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In this work, we present an atomic-scale investigation of L10-FePt particles that are partly or fully embedded in a single-crystalline MgO matrix. Hundreds of particles in different orientations, of different sizes, and with different side contact facets are statistically and quantitatively analyzed. It is found that the presence of side contact facets does not introduce any misorientation in particles with the c axis out-of-plane (OP), even in those of small sizes. In addition, a markedly higher proportion of in-plane (IP) variants is found in smaller particles of sizes less than 10 nm, and most IP variants and the IP part in multi-variants have a large area of side contact facets or are even fully embedded. Those results can be explained by the fact that the transformation strain and interface strain jointly affect the particle orientation, and the competition between total strain energy in the film plane and in lateral planes plays a key role in determining particle orientation. Thus, a suggestion on the L10-FePt nanoparticle film production can be proposed that a moderate area of side contact facets may help keep a perfect OP orientation in the OP particles without increasing the proportion of IP variants. Additionally, our work can provide reference information on the variant orientation preference during a post-annealing process in nanoparticle films on a rough substrate or embedded in a matrix as well as in core–shell material systems. [ABSTRACT FROM AUTHOR]

Modulated reflectance (contactless electroreflectance (CER), photoreflectance (PR), and piezoreflectance (PzR)) has been applied to study direct optical transitions in bulk MoS2, MoSe2, WS2, and WSe2. In order to interpret optical transitions observed in CER, PR, and PzR spectra, the electronic band structure for the four crystals has been calculated from the first principles within the density functional theory for various points of Brillouin zone including K and H points. It is clearly shown that the electronic band structure at H point of Brillouin zone is very symmetric and similar to the electronic band structure at K point, and therefore, direct optical transitions at H point should be expected in modulated reflectance spectra besides the direct optical transitions at the K point of Brillouin zone. This prediction is confirmed by experimental studies of the electronic band structure of MoS2, MoSe2, WS2, and WSe2 crystals by CER, PR, and PzR spectroscopy, i.e., techniques which are very sensitive to critical points of Brillouin zone. For the four crystals besides the A transition at K point, an AH transition at H point has been observed in CER, PR, and PzR spectra a few tens of meV above the A transition. The spectral difference between A and AH transition has been found to be in a very good agreement with theoretical predictions. The second transition at the H point of Brillouin zone (BH transition) overlaps spectrally with the B transition at K point because of small energy differences in the valence (conduction) band positions at H and K points. Therefore, an extra resonance which could be related to the BH transition is not resolved in modulated reflectance spectra at room temperature for the four crystals. [ABSTRACT FROM AUTHOR]

The Wigner formalism was used to study electron transport in the resonant-tunneling diode under the effects of an in-plane magnetic field. The transport equation is derived from the Wigner distribution function. A solution is derived for the function from which the charge distribution and tunnel current are calculated. The magnetic effects of electron tunneling are also presented.

Solid C60/n-GaN heterojunctions were formed and their electrical characteristics were determined. It was observed that the heterojunction is a strongly rectifying contact with a rectification ratio greater than 1,000,000 and with and ideality factor close to 1. The current-temperature measurement revealed an exponential decrease in current with increasing reciprocal temperature, from which the effective barrier height was computed to be 0.535 eV.

High quality Zn0.92Cd0.08O/ZnO multiple quantum wells with smooth interfaces have been prepared on c-plane sapphire substrates by pulsed laser deposition. The periodic structure has been characterized by scanning transmission electron microscope and energy dispersive x-ray spectroscopy line scans. The temperature dependent photoluminescence of Zn0.92Cd0.08O/ZnO exhibits an inconspicuous S-shaped property due to a combined effect of the slightly disordered ZnCdO alloy. We can observe both quantum confinement effects and quantum-confinement Stark effect in the quantum wells. We can modulate the well emission energy from 2.90 to 3.085 eV by varying the well thickness at room temperature. [ABSTRACT FROM AUTHOR]

A change in the dimensionality of an energy band in a semiconductor is done by reducing the dimension of its physical size. Here, we show that by spatially deforming a two-layer heterostructure into a wrinkled pattern, the minimum of the energy profile transforms from a two-dimensional plane at the hetero-interface into a one-dimensional path that lies along the wrinkled edge. This change alters the carrier path, causing the carriers to travel along a one-dimensional sinusoidal path, which may lead to an application. The present investigation shows that the dimensionality of the energy profile can be engineered by changing the morphology of the epilayers and provides insight into possible applications of the wrinkled pattern. [ABSTRACT FROM AUTHOR]

Single crystals of Bi2-xPbxSr2Co2Oy (0 ≤ x ≤ 0.55) have been grown using optical floating-zone method. The chemical compositions were determined using combined electron probe microanalysis and iodometric titration. Physical properties including electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) were measured using single crystal specimens. Successful hole doping through Pb substitution is confirmed through combined iodometry titration, electrical transport, and Seebeck coefficient measurements. Significant reduction on both in-plane resistivity and thermal conductivity was found as a result of Pb substitution to the Bi site. The thermoelectric figure-of-merit ZT for x ∼ 0.55 is raised 20 folds from the undoped sample at room temperature. [ABSTRACT FROM AUTHOR]

In situ high-resolution synchrotron x-ray diffraction reveals a local minimum in rhombohedral distortion angle αR (associated with an inflection in the lattice constant aR) near 400 and 350 °C in BiFeO3 (BFO) and (BiFeO3)0.95(BaTiO3)0.05 (BFO-5%BT), respectively. It suggests a coupling between ferroelectric and magnetic parameters near the antiferromagnetic-paramagnetic transition, which is responsible for the broad frequency-dependent dielectric maxima. A rhombohedral (R)-orthorhombic (O)-cubic (C) transition sequence takes place near 820 and 850 °C in BFO upon heating. BFO-5%BT exhibits a R-C transition near 830 °C. The BaTiO3 substitution can enhance dielectric and ferromagnetic responses and reduce electric leakage. The dielectric loss of BFO-5%BT remains less than 0.04 below 150 °C. [ABSTRACT FROM AUTHOR]

The magnetism-induced ferroelectricity in the E-type orthorhombic HoMnO3 (o-HMO) films grown on Nb-doped and undoped SrTiO3(001) substrates was studied. The temperature dependent magnetization in these films evidently exhibits an antiferromagnetic ordering around 44 K and an anomalous second magnetic ordering along the c-axis near 35 K. Interestingly, at this anomalous transition temperature, an associated ferroelectric polarization was probed by the P-E hysteresis measurements, indicating the intimated coupling between the ferroelectric response and the reordering of Mn spins, which has never been disclosed previously by dielectric constant measurements. [ABSTRACT FROM AUTHOR]

In this work, we use ultrafast optical pump-optical probe spectroscopy to probe the polaron dynamics in La0.7Ca0.3MnO3 (LCMO) thin films. The temporal evolution in transient reflectivity change ΔR/R exhibits two relaxing components: a fast component with a time constant of subpicosecond and a slow component with time constant ranging from tens of picoseconds to hundreds of picoseconds. The amplitude of the fast component, though has been seldom discussed before, exhibits the similar temperature dependence with that of the resistivity and the neutron scattering intensity due to nanoscale correlated polarons. The results strongly suggest that the fast photoinduced reflectivity change may have been due to the photoexcitation and trapping process of correlated Jahn–Teller polarons in the paramagnetic and ferromagnetic phases and, thus, implies the presence of electronic inhomogeneity in LCMO manganites. [ABSTRACT FROM AUTHOR]

Both La0.375Pr0.25Ca0.375MnO3 (LPCMO) and La0.625Ca0.375MnO3 (LCMO) were found to exhibit coexistence of competing orders (phase separation) over a wide temperature range. However, substantial hysteretic behaviors in both of the temperature-dependent resistance [R(T)] and magnetization [M(T)] [also known as the persistent magnetic memory effect (PMME)] are only displayed in LPCMO. The results indicate that, in LPCMO, the size distribution of the coexisting charge-ordered insulating and metallic ferromagnetic (FM) phases plays a determinant role in the PMME effects in different temperature regimes. Moreover, due to the direct competition between the two coexisting phases, the system is most susceptible to the external applied field in the hysteretic temperature region. On the other hand, in LCMO, the phase transition between paramagnetic and FM is more like an isomorphic transition in pure materials, and thus does not show significant hysteresis. [ABSTRACT FROM AUTHOR]

Orthorhombic YMnO3 thin films with (200), (020), and (001) orientations were, respectively, obtained by pulsed laser deposition on SrTiO3(110), LaAlO3(110), and SrTiO3(001) substrates. The results demonstrate that the strain between film and substrate can serve as an alternative in transforming the thermodynamically stable hexagonal YMnO3 into the orthorhombic phase, which previously could be obtained with high-pressure high temperature syntheses and epitaxy-stabilized thin film processes. More importantly, these films allow us, for the first time, to unambiguously disclose the intrinsic magnetic property along different crystallographic orientations. Our results show that, although the antiferromagnetic (AFM) ordering remains the same, there is an additional spin reordering transition which is very much dependent on the crystallographic orientation along which the measuring field was applied and on the in-plane crystallographic alignment of the films. Detailed analyses indicate that the origin of the observed second reordering may be due to some strain-induced canted AFM state instead of the incommensurate lock-in transitions conceived previously. [ABSTRACT FROM AUTHOR]

Two different types of nonlinear current-voltage characteristics are observed in oxygen-deficient La0.67Ca0.33MnO3-y (LCMO) films at temperatures below the insulator-metal transition. The paraboliclike dynamic conductance G(V), defined as dI/dV, curves near the zero bias observed in highly oxygen-deficient LCMO films implies the contribution from the spin-dependent tunneling transport between ferromagnetic clusters, with magnetic-disordered regions serving as tunneling barriers. On the other hand, for the slightly oxygen-deficient LCMO films, dips around the zero bias were observed in nonlinear G(V) curves and have been attributed to spin-flip scattering, with oxygen vacancies serving as scattering centers. [ABSTRACT FROM AUTHOR]

A two-step treatment by argon (Ar) and hydrogen plasma beam scanning was developed to modify the surface bonds of a hydrogenated amorphous carbon (a-C:H) film on indium tin oxide glass. The modified a-C:H film is an excellent layer for liquid crystal alignment, on which the pretilt angle of a nematic liquid crystal (ZLI-2293) can be adjusted by the two-step scanning treatment. The chemical bonding characteristics of the as-scanned a-C:H films were measured using micro-Raman and x-ray photoemission spectroscopies. The antiparallel cells were filled with the nematic liquid crystal on the as-scanned a-C:H film to measure the pretilt angle. Experimental results indicate that the carbon dangling bonds are generated through a bond-breaking process during the Ar plasma beam scanning step (first step). The hydrogen plasma beam scanning step (second step) can passivate some of the carbon dangling bonds that are generated in the first step. The pretilt angle decreases as the hydrogen plasma beam scanning time increases. The decrease of pretilt angle is due to the formation of C–H bonds that passivate the a-C:H film and limit the formation of C–O bonds in air. [ABSTRACT FROM AUTHOR]

The angular dependence of magnetoresistance (MR) of the La0.7Ca0.3MnO3 thin film biepitaxial step junction (BSJ) shows a simple sin2(θ) dependence in the in-plane high-field magnetoresistance, with θ being the angle between the applied field and current. This behavior is similar to the spin-orbit coupling-induced anisotropic magnetoresistance (AMR) commonly observed in transition ferromagnetic metals, except for two salient features. First, the maximum MR in the present case occurs at an oblique angle between the applied field (H) and electric current (I), while it is usually observed to occur when H∥I. Second, the AMR in the plane perpendicular to the film surface displays a remarkable value (Δρ/ρ∼8%), which is about an order of magnitude larger than that of the in-plane AMR. Such a large AMR cannot be solely explained by spin-orbit coupling effect. We suggest instead that the metallic and ferromagnetic inhomogeneous granules existing in the BSJ region might have acted as the source of spin-polarized scattering giving rise to the enhanced AMR when the colossal magnetoresistance was measured across the biepitaxial step boundaries. [ABSTRACT FROM AUTHOR]

A plasma beam scanning treatment has been developed to modify the surface of the hydrogenated amorphous carbon (a-C:H) film on the indium tin oxide glass. The plasma beam scanning treatment makes the a-C:H film an excellent layer for liquid-crystal alignment. The qualities of a-C:H films were characterized by using atomic force microscope, micro-Raman spectroscopy, and field-emission scanning electron microscope. The ultrathin a-C:H films were deposited at 50% CH4/(H2+CH4) gas ratio, 100 W radio-frequency power, and a gas pressure of 10 mtorr for 15 min by capacitive-coupled plasma chemical-vapor deposition method. The twist nematic cells were filled with liquid crystal (ZLI-2293) on the a-C:H film treated with different nitrogen plasma beam scanning time. The grooving mechanism is considered not responsible for the liquid-crystal (LC) alignment. Raman spectra suggest that a bond-breaking process of aromatic rings occurs in the a-C:H film. The O1s, C1s, and N1s core-level spectra support that the nitrogen plasma beam scanning treatment induces a bond-breaking process of aromatic rings to create available carbon dangling bonds for the formation of C–O bonds. The newly formed C–O bonds are “directional,” which favor the LC alignment on the a-C:H film. [ABSTRACT FROM AUTHOR]

A general, quantitative relationship between the photon-transport mean free path (l*) and resin sensitivity (DP) in multiple-scattering alumina/monomer suspensions formulated for ceramic stereolithography is presented and experimentally demonstrated. A Mie-theory-based computational method with structure factor contributions to determine l* was developed. Planar-source diffuse transmittance experiments were performed on monodisperse and bimodal polystyrene/water and alumina/monomer systems to validate this computational tool. The experimental data support the application of this l* calculation method to concentrated suspensions composed of nonaggregating particles of moderately aspherical shape and log-normal size distribution. The values of DP are shown to be approximately five times that of l* in the tested ceramic stereolithography suspensions. [ABSTRACT FROM AUTHOR]

Single-phase electron-doped manganite thin films with nominal composition of La0.7Ce0.3MnO3 (LCeMO) have been prepared on SrTiO3 (100) substrates by pulsed laser deposition. The conditions for obtaining purely single-phase LCeMO films lie within a very narrow window of substrate temperature (Ts∼720 °C) and laser energy density (ED∼2 J/cm2) during deposition. In situ postdeposition annealing, mainly to relax the possible epitaxial in-plane tensile strain between the film and the substrate, leads to an increasing c-axis lattice constant accompanied by the formation of secondary CeO2 phase and higher metal-insulator transition temperature. This is indicative of a strong coupling between the electron and lattice degree of freedom. [ABSTRACT FROM AUTHOR]

Unoccupied states of the (110) YBa[sub 2]Cu[sub 3]O[sub 6.9] (YBCO) thin films were investigated by the Eab and Ec polarized O 1 s x-ray absorption near edge structure (XANES) spectroscopy. With correction of the self-absorption effect, the Eab O 1 s XANES spectra of the (110) YBCO films obtained from the normal incidence geometry and grazing incidence geometry are very similar. After the self-absorption correction, the Ec spectrum of the (110) YBCO film obtained from the normal incidence geometry is almost identical to that of the (001) YBCO film obtained from the grazing incidence geometry. Hole distribution over the different oxygen sites has been derived. The hole number in the apical sites in some thin films obtained in the present investigation is larger than that from the previous x-ray absorption studies of single crystals and from the theoretical calculations. The comparison of the XANES spectra between the (001) and (110) YBCO thin films is also presented. [ABSTRACT FROM AUTHOR]

Single phase TiO[sub 2] thin films, of either rutile or anatase structure, have been prepared on SrTiO[sub 3](STO)(100) substrates by in situ pulsed laser deposition (PLD). Thermodynamically unfavorable, for films deposited on STO(100) substrate directly, pure anatase TiO[sub 2](001) films were formed even when a rutile TiO[sub 2] (110) substrate was used as a target. On the other hand, pure rutile TiO[sub 2](110) films were obtained by oxidizing PLD TiN films in-situ at temperatures higher than 700 °C. The optimized deposition conditions for preparing TiN and TiO[sub 2] films were reported. The crystalline structure, surface morphology, and electronic structure of these films were examined. A mechanism of the process of film formation is also proposed. [ABSTRACT FROM AUTHOR]

Polarization dependent x- ray absorption near- edge spectra (XANES) of the O 1s was measured on a highly in- plane aligned a- axis YBa2Cu3O7-delta (YBCO) thin film. The results lend strong support to those obtained by using detwinned YBCO single crystals in all crystalline orientations.

Presents information on a study which considered front formation and steady-state front motion in a one-dimensional polymer system undergoing case-II diffusion. Analysis of the problem with a steady-state moving front; Results of the study; Conclusions.

Presents information on a study which considered the swelling of a polymer glass by sorption of a small molecule penetrant in a regime characterized by so-called case-II diffusion. Methodology of the study; Results and discussion.

Deals with a study which investigated submicron indium phosphide transferred electron devices. Method used to model the direct current characteristics of near-micron structures; Background on the physical origins of the length effect in submicron structures; Description of the static characteristics of transferred electron devices.

NiFe inserted layer with different thicknesses on the dielectric properties of multiferroic AlN/NiFe/AlN multilayer films fabricated on the B270 glass substrates by the reactive sputtering technique was studied. The variation of dielectric constant for multilayer films is dependent on the thickness of the NiFe inserted layer observed from 40 Hz to 30 MHz. In this work, single AlN layer exhibits dielectric constant value of around 6.5. However, we find that the dielectric constant of the AlN/NiFe/AlN multilayer films is raised up to 60 for even with a 1 nm thick NiFe inserted layer. Additionally, this work also indicates that the dielectric tunability of AlN/NiFe/AlN films is dependent on the external magnetic field. These results conclude some magnetoelectric properties of AlN films those in relation to the NiFe ferromagnetic inserted layer. Possible mechanisms for the enhanced dielectric constant in the AlN/NiFe/AlN films have been discussed in the paper. [ABSTRACT FROM AUTHOR]

The dichotomy of photoinduced quasiparticle dynamics in the anisotropic high Tc superconductors (YBa2Cu3O7) is revealed by using the orientation-resolved femtosecond reflection spectroscopy in the specially designed thin films. The transient reflectivity ΔR/R along the ab diagonal and b axis are totally different in the slow relaxation process which relates to the opening of the superconducting gap. In addition, the distribution of the temperature evolution of ΔR/R on the CuO2 planes of YBa2Cu3O7 may indicate the d-wave symmetry of the superconducting gap in high Tc superconductors. [ABSTRACT FROM AUTHOR]

With the rapid development of automation techniques, the claw-poled stepping motors are widely used, especially in optical scanners. Most research on stepping motors has concentrated on electrical properties, but a few papers have reported on the performance in relation to the magnetic-field distribution. The purpose of this study is to analyze the effect of the shape of the stator tooth and to search for the optimal parameters using a magnetic-circuit simulation technique. Through numerical calculations, the optimal performance conditions can be obtained by varying the ratio between the two bases of the trapezoid teeth between 1/5 and 1/3, and varying the ratio between the heights of individual teeth in relation to the separation between the two yokes from 11/15 to 13/15. [ABSTRACT FROM AUTHOR]

Magnetization reversal phenomena in submicron half-ring patterned wires with different corner structures have been investigated. The wires with corner structures of rectangular, semicircle, and triangular shapes were connected in series by two or five half-rings. The variation of domain structures with magnetic field is illustrated by electron transport measurements, simulation, and magnetic force microscopy (MFM) images. The switching behavior depends on the corner structures connecting the half-ring structures. These results are consistent with the domain pattern and magnetic phase shift observation provided by the MFM measurements. [ABSTRACT FROM AUTHOR]

Domain wall pinning force in the junctions (corners), with different shapes of square, semicircle, or triangle, of half-ring in-series wires is considered to study the current injection induced wall movements. This geometry has less thermal activation at the region of domain wall nucleation in contrast to notch structures. The wires with square corners have the largest domain pinning force to resist polarized current-induced magnetization reversal, judging from the largest slope in the current-field dependence (ΔI/ΔH=0.274). [ABSTRACT FROM AUTHOR]

Polarization-dependent x-ray absorption near-edge spectra (XANES) of the O 1s has been measured on a highly in-plane aligned a-axis YBa[sub 2]Cu[sub 3]O[sub 7-δ] (YBCO) thin film. The in-plane XANES, with the electric field E of the linearly polarized synchrotron light being parallel to the b or c axis of YBCO films (E//b or E//c) were obtained in a normal-incidence alignment. The XANES for E//a was then calculated from the data obtained by varying the angle. The results lend strong support to those obtained by using detwinned YBCO single crystals in all crystalline orientations, including the extrapolated c-axis spectra. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The macro-size magnetic colloidal particles in both distilled water and oleic acid were prepared by using Fe[sub 3]O[sub 4] ferrofluids (SMG018), the sodium dodecyl sulfate (SDS), and distilled water or oleic acid. The optical transmission of these ferrofluid emulsions has been investigated as functions of concentration of SDS between 0.64 and 3.73 wt %, incident optical wavelengths between 450 and 750 nm, and applied magnetic fields up to 141 Oe. The optical transmission shows maximum with concentration of SDS near 3.13 and 1.90 wt % for samples in distilled water and oleic acid, respectively. In general, under an applied magnetic field, the size of the magnetic colloidal particles for samples in oleic acid is smaller than that of samples in distilled water; however, the concentration of the magnetic colloidal particles is the opposite. This can be explained due to the different aggregation ability of the magnetic colloidal particles in both distilled water and oleic acid. The optical transmission of the samples is observed to be reversed proportional to the area covered by the magnetic colloidal particles. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which examined the optical, electrical and magnetic properties of neodymium iron boron films. Experimental methods; Observations of the oscillatory behavior with thickness of the films; Anomalous behaviors near the Curie temperature.

Provides information on a study which examined rare-earth element erbium, which was deposited onto (100) oriented Zn-doped p-type InP to form Schottky barriers. Material attractive for high-speed optoelectronic and high power microwave devices; Prerequisite essential for the development of advanced devices; Measurements in the I-V-T method; Technique used for measuring the reverse bias capacitance-voltage characteristics.

Presents a study on the influence of crystal structure on the magnetoresistance of cobalt (Co)/chromium (Cr) multilayers. Characteristics of epitaxial Co/Cr multilayers; Definition of the giant magnetoresistance in multilayers; Effects due to the spin dependent scattering at the interfacial regions of the superlattice.