented textured degree have been prepared. The samples have achieved a d33* value with 532 pm/V and better thermal stability between room temperature to 150 °C than the non-textured samples. Moreover, ultrasonic transducers with a 25 MHz center frequency have been designed and fabricated by the textured Sm–KNLN–BZ–BNT ceramics. The peak-to-peak of the transducers has reached a 1.78 V high level, which demonstrated the textured Sm–KNLN–BZ–BNT ceramics are a good candidate for acoustic applications. [ABSTRACT FROM AUTHOR]

Density functional theory calculations are performed to systematically investigate the electronic and magnetic properties of few-layer and bulk Fe3SiSe2 (FSS). We predict that the bulk FSS has a metallic ground state and a layered structure displaying intralayer ferromagnetic ordering and interlayer antiferromagnetic ordering. The itinerant magnetism in the FSS was determined by the Stoner criterion. Predictions of the absence of unstable phonon modes and a moderate cleavage energy of only 28.3 meV/Å2 suggest the possibility of stabilizing FSS in a monolayer form. The calculated spin–orbit coupling facilitates not only a large magnetocrystalline anisotropy energy, around 500 μeV/Fe, but also spontaneous valley polarization in odd-numbered layer systems. These systems have net magnetic moments as the magnetic moments of AFM-ordered layers are not fully compensated in the odd-numbered layer case and are predicted to show 2D metallic behaviors. The magnitude of the valley polarization in odd-numbered layered systems decreases from 18 meV with layer number but is absent in even-layered structures, thus showing an odd–even oscillation effect. Experimental realization of this bidimensional metallic magnet is, therefore, expected to widen the arena of two-dimensional materials that show exotic phenomena. [ABSTRACT FROM AUTHOR]

Two-dimensional ferromagnetic topological semi-metals have attracted much interest owing to their fascinating spintronic applications. Using first-principles calculations, we propose a stable transition metal nitrogen halide compound, namely, VNI monolayer, to display intrinsic ferromagnetism with high Curie temperature TC (∼510 K) and strong out-of-plane magnetism. It is found to be a topological Weyl nodal line material, which can be fully spin-polarized by controlling the on-site Coulomb interaction. Its nodal line can be destroyed by orienting the magnetization axis. Additionally, biaxial strain enables efficient tuning of the magnetic properties by switching the easy magnetic axis from an out-of-plane to in-plane direction with an enhanced TC to 540 K. These results highlight the great application potential of a VNI monolayer in low-dimensional topological magnets. [ABSTRACT FROM AUTHOR]

Textured process is considered an effective way to enhance the performance of piezoelectric ceramics. To obtain lead-free piezoelectric KNN-based ceramics with high performance, ⟨001⟩c-textured lead-free piezoelectric 0.915(K0.45Na0.5Li0.05)–0.075BaZrO3–0.01Bi0.5Na0.5TiO3 (KNLN–BZ–BNT) ceramics with the addition of 5 mol. % NaNbO3 templates were prepared, and the improved piezoelectric properties and thermal stability were expectedly achieved. For textured ceramics, the textured degree is one of the very important parameters and strongly depends on the amount of templates. Therefore, in this work, the effect of the amount of templates on the textured degree and electrical properties of ⟨001⟩c-textured KNLN–BZ–BNT ceramics were investigated in detail. It was found that the templates take a positive effect when the template amount is low, in which the textured degree and electrical properties increased with the amount of templates. In contrast, excess templates could induce a severe shift of stoichiometry within the textured ceramics, accompanied by degraded performances. As a result, for the ceramics with template amount less than 4 mol. %, enhanced textured degree and electrical properties were obtained. When the template amount exceeds 5 mol. %, the textured degree and electrical properties become degraded. The textured ceramic with the 4 mol. % template shows the highest textured degree of 93% and the highest piezoelectric constants of d33 = 360 pC/N and d 33 ∗ = 615 pm/V. Combining a vertical morphotropic phase boundary with an appropriate template amount of 4 mol. %, the ceramics exhibit superior thermal stability within the temperature range of 30–200 °C. [ABSTRACT FROM AUTHOR]

We present a device that can achieve controlled transport of colloidal microparticles using an array of micro-electrodes. By exciting the micro-electrodes in regular sequence with an AC voltage, a time-varying moving dielectrophoretic force-field is created. This force propels colloidal microparticles along the electrode array. Using this method, we demonstrate bidirectional transport of polystyrene micro-spheres. Electromagnetic simulation of the device is performed, and the dielectrophoretic force profile around the electrode array is mapped. We develop a Brownian dynamics model of the trajectory of a particle under the influence of the time-varying force-field. Numerical and experimental results showing controlled particle transport are presented. The numerical model is found to be in good agreement with experimental data. The developed numerical framework can be useful in designing and modeling lab-on-a-chip devices that employ external non-contact forces for micro-/nanoparticle manipulation. [ABSTRACT FROM AUTHOR]

Bismuth sodium titanate and related compounds are promising lead-free ferroelectric materials potentially useful in a wide range of piezoelectric applications. The domain structure plays an important role in determining the piezoelectric and ferroelectric properties and thereby the performance of electromechanical transducers. In this work, piezoresponse force microscopy (PFM) is used to gain insights into the mesoscopic-scale domain structure and its evolution under electric field in the (1−x)Bi0.5Na0.5TiO3-xBaTiO3 (BNT-BT) piezoceramics with compositions varying from x = 0 to x = 0.08. A phase transition from the rhombohedral phase to the tetragonal phase is observed with increasing BT contents. A relationship is established between the relaxor behavior and the domain structures imaged by PFM, i.e., short-range polar regions without visible domains in relaxor ceramics of pure BNT, while long-range ordered polar states with clear domains in ferroelectric ceramics with the addition of BT content. Distinct micro-domains are observed in the ceramics with compositions close to the morphotropic phase boundary (MPB), but the domain size drops to nanometers in the MPB composition with an increasing domain wall density. An electric field can induce the transformation from the relaxor behavior to a ferroelectric state, accompanied by an increase in domain sizes and a rearrangement/reorientation of the polar domains. This study of domain structure and its evolution in BNT-BT provides a better understanding of the relationship between the crystal structure, mesoscopic-scale domains, and macroscopic properties in these important lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

The heterogeneous epitaxial system of BaTiO3/Ge (BTO/Ge) is of great interest for both fundamental research and device applications, thanks to its quasi-lattice-matching feature and the integration of functional oxides on semiconductors. Currently, the heteroepitaxial growth of crystalline BTO films on Ge includes the utilization of ultrahigh vacuum tools and complex surface passivation pre-treatment as well as careful control of oxygen partial pressure during the growth. Meanwhile, oxygen vacancies in oxides strongly impact their structural and electrical properties. Here, we report a facile method to directly grow single crystalline BTO films on Ge using pulsed laser deposition. The strict control of oxygen partial pressure ensures a sharp interface with an atom-to-atom registry and also leads to the oxygen-deficient characteristics of BTO. The epitaxial relationship of BTO and Ge is [110] BTO (001)//[100] Ge (001). Detailed crystallographic studies on BTO films with different thicknesses show that, for the films with a thickness less than 20 nm, BTO shows a mixture of tetragonal and cubic phases due to the oxygen vacancies and the strain from the Ge substrate and the cubic phase eventually dominates as the film thickness increases. Such oxygen-deficient BTO films reveal conducting characteristics rather than dielectric properties. The oxygen vacancies can be partly "cured" after a low temperature annealing process. These results not only demonstrate the possibility to directly grow single crystalline oxides on semiconductors without surface passivation but also highlight the importance of oxygen vacancies and lattice strain on the crystallographic and electrical properties of BTO films. [ABSTRACT FROM AUTHOR]

Strong coupling between light and matter occurs when the two interact such that new hybrid modes, the so-called polaritons, are formed. Here, we report on the strong coupling of both the electric and the magnetic degrees of freedom to an ultrafast terahertz (THz) frequency electromagnetic wave. In our system, optical phonons in a slab of ferroelectric lithium niobate are strongly coupled to a THz electric field to form phonon-polaritons, which are simultaneously strongly coupled to magnons in an adjacent slab of canted antiferromagnetic erbium orthoferrite via the magnetic-field component of the same THz pulse. We juxtapose experimental results of bare slabs consisting of the two materials with a photonic crystal cavity, consisting of a two-dimensional array of air holes cut into the hybrid slab. In both cases, the strong coupling leads to the formation of new magnon-phonon-polariton modes, which we experimentally observe in the time domain as a normal-mode beating and which corresponds in the frequency domain to an avoided crossing. Our simple yet versatile waveguide platform provides a promising avenue through which to explore ultrafast THz spintronics, quantum electrodynamics, sensing, and spectroscopic applications. [ABSTRACT FROM AUTHOR]

As the reach points of different phases with complex structural features, a morphotropic phase boundary (MPB) in ferroelectric and ferromagnetic solid solutions can significantly enhance the piezoelectric performance and magnetostrictive response, respectively. Recently, the phase-change functional responses related to the multiferroic MPB are proposed to be a promising way to enhance the magnetoelectric coupling in BiFeO3-based single phase multiferroics. In this work, we verify the tunable magnetic ordering and the construction of the multiferroic MPB by engineering the chemical concentrations of the ferroelectric/non-magnetic PbTiO3 end in the (1 – x)Bi0.9Dy0.1FeO3-xPbTiO3 binary solid solution ceramic system. Based on the results obtained in this work and reported in the literature, the structure-ferroic properties phase diagram of the BiFeO3-DyFeO3-PbTiO3 ternary system is established, where a compositional region with coexisting ferroelectric polarization and ferromagnetic moment is found. More importantly, a multiferroic MPB line separating two chemical regions with distinct crystal structures and ferroic orderings is discovered in the phase diagram. The phase changing nature of MPB compositions with temperature and compositions is investigated from room temperature to high temperature paraelectric phase. This work could provide a promising system to explore the highly desired colossal effects on magnetoelectric coupling in single phase multiferroics by phase-change functional responses. [ABSTRACT FROM AUTHOR]

The ever-increasing demand for larger surface area, well-defined, and conformal multi-layer nanostructures in gas sensor, catalyst and solar cell applications has propelled the exploration of such nanostructures within an atomic resolution. The atomic layer deposition (ALD) technique is ideal for the synthesis of these nanostructures due to its excellent step coverage ability on high aspect ratio nanostructures. In this work, different coaxial nanotube networks are successfully fabricated by electrospinning and ALD, with a well-controlled phase. We systematically studied the temperature-induced microstructures and photoluminescence property evolution of the nanotube network. The Al2O3/ZnO/Al2O3 tri-layer nanotube network is obtained by sintering at 400 °C, and a ZnAl2O4 core-shell nanotube structure has formed by the Kirkendall effect by further post-annealing at 700 °C. Oxygen accumulation is clearly observed at the small neck feature, but the Zn and Al elements are uniformly distributed along the whole nanotube. Photoluminescence emission obtained in this work is so broad that it almost covers the whole visible light wavelength range. The results indicate that the microstructures and photoluminescence properties can be well-controlled by the post-annealing temperature. It provides an available platform for realizing conformal 3D nano-devices. [ABSTRACT FROM AUTHOR]

Topological semimetals represent one of the most interesting classes of materials that continue to attract worldwide interest. Here, we report magnetotransport properties of MPn2-type (M=Nb, Ta; Pn=P, As, Sb) NbSb2 single-crystal semimetals with a centrosymmetric C12/m1 space group, paramagnetic ground state, and non-saturation parabolic-like magnetoresistance. The NbSb2 crystals show metallic conductivity down to 2K and undergo a metal-to-insulator-like transition under a magnetic field B (B ≥ 4 T) and exhibit a resistivity plateau in the lowtemperature region (T ≤ 10K), where the value of resistivity strongly depends on the magnitude and direction of the magnetic field. Upon sweeping the magnetic field from 0 to 14.5 T in the transverse configuration at T=1.5K, the NbSb2 crystal shows a large positive magnetoresistance (4.2 x 10³% at B=14.5 T) with Shubnikov-de Haas (SdH) oscillation. Hall measurements reveal that both the carrier compensation between electrons and holes and the high mobility and large mean free path of carriers contribute to the large magnetoresistance. Fast Fourier transform analyses of angle-resolved SdH oscillation indicate that the Fermi surface of the NbSb2 crystal is quasi-two-dimensional with three-dimensional components. These findings, together with the theoretically calculated electronic band structure obtained within the framework of density functional theory, suggest that NbSb2 is a good candidate compensated semimetal for further theoretical and experimental investigation of this family of materials. [ABSTRACT FROM AUTHOR]

The fabrication and properties of BZN thin films prepared by a metalorganic deposition (MOD) process is reported. The structures, morphologies, and dielectric properties of films with two compositions such as(Bi1.5Zn0.5) (Zn0.5 Nb1.5)O7 and Bi2(Zn1/3 Nb2/3)(sub 2)O7, are investigated.

Zn1-xYbxO (0⩽x⩽0.02) thin films have been prepared by inductively coupled plasma enhanced physical vapor deposition method. All the Yb-doped ZnO thin films show room-temperature ferromagnetism. The correlation between oxygen vacancy and magnetism in Yb-doped ZnO thin films is studied. It is found that Yb irons initially substitute for Zn sites when x⩽0.01 and then enter the interstitial sites of ZnO with increasing Yb concentration of x>0.01. The ferromagnetism is induced by the coexistence of oxygen vacancy and Yb point defects. A strong correlation between oxygen vacancy and saturation magnetization is observed. [ABSTRACT FROM AUTHOR]

The structure, dielectric and ferroelectric properties of the bilayered Bi0.9Dy0.1FeO3/K0.5Na0.5NbO3 (BDF/KNN) lead-free thin films deposited on the Pt/TiO2/SiO2/Si substrates by pulsed laser deposition with different thickness ratios have been characterized. It is found that the introduction of the bottom KNN layer can effectively reduce the leakage current of the composite film, allowing the high polarization of the BDF layer to be displayed. The bilayered film with KNN to BDF thickness ratio of 1.2 exhibits the best dielectric and ferroelectric properties, with a remanent polarization 2Pr = 16.3 μC/cm2. The polar domain structure of that film has been imaged by means of piezoresponse force microscopy (PFM) and the switching of the polarization has been realized under an applied electric field of ±12 V, confirming the ferroelectricity in the BDF/KNN composite film. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy is a powerful method for characterizing the electrical properties of materials and their interfaces. In this study we use capacitance measurements to investigate the degradation of electrically aged bottom-emitting organic light-emitting diodes with different polymeric hole injection layers. The devices comprise a heterojunction between a hole transporting triphenyl-diamine and an electron transporting and green emitting aluminum chelate complex [Alq3, tris-(8-hydroxyquinoline) aluminum]. A detailed analysis of the capacitance as function of frequency and dc bias yields information about trapped and interfacial charges as well as the dynamics of injected charges. We find that the loss of luminance and the increase in drive voltage of stressed devices is accompanied by a deterioration of hole injection and the formation of positively charged quenching centers at or close to the organic heterojunction. Using a new polymeric hole injection layer leads to improved device stability. [ABSTRACT FROM AUTHOR]

Bismuth doped SrTiO3 material has shown very interesting phenomena. Dielectric and ferroelectric relaxations have been recently reported in bismuth doped SrTiO3 ceramics in the lower temperature range. Thin films of bismuth doped SrTiO3 [(Sr1-1.5xBix)TiO3] (x=0.0,0.05,0.10) have been prepared by a sol-gel method and investigated in this work. The phases and surface morphologies of thin films were analyzed to assess the structures and crystallization. The structure of the thin films is revealed as a cubic perovskite structure with no other phase detected. The dielectric properties and dielectric tunability of (Sr1-1.5xBix)TiO3 thin films have been studied as a function of doping amount of bismuth and discussed in detail. [ABSTRACT FROM AUTHOR]

PbZr0.52Ti0.48O3 (PZT) thick films are prepared by a polymer-assisted metallo-organic compound decomposition process. The addition of a polymer, poly(vinyl acetate) (PVAc), in PZT precursor solutions promotes the formation of the perovskite phase. Meanwhile, the crack formation is effectively suppressed. The single-layer thickness of PZT films increases from 0.07 to 0.22 μm. It is found that PZT recrystallizes after the PVAc-related organic compounds are decomposed. Nanosized pores are observed in the morphological surfaces of PZT thick films. The crack-free PZT thick films with thickness of 1.3 μm by the repeated deposition exhibit good electrical properties with dielectric constant of 996, dielectric loss around of 3%, remanent polarization of 36.3 μC/cm2, and coercive field of 78.5 kV/cm, which are potential candidates for microelectromechanical system (MEMS) applications. [ABSTRACT FROM AUTHOR]

We have used resonance methods to determine the variation of all the independent piezoelectric, elastic, and dielectric material coefficients, as well as the corresponding electromechanical coupling factors, of soft and hard doped piezoelectric lead zirconate titanate (PZT) ceramics with compositions near the morphotropic phase boundary, as a function of temperature ranging between -165 and 195 °C. The material coefficients were obtained by analyzing the fundamental resonance of the impedance or admittance spectra as a function of frequency for several sample resonance geometries. The piezoelectric coefficients d33, -d31, and d15, as well as the dielectric permittivity coefficients [variant_greek_epsilon]11T and [variant_greek_epsilon]33T, generally increased with temperature for both soft and hard PZT samples. However, the elastic compliance coefficients s11E, -s12E, s33E, and s55E exhibited abnormal variations seen as broad peaks over parts of the tested temperature range. Additionally, thermal hystereses were observed in all the studied material coefficients over the temperature cycle. Finally, it was noted that, overall, the material coefficients of soft PZT varied significantly more than those of hard PZT under changing temperature conditions. [ABSTRACT FROM AUTHOR]

A simple physical picture, useful for extended applications of a well-demonstrated phenomenological polarization model [J. C. Piquette and S. E. Forsythe, J. Acoust. Soc. Am. 101, 289 (1997)] is presented. The Weiss model of interacting dipoles (orginally suggested by Weiss for magnetic dipoles but applied here to electric dipoles) is generalized for high field levels. The generalization permits the model to describe the polarization measurements well, across a significant temperature range extending well below T[sub max], for applied electric field levels as high as 1.35 MV/m. The measurements reported here were acquired from various polycrystalline samples of lead magnesium niobate (PMN) in a solid solution with lead titanate (PT) doped with lanthanum (La), having T[sub max] values ranging from -11 to +41 °C. Agreement between theory and data is good. (The overall rms error of fit is less than 0.5% in all cases considered.) The new model, when combined with a suitable model of hysteresis, is useful for describing and controlling the behavior of PMN, which is a material that is useful in actuator and transducer applications where a relatively large strain is desired. The theory, in its present form, does not account for relaxor (frequency-dependent) aspects of the material behavior, and is applied here only to data acquired quasistatically. Moreover, only the case in which no external stress is applied to the material is considered. [ABSTRACT FROM AUTHOR]

The molecular-based magnetic materials AFeIIFeIII(C2O4)3 have a honeycomb structure in which FeII(S=2) and FeIII(S=5/2) occupy sites alternately, which is described by mixed spin-2 and spin-5/2 Ising model with ferrimagnetic interlayer coupling. Within the effective-field theory with self-spin correlations, the effects of the biaxial crystal field on the magnetization, initial susceptibility, and internal energy of this molecular-based system have been studied numerically [ABSTRACT FROM AUTHOR]

Presents a study which examined the geometrical optics analysis of electromagnetic-missile backscattering. Background on the concept of electromagnetic missile; Significance of the missile; Advantage of a property of slow energy; Analysis of the electromagnetic missile backscattering.

Highly [001] oriented lead-free (K0.48Na0.52)NbO3 thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition. The microstructure and electrical properties of the thin films are a strong function of deposition temperature. Highly preferentially [001] oriented thin films were obtained at the deposition temperature of 740 °C. The film exhibits a dielectric constant of 422 and a dielectric loss of 0.058 at 1 kHz. The P-E hysteresis loop shows that the film possesses a large remnant polarization of 11 μC/cm2 and a moderate coercive field of 72 kV/cm. The Ohmic conduction is dominant at the low field for the films except the film deposited at 680 °C. However, the Poole-Frenkel conduction mechanism is dominant at the high field for the films except the film deposited at 700 °C. [ABSTRACT FROM AUTHOR]

We report the Ti-doping effects on the total magnetization of perovskite SmFe1-xTixO3 samples with x = 0, 0.1, 0.2, and 0.3. X-ray diffraction and Raman spectroscopy studies indicate that with the increase of Ti doping concentration, the lattice parameter b decreases and the oxygen octahedron is compressed along b axis. Such lattice distortion is also reflected by the changes of antisymmetric stretching mode and symmetric stretching mode of the oxygen octahedron through Raman spectra measurement. An enhancement of the interaction between Sm-4f and Fe-3d electrons is observed due to Ti-doping. This strong interplay between Sm-4f and Fe-3d electrons weakens the total magnetization and considerably suppresses the weak ferromagnetism of Fe sublattice starting from 260 K. [ABSTRACT FROM AUTHOR]

Mn doped PbZr0.52Ti0.48O3 (PZT) thick films with highly (100) preferential orientation have been prepared by chemical solution deposition according to doping concentration of 0, 0.5, 1, 2, and 3 mol. %. The effect of Mn-doping on structures and electrical properties of PZT thick films has been investigated. With increasing Mn doping concentration, the dielectric constant first increases and then decreases. PZT film with 0.5 mol. % Mn doping has a maximum value of 2252 and a dielectric loss of 0.011 at 1 kHz. Mn doping below 3 mol. % could effectively reduce the leakage current density of PZT films. The mechanism of Mn doping on dielectric and ferroelectric properties of PZT thick films has been investigated and discussed. [ABSTRACT FROM AUTHOR]