Table of contents

We present recent achievements and perspectives for the encoding of qubits with molecular spin clusters.

Arrays of self-assembled polystyrene spheres with various particle sizes have been used as a substrate to study the exchange bias effect along the out-of-plane direction of Pt/Co multilayers capped with IrMn layers. The evolution of the reversal process of the resulting magnetic nanocaps was investigated by magnetic force microscopy (MFM) and magnetic transmission x-ray microscopy (M-TXM). Tip–sample interaction-induced irreversible and reversible switching events have been observed during multiple scanning cycles in MFM imaging which are ascribed to the so-called training effect. During M-TXM imaging a drastic change in morphology has been found due to the x-ray exposure, leading to the formation of much larger spherical particles. Interestingly, these merged particles reveal again an exchange coupled single-domain magnetic cap with magnetic behaviour similar to magnetic films deposited directly on spheres of similar size.

We report on a systematic electrical transport study of the effect of an exchange tab on the magnetization switching process of magnetic nanowires. The exchange tab consists of a small segment of a ferromagnetic layer coupled antiferromagnetically to a small portion of the magnetic wire via a thin Ru spacer. The magnetic force microscopy image shows that the exchange tab has a single domain structure. The magnetoresistance of exchange tab stabilized nanowires is characterized by a reversible switching process in both the longitudinal and the transverse field directions. The former is in sharp contrast to the magnetoresistance curve of nanowires with the same geometry but without an exchange tab. The dependence of the exchange field on the tab size has also been investigated, which revealed that a shorter tab generally leads to a stronger coupling between the tab and the nanowire. Micromagnetic modelling has been carried out to interpret the experimental results.

Sr_2−xLa_xMnTiO₆ (0.25 ≤ x ≤ 1) orthorhombic perovskite-like system has been synthesized by the ceramic method. Structural characterization from x-ray and neutron diffraction shows a random distribution of Sr/La and Mn/Ti cations, in A- and B-sublattices, respectively, in all the cases. These materials show complex magnetic behaviour which can be interpreted in terms of frustrated FM interactions, considering a cluster-glass picture. M–I transitions have been observed for x = 0.75, 1 and negative MR responses in the ranges of 1000% and 90% have been detected at 40 K and 210 K, respectively. Magnetization (ZFC and FC) measurements in ac and dc are interpreted considering the existence of superparamagnetic clusters embedded in a paramagnetic matrix.

Magnetic and resistivity measurements were used to examine the ternary rare earth compound GdPdSb. A second magnetic transition below the antiferromagnetic ordering temperature T_N was found, indicating a possible ferromagnetic ordering. The electronic structure of GdPdSb was also examined using first principles electronic structure calculations. It was found that the antiferromagnetic configuration is more stable than the ferromagnetic configuration, but that the energy difference is very small between these configurations. For this reason, ferromagnetic behaviour could be expected at low temperature. According to band structure calculations, ferromagnetically ordered GdPdSb is a possible half metal, the first half metallic ferromagnet with the hexagonal LiGaGe structure type.

We study how paramagnetic colloids in external magnetic fields can be used as sensitive force detectors in liquid systems. An experimental setup has been constructed which uses optical tweezers to calibrate the force between paramagnetic dipoles. In the operative mode the optical tweezers are switched off and the unknown force is measured by tuning a magnetic field and therefore the dipolar interaction between the two paramagnetic dipoles. The setup can be used to measure the force versus distance as well as for probing critical bond forces in the range between 5 fN and 1 pN. We apply the system to measure capillary forces at a water–air interface and for probing polyelectrolyte bridges between colloids.

We found that the ultra-thin insertion of a mix of Fe and Fe oxide in the pinned layer substantially enhanced the performance of a spin valve. With the exchange bias field kept large, the giant magnetoresistance (GMR) reached 11.3%, which corresponded to a 46% increase in GMR compared with the GMR of spin valves without the insertion. We attribute this considerable enhancement to spin-dependent scattering boosted by the combined effect of the modified local electronic structures at the Fe and specular reflections at the α-Fe₂O₃ of the insertion.

At ultra high field strength (>4 T), the RF-wavelength relative to the dimension of the human body leads to significant excitation field (B₁) inhomogeneity arising out of wave propagation effects. The excitation field is thus spatio-temporal and in conjunction with the increase in tissue conductivity, wave propagation phenomena can no longer be ignored. We thus find the propagation of radiation at ultra high fields new phenomena commonly observed in quantum optics but traditionally negligible in NMR such as spatio-temporal phase modulation of the excitation field such that the identity between pulse area and flip angle is no longer valid. In this paper, the emergence of field propagation phenomena in NMR experiments is analytically and experimentally demonstrated. It is shown that in addition to the well-studied dielectric resonance phenomena at high magnetic fields, propagation effects transform the excitation pulse into an adiabatic excitation. The high field strength also means that nonlinear effects such as self-induced transparency, propagation phenomena such as transient four wave mixing, are now possible in NMR experiments. It is shown and experimentally demonstrated at 7 T that additional constraints due to phase matching considerations are imposed on the formation of echoes in high field NMR.

Magnetic force microscopy (MFM) has been used to analyse the behaviour of domain walls in uniaxial amorphous Co_xSi_1−x films patterned with diluted arrays of antidots by electron beam lithography. The walls are found to be pinned by the antidot array when the antidot density is high enough along the easy axis. The expansion of reversed nuclei under the influence of the tip stray field has been observed in several consecutive MFM images of the same area, showing how the competition between line tension effects and pinning by the patterned holes governs the creep motion of the 180° walls across the array of antidots.

Coil shapes for generating the perfect field in superconducting dipoles, quadrupoles and sextupoles are known. However, for combined function superconducting magnets coil shapes are not available in the literature. Here we provide the coil shapes which can generate mixed dipole–quadrupole and dipole–sextupole fields.

The determination of materials erosion thresholds is of key importance for laser micromachining processes themselves and their applications. At laser-induced backside wet etching (LIBWE) of fused silica with organic liquid toluene employing an excimer laser (λ = 248 nm, τ_p = 25 ns), the threshold fluence is reduced from 1.10 J cm⁻² to 0.22 J cm⁻² with an increasing number of pulses from a single pulse to an almost infinite quantity, respectively. A similar effect is observed with an increasing laser spot size. Here, the threshold fluence decreases from 0.52 to 0.30 J cm⁻² with the growing size of the laser spot from 400 to 4225 500 µm². As the origin of the incubation effect, a laser-induced liquid-mediated process of surface modification of the fused silica sample is discussed. A first incubation model for LIBWE is developed and applied to the experimental data that comprise an enhancement of the solid–liquid interface absorbance by a layer of decomposition products from photochemical fragmentation of the liquid.

A two-dimensional photonic crystal (PC) polarization coupler is mainly studied in this work. The photonic band structure and band gap map are calculated by using the plane wave expansion method. The finite-difference time-domain method is applied to analyse the coupling properties of the PC coupler with a square lattice. The coupling ratio is dependent on the coupling interaction length and the shape variation of scatterers between the two coupling channels. The simulation results show that the coupling property is sensitive to the interaction coupling length, and the coupling length increases with frequency for a perfect periodic coupler. The coupler with any coupling ratio can be achieved by adjusting the coupling interaction length. The shape variation of scatterers between the two coupling channels reduces the coupling length significantly and changes the coupling characteristics at certain frequencies inside the band gap.

Direct silicon wafer bonding and decohesion are simulated using a spectral scheme in conjunction with a rate-dependent cohesive model. The cohesive model is derived assuming the presence of a thin continuum liquid layer at the interface. Cohesive tractions due to the presence of a liquid meniscus always tend to reduce the separation distance between the wafers, thereby opposing debonding, while assisting the bonding process. In the absence of the rate-dependence effects the energy needed to bond a pair of wafers is equal to that needed to separate them. When rate-dependence is considered in the cohesive law, the experimentally observed asymmetry in the energetics can be explained. The derived cohesive model has the potential to form a bridge between experiments and a multiscale-modelling approach to understand the mechanics of wafer bonding.

A simple algorithm that generalizes the diffraction enhanced imaging (DEI) technique is introduced and discussed by means of simulated and experimental data. While the original DEI algorithm by Chapman et al (1997 Phys. Med. Biol.42 2015) is limited to objects featuring absorption and refraction only, also ultra-small-angle scattering is considered here. Utilizing only three images in input three parametric images are produced conveying information relative to the three effects. The quality of the parametric images depends on the choice of the input images, as is demonstrated by means of a Monte Carlo simulation. With an appropriate choice, the algorithm gives accurate results on simulated and experimental datasets, as long as the refraction and scattering angles introduced by the object are small compared with the width of the rocking curve. The proposed algorithm can be implemented in several applications, as a valid alternative to multiple-image methods, particularly when time and dose constraints are relevant.

This paper reports on the intense broadband photoluminescence (PL) emission from the ZnO/porous silicon nanocomposite films. The porous silicon (PS) samples were formed by electrochemical anodization on p-type (1 0 0) silicon wafer and ZnO thin films are deposited by the sol–gel spin coating technique in the pores of PS. The average pore size of PS samples is 30 nm. The glancing angle x-ray diffraction pattern of as-deposited and annealed films shows that the quality of (0 0 2) oriented ZnO nanocrystallites improves with annealing at moderate temperature and are polycrystalline in nature. The average crystallize size was found to be 40 nm. The surface topography of the ZnO/PS nanocomposite films has been studied using atomic force microscopy. The mechanism and interpretation of broadband PL from 400 to 900 nm of the nanocomposites are discussed using oxygen-bonding and native defects models for PS and ZnO, respectively. These nanocomposite films could be used as a source of broadband luminescence across most of the visible spectrum.

Theoretical investigation of the onset voltage of negative corona on stranded conductors is described in this paper. The method of calculation is based on the criterion developed for the formation of repetitive negative corona Trichel pulses. This calls first for an accurate calculation of the electric field in the vicinity of stranded conductors. The investigated gap is a three-dimensional field problem. To solve this problem, a new modification of the charge simulation technique is presented, where the simulation charges are helical of infinite length. Laboratory measurements of the onset voltage on stranded conductors are carried out to check the accuracy of the present calculations. The effects of varying the field nonuniformity on the onset voltage values are investigated. The calculated onset voltage values for stranded conductors agree satisfactorily with those measured experimentally.

The statistical fluctuations can dramatically change the dynamics of low current barrier microdischarges when the number of charged particles in the discharge gap is small. The systematic approach is developed to incorporate into the equations of the commonly used fluid model the main stochastic processes in Townsend barrier discharges. It is shown that when natural discharge oscillations are undamped, the fluctuations in the number of ions in the gap eventually lead to disruption of the discharge (i.e. to the state when all charged particles are swept out of the gap). For damped oscillations, the level of fluctuations is limited. It is also shown that fluctuations of the shape of the ion distribution over the gap are negligible.

A photo-triggered discharge has been used to study the production kinetic mechanisms and the reactivity of the hydroxyl radical in a N₂/O₂ mixture (5% oxygen) containing ethane or ethene for hydrocarbon concentration values in the range 1000–5000 ppm, at 460 mbar total pressure. The discharge (current pulse duration of 60 ns) has allowed the generation of a transient homogeneous non-equilibrium plasma, and the time evolution of the OH density has been measured (relative value) in the afterglow (up to 200 µs) by laser induced fluorescence (LIF). Experimental results have been explained using predictions of a self-consistent 0D discharge and plasma reactivity modelling, and reduced kinetic schemes for OH have been validated. It has been shown that recombination of H- and O-atoms, as well as reaction of O with the hydroperoxy radical HO₂, plays a very important role in the production of OH radicals in the mixture with ethane. H is a key species for production of OH and HO₂ radicals. As for ethane, O, H and HO₂ are key species for the production of OH in the case of ethene, but carbonated radicals, following the partial oxidation of the hydrocarbon molecule by O, also play a non-negligible role. The rate constant for O- and H-atom recombination has been estimated to be 3 × 10⁻³⁰ cm⁶ s⁻¹ at near ambient temperature, consistent with LIF measurements on OH for both mixtures with ethane and ethene.

Expanding thermal plasma (ETP) is a versatile technology for thin film deposition process with directional plasma flux and high deposition rates. This process involves expansion of supersonic plasma jets through a steep pressure ratio into a chamber maintained at near vacuum. Usually the plasma jets deviate from chemical and thermal equilibrium and the continuum approach is insufficient to describe the phenomena. In the current work, the continuum approach based Navier–Stokes equations have been implemented to study and understand the jet expansion process in a typical dual-arc plasma deposition reactor. The numerical predictions have been compared against in-house experimental data obtained by thermocouple measurements. For the range of back pressures (6–200 Pa) considered, it was observed that the jet core is supersonic and transitions to a subsonic zone downstream without the formation of any Mach disc for the prevalent operating parameters. Indications of thick and smeared barrel shocks were however observed in the computed flow-thermal fields. The modelled fluid was assumed to be a perfect gas with temperature dependent specific heats, thermal conductivity and viscosity coefficients, with constant Prandtl number of order unity. The radial spreads of the jets increase with increasing pressure ratio thus leading to enhanced interactions within reduced distances downstream of the nozzle exit. The jet core Mach number also increases, but moderately, with decreasing backpressure. It is concluded that within reasonable accuracy, continuum approach based calculations are able to capture most of the important phenomena involved in compressible, high-temperature, supersonic jet expansion processes which are essential in designing chambers relevant to the mentioned processes.

Medium voltage (MV) cells have to respect standards (for example IEC ones (IEC TC 17C 2003 IEC 62271-200 High Voltage Switchgear and Controlgear—Part 200 1st edn)) that define security levels against internal arc faults such as an accidental electrical arc occurring in the apparatus. New protection filters based on porous materials are developed to provide better energy absorption properties and a higher protection level for people. To study the filter behaviour during a major electrical accident, a two-dimensional model is proposed. The main point is the use of a dedicated numerical scheme for a non-conservative hyperbolic problem. We present a numerical simulation of the process during the first 0.2 s when the safety valve bursts and we compare the numerical results with tests carried out in a high power test laboratory on real electrical apparatus.

The dielectric-barrier (DB) discharge is an important approach to generate uniform non-equilibrium atmospheric-pressure glow discharges. We report run-to-run variations, asymmetric pulse formation and long time-scale transient phenomena in these discharges. For similar DB discharge geometric and operating conditions, we observe significant run-to-run variations as manifested in the different voltage–current waveforms at the start of each new run. These run-to-run variations are also accompanied by asymmetric pulses at the start of each run. The variations are observed to drift to a repeatable true steady-state condition on time scales of order tens of minutes to hours. Asymmetric pulse waveforms drift to a symmetric pulse waveform at the true steady state. We explore reasons for these phenomena and rule out thermal drift during a discharge run and gas-phase impurity buildup as potential causes. The most plausible explanation appears to be variations in the surface characteristics of the DBs between two consecutive runs owing to varying inter-run environmental exposure and the conditioning of the dielectric surface during a run owing to plasma–surface interactions. We speculate that the dielectric surface state affects the secondary electron emission coefficient of the surface which in turn is manifested in the discharge properties. A zero-dimensional model of the discharge is used to explore the effect of secondary electron emission.

This paper deals with an adhesion test of coatings using laser-driven shock waves. Physical aspects concerning laser–matter interaction, shock wave propagation and interface fracture strength are described. This comprehensive approach using two numerical codes (HUGO and SHYLAC) allows the determination of mechanisms responsible for coating debonding and a quantitative evaluation of fracture strength. From this description, a coating test protocol is also designed. To diagnose coating debonding, it is based on the analysis of experimental rear free surface velocity profiles measured by velocity interferometer system for any reflectors (VISAR). Ni electrolytic coating (70–90 µm) deposited on a Cu substrate (120–190 µm) is used for the experimental validation of the test. The fracture strength is 1.49 ± 0.01 GPa for a laser pulse duration of 10 ns at 1.064 µm.

Nanofluids, which are produced by dispersing nanoparticles into conventional fluids, exhibit anomalously high thermal conductivity. Most experiments demonstrated that the nanolayer surrounding the solid particles and the clusters formed by nanoparticles' aggregation may play an important role in the enhancement of thermal conductivity of nanofluids. By taking into account the nanolayer and nanoparticles' aggregation, a new model for the effective thermal conductivities of nanofluids is proposed. This model is expressed as a function of the thickness of the nanolayer, the nanoparticle size, the nanoparticle volume fraction and the thermal conductivities of suspended nanoparticles and base fluid. The theoretical predictions on the effective thermal conductivities of nanofluids are shown to be in good agreement with the available experimental data.

A nanofabrication approach based on advanced e-beam lithography and electrodeposition successfully produced high-resolution (≈40 nm line width) metal structures with high aspect ratio (>12) and high density. The combination of these characteristics is essential for hard-x-ray optical components such as zone plates, for x-ray lithography masks and for other devices.

N-doped, p-type ZnO (ZnO : N) thin films were prepared by magnetron sputtering using NO as the N-doping source. The introduction of Ar in the growth ambient could evidently improve the p-type conductivity and crystal quality of the ZnO : N films, with the lowest room-temperature resistivity of 3.51 Ω cm obtained at an optimal Ar partial pressure of 30%. The p-type ZnO : N films have high optical quality, as suggested by temperature-dependent photoluminescence spectra. The N_O substitution acceptor state with an energy level of 180 meV was identified from the free-to-neutral-acceptor (e, A ⁰) transition. The N_O-acceptor bound-exciton binding energy was derived to be 17 meV from the neutral-acceptor-bound-exciton and free exciton emissions. The Haynes factor was about 0.094 for the N_O acceptor in ZnO. Besides the N_O acceptor, a zinc vacancy (V_Zn) acceptor state with an energy level of 255 meV was also identified in ZnO : N from the (e, A ⁰) transition, which might also contribute to the observed p-type conductivity.

We studied the development of interfacial energy γ of alkanethiol self-assembled monolayers on Ag/mica substrates by force-displacement spectroscopy using an atomic force microscope. Self-assembled monolayers of decanethiol [CH₃ (CH₂)₉SH] and octadecanethiol [CH₃ (CH₂)₁₇SH] were studied. The growth of the monolayer as a function of time was studied by an ellipsometer for three different concentrations of decanethiol and octadecanethiol. The thiols led to well-ordered self-assembled monolayer that showed atomic resolution images by lateral force microscopy mode. The behaviour of γ showed non-monotonic variation in stages of adsorption, which was more prominent for short chain length decanethiol. The γ reached a limiting value of 12 mJ m⁻² for decanethiol and 7 mJ m⁻² for octadecanethiol.

A wet chemical surface treatment for InAs epilayers is investigated to remove the native semiconductor oxide prior to growth of a MgO tunnel barrier and Co ferromagnetic electrode by dc magnetron sputtering. Use of a HCl etch followed by (NH₄)₂S as the pre-growth surface treatment resulted in pinhole-like features in the tunnel barrier, as observed by conducting atomic force microscopy, but this detrimental effect is avoided if the etch procedure is repeated twice. High resolution transmission electron microscopy revealed that the etched samples had uniform tunnel barriers and reducing the growth temperature of the barrier from 200 to 100 °C significantly improved the abruptness of the semiconductor/barrier interface. Electrical characterization of barrier properties illustrated that all the etched samples showed parabolic differential conductance curves indicative of tunnelling behaviour at 300 K.

We report differential sputter yield measurements for Xe⁺ ions incident on molybdenum for ion incidence angles of 0°, 15°, 30° and 45°, and ion energies of 250, 350, 500 and 750 eV. The angularly resolved profiles are obtained with a quartz crystal microbalance that is moved to a series of locations above the target. Total sputter yields found by integrating the differential sputter yields are in accord with the literature values. For normally incident ions the profiles are under-cosine, while for obliquely incident ions the profiles show azimuthal variation with pronounced forward sputtering lobes. We discuss the use of published expressions from Zhang and Zhang (2004 Radiat. Eff. Defects Solids159 301–7) for describing the measured profiles. We find that the profiles can be reasonably described with these expressions by using two free parameters: the total sputter yield (Y) and a characteristic energy (E^*). We compare changes in angular sputtering profiles from lightly versus heavily sputtered targets.

To investigate the reflection of light in quasiregular dielectrics, we study here the optical properties of porous-silicon-based Fibonacci and Thue–Morse heterostructures. The multilayered systems are fabricated in such a way that each element in the two-block substitutional sequence has a polytype structure. Both delta-like and traditional configurations are considered. The results for the optical reflectance are analysed. Numerical simulation for the transmittance of delta structures along the lines of the transfer matrix approach is also presented.

Recently new electronic structures were introduced which are composed of tunable electronically anisotropic materials deposited onto semiconductors (TEAMS). A subgroup of these TEAMS structures is tunable electronic materials with pores in oxide on semiconductors (TEMPOS), the pores usually being etched ion tracks in silicon oxide filled with (semi)conducting material and the semiconductor substrate usually being of silicon. These structures, especially TEMPOS structures, are expected to be to some extent radiation hard and resistant against high voltage pulses due to their inherent construction principles.

In this work, the first test experiments have been undertaken to check this assumption. It has been observed that, indeed, there exist TEAMS structures which are rather stable under severe external influences, but there are also others which are less stable under the same conditions. The degree of hardness against high energy radiation and high voltage electrical pulses appears to depend primarily on the chemical composition of the material embedded in these electronic structures.

Zirconium tungstate was successfully synthesized by rapid solidification with a CO₂ laser. Scanning electron microscope observation shows that nano-threads/rods grew horizontally on the surface region and vertically in the interior. The nano-threads in the interior are composed of densely packed nano-crystallites. Raman spectroscopic study shows that the samples solidified in an orthorhombic structure when the laser scan speed was ≥2 mm s⁻¹. This is explained by a compressive stress induced during the rapid solidification process due to a sudden drop of temperature from the molten pool to the ambient. The possibilities for tuning the strength of the compressive stress and controlling the production of different phases of ZrW₂O₈ are proposed. It is analysed and confirmed that the compressive stress can be effectively reduced by lowering laser scan speed. ZrW₂O₈ samples with cubic structure are produced with laser scan speed <2 mm s⁻¹.

The high reflection (HR) mirror composed of dielectric stacks with excellent spectrum characteristics and high damage resistant ability is critical for fabricating multilayer dielectric (MLD) grating for pulse compressor. The selection of the SiO₂ material as the top layer of the HR mirror for grating fabrication is beneficial for improving the laser-induced damage threshold of MLD grating as well as minimizing the standing-wave effect in the photoresist during the exposure process. Based on an (HLL)⁹H design comprising quarter-waves of HfO₂ (H) and half-waves of SiO₂ (L), we obtain an optimal design of the HR mirror for MLD grating, the SiO₂ top layer of which is optimized with a merit function including both the diffraction efficiency of the MLD grating and the electric field enhancement in the grating. Dependence of the performance of the MLD grating on the fabrication error of the dielectric mirror is analysed in detail. The HR mirror is also fabricated by E-beam evaporation, which shows good spectral characteristics at the exposure wavelength of 413 nm and at the operation wavelength of 1053 nm and an average damage threshold of 10 J cm⁻² for a 12 ns pulse.

Li-doped p-type Zn_0.95Mg_0.05O thin films have been achieved on glass substrates by pulsed laser deposition. X-ray diffraction shows that all the films exhibit good crystallinity with a highly c-axis preferential orientation. The results of the Hall measurements indicate that p-type conduction in Li-doped Zn_0.95Mg_0.05O films is strongly dependent on the oxygen pressure. Films deposited at 5 and 25 Pa show n-type conduction. However, at the oxygen pressure of 15 and 20 Pa, the films show definitive p-type conductivity. The maximal hole concentration was found to be 1.26 × 10¹⁸ cm⁻³ at a working pressure of 20 Pa with a resistivity of 17.82 Ω cm and Hall mobility of 0.285 cm² V⁻¹ s⁻¹. Furthermore, all the p-type Zn_0.95Mg_0.05O films possess high average transmittance of ∼90% in the visible region and a band gap of 3.41 eV at room temperature.

In this work, we present a study on the magnetic properties of Joule-heated CoFeSiB glass-covered amorphous microwires under applied stress. A comparison between the magnetic properties of four samples is made: (i) as cast, Joule-heated under (ii) dc current or ac current of (iii) 100 Hz or (iv) 500 Hz. The stress modifies the anisotropy and the domain structure in such a way that it can be studied through magnetoimpedance measurements and ferromagnetic resonance (FMR) dispersion relations (DR) extracted from them. From the fitting of the FMR DR, the magnitude and the orientation of the transverse anisotropy field, as well as an insight into the micromagnetic structure of the microwires were obtained. It was concluded that longitudinal anisotropy dominates the microwire behaviour under zero stress. By applying an increasing stress to the microwires, the inner core with longitudinal anisotropy is surrounded by two concentric outer shells with almost circumferential anisotropies. These magnetic configurations can be explained in terms of the residual stress arising from the wire's manufacturing procedure and the additional applied stress.

Magnetism and permittivity properties of polycrystalline Cd_0.5Fe_0.5Cr₂S₄ have been investigated. Cd_0.5Fe_0.5Cr₂S₄ is a ferrimagnet with a Curie temperature of 137 K, and exhibits large permittivity and loss tangent in the frequency range 30 kHz–1 MHz. A kink is observed on the curve of the temperature-dependent permittivity near its magnetic transition point, implying the existence of a magnetodielectric effect.

A magnetic entropy change of 25.4 mJ cm⁻³ K⁻¹ at H = 1.5 T in CrO₂ nano-rods is observed, which is one of the largest magnetocaloric effects ever reported among those oxides. In this work, a molecular field model, Landau theory and Debye approximation are used to unveil the origins of the magnetic entropy change associated with a second phase transition in the system. The theoretical estimates indicate that the entropy change results mainly from a field-induced spin ordering, whereas the lattice entropy contribution is approximately 0.112–0.335 mJ cm⁻³ K⁻¹. Finally, the electronic entropy change is considered to be negligible. The work is of significance not only in the understanding of the magnetic oxide refrigerant with large magnetic entropy change but also in the exploitation of a new class of potential magnetic refrigerants with large magnetostriction.

Ultrasonic attenuation, specific heats at constant pressure, static and dynamic light scattering as well as shear viscosity data of the perfluoromethylcyclohexane–carbon tetrachloride critical system have been re-evaluated in the light of the Bhattacherjee–Ferrell dynamic scaling model. The experimental sonic attenuation coefficients yield the theoretical form of the scaling function if a noncritical relaxation term is assumed to contribute to the total spectra in addition to the critical contribution. Evidence from noncritical ultrasonic spectra suggests the noncritical relaxation to be due to rotational isomerization of the perfluoromethylcyclohexane molecule. The amplitudes in the power laws of the fluctuation correlation length, the mutual diffusion coefficient and the relaxation rate of concentration fluctuations are ξ₀ = (0.228 ± 0.021) nm, D₀ = (1.24 ± 0.04) × 10⁹ m² s⁻¹, and Γ₀ = (47.5 ± 13) × 10⁹ s⁻¹, respectively. The amplitude of the critical term in the heat capacity is C_pc = (0.093 ± 0.002) J g⁻¹ K⁻¹ and the adiabatic coupling constant results as g = 0.126.

The dynamics of a weakly nonlinear modulated wave in a discrete electrical transmission line with negative nonlinear resistance and dissipative effects is investigated. This leads to the propagation of envelope modulation in the line modelled by the discrete complex Ginzburg–Landau equation. For an initial modulated plane wave propagating in the line, the criteria for modulational instability as well as the threshold amplitude are derived. The evolution of modulated waves which have the shape of an envelope soliton and the chaotic-like behaviour of the system are also examined. We show that dissipation can affect patterns propagating into the system. Numerical simulations demonstrate the validity of theoretical predictions.