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The understanding of a coercivity mechanism in high performance Nd–Fe–B permanent magnets relies on the analysis of magnetic properties of all phases present in magnets. By adding Cu in such compounds, a new Nd6Fe13Cu grain boundary phase is formed; however, the magnetic properties of this phase and its role in the magnetic decoupling of matrix Nd2Fe14B grains are still insufficiently studied. In this work, we have grown Nd6Fe13Cu single crystals by the reactive flux method and studied their magnetic properties in detail. It is observed that below the Néel temperature (TN = 410 K), Nd6Fe13Cu is antiferromagnetic in zero magnetic field; whereas when a magnetic field is applied along the a-axis, a spin-flop transition occurs at approximately 6 T, indicating a strong competition between antiferromagnetic and ferromagnetic interactions in two Nd layers below and above the Cu layers. Our atomistic spin dynamics simulation confirms that an increase in the temperature and/or magnetic field can significantly change the antiferromagnetic coupling between the two Nd layers below and above the Cu layers, which, in turn, is the reason for the observed spin-flop transition. These results suggest that the role of an antiferromagnetic Nd6Fe13Cu grain boundary phase in the coercivity enhancement of Nd–Fe–B–Cu magnets is more complex than previously thought, mainly due to the competition between its antiferro- and ferromagnetic exchange interactions. [ABSTRACT FROM AUTHOR]

We have systematically studied magnetotransport properties in van der Waals (vdW) magnetic materials, (Fe1−xCox)5GeTe2, where the magnetic phase changes from the ferromagnetic with the perpendicular magnetic anisotropy (PMA; x = 0 , 0.05) or with the in-plane magnetic anisotropy (IMA; x = 0.19) to the antiferromagnetic (x = 0.46) with the PMA. We have demonstrated that such magnetic properties seen in bulk still remain even in thin film devices. An anomalous Hall resistance with magnetic hysteresis was clearly observed in the low Co substitution (x = 0 , 0.05). The anomalous Hall effect was still observable for x = 0.19, but the magnetic hysteresis vanishes because of the IMA. In the antiferromagnetic region, there was no anomalous Hall effect in the low magnetic field range, but a clear hysteresis was observed at 2.5 T where the spin–flop transition takes place. This hysteresis can be seen only below 30 K and monotonically decreases with increasing temperature. We argue that the defects at a specific site in this system and also the resistance upturn below 30 K could be related to the hysteric behavior at the spin–flop transition. Our findings provide a recipe for the use of (Fe1−xCox)5GeTe2 with different Co substitutions to construct vdW magnetic devices. [ABSTRACT FROM AUTHOR]

We have systematically studied magnetotransport properties in van der Waals (vdW) magnetic materials, (Fe1−xCox)5GeTe2, where the magnetic phase changes from the ferromagnetic with the perpendicular magnetic anisotropy (PMA; x = 0 , 0.05) or with the in-plane magnetic anisotropy (IMA; x = 0.19) to the antiferromagnetic (x = 0.46) with the PMA. We have demonstrated that such magnetic properties seen in bulk still remain even in thin film devices. An anomalous Hall resistance with magnetic hysteresis was clearly observed in the low Co substitution (x = 0 , 0.05). The anomalous Hall effect was still observable for x = 0.19, but the magnetic hysteresis vanishes because of the IMA. In the antiferromagnetic region, there was no anomalous Hall effect in the low magnetic field range, but a clear hysteresis was observed at 2.5 T where the spin–flop transition takes place. This hysteresis can be seen only below 30 K and monotonically decreases with increasing temperature. We argue that the defects at a specific site in this system and also the resistance upturn below 30 K could be related to the hysteric behavior at the spin–flop transition. Our findings provide a recipe for the use of (Fe1−xCox)5GeTe2 with different Co substitutions to construct vdW magnetic devices. [ABSTRACT FROM AUTHOR]

Interlayer antiferromagnetic coupling rare-earth/transition-metal bilayer ferrimagnet systems have attracted much attention because they present different unusual temperature- and field-dependent nontrivial magnetic states and dynamics. These properties and the implementation of their applications in spintronics highly depend on the significant temperature dependence of the magnetic exchange stiffness constant A. Here, we quantitatively determine the temperature dependence of magnetic exchange stiffness A P y − G d and AGd in the artificially layered ferrimagnet consisting of a Py/Gd bilayer, using a measurement of anisotropic magnetoresistance of the bilayer thin film at different temperatures and magnetic fields. The obtained temperature dependencies of A P y − G d and AGd exhibit a scaling power law with the magnetization of Gd. The critical field of spin–flop transition and its temperature dependence can also be directly obtained by this method. Additionally, the experimental results are well reproduced by micromagnetic simulations with the obtained parameters A P y − G d and AGd, which further confirms the reliability of this easily accessible technique. [ABSTRACT FROM AUTHOR]

We consider the sixteen vertex model, and we describe, phenomenologically, the main features of the square ice magnetic structure factor. Using Monte Carlo simulations, we show that in the high-temperature regime, the magnetic structure factor of the square ice can be seen as the superposition of two distinct magnetic structure factors associated with two other models. In particular, we provide empirical arguments to explain why intensity is present in some regions of reciprocal space and absent in other locations. We also tentatively explain why the so-called pinch points, evidencing the algebraic nature of the spin-spin correlations once the system is brought into its ground state manifold, appear for certain wavevectors only. [ABSTRACT FROM AUTHOR]

We demonstrate that the angular momentum compensation temperature TA, at which the net angular momentum in the sample disappears, can be controlled in Ho3Fe5O12 by partially substituting Dy for Ho. TA can be detected using the Barnett effect, by which mechanical rotation magnetizes an object due to spin-rotation coupling. We found that TA increases with the Dy content and clarified that TA of Ho1.5Dy1.5Fe5O12 coincides with room temperature. The Barnett effect enables us to explore materials applicable to magnetic devices utilizing the angular momentum compensation only by rotating the powder sample at room temperature. [ABSTRACT FROM AUTHOR]

Pronounced room temperature vertical shifts in the magnetic hysteresis loops of granular, highly polycrystalline and ferromagnetic-like BiFeO3 thin films are observed upon field-cooling from a temperature above the Néel temperature of bulk BiFeO3. This is ascribed to the interplay between the preferential alignment, established by the field-cooling process, of the net magnetic moment, which arises from uncompensated antiferromagnetic spins, and the pinning of a fraction of these spins at the particle boundaries. Conversely, field-cooling of an epitaxially grown BiFeO3 film results in no vertical shift, confirming the effective role played by the particle boundaries (i.e., morphology) of the granular-like BiFeO3 films in the process of spin frustration. [ABSTRACT FROM AUTHOR]

We investigate control of plasmonic-photonic coupling in flat metallic nanoantenna arrays. We demonstrate that when the nanoantennas are packed together along their short axis (transverse lattice constant) and the incident light polarization is along their long axis, they can support lattice-induced plasmonic resonance coupled to a super-photonic mode that densely fills the superstrate volume. Our results show that at a certain wavelength, this resonance joins the plasmonic tip modes of the nanoantennas, forming meta-dipole modes. These modes have field profiles similar to those of the natural plasmonic dipole modes of individual nanoantennas, but they occur at much shorter wavelengths and offer a very high bulk refractive index sensitivity (925 ± 12 nm/RIU). We show that with an increase in the transverse lattice constant, such a sensitivity decreases as the meta-dipole modes disappear. Under this condition, the refractive index sensitivity supported by natural modes of the nanoantennas increases, as the plasmonic edge mode suppression caused by charge rearrangement decreases. [ABSTRACT FROM AUTHOR]

Spin-laser structures such as spin-polarized vertical-cavity surface-emitting lasers are semiconductor devices in which the radiative recombination processes involving spin-polarized carriers result in an emission of circularly polarized photons. Nevertheless, additional linear in-plane anisotropies in the cavity, e.g., interfacial and surface anisotropies, generally lead to preferential linearly polarized laser emission and to possible coupling between modes. We present Mueller matrix ellipsometric study of non-intentionally doped InGaAs/GaAsP laser structures devoted for optical pumping operations in the spectral range from 0.73 to 6.4 eV in order to disentangle surface and quantum wells contributions to the linear optical birefringence of the structures. The measurement of full 4 × 4 Mueller matrix for multiple angles of incidence and in-plane azimuthal angles in combination with proper parametrization of optical functions has been used for extraction of optical permittivity tensor components along [110] and [110] crystal axis of surface strained layers and quantum wells grown on [001]-substrate. Such spectral dependence of optical tensor elements is crucial for modeling of spin-laser eigenmodes, resonance conditions, and also for understanding of sources of structure anisotropies. [ABSTRACT FROM AUTHOR]

The development of spintronics and spin-caloritronics devices needs efficient generation, detection, and manipulation of spin current. The thermal spin current from the spin-Seebeck effect has been reported to be more energy efficient than the electrical spin injection methods. However, spin detection has been the one of the bottlenecks since metals with large spin-orbit coupling is an essential requirement. In this work, we report an efficient thermal generation and interfacial detection of spin current. We measured a spin-Seebeck effect in Ni80Fe20/p-Si (25 nm)/p-Si (50 nm) (polycrystalline) bilayers without a heavy metal spin detector. p-Si, having a centrosymmetric crystal structure, has insignificant intrinsic spin-orbit coupling, leading to negligible spin-charge conversion. We report a giant inverse spin-Hall effect, essential for the detection of spin-Seebeck effects, in the Ni80Fe20/p-Si bilayer structure, which originates from Rashba spin orbit coupling due to structure inversion asymmetry at the interface. In addition, the thermal spin pumping in p-Si leads to spin current from p-Si to the Ni80Fe20 layer due to the thermal spin galvanic effect and the spin-Hall effect, causing spinorbit torques. The thermal spin-orbit torques lead to collapse of magnetic hysteresis of the 25nm thick Ni80Fe20 layer. The thermal spin-orbit torques can be used for efficient magnetic switching for memory applications. These scientific breakthroughs may give impetus to the silicon spintronics and spin-caloritronics devices. [ABSTRACT FROM AUTHOR]

Manipulating operation states of coupled spin-torque nano-oscillators (STNOs), including their synchronization, is essential for applications such as complex oscillator networks. In this work, we experimentally demonstrate selective control of two coupled vortex STNOs through microwaveassisted switching of their vortex core polarities. First, the two oscillators are shown to synchronize due to the dipolar interaction in a broad frequency range tuned by an external biasing field. Coherent output is demonstrated along with strong linewidth reduction. Then, we show individual vortex polarity control of each oscillator, which leads to synchronization/desynchronization due to accompanied frequency shift. Our methods can be easily extended to multiple-element coupled oscillator networks. [ABSTRACT FROM AUTHOR]

The spin-spin correlations in hollow (H) and full (F) maghemite nanoparticles (NPs) have been studied by X-ray magnetic circular dichroism (XMCD). An unexpected XMCD signal was detected and analyzed under the application of a small field (μH=160 Oe) and at remanence for both F and H NPs. Clear differences in the magnitude and in the lineshape of the XMCD spectra between F and H NPs emerged. By comparing XMCD measurements performed with a variable degree of surface sensitivity, we were able to address the specific role played by the surface spins in the magnetism of the NPs. [ABSTRACT FROM AUTHOR]

We have investigated the recently discovered Rashba-Edelstein magnetoresistance (REMR) in Bi/Ag/CoFeB trilayer structures with different temperatures, Bi thicknesses, and magnetic fields via the angular-dependent magnetoresistance (ADMR) measurements. We found that the magnitude of the REMR shows a small variation with changing temperature, which is consistent with the previous work on the temperature evolution of the inverse Rashba-Edelstein effect. Furthermore, the ADMR measurements with different thicknesses of Bi layers and external magnetic fields revealed that the contribution from the field-dependent magnetoresistance is not negligibly small for thicker Bi films (≥10 nm) at low temperature. [ABSTRACT FROM AUTHOR]

We report on the in situ engineering of hybrid Co-picene magnetic structures with variable spin coupling using a low-temperature scanning tunneling microscope. Single picene molecules adsorbed on Au(111) are manipulated to accommodate individual Co atoms one by one, forming stable artificial hybrid structures with magnetism introduced by the Co atoms. By monitoring the evolution of the Kondo effect at each site of Co atom, we found that the picene molecule plays an important role in tuning the spin coupling between individual Co atoms, which is confirmed by theoretical calculations based on the density-functional theory. Our findings indicate that the hybrid metal-molecule structures with variable spin coupling on surfaces can be artificially constructed in a controlled manner. [ABSTRACT FROM AUTHOR]

We use broadband ferromagnetic resonance spectroscopy to systematically measure the Landau-Lifshitz damping parameter, perpendicular anisotropy, and the orbital moment asymmetry in Co90Fe10/Ni multilayers. No relationship is found between perpendicular magnetic anisotropy and the damping parameter in this material. However, inadequate accounting for inhomogeneous linewidth broadening, spin-pumping, and two-magnon scattering could give rise to an apparent relationship between anisotropy and damping. In contrast, the orbital-moment asymmetry and the perpendicular anisotropy are linearly proportional to each other. These results demonstrate a fundamental mechanism by which perpendicular anisotropy can be varied independently of the damping parameter. [ABSTRACT FROM AUTHOR]

An unusual overwinding and a subsequently unwinding behavior of helix of filament with twisted microstructures under stretch is analyzed from the nonlinear variation of material chirality (i.e., chirality in material properties), motivated by recent single-molecule experiments for B-DNA. We establish a refined Cosserat rod model, which reproduces the deformation behaviors of filament incorporating its microscopic chirality. The helix of filament with twisted microstructures is found to exhibit a DNA-like nonlinear variation of material chirality under large elongation. The multiscale interactions between microscopic chirality of twisted microstructures and macroscopic chirality of helix determine the nonlinear coupling behaviors of hierarchically chiral structured materials. These results provide a fundamental principle for understanding the functions and mechanisms of chiral materials. [ABSTRACT FROM AUTHOR]

The ultrafast carrier dynamics of the multiferroic BiFeO3 film in a broad temperature range is investigated using optical pump-probe spectroscopy. The photoexcited electrons release their energy with optical phonons emission through electron-phonon coupling in about 1 ps. The following intermediate process is identified as dynamical spin-lattice coupling in several picoseconds. Furthermore, the peak values of the optical reflectivity and the time constants of carrier relaxation channels show significant changes while the temperature varies from 137.5K to around 195 K, this aligns with the previously reported hidden phase transition. Our study demonstrates that ultrafast spectroscopy is a sensitive method to look into the dynamical interactions among the on-site high-energy electrons accumulated in the p conduction band of Bi, coherent optical phonon, as well as the spin degree of freedom. These features play crucial roles in the characterization of phase transitions. [ABSTRACT FROM AUTHOR]

We propose a method to flip the spin completely by an adiabatic transport of quantum dots. We show that it is possible to flip the spin by inducing a geometric phase on the spin state of a quantum dot. We estimate the geometric spin flip time (approximately 2 ps) which turned out to be much shorter than the experimentally reported decoherence time (approximately 100 ns) that would provide an alternative means of fliping the spin before reaching decoherence. It is important that both the Rashba coupling and the Dresselhaus coupling are present for inducing a phase necessary for spin flip. If one of them is absent, the induced phase is trivial and irrelevant for spin-flip. [ABSTRACT FROM AUTHOR]

All-optical tunable plasmonic-mode coupling is realized in a nonlinear photonic metamaterial consisting of periodic arrays of gold asymmetrically split ring resonators, covered with a poly[(methyl methacrylate)-co-(disperse red 13 acrylate)] azobenzene polymer layer. The thirdorder optical nonlinearity of the azobenzene polymer is enormously enhanced by using resonant excitation. Under excitation with a 17-kW/cm², 532-nm pump light, plasmonic modes shift by 51 nm and the mode interval is enlarged by 30 nm. Compared with previous reports, the threshold pump intensity is reduced by five orders of magnitude, while extremely large tunability is maintained. [ABSTRACT FROM AUTHOR]

The power deposition on a tungsten surface exposed to combined pulsed/continuous high power plasma is studied. A study of the correlation between the plasma parameters and the power deposition on the surface demonstrates the effect of particle recycling in the strongly coupled regime. Upon increasing the input power to the plasma source, the energy density to the target first increases then decreases. We suggest that the sudden outgassing of hydrogen particles from the target and their subsequent ionization causes this. This back-flow of neutrals impedes the power transfer to the target, providing a shielding of the metal surface from the intense plasma flux. [ABSTRACT FROM AUTHOR]

Most technologically relevant ferroelectrics typically lose piezoelectricity above the Curie temperature. This limits their use to relatively low temperatures. In this Letter, exploiting a combination of flexoelectricity and simple functional grading, we propose a strategy for high-temperature electromechanical coupling in a standard thin film configuration. We use continuum modeling to quantitatively demonstrate the possibility of achieving apparent piezoelectric materials with large and temperature-stable electromechanical coupling across a wide temperature range that extends significantly above the Curie temperature. With Barium and Strontium Titanate, as example materials, a significant electromechanical coupling that is potentially temperature-stable up to 900 ℃ is possible. [ABSTRACT FROM AUTHOR]

We demonstrate a hole double quantum dot in an undoped GaAs/AlGaAs heterostructure. The interdot coupling can be tuned over a wide range, from formation of a large single dot to two wellisolated quantum dots. Using charge sensing, we show the ability to completely empty the dot of holes and control the charge occupation in the few-hole regime. The device should allow for control of individual hole spins in single and double quantum dots in GaAs. [ABSTRACT FROM AUTHOR]

We report on a characterization of fundamental gain dynamics in recently developed InAs/InP quantum-dot semiconductor optical amplifiers. Multi-wavelength pump-probe measurements were used to determine gain recovery rates, following a powerful optical pump pulse, at various wavelengths for different bias levels and pump excitation powers. The recovery was dominated by coupling between the electronic states in the quantum-dots and the high energy carrier reservoir via capture and escape mechanisms. These processes determine also the wavelength dependencies of gain saturation depth and the asymptotic gain recovery level. Unlike quantum-dash amplifiers, these quantum-dots exhibit no instantaneous gain response, confirming their quasi zerodimensional nature. [ABSTRACT FROM AUTHOR]

We investigate the control of 0-Π transition in Josephson junctions consisting of a highly spin-polarized ferromagnet coupled to two iron pnictide superconductors (SCs). It is shown that, a 0-Π transition as a function of interband coupling strength is always exhibited, which can be experimentally used to discriminate the s± -wave pairing symmetry in the iron pnictide SCs from the s++ -wave one in MgB2. By tuning the doping level in the s± -wave SCs, one can vary the interband coupling strength so as to obtain the controllable 0-Π transition. This device may be realized with current technologies and has practical use in Cooper pair spintronics and quantum information. [ABSTRACT FROM AUTHOR]

A five-phase laminate composite transducer based on nanocrystalline soft magnetic FeCuNbSiB alloy is presented, whose magnetoelectric (ME) coupling characteristics have been investigated. It is found that the resonant ME voltage coefficient of FeCuNbSiB/Terfenol-D/Pb(Zr1-x,Tix)O3 (PZT)/Terfenol-D/FeCuNbSiB (FMPMF) five-phase transducer is much larger than that of traditional Terfenol-D/PZT/Terfenol-D (MPM) transducer, resulting from the enhancement of the effective mechanical quality factor and effective piezomagnetic coefficient of the transducers. Appropriate FeCuNbSiB layer thickness is propitious to the resonant and low-frequency ME coupling characteristics. The maximum resonant ME voltage coefficient achieves 4.81 V/Oe with FeCuNbSiB layer thickness is 60 μm under the DC bias magnetic field Hb=77 Oe, which is 1.48 times as great as that of traditional MPM transducer. In addition, the maximum ME voltage coefficient at low frequency is 51.2 mV/Oe under the DC bias magnetic field Hb=442 Oe, which is 1.26 times as great as that of traditional MPM transducer. It indicates that the mentioned five-phase laminate composite transducers have great potential for the application of highly sensitive dc magnetic field sensing and vibration energy harvesting. [ABSTRACT FROM AUTHOR]

We investigate the electron-spin injection dynamics via tunneling from an In0.1Ga0.9As quantum well (QW) to In0.5Ga0.5As quantum dots (QDs) in coupled QW-QDs nanostructures. These coupled nanostructures demonstrate ultrafast (5 to 20 ps) spin injection into the QDs. The degree of spin polarization up to 45% is obtained in the QDs after the injection, essentially depending on the injection time. The spin injection and conservation are enhanced with thinner barriers due to the stronger electronic coupling between the QW and QDs. [ABSTRACT FROM AUTHOR]

Pairwise quantum correlations in the ground state of an N-spins antiferromagnetic Heisenberg chain are investigated. By varying the exchange coupling between two neighboring sites, it is possible to reversibly drive spins from entangled to disentangled states. For even N, the two-spin density matrix is written in the form of a Werner state, allowing identification of its single parameter with the usual spin-spin correlation function. The N = 4 chain is identified as a promising system for practical demonstrations of non-classical correlations and the realization of Werner states in familiar condensed matter systems. Fabrication and measurement ingredients are within current capabilities. [ABSTRACT FROM AUTHOR]

We report on the detection of a zero-field spin dependent current response in Si based metal-oxide-semiconducting field-effect transistors. We argue that this phenomenon results from spin dependent recombination (SDR) due to the mixing of the energy levels involved in the singlet and triplet pairs which form prior to recombination involving Pb centers at the Si/SiO2 interface. We demonstrate a very strong correlation between the zero-field response, the low-field magnetic resonant response, and electrical gated current interface trap measurement. Our results provide strong evidence that previous magnetoresistance measurements made in silicon devices arise from deep level defects that cause SDR. [ABSTRACT FROM AUTHOR]

We report on molecular beam epitaxy growth of bilayer Bi(111) films on topological insulator Bi2Te3. In situ scanning tunneling microscopy/spectroscopy shows that Bi growth mode changes from quasi bilayer-by-bilayer to step-flow with increasing substrate temperature. Bilayer Bi(111) exhibits an electron donor behavior, causing an 80 meV downshift of the Dirac point of Bi2Te3. Local work function difference between the bilayer films and Bi2Te3 films is measured to be 390 meV. Based on the observations, we propose a schematic energy-band diagram which reveals band bending effect at the Bi/Bi2Te3 interface. Our work paves a way to explore the exotic topological properties of bilayer islands and thin films of Bi. [ABSTRACT FROM AUTHOR]

In this work, the spin-spin relaxation of protons in ferrofluids is characterized using a high-Tc SQUID-based detector in microtesla fields. We found that spin-spin relaxation rate is enhanced in the presence of superparamagnetic nanoparticles. The enhanced relaxation rates are attributed to the microscopic field gradients from magnetic nanoparticles that dephase protons' spins nearby. The relaxation rates decrease when temperatures increase. Additionally, the alternating current magnetic susceptibility was inversely proportional to temperature. Those characteristics explained the enhanced Brownian motion of nanoparticles at high temperatures. Characterizing the relaxation will be helpful for assaying bio-molecules and magnetic resonance imaging in microtesla fields. [ABSTRACT FROM AUTHOR]

We report the direct measurement of spin transport characteristics in a GaN spin valve, with a relatively defect-free single GaN nanowire (NW) as the channel and FeCo/MgO as the tunnel barrier spin contact. Hanle spin precession and non-local transport measurements are made in an unintentionally doped nanowire spin valves. Spin diffusion length and spin lifetime values of 260 nm and 100 ps, respectively, are derived. Appropriate control measurements have been made to verify spin injection, transport, and detection. [ABSTRACT FROM AUTHOR]

Temporal developments of photocurrents excited by an infrared radiation pulse in quantum well/dot infrared photodetectors with different optical coupling structures have been theoretically studied. It is shown that the light diffraction in a conventional reflective grating structure is a near-field effect containing severe crosstalk from neighboring pixels. A concave reflector not only eliminates the crosstalk but also strongly diffracts and focuses the incident electric field into deep active layers, which significantly increases the photocurrents in the photodetectors. [ABSTRACT FROM AUTHOR]

A study on the bound states of Fe impurities in GaN by ultraviolet photoluminescence (PL) emissions is presented. Two elusive PL lines were observed at 3.463 eV (L1) and 3.447 eV (L2), respectively. The intensities of the two lines are proportional to the Fe concentration. The temperature dependence of L1 and L2 revealed acceptor-like and strong localized characteristic, respectively. Furthermore, Raman analysis indicated that L2 is correlated to an exciton bound to a nitride-vacancy (VN) related complex, i.e., [Fe2+-VN]. By co-doping with Si, the [Fe2+-VN]-related bound state will enable the spin-coupling between isolated iron ions. [ABSTRACT FROM AUTHOR]

The energy loss rate (ELR) of a charged particle in a HgTe/(HgTe, CdTe) quantum well is investigated. We consider scattering of a charged particle by the bulk insulating states in this type of topological insulator. It is found that the ELR characteristics due to the intraband excitation have a linear energy dependence while those due to interband excitation depend on the energy exponentially. An interesting quantitative result is that for a large range of the incident energy, the mean inelastic scattering rate is around a few terahertz. [ABSTRACT FROM AUTHOR]

By taking the coupling effects caused by the difference between the effective masses of silicon and gate oxide into consideration, the effects of in-plane momentum on the quantization in the electron motion perpendicular to the Si/SiO2 interface of a nanometer metal-oxide-semiconductor device with p-type silicon substrate are described. The results show that the coupling, which largely affects the quantization of the perpendicular motion of channel electrons in the inversion layer, should be considered when the in-plane momentum of channel electrons is high. [ABSTRACT FROM AUTHOR]

The authors demonstrated the strong sublevel coupling on the intersubband absorption at telecommunication wavelengths in asymmetric II-VI double quantum wells consisting of a deep CdS well and a shallow ZnSe well coupled by a 1-monolayer-thick BeTe barrier. With increasing ZnSe well thickness, the sublevel coupling between excited states first increases to a maximum and then decreases, which results in a transition energy anticrossing and a reverse intensity evolution for e1-e2 and e1-e3 transitions. These results are in good agreement with the self-consistent Schrödinger-Poisson calculation. For optical switch applications, the sublevel-coupling-dependent relaxation time could be increased to lower the switching energy. [ABSTRACT FROM AUTHOR]

The authors demonstrate the metallic-structure dependent surface plasmon (SP) coupling behaviors with a blue-emitting InGaN/GaN quantum well (QW), which is 10 nm away from the metallic structures. The SP-QW coupling behaviors in the areas of semiconductor surface coated with silver thin film and silver nanoparticles are compared. It is found that both the suppression of photoluminescence (PL) intensity and the reduction of time-resolved PL (TRPL) decay time strongly depend on the metallic morphology. A phenomenological model of carrier relaxation in the SP-QW coupling process is built to fit the TRPL decay profiles for calibrating the reasonable decay time constants of carrier and SP. [ABSTRACT FROM AUTHOR]

Aggregates of monodisperse iron-based nanoparticles were investigated by small-angle neutron scattering. The field dependence of the scattering intensity showed marked differences for particles depending on size and degree of oxidation. The angular dependence of the intensity indicated magnetic regions within an oxidized sample with spins perpendicular to the applied field, which dominated the scattering at the diffraction peak. The unexpected results are interpreted in terms of an iron core that is exchange coupled to an iron oxide shell. [ABSTRACT FROM AUTHOR]

We present an experimental and theoretical study of the size dependence of the coupling between electron–hole pairs and longitudinal-optical phonons in Ga[sub 1-x]In[sub x]N/GaN-based quantum wells and quantum boxes. We found that the Huang–Rhys factor S, which determines the distribution of luminescence intensities between the phonon replicas and the zero-phonon peak, increases significantly when the vertical size of the boxes or the thickness of quantum well increases. We assign this variation to (1) the strong electric field present along the growth axis of the system, due to spontaneous and piezoelectric polarizations in these wurtzite materials, and (2) the localization on separate sites of electrons and holes in the plane of the wells or boxes, due to potential fluctuations in the ternary alloy. Indeed, envelope-function calculations for free or localized excitons, with electron–hole distance only controlled by Coulomb interaction, do not account quantitatively for the measured behavior of the S factor. In fact, the latter is rather similar to what is obtained for donor–acceptor pairs, with a statistical distribution of distances between localization centers for electrons and holes. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on the junction magnetoresistance in magnetic tunnel junctions of the hard-soft type with magnetic layers separated by a ZnS barrier. The hard magnetic bottom electrode consists of an artificial antiferromagnetic structure in which the rigidity is ensured by the antiferromagnetic exchange coupling between two FeCo layers through a Ru spacer layer. The samples were grown by sputtering on Si (111) wafers at room temperature and have the following structure: Fe[sub 6 nm]Cu[sub 30 nm](CoFe)[sub 1.8 nm]Ru[sub 0.8 nm](CoFe)[sub 3 nm]ZnS[sub x](CoFe)[sub 1 nm]Fe[sub 4 nm]Cu[sub 10 nm]Ru[sub 3 nm]. The square tunnel elements, with lateral sizes of 10, 20, 50, and 100μm, exhibit typical tunnel resistance of 2-3 kΩ μm2 and nonlinear zero field current-voltage (J-V) variation. The most interesting result is the observation of junction magnetoresistance of about 5% at room temperature with a 2 nm thick ZnS barrier. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines a broadly electrically tunable narrow-band, wavelength selective, grating-assisted coupling between vertically stacked buried rib InGaAsP/InP channel waveguides. Implication for photonic devices and integrated circuits; Use of a current injection induced refractive index change for tuning; Composition of a current injection tuned device.

Demonstrates long-range coupling and phase locking of ten-element resonant antiguided arrays through radiation leakage. Occurrence of coupling for interarray separations; Intermodal discrimination between in-phase and adjacent higher-order modes.

Analyzes the infrared radiative efficiency for gallium arsenide/aluminum gallium arsenide multiquantum well structures. Angular dependence of infrared emission; Importance of etched surface grating structure to produce effective coupling efficiencies; Calculation of radiative decay rates for different infrared wavelength ranges.

Structured plasmonic metamaterial devices offer the design flexibility to be size scaled for operation across the electromagnetic spectrum and are extremely attractive for generating electromagnetically induced transparency and slow-light behaviors via coupling of bright and dark subwavelength resonators. Here, we experimentally demonstrate a thermally active superconductor-metal coupled resonator based hybrid terahertz metamaterial on a sapphire substrate that shows tunable transparency and slow light behavior as the metamaterial chip is cooled below the high-temperature superconducting phase transition temperature. This hybrid metamaterial opens up the avenues for designing micro-sized active circuitry with switching, modulation, and 'slowing down terahertz light' capabilities. [ABSTRACT FROM AUTHOR]

A differential all-optical resonance tuning of whispering-gallery-modes (WGMs) in a system of three coupled microdisks in a line arrangement is investigated. Utilizing the temperature induced nonlinear effects observable in coupled WGM microresonators, a tunable, narrow bandwidth, three-wavelength filter is demonstrated. Variable tuning scenarios for the signal resonances are achieved at the same sample, depending on the coupling conditions of the control signal at low control powers of up to 4 mW only. [ABSTRACT FROM AUTHOR]

The emission intensity of an organic light-emitting diode at normal viewing angle and the total external emission efficiency have been increased by factors of 9.6 and 3.0, respectively, by applying spherically shaped patterns to the back of the device substrate. The technique captures light previously lost to waveguiding in the substrate and, with proper choice of substrate, light previously lost to waveguiding in the organic/anode layers. A method of applying the technique using laminated films and an optical model for evaluating coupling efficiency are also presented. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]