Table of contents

Electric-field-induced control of magnetic properties at room temperature has attracted considerable attention owing to its significant potential for facilitating the construction of ultralow-power-consumption electric devices. Voltage-controlled magnetic anisotropy (VCMA) effect in ultrathin ferromagnetic metals has shown that the magnetization of nanomagnets can be controlled by electric fields in extremely short periods (down to 0.1 ns). The VCMA effect in metals can be the ultimate technology for the operation of spintronics devices, such as nonvolatile random access memory, where high-speed operation with high writing endurance is indispensable. This review summarizes experimental studies of the VCMA effect. First, studies on VCMA in various systems are reviewed. Then, useful experimental and theoretical methods for VCMA research, i.e. electrical measurements using magnetic tunnel junction devices, x-ray magnetic circular dichroism spectroscopy, and first-principles studies, are described. Finally, the oxygen ion migration mechanism for electrochemical VCMA and the orbital magnetic moment and electric quadrupole mechanisms for purely electronic VCMA are discussed in detail.

On-chip optical interconnects heterogeneously integrated on silicon wafers by transfer-print technology are presented for the first time. Thin (<5 µm), micron sized light-emitting diodes (LEDs) and photo diodes (PDs) are prefabricated and transfer-printed to silicon wafer with polymer waveguides built between them. Data transmission with total power consumption as low as 1 mW, signal to noise ratio of  >250 and current transfer ratio of 0.1% in a compact volume of  <0.0004 mm³ are demonstrated. Experiment shows that the polymer waveguide between the LED and PD plays a key role in enhancing the data transmission efficiency. Reciprocal performance for bidirectional transmission is also achieved. The results show the potential for cost-effective and low profile form-factor on-chip opto-isolators.

Visualizing and quantifying molecular motion and interactions inside living cells provides crucial insight into the mechanisms underlying cell function. This has been achieved by super-resolution localization microscopy and single-molecule tracking in conjunction with photoactivatable fluorescent proteins (PA-FPs). An alternative labelling approach relies on genetically-encoded protein tags with cell-permeable fluorescent ligands which are brighter and less prone to photobleaching than fluorescent proteins but require a laborious labelling process. Either labelling method is associated with significant advantages and disadvantages that should be taken into consideration depending on the microscopy experiment planned. Here, we describe an optimised procedure for labelling Halo-tagged proteins in live Escherichia coli cells. We provide a side-by-side comparison of Halo tag with different fluorescent ligands against the popular photoactivatable fluorescent protein PAmCherry. Using test proteins with different intracellular dynamics, we evaluated fluorescence intensity, background, photostability, and results from single-molecule localization and tracking experiments. Capitalising on the brightness and extended spectral range of fluorescent Halo ligands, we also demonstrate high-speed and dual-colour single-molecule tracking.

This paper experimentally discusses roles of dinitrogen pentoxide (N₂O_5gas) in the air plasma effluent gas on the effluent gas exposed liquid water, through nitrate () generation and nitration processes in the liquid phase. The generation from N₂O_5gas is suppressed approximately up to 50% by a competing reaction with a p-hydroxyl-phenyl-acetate (p-HPA) at pH  =  11. This indicates a near-surface generation of an intermediate species derived from N₂O_5gas, which turns to . Also, it is found that the nitration reaction rate observed with NiSPY-3N can be of the order of the generation rate. From experimental results on the air plasma effluent gas and the liquid phase species, the role of the N₂O_5gas exposure to the liquid surface is interpreted as an intermediate species supply to the liquid surface, such as the solvated nitronium ion (). This deduced roles of N₂O_5gas can contribute to developments and understanding of the N₂O_5gas-involved plasma biological applications.

The double-shifted magnetic hysteresis loops, which are accompanied by the formation of bi-domain state, are normally observed after zero field cooling a demagnetized sample or as-deposited ferromagnetic (FM)/antiferromagnetic (AFM) structures. In the pioneer works, this phenomenon was explained by the imprinting of ferromagnetic FM domain in AFM layer, however the interaction between the FM and AFM domain has never been discussed. In this work, we observed double-shifted magnetic hysteresis loops and bi-domain state in [Co 0.3/Ni 0.4i]_N/IrMn multilayers with perpendicualr magnetic anisotropy. By comparing the domain patterns in (Co 0.3/Ni 0.4)_N/IrMn multilayers, we may conclude that the bi-domain state in FM/AFM structure is related to both the FM and AFM domain, and the domain size is determined by the minimum of the total energy in the FM/AFM system through the interficial coupling.

The magnetization dynamics of single Co/Cu/Co spin valves, embedded in electrodeposited nanowires of 30 nm avarage diameter, was observed using the spin-diode effect. The electrically-detected magnetic resonances were compared when using modulation of either the magnetic field or a laser irradiation. The effect of temperature modulation was accounted for by introducing the temperature dependence of the saturation magnetization and anisotropy, as well as thermal spin-transfer torque (TSTT). The predictions of the model are compared with experimental data. Two forms of modulation give rise to qualitative differences in the spectra that are accounted for by the model only if both temperature-modulated magnetization and TSTT are introduced in the model. On the contrary, the temperature modulation of the magnetic anisotropy has a smaller contribution.

A novel dual-output magnetoelectric (ME) gyrator operating in an acoustic resonance mode and based on a Pb(Zr_xTi_1−x)O₃ (PZT)/Metglas/PZT (P–M–P) trilayer structure is discussed. The dual-output with different current-to-voltage (I–V) conversion ratios and different voltage levels result from the use of piezoelectric layers with different thicknesses as the output capacitive port. Under open circuit conditions, the maximum I–V conversion ratios of the two outputs were 5.7 and 13.5 kV A⁻¹ at a frequency of 50.4 kHz. A high power efficiency (ƞ) of 91.7% was achieved and remained relatively stable (⩾86%) under increasing power drive to a power density of 45 W in⁻³. These excellent power transfer and multi-output characteristics offer unique possibilities for possible use of ME gyrators in modern power electronic devices.

Lead-free, high piezocoefficient 0.5Ba(Zr_0.2Ti_0.8)O₃–0.5(Ba_0.7Ca_0.3)TiO₃ film is fabricated on soft magnetic Ni foil as a substrate using a pulse laser deposition technique for the magnetoelectric studies. The x-ray diffraction analysis confirms the phase pure formation of polycrystalline ferroelectric film along with the presence of NiO formed during the high temperature growth process. The obtained lattice parameters suggest that the native oxide could favour the coherent growth of a ferroelectric layer. The film exhibits ferroelectric characteristics with a polarization value of 23 µC cm⁻² at 225 kV cm⁻¹. The fabricated heterostructure displayed a high magnetoelectric coupling coefficient with the maximum magnetoelectric voltage coefficient (α₃₁) value of 1.08 V cm⁻¹ Oe⁻¹ at low field of 44 Oe. It is noteworthy to mention that the observed α₃₁ is comparable to the earlier reported toxic lead-based similar systems. The comparison between the experimental and calculated α₃₁ values suggests that the strain transfer percentage efficiency is around 69%, which is responsible for the observed large ME coupling. These experimental findings give a way to achieve high magnetoelectric coefficients by fabricating the oxide piezoelectric layer directly on the clamping free magnetic substrate.

Magnetic bubbles are topological spin textures that offer interesting physics and great promise for next-generation information storage technologies. The main obstacles so far are that magnetic bubbles are generated with no field stimuli in new material systems at room temperature. Here, we report the observation of individual magnetic bubbles and its high-frequency measurement at room temperature in an exchange-coupled [Co/Pd]₄/Py multilayers. We demonstrate that the emergence of magnetic bubbles at remanence can be tuned by the in-plane tilted magnetic field (roughly 3°) along the film plane at room temperature. High frequency results indicate that the presence of magnetic bubbles leads to broadening of the magnetic permeability spectrum lines (due to the non-uniformity of the magnetic moments). Our findings may help to facilitate the application of bubble-based devices at room temperature in exchange-coupled magnetic multilayers.

Two-dimensional transition metal dichalcogenides (TMDCs), as promising alternative plasmon supporting materials to graphene, exhibit potential applications in sensing. Here, we propose a TMDCs-mediated long range surface plasmon resonance (LRSPR) imaging biosensor, which shows tremendous improvements in both imaging sensitivity (2) and detection accuracy (10) as compared to conventional surface plasmon resonance (cSPR) biosensors. It is found that the imaging sensitivity of the LRSPR biosensor can be enhanced by the integration of TMDC layers, which is different from the previously reported graphene-mediated cSPR imaging sensor, whose imaging sensitivity decreases with the number of graphene layers. This imaging sensitivity enhancement effect for the TMDCs-mediated LRSPR sensor originates from the propagating nature of the LRSPR at both interfaces of sensing medium/gold and gold/cytop layer (with a matching refractive index as sensing medium). By tuning the thickness of gold film and cytop layer, it is possible to achieve optimized imaging sensitivity for LRSPR sensors with any known integrated number of TMDC layers and an analyte refractive index. The proposed TMDCs-mediated LRSPR imaging sensor could provide potential applications in chemical sensing and biosensing.

An amplitude-adjustable metasurface has been proposed to suppress the side-lobe level over an extra-wide frequency band. A polarization-selective unit cell is designed to constitute the metasurface, which can manipulate the amplitudes of the co-polarization reflection coefficients and cross-polarization transmission coefficients, while the phases remain unchanged. The amplitude of the metasurfaces is discretely Taylor-distributed. For example, two metasurfaces were designed to achieve side-lobe level suppression (SLLS), of reflected and transmitted beams, respectively. The simulations demonstrated that two metasurfaces have good performance on SLLS of reflected/transmitted beams, with approximately  −20 dB SLL in a wide frequency region. It is expected that the designed amplitude-adjusted metasurfaces may find potential application in antennas and stealth techniques.

A gliding arc plasmatron (GAP), which is very promising for purification and gas conversion, is characterized in nitrogen using optical emission spectroscopy and high-speed photography, because the cross sections of electron impact excitation of N₂ are well known. The gas temperature (of about 5500 K), the electron density (up to 1.5  ×  10¹⁵ cm⁻³) and the reduced electric field (of about 37 Td) are determined using an absolutely calibrated intensified charge-coupled device (ICCD) camera, equipped with an in-house made optical arrangement for simultaneous two-wavelength diagnostics, adapted to the transient behavior of a GA channel in turbulent gas flow. The intensities of nitrogen molecular emission bands, N₂(C–B,0–0) as well as (B–X,0–0), are measured simultaneously. The electron density and the reduced electric field are determined at a spatial resolution of 30 µm, using numerical simulation and measured emission intensities, applying the Abel inversion of the ICCD images. The temporal behavior of the GA plasma channel and the formation of plasma plumes are studied using a high-speed camera. Based on the determined plasma parameters, we suggest that the plasma plume formation is due to the magnetization of electrons in the plasma channel of the GAP by an axial magnetic field in the plasma vortex.

The influence of the N₂ admixture ratio on a He–N₂ uniform atmospheric pressure glow discharge (APGD) generated using an asymmetric 20 µs, 10 kHz bipolar applied voltage pulse is systematically investigated, using electrical and optical emission spectroscopic measurements as diagnostic tools. We focused our investigation on understanding the discharge characteristics of the plasma ignited after an off-voltage period of 80 µs duration. The measured breakdown voltages for various N₂ admixture ratios of up to 3% are compared with a theoretically calculated breakdown voltage, taking into account the secondary electron emission coefficient of the dielectric surface. The results indicate that the value of the secondary emission coefficient should increase from 0.1 to 0.5 to realize the experimentally obtained breakdown voltage variation within a 3% N₂ admixture ratio. Using experimentally obtained values of the breakdown voltage, discharge current densities for different N₂ admixture ratios, and 66 reactions among electrons, helium and N₂, the variations of the N₂ (A), N₂ (C) and (B) state densities with N₂ admixture ratio are calculated. The N₂ admixture ratio dependence of the calculated N₂ (C) and (B) state densities are similar to the N₂ admixture ratio dependences of the emission intensities of the 337 nm band of the N₂ second positive system (SPS) and the 391.4 nm band of the first negative system, respectively. Experimental observation and numerical investigation indicates that below a 1% N₂ admixture ratio, the He (2³S) metastable state has a strong influence on the discharge characteristics, and above a 2% N₂ admixture ratio, the N₂ (A) metastable state influences the discharge behavior. The N₂ (A) metastable state density is estimated experimentally using the emission intensity ratio of the 337 nm band of N₂ SPS and the 247 nm band of a NO-γ system. The experimentally estimated and theoretically calculated value of N₂ (A) metastable state density is of the same order of 10¹³ cm⁻³. The estimated N₂ (A) metastable state density shows a rapid increase above a 2% N₂ admixture ratio, which supports the idea that the secondary emission coefficient increases due to an increase in N₂ (A) flux.

Ferrimagnetic iron oxide nanoparticle monolayers on top of ferroelectric BaTiO₃ substrates were prepared and a magnetoelectric coupling effect was observed. We employed hereby a magnetoelectric AC susceptibility setup as modification of a commercial superconducting quantum interference device magnetometer. The magnetoelectric coefficient shows two jumps at the BaTiO₃ phase transition temperatures. Moreover, the magnetic depth profile of the nanoparticle monolayer was probed by polarized neutron reflectivity. The data recorded at various electric field values show that the electric field is able to alter the magnetism of the nanoparticle monolayer by a strain mediated magnetoelectric coupling effect.

Pseudomonas aeruginosa is an opportunistic pathogen that has a high resistance to antibiotics and can cause disease in patients with immune deficiency. Therefore, in the present study, the antimicrobial effects of imipenem-functionalized spherical and rod gold nanoparticles (SGNPs and RGNPs) have been investigated on P. aeruginosa. Firstly, SGNPs and RGNPs were synthesized by citrate reduction and seed-growth methods, respectively. The SGNPs and RGNPs were conjugated with imipenem (Imp-SGNPs and Imp-RGNPs). The size, potential and morphology of the SGNPs and RGNPs were determined by different techniques including; TEM, DLS and UV–vis spectra. Different concentrations of Imp-SGNPs and Imp-RGNPs were used to determine the bacterial growth rate and minimum inhibitory concentration (MIC) by UV–vis spectrophotometry according to CLSI standard protocol. The results indicated that the drug loading on the surface of SGNPs and RGNPs was 60.5% and 54%, respectively. The Imp-SGNPs and Imp-RGNPs exhibited greater antibacterial activity compared to that of imipenem alone. The highest antibacterial activity of GNPs was observed in the Imp-RGNPs against P. aeruginosa. The MIC for 90% inhibition (MIC90) for imipenem, Imp-SGNPs and Imp-RGNPs was determined to be 43 µg ml⁻¹, 21 µg ml⁻¹ and 5.7 µg ml⁻¹, respectively. These results indicated that the new nano-carrier systems with GNPs have great potential for enhanced antibacterial activities.