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The dielectric and magnetic properties of ceramics based on barium titanate and solid solutions of barium strontium titanate doped with iron and gadolinium ions at concentrations below 5 mol.% have...

Nondestructive scanning probe microscopy of fragile nanoscale objects is currently in increasing need. In this paper, we report a novel atomic force microscopy mode, HybriD Piezoresponse Force Microscopy (HD-PFM), for simultaneous nondestructive analysis of piezoresponse as well as of mechanical and dielectric properties of nanoscale objects. We demonstrate this mode in application to self-assembled diphenylalanine peptide micro- and nanotubes formed on a gold-covered substrate. Nondestructive in- and out-of-plane piezoresponse measurements of tubes of less than 100 nm in diameter are demonstrated for the first time. High-resolution maps of tube elastic properties were obtained simultaneously with HD-PFM. Analysis of the measurement data combined with the finite-elements simulations allowed quantification of tube Young's modulus. The obtained value of 29 ± 1 GPa agrees well with the data obtained with other methods and reported in the literature.

The study of novel thermal effects associated with spin current is fundamental to understanding the relationship between magnetoelectric and thermal phenomena. The central focus of attention of our research is on the spin analog of the Thomson effect as the most promising in terms of its use in heat switches of solid-state coolers. In order to model heat flows, the heat conduction equation is derived in the presence of magnetic and electric fields. Applying the developed theoretical framework, the spin Thomson coefficient is calculated for a yttrium-iron garnet plate. It is demonstrated that this coefficient strongly depends on the thickness of the plate. The corresponding estimates of the heat flux carried by the spins are also obtained. For a 200 nm plate, it is 6.81 W/cm2, which is comparable to the heat fluxes in the best thermal switches. Moreover, the results of the paper indicate at the possibility of further increase in the flux by an optimal choice of plate thickness and magnitude of magnetic field.

We investigated the magnetoelectric properties of a new laminate composite material based ony + 140°-cut congruent lithium niobate piezoelectric plates with an antiparallel polarized “head-to-head” bidomain structure and metglas used as a magnetostrictive layer. A series of bidomain lithium niobate crystals were prepared by annealing under conditions of Li2O outdiffusion from LiNbO3with a resultant growth of an inversion domain. The measured quasi-static magnetoelectric coupling coefficient achieved |αE31| = 1.9 V·(cm Oe)−1. At a bending resonance frequency of 6862 Hz, we found a giant |αE31| value up to 1704 V·(cm Oe)−1. Furthermore, the equivalent magnetic noise spectral density of the investigated composite material was only 92 fT/Hz1/2, a record value for such a low operation frequency. The magnetic-field detection limit of the laminated composite was found to be as low as 200 fT in direct measurements without any additional shielding from external noises.

The influence of UV and visible radiations on the insulating properties of metal-insulator-metal structures based on single-crystalline strontium titanate is investigated. It is found that the capacitance of the structure stably grows under irradiation by light with a wavelength from the intrinsic absorption range both at low temperatures and at room temperature. Mechanisms underlying this effect are discussed.

The results of investigations of the dielectric, magnetic, and structural properties of films with multiferroic properties have been presented. Two methods of the formation of multiferroic media have been analyzed: the method based on the formation of multilayer structures containing ferroelectric and ferromagnetic films and the method of introducing magnetic elements into a ferroelectric material in concentrations sufficient to induce magnetic properties in the composite material.

Barium titanate based ceramics is the most common class of lead-free ceramics due to its high values of dielectric constant, polarization, piezo- and electrocaloric effects. In this paper dielectric properties and electrocaloric effect in ceramics based on solid solution of barium-calcium titanate had been studied. It was shown, that increasing of calcium titanate in solid solution leads to increasing of dielectric constant and electrocaloric effect, simultaneouslyit leads to decreasing of leakage currents. While increasing fraction of calcium titanate from 0% to 10%, dielectric constant at frequency of 1 kHz rises from 10500 to 13600, maximum adiabatic electrocaloric response at ΔE = 1.3 V/μm rises from 0.5 K to 0.7 K.

In ceramics, based on a solid solution of strontium barium niobate (0.7SBN) doped with cerium and gadolinium in various concentrations, an investigation was made of dielectric constant, electrical polarization, and the electrocaloric effect. For 0.7SBN ceramics, it was found that the addition of cerium (0.2%) leads to a decrease in the electrocaloric effect compared to pure 0.7SBN, and the addition of gadolinium (˂1%) to an increase in the electrocaloric effect.

Properties of the high-frequency spin-electromagnetic wave chaos developed in active ring oscillators have been investigated. A multiferroic structure composed of yttrium iron garnet film and barium strontium titanate (BST) slab served as a nonlinear dispersive medium of the oscillator. Dual control of the fractal dimension of the chaotic signal attractor was realized by variation of the ring gain and dielectric permittivity of the BST slab.

Properties of spin-electromagnetic wave chaos developed in active ring oscillators have been investigated. A multiferroic structure composed of yttrium iron garnet film and barium strontium titanate (BST) slab served as a nonlinear dispersive medium of the oscillator. Dual control of the fractal dimension of the chaotic signal attractor was realized by variation of the ring gain and dielectric permittivity of the BST slab.

As the risk of porcine endogenous retrovirus (PERV) infection is a major obstacle to the xenotransplantation of porcine tissue, we investigated whether an AN69 hollow fibre membrane, used for islets of Langerhans transplantation, could prevent the transfer of PERVs and thus reduce the risk of PERV infection. PK15 cells were used as a PERV source. A specific and highly sensitive RCR was used for detection of a PERV provirus DNA (gag region) and a porcine mtDNA. Human U293 cells were incubated in vitro with encapsulated PK15 cells, concentrated encapsulated PK15 supernatant, or concentrated PK15 supernatant as a control. CD1 mice were implanted in vivo with encapsulated PK15 cells or injected with PK15 supernatant. We found no infection in human cells incubated with either encapsulated PK15 supernatant or in 10 out of 11 samples after coincubation with encapsulated PK15 cells. Infection of human cells was, however, detected in 1 out of 11 samples after coincubation with encapsulated PK15 cells. The presence of PERV provirus DNA and porcine mtDNA was detected in all the investigated tissues of the mice injected with PK15 supernatant and in various tissues of the mice implanted with encapsulated PK15 cells. Four weeks after the last injection of PK15 supernatant or a fiber explantation, no mouse showed any presence of PERV provirus DNA or porcine mtDNA. Our results demonstrate that AN69 hollow fiber membrane will reduce but not abolish the risk of PERV infection. Because the real risk of PERV infection still remains unknown, it is necessary to investigate further the real protection that could be provided by hollow fibers to ensure the safety of clinical xenotransplantation.

As the investigated sample in our experiments we used the film of niobium on the sapphire substrate, and ceramics CTS ‐19 with the preliminary cooled amplifier was used as the acoustic sensor. Acoustic sensor was fastened to the back side of the substrate. In the experiments we measured the spectrum at the boiling of liquid nitrogen; characters of the frequency dependence of spectrums for helium and nitrogen were identical.