[en] We present the expressions of nonlinear effective susceptibilities of antiferromagnetic/nonmagnetic superlattices with an effective-medium method, and then on this basis investigate nonlinear dispersion properties of antiferromagnetic polaritons in the superlattices. In the geometry used in the paper, the y-axis is normal to the interface, and the z-axis is pointed along the anisotropy axis. The theoretical analysis and numerical calculations show: (i) The nonlinearity has no contributions to the waves traveling along the three axes, and to the waves in the x-y plane. (ii) The nonlinear shift in wave number is either upward or downward, depending on the mode frequency larger or less than the resonance frequency, for the wave traveling along the other directions

[en] This paper presents the formalism for transmission of normally incident electromagnetic radiation through a finite superlattice of alternating magnetic and non-magnetic layers. It is assumed that the ordering direction and static field, if any, are perpendicular to the interfaces so that the eigenmodes for propagation are the states of circular polarization. The transmission and reflection coefficients are expressed in terms of the transfer matrix for propagation across a unit cell of the superlattice. The results are illustrated for a ferromagnet/non-magnet superlattice. Prominent features are seen related first to resonances in the magnetic permeability and second to the stop bands of the Bloch waves of the superlattice. In transparency regions, fringes occur due to the overall thickness of the superlattice

[en] Strontium titanyl oxalate (STO) particles were synthesized with the co-precipitation method. Suspensions made by dispersing the STO particles in silicone oil exhibit an excellent electrorheological (ER) effect with high yield stress, high shear stress at higher shear rate, and low current density. By analyzing the Fourier transform infrared spectra of STO particles heated at different temperatures and measuring the yield stresses of the corresponding ER fluids, it is confirmed that the polar molecules absorbed on the particles play a crucial role in the giant ER effect. The phenomena observed in STO ER fluids can be explained by using the model of a polar molecule dominated electrorheological (PM-ER) effect

[en] Electrosorption of ions from aqueous solutions with carbon nanotubes and nanofibers (CNTs-CNFs) composite film electrodes has been demonstrated. The large area CNTs-CNFs film was directly grown on Ni plate by low pressure and low temperature thermal chemical vapor deposition. The CNTs-CNFs electrodes have great advantages such as low cost, easy operation, long-term reproducibility, and integrity of monolithic CNTs-CNFs film and current collector. Batch-mode experiments at low voltage (0.4-2 V) were conducted in a continuously recycling system to investigate the electrosorption process. Purification of water with good reproducibility was achieved because of optimal pore size distribution of CNTs-CNFs composite films

[en] Since the first successful running of the people-carrying high temperature superconducting (HTS) Maglev test vehicle on 31 December 2000, about 27,000 people have taken it, and the accumulated running distance is about 400 km. The levitation force of the onboard HTS equipment is measured periodically, and new experimental results measured on 5 March 2003 show that the performance of the onboard HTS Maglev equipment is almost the same as that of two years ago. Experimental results indicate that the long-term stability of the HTS Maglev vehicle is good. This further proves the feasibility of the HTS Maglev vehicle for practical transportation. It is worth mentioning that all the results are measured at a low speed; however, investigations of the dynamic performance of the HTS Maglev vehicle at high speed are necessary for practical application. Research on the dynamic performance of the HTS Maglev vehicle is ongoing

[en] We synthesize a series of orthorhombic polycrystalline YMn_1-xCr_xO₃ (o-YMCO, x < 0.3) samples using high-pressure sintering, and investigate the multiferroicity by various characterization techniques. It is identified that Cr doping remarkably enhances the ferromagnetism, and the ferroelectric polarization is also significantly modulated. The enhanced ferromagnetism is argued to originate from the ferromagnetic interactions between neighbouring Cr³⁺ spins and Mn³⁺ spins. While the microscopic mechanism for polarization generation remains to be clarified, it may be argued, based on the response of polarization against external magnetic field, that Cr doping induces a partial transition from the symmetric exchange striction mechanism in o-YMnO₃ to the asymmetric exchange striction mechanism in o-YMCO for ferroelectricity generation. (paper)

[en] Disc-modified nanohelices (DNHs) of ZnO were synthesized by thermal evaporation. The ZnO DNHs are constructed by nanowires which are regularly attached with discs. The axis of the DNH structure is along the ZnO[0001] direction. The pitch distance, the mean diameter, and the thickness of the nanowires are uniform for each ZnO DNH. Within one period there are 12 discs symmetrically attached on the surfaces of the nanowires. The discs are composed of nanometre-sized ZnO crystal cores and amorphous SiO₂ shells. The mechanism of formation of the nanostructures is also discussed

[en] This paper reports the characterization of scandium aluminum nitride (Al_1−xSc_xN, x   =  27%) films and discusses surface acoustic wave (SAW) devices based on them. Both AlScN and AlN films were deposited on silicon by sputtering and possessed columnar microstructures with (0 0 0 2) crystal orientation. The AlScN/Si SAW devices showed improved electromechanical coupling coefficients ( K ², ∼2%) compared with pure AlN films (<0.5%). The performance of the two types of devices was also investigated and compared, using acoustofluidics as an example. The AlScN/Si SAW devices achieved much lower threshold powers for the acoustic streaming and pumping of liquid droplets, and the acoustic streaming and pumping velocities were 2  ×  and 3  ×  those of the AlN/Si SAW devices, respectively. Mechanical characterization showed that the Young’s modulus and hardness of the AlN film decreased significantly when Sc was doped, and this was responsible for the decreased acoustic velocity and resonant frequency, and the increased temperature coefficient of frequency, of the AlScN SAW devices. (paper)

[en] The two key parameters for levitation performance over a permanent magnet (PM) guideway are the levitation force and the stiffness of the high temperature superconductor (HTS) YBaCuO bulk. Their distributions along a lateral displacement (LD) were measured in zero-field-cooling (ZFC) and in field-cooling (FC) conditions. There are two cases of applied magnetic field for a single HTS bulk: symmetrical or unsymmetrical about the bulk axis. Although the levitation force has a linear relationship with the applied field in the symmetrical case, such a linear relationship disappears once the applied field becomes unsymmetrical. Furthermore, the levitation stiffness is measured in FC, and they still change more drastically than the levitation force in ZFC. In particular, the levitation stiffness has a linear relationship with the associated levitation force, whether the applied field is symmetrical or unsymmetrical. Its lateral distribution at a gap of 20 mm in FC agrees with the levitation force distribution at a gap of 10 mm in ZFC