Giant Faraday rotation in Fe–ZnSe granular films

The giant magneto-optical Faraday effect (giant Faraday rotation) of ferromagnetic metal–semiconductor matrix Fe–ZnSe granular films prepared by radio frequency sputtering is studied. The result shows that the Faraday rotation angle θ_F value of the granular films sample with Fe volume fraction x=35% is of the order of 10⁵ °/cm at room temperature. Temperature dependence of the θ_F of Fe_0.35(ZnSe)_0.65 granular films shows that θ_F value, below 150 K, increases rapidly with the decrease of the temperature, and when T=10 K θ_F value is 6×10⁵ °/cm. Through the study of the structure and dependence of magnetic properties on temperature, it has been found that the remarkable increase of the θ_F value of Fe_0.35(ZnSe)_0.65 granular films below 150 K seems to arise from the sp–d exchange interaction inside the granular films.     

Magneto-optic Faraday effect in maghemite nanoparticles/silica matrix nanocomposites prepared by the Sol–Gel method

Bulk monolithic samples of γ-Fe₂O₃/SiO₂ composites with different iron oxide/silica ratios have been prepared by the sol–gel technique. Iron oxide nanoparticles are obtained in-situ during heat treatment of samples and silica matrix consolidation. Preparation method was previously optimized to minimize the percentage of antiferromagnetic α-Fe₂O₃ and parallelepipeds of roughly 2×5×12 mm³, with good mechanical stability, are obtained. RT magnetization curves show a non-hysteretic behavior. Thus, magnetization measurements have been well fitted to an expression that combines the Langevin equation with an additional linear term, indicating that some of the nanoparticles are still superparamagnetic as confirmed by X-ray diffraction and electron microscopy measurements. Zero field cooled /field cooled experiments show curves with slightly different shapes, depending on the size and shape distribution of nanoparticles for a given composition. Magneto-optical Faraday effect measurements show that the Faraday rotation is proportional to magnetization of the samples, as expected. As a demonstration of their sensing possibilities, the relative intensity of polarized light, measured at 5° from the extinction angle, was plotted versus applied magnetic field.     

The effect of Zn on precipitation in Al–Mg–Si alloys

Effects of addition of Zn (up to 1 wt%) on microstructure, precipitate structure and intergranular corrosion (IGC) in an Al–Mg–Si alloys were investigated. During ageing at 185?°C, the alloys showed modest increases in hardness as function of Zn content, corresponding to increased number densities of needle-shaped precipitates in the Al–Mg–Si alloy system. No precipitates of the Al–Zn–Mg alloy system were found. Using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), the Zn atoms were incorporated in the precipitate structures at different atomic sites with various atomic column occupancies. Zn atoms segregated along grain boundaries, forming continuous film. It correlates to high IGC susceptibility when Zn concentration is ~1wt% and the materials in peak-aged condition.     

The effect of Cu on precipitation in Al–Mg–Si alloys

TEM investigations of two alloys isothermally heat treated at 175°C and 260°C show how Cu additions to the Al–Mg–Si system affect precipitation. Both alloys had a solute content Mg?+?Si?=?1.3 at.%, 0.127 at.% Cu, but with Mg/Si 0.8 and 1.25. Cu-containing Guinier-Preston (GP) zones and three types of Q′ precursors are identified as most common phases at peak-hardness conditions, whereas β″ accounts for maximum 30% of the total number of precipitates. The precursors have needle (L and S precipitates) or plate (C precipitate) morphologies. They consist of different arrangements of Al, Mg and Cu atoms on a grid defined by triangularly arranged Si planes parallel with and having the same period as {100} Al planes. The Si grid is composed of nearly hexagonal sub-cells of a?=?b?=?4.05?Å, c?=?4.05?Å. The Cu arrangement on the grid is often disordered in the needle precursors. The plate precursor is ordered, with a monoclinic unit cell of a?=?10.32?Å, b?=?8.1?Å, c?=?4.05?Å, γ?=?101°.     

Spin–orbit scattering effect on electron–electron interactions in disordered metals

We have measured the low-temperature resistivities of a series of bulk crystalline disordered Ti_73−xAl₂₇Sn_x alloys (x≲5) as well as the sheet resistances of a number of thin ferromagnetic Ni films (≈120 Å thick) sandwiching an ultrathin Ag or Au (≲5 Å) layer. The level of impurities (concentration of Sn in the former case, and thickness of Ag or Au in the latter case) is progressively increased in order to enhance the spin–orbit scattering in a controllable manner. The influence of the spin–orbit scattering on the electron–electron interaction effects is studied from the temperature dependence of resistivities (sheet resistance) at low temperatures. We find that the electron–electron interaction contribution to the resistivities (sheet resistances) increases slightly with increasing spin–orbit scattering. Our observation is discussed in terms of the current theoretical concept for the electron–electron interactions in disordered metals.     

Fabry–Perot effect on dimer nanoantennas

In this work, we investigate the interaction between a single quantum emitter and dimer nanoantennas through a Fabry–Perot structure composed of an appropriate combination of two dielectric layers. This type of dielectric configuration is well known in the microwave region to increase the antenna performance, such as directivity, radiation efficiency, and radiation resistance. Here, the Fabry–Perot concept is transposed to the optical domain. The single emitter couples to the antenna through the dielectric structure, giving rise to a wide aperture field on top of the dielectrics with the same polarization of the emitter. This purely polarized aperture field can be used to excite one or more conveniently spaced nanoantennas. We demonstrate by 3D numerical calculations that the directivity and excitation rate of a single dimer is highly increased. Also, we show that multiple dimers arranged in an array configuration can be enhanced due to the wide aperture field generated by a single emitter.     

Rashba spin–orbit effect on dwell time in graphene asymmetrical barrier

Monodisperse and spherical α-alumina nanoparticles with a narrow size distribution in range of 11–18 nm have been prepared via the simple chemical precipitation and a new heat-treatment method, namely isolation-medium-assisted calcination. As-prepared α-alumina nanoparticles were characterized by means of X-ray diffraction analyses (XRD), thermogravimetry and differential thermal analyzer (TG–DTA), Fourier transform infrared spectroscopy, and field emission transmission electron microscope (TEM). XRD results confirm that the α-alumina in corundum structure is obtained by heating at 1,000 °C for 3 h. And TEM observations reveal the additional isolation medium surrounded α-alumina precursor forms the lamella, which effectively reduces direct contacts between precursor particles and prevents the agglomerating of the aluminum hydroxides during drying process and then the sintering and growth of the alumina nanoparticles are avoided during calcination. The highly uniform and monodisperse α-alumina nanoparticles are obtained.     

Condensation of gold vapour on silicone oil – effect of the liquid substrate

When gold vapour condenses onto a liquid substrate, the inherent structure of the liquid could influence the condensate growth and coverage. A thorough comparison between the liquid (silicone oil) and solid (amorphous carbon) substrates is reported by analysing the changes in their condensate growth. Low condensate coverage with large areas of empty regions is observed on the liquid surface in contrast to the solid carbon surface displaying uniformly distributed gold clusters at all times. This is deduced to be caused by the incoming gold atoms restricting the liquid molecules’ degrees of freedom upon binding. This effect could perturb the entire liquid structure, causing the liquid to collectively act against the adsorption of gold atoms. This could lead to differences in growth kinetics on the liquid substrate and can account for the observed dissimilarity in condensate coverage. The substrate structure effect discussed here serves as a step forward for utilizing liquid substrates for a variety of potential applications.     

Alloying effect on grain-size dependent deformation twinning in nanocrystalline Cu–Zn alloys

Grain-size dependency of deformation twinning has been previously reported in nanocrystalline face-centred-cubic metals, which results in an optimum grain-size range for twin formation. Here, we report, for the first time in experiments, the observed optimum grain sizes for deformation twins in nanocrystalline Cu–Zn alloys which slightly increase with increasing Zn content. This result agrees with the reported trend but is much weaker than predicted by stacking-fault-energy based models. Our results indicate that alloying changes the relationship between the stacking-fault and twin-fault energy and therefore affects the optimum grain size for deformation twinning. These observations should be also applicable to other alloy systems.     

Time-dependent Aharonov–Casher effect on noncommutative space

In this paper,we study the time-dependent Aharonov-Casher effect and its corrections due to spatial noncommutativity.Given that the charge of the infinite line in the Aharonov-Casher effect can adiabatically vary with time,we show that the original Aharonov-Casher phase receives an adiabatic correction,which is characterized by the time-dependent charge density.Based on Seiberg-Witten map,we show that noncommutative corrections to the time-dependent Aharonov-Casher phase contains not only an adi...     

Spin-flip scattering effect on the current-induced spin torque in ferromagnet–insulator–ferromagnet tunnel junctions

We have investigated the current-induced spin transfer torque of a ferromagnet–insulator–ferromagnet tunnel junction by taking the spin-flip scatterings into account. It is found that the spin-flip scattering can induce an additional spin torque, enhancing the maximum of the spin torque and giving rise to an angular shift compared to the case when the spin-flip scatterings are neglected. The effects of the molecular fields of the left and right ferromagnets on the spin torque are also studied. It is found that τ^Rx/I_e (τ^Rx is the spin-transfer torque acting on the right ferromagnet and I_e is the tunneling electrical current) does vary with the molecular fields. At two certain angles, τ^Rx/I_e is independent of the molecular field of the right ferromagnet, resulting in two crossing points in the curve of τ^Rx/I_e versus the relevant orientation for different molecular fields.     

Influence of Cr on microstructure and elastocaloric effect in Ni–Mn–In–Co–Cr polycrystalline alloys

Ni–Mn-based metamagnetic shape memory alloys have been proposed as potential elastocaloric refrigerants. The intrinsic brittleness of the alloys has limited their cooling application. Introducing a soft second phase is an effective way to reduce the brittleness. From the viewpoint of application, the effect of second phase on elastocaloric effect should be illustrated. In this paper, we have investigated the microstructure, martensitic transformation and elastocaloric effect of Ni₄₅Mn_37-xIn₁₃Co₅Cr_x ($x=0,1\text{ and }2$) polycrystalline alloys. Single-phase and precipitates-containing microstructures are obtained for the undoped and doped alloys, respectively. The precipitates in Cr-doped alloys enhances the fracture strength but significantly hinders the martensitic transformation. Balancing the fracture strength and martensitic transformation, the Ni₄₅Mn₃₆In₁₃Co₅Cr alloy with small amount of precipitates along grain boundaries exhibits large cooling effects of 4–6 K in the temperature range of 317–353 K.     

The Mössbauer effect on 119Sn and 197Au nuclei in gold,palladium and platinum matrices

The probabilities for recoilles resonant absorption of 77.3 keV λ-rays by ¹⁹⁷Au and 23.8 keV λ-rays by ¹¹⁹Sn in matrices of gold, palladium and platinum have been calculated in the temperature ranges 4.2–100 K and 80–400 K, respectively. The calculated results show a good agreement with the experimental data.     

Annealing effect on phase transformation in nano structured Ni–Mn–Ga ferromagnetic shape memory alloy

Nano structured Ni_52.6Mn_23.7Ga_24.3 alloy was prepared using the ball milling technique. High martensitic transition temperatures are observed in the range between 336 and 367 K. The X-ray diffraction profile revealed that annealed Ni–Mn–Ga powder at 1073 K displays mixture phases of austenite and martensite. Annealing at 1173 K induces phase transformation from mixture phase to Heusler L2₁ structure, which confirms the high-temperature shape memory effect. On the contrary, the milled sample shows no evidence of shape memory effect. Furthermore, annealing at higher temperature (1273 K) shows the accumulation of oxidation, which leads to the loss of shape memory effect. The grain size increases with increasing annealing temperature and causes deterioration in the soft magnetic properties.     

The Aharonov–Bohm effect in scattering theory

The Aharonov–Bohm effect is considered as a scattering event with nonrelativistic charged particles of the wavelength which is less than the transverse size of an impenetrable magnetic vortex. The quasiclassical WKB method is shown to be efficient in solving this scattering problem. We find that the scattering cross section consists of two terms, one describing the classical phenomenon of elastic reflection and another one describing the quantum phenomenon of diffraction; the Aharonov–Bohm effect is manifested as a fringe shift in the diffraction pattern. Both the classical and the quantum phenomena are independent of the choice of a boundary condition at the vortex edge, providing that probability is conserved. We show that a propagation of charged particles can be controlled by altering the flux of a magnetic vortex placed on their way.     

Aharonov–Bohm effect in the ghost interference

Chaotic systems demonstrate complex behaviour in their state variables and their parameters, which generate some challenges and consequences. This paper presents a new synchronisation scheme based on integral sliding mode control (ISMC) method on a class of complex chaotic systems with complex unknown parameters. Synchronisation between corresponding states of a class of complex chaotic systems and also convergence of the errors of the system parameters to zero point are studied. The designed feedback control vector and complex unknown parameter vector are analytically achieved based on the Lyapunov stability theory. Moreover, the effectiveness of the proposed methodology is verified by synchronisation of the Chen complex system and the Lorenz complex systems as the leader and the follower chaotic systems, respectively. In conclusion, some numerical simulations related to the synchronisation methodology is given to illustrate the effectiveness of the theoretical discussions.     

The Aharonov–Bohm effect in graphene rings

This is a review of electronic quantum interference in mesoscopic ring structures based on graphene, with a focus on the interplay between the Aharonov–Bohm effect and the peculiar electronic and transport properties of this material. We first present an overview on recent developments of this topic, both from the experimental as well as the theoretical side. We then review our recent work on signatures of two prominent graphene-specific features in the Aharonov–Bohm conductance oscillations, namely Klein tunneling and specular Andreev reflection. We close with an assessment of experimental and theoretical development in the field and highlight open questions as well as potential directions of the developments in future work.