Field-dependent Transmission Research Articles

Traverse electric field effect on wave vector filtering in a magnetically modulated semiconductor nanostructure

We theoretically study the effect of traverse electric field on wave vector filtering (WVF) in a magnetically modulated nanostructure, which can be constructed by patterning ferromagnetic (FM) stripes on top and bottom of GaAs/Al[Formula: see text]Ga[Formula: see text]As heterostructure. Using the transfer matrix method, electric field-dependent transmission is calculated by using Weber function for electrons across the structure. We find that WVF efficiency is manipulable by adjusting direction or strength of electric field. Thus, an electrically-tunable momentum filtering device can be obtained.

Optical Fiber Magnetic Field Sensors Based on Magnetic Fluid: A Review.

Magnetic field sensing is an important issue for many application areas, such as in the military, industry and navigation. The current sensors used to monitor this parameter can be susceptible to electromagnetic interferences, however due to their advantages over the traditional sensors, the optical fiber devices could be an excellent alternative. Furthermore, magnetic fluid (MF) is a new type of functional material which possesses outstanding properties, including Faraday effect, birefringence, tunable refractive index and field dependent transmission. In this paper, the optical fiber magnetic field sensors using MF as sensing element are reviewed. Due to the extensive literature, only the most used sensing configurations are addressed and discussed, which include optical fiber grating, interferometry, surface plasmon resonance (SPR) and other schemes involving tailored (etched, tapered and U-shaped) fibers.

Mössbauer Spectroscopic Characterization of Iron(III)-Polysaccharide Coordination Complexes: Photochemistry, Biological, and Photoresponsive Materials Implications.

While polycarboxylates and hydroxyl-acid complexes have long been known to be photoactive, simple carboxylate complexes which lack a significant LMCT band are not typically strongly photoactive. Hence, it was somewhat surprising that a series of reports demonstrated that materials synthesized from iron(III) and polysaccharides such as alginate (poly[guluronan-co-mannuronan]) or pectate (poly[galacturonan]) formed photoresponsive materials that convert from hydrogels to sols under the influence of visible light. These materials have numerous potential applications in areas such as photopatternable materials, materials for controlled drug delivery, and tissue engineering. Despite the near-identity of the functional units in the polysaccharide ligands, the reactivity of iron(III) hydrogels can depend on the configuration of some chiral centers in the sugar units and in the case of alginate the guluronate to mannuronate block composition, as well as pH. Here, using temperature- and field-dependent transmission Mössbauer spectroscopy, we show that the dominant iron compound detected for both the alginate and pectate gels displays features typical of a polymeric (Fe3+O6) system. The Mössbauer spectra of such systems are strongly dependent on temperature, field, size, and crystallinity, indicative of superparamagnetic relaxation of magnetically ordered nanoparticles. Pectate and alginate hydrogels differ in the size distribution of the iron oxyhydroxy nanoparticles, suggesting that in general smaller nanoparticles are more reactive. Potential biological implications of these results are also discussed.

Analysis of the static magnetic field-dependent optical transmission of Ni nanorod colloidal suspensions

The magnetic field-dependent optical transmission of dilute Ni nanorod aqueous suspensions was investigated. A series of four samples of nanorods were synthesized using the AAO template method and processed to stable colloids. The distributions of their length and diameter were characterized by analysis of TEM images and revealed average diameters of ∼25 nm and different lengths in the range of 60 nm–1100 nm. The collinear magnetic and optical anisotropy was studied by static field-dependent transmission measurements of linearly polarized light parallel and perpendicular to the magnetic field direction. The experimental results were modelled assuming the field-dependent orientation distribution function of a superparamagnetic ensemble for the uniaxial ferromagnetic nanorods in liquid dispersion and extinction cross sections for longitudinal and transversal optical polarization derived from different approaches, including the electrostatic approximation and the separation of variables method, both applied to spheroidal particles, as well as finite element method simulations of spheroids and capped cylindrical particles. The extinction cross sections were compared to reveal the differences associated with the approximations of homogeneous polarization and/or particle shape. The consequences of these approximations for the quantitative analysis of magnetic field-dependent optical transmission measurements were investigated and a reliable protocol derived. Furthermore, the changes in optical cross sections induced by electromagnetic interaction between two nanorods in parallel end-to-end and side-by-side configuration as a function of their separation were studied.

Rotational Motion Control of a Washing Machine Using Electrorheological Clutches and Brakes

In this work, a rotational motion control of a washing machine featuring an electrorheological (ER) clutch/brake actuators is investigated. After analysing the field-dependent transmission and braking torques of the actuator on the basis of Bingham model, two sets of ER clutch/brake actuators are manufactured. The dynamic model of the actuators is then formulated by considering time constants. Subsequently, the actuators are applied to a small-sized pulsator type washing machine for rotational motion control. The control system model represented by spin-basket and pulsator motions is established and PID controllers are designed for two motions. The controllers are experimentally realized for washing and dehydrating motions under various loads. In addition, durability test for the washing motion control has been undertaken to demonstrate practical feasibility.

Band structure calculation of field emission from AlxGa1−xN as a function of stoichiometry

The field emission current density j from the ternary alloys AlxGa1−xN is theoretically calculated as a function of stoichiometry. The material parameters of AlxGa1−xN are obtained as weighted averages of those of AlN and GaN. Using the method of W. W. Lui and M. Fukuma [J. Appl. Phys. 60, 1555(1986)], the transmission coefficients are numerically calculated using Airy functions that are solutions of the Schrödinger equation in a piecewise linear potential region. Band structure effects in the calculation of j are included using the projection of the energy ellipsoids on the emission surfaces. The results for j show a strong dependence of the field emission on the stoichiometric composition, which reflects the composition dependence of the electron affinity. The Fowler–Nordheim plots and calculated field electron energy distribution curves both exhibit structures which suggest different field-dependent transmission probabilities in the low and high field regimes.

Far infrared magneto-optical spectrophotometer

A high-sensitivity far infrared magneto-optical spectrophotometer, capable of measuring the dependences of the transmission and reflection of samples over a wavelength range of 40 to 1200 mu m on the temperature and the magnetic field, is described. The modular design enables measurements in both partly or fully polarized light, as well as obtaining dependences on the orientation of the light polarization plane with respect to the sample axes. Examples of the temperature and magnetic field dependent transmission spectra of a YbIG sample are demonstrated.

Magnetic Resonance and Electromagnetic Wave Propagation in Materials Havingg-Factor Anisotropies

A method is presented for deriving from an ionic spin Hamiltonian a classical equation of motion of the magnetization which remains valid for materials in which the $g$ factor is anisotropic. The Hamiltonian invoked to illustrate the method includes the Zeeman term as well as terms corresponding to the local field, anisotropic exchange, and "one-ion" anisotropy. This new equation of motion is used first to calculate, in the magnetostatic limit, the small-signal complex susceptibility of the Ising-like antiferromagnet DyP${\mathrm{O}}_{4}$ exposed to a saturating static magnetic field and then, in conjunction with Maxwell's equations, to treat the "dimensional resonances" arising from electromagnetic propagation effects. After introducing approximations appropriate to Ising-like systems, an explicit expression is obtained for the field-dependent transmission through a monocrystalline DyP${\mathrm{O}}_{4}$ slab whose thickness is comparable to the wavelength. Propagation effects are shown to offer a possible explanation of the asymmetric line shape observed in a recent far-infrared laser resonance experiment on DyP${\mathrm{O}}_{4}$ and to constitute a probably unique explanation of the experimental fact that the transmission at fields near resonance can exceed that at fields far from resonance. More generally, propagation effects are shown to be difficult to avoid at any wavelength in transversely excited, strongly Ising-like systems.