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A nanograined YBCO target, where a great number of grain boundaries, pores etc. exist, is shown to hold an alternative approach to future pulsed laser deposition based high-temperature superconductor thin film and coated conductor technologies. Although the nanograined material is introduced earlier, in this work, we comprehensively demonstrate the modified ablation process, together with unconventional nucleation and growth mechanisms that produces dramatically enhanced flux pinning properties. The results can be generalized to other complex magnetic oxides, where an increased number of defects are needed for modifying their magnetic and electrical properties, thus improving their usability in the future technological challenges. [ABSTRACT FROM AUTHOR]

In order to understand how the doping with self-assembled nanorods of different sizes and concentrations as well as applied magnetic fields affect the critical current anisotropy in YBa2Cu3O7−x (YBCO) thin films close to YBCO c-axis, we present an extensive and systematic computational study done by molecular dynamics simulation. The simulations are also used to understand experimentally measured Jc(θ) curves for BaHfO3, BaZrO3 and BaSnO3 doped YBCO thin films with the help of nanorod parameters obtained from transmission electron microscopy measurements. Our simulations reveal that the relation between applied and matching field plays a crucial role in the formation of Jc(θ)-peak around YBCO c-axis (c-peak) due to vortex-vortex interactions. We also find how different concentrations of different size nanorods effect the shape of the c-peak and explain how different features, such as double c-peak structures, arise. In addition to this, we have quantitatively explained that, even in an ideal superconductor, the overdoping of nanorods results in decrease of the critical current. Our results can be widely used to understand and predict the critical current anisotropy of YBCO thin films to improve and develop new pinscapes for various transport applications. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanorods were manufactured using the aqueous chemical growth (ACG) method, and the effect of thermal acetylene treatment on their morphology, chemical composition, and optical properties was investigated. Changes in the elemental content of the treated rods were found to be different than in previous reports, possibly due to the different defect concentrations in the samples, highlighting the importance of synthesis method selection for the process. Acetylene treatment resulted in a significant improvement of the ultraviolet photoluminescence of the rods. The greatest increase in emission intensity was recorded on ZnO rods treated at the temperature of 825 °C. The findings imply that the changes brought on by the treatment are limited to the surface of the ZnO rods. [ABSTRACT FROM AUTHOR]

Photo-induced magnetization has been studied in small-bandwidth manganite PrCaMnO ( x = 0.1) (PCMO) bulk and thin films. It is observed that the persistent change in magnetization under optical excitation is much stronger in epitaxial thin films of PCMO compared to the bulk. This change is manifested in a change of both coercive field and Curie temperature of the thin films. Stronger photo-induced effect in the thin films might have their origin in the substrate-induced strain effect on the magnetic properties. [ABSTRACT FROM AUTHOR]

This article presents a comparative study of persistent photo-induced magnetization in intermediate and low bandwidth perovskite manganite thin films, and analyzes the possible mechanisms for the observed differences in light of their structural and magnetic properties. Intermediate bandwidth manganite LaCaMnO (LCMO) and low bandwidth manganite PrCaMnO (PCMO), both show persistent change in magnetization under light. However, under illumination, while LCMO shows increased ferromagnetic (FM) interaction both in low and saturation field regime, PCMO shows increased FM interaction at low fields and decreased FM behavior near saturation fields. Also relaxation of photo-induced magnetization shows stretched exponential nature in LCMO compared to much faster relaxation, beyond detection limit in PCMO. Comparison between these two systems will provide important insight of the underlying physics of persistent photo-induced magnetization of perovskites manganites and will consequently facilitate their application in magneto-optical devices, photodiodes and photovoltaics. [ABSTRACT FROM AUTHOR]

High dielectric constant and its dependence on structural strain and grain boundaries (GB) in LaSrMnO (LSMO) thin films are reported. X-ray diffraction, magnetization, and magneto-transport measurements of the LSMO films, made by pulsed laser deposition on two different substrates-MgO and SrTiO (STO), were compared to co-relate magnetic properties with dielectric properties. At room temperature, in the ferromagnetic phase of LSMO, a high dielectric constant (6 × 10) was observed up to 100 kHz frequency for the films on MgO, with polycrystalline properties and more high-angle GB related defects, while for the films on STO, with single-crystalline properties but strained unit cells, high dielectric constant (≈10) was observed until 1 MHz frequency. Also, a large dielectric relaxation time with significant broadening from the Debye single-dielectric relaxation model has been observed in samples with higher GB defects. Impedance spectroscopy further shows that large dielectric constant of the single-crystalline, strained LSMO film is intrinsic in nature while that in the polycrystalline films are mainly extrinsic due to higher amount of GBs. The presence of high dielectric constant value until high frequency range rules out the possibility of 'apparent giant dielectric constant' arising from the sample-electrode interface. Coexistence of ferromagnetism and high dielectric constant can be very useful for different microelectronic applications. [ABSTRACT FROM AUTHOR]

Streptococcus suis Dpr belongs to the Dps family of bacterial and archaeal proteins that oxidize Fe to Fe to protect microorganisms from oxidative damage. The oxidized iron is subsequently deposited as ferrihydrite inside a protein cavity, resulting in the formation of an iron core. The size and the magnetic properties of the iron core have attracted considerable attention for nanotechnological applications in recent years. Here, the magnetic and structural properties of the iron core in wild-type Dpr and four cavity mutants were studied. All samples clearly demonstrated a superparamagnetic behavior in superconducting quantum interference device magnetometry and Mössbauer spectroscopy compatible with that of superparamagnetic ferrihydrite nanoparticles. However, all the mutants exhibited higher magnetic moments than the wild-type protein. Furthermore, measurement of the iron content with inductively coupled plasma mass spectrometry revealed a smaller amount of iron in the iron cores of the mutants, suggesting that the mutations affect nucleation and iron deposition inside the cavity. The X-ray crystal structures of the mutants revealed no changes compared with the wild-type crystal structure; thus, the differences in the magnetic moments could not be attributed to structural changes in the protein. Extended X-ray absorption fine structure measurements showed that the coordination geometry of the iron cores of the mutants was similar to that of the wild-type protein. Taken together, these results suggest that mutation of the residues that surround the iron storage cavity could be exploited to selectively modify the magnetic properties of the iron core without affecting the structure of the protein and the geometry of the iron core. [ABSTRACT FROM AUTHOR]

Striving to improve the critical current density Jc of superconducting YBa2Cu3O6+x (YBCO) thin films via enhanced vortex pinning, the interplay between film growth mechanisms and the formation of nanosized defects, both natural and artificial, is systematically studied in undoped and BaZrO3 (BZO)-doped YBCO thin films. The films were grown via pulsed laser deposition (PLD), varying the crystal grain size of the targets in addition to the dopant content. The microstructure of the PLD target has been observed to have a great impact on that of the deposited thin films, including the formation of vortex pinning centers, which has direct implications on the superconducting performance, especially on the isotropy of flux pinning properties. Based on experimentally measured angular dependencies of Jc, coupled with a molecular dynamics (MD) simulation of flux pinning in the YBCO films, we present a quantitative model of how the splay and fragmentation of BZO nanorods artifically introduced into the YBCO film matrix explain the majority of the observed critical current anisotropy. [ABSTRACT FROM AUTHOR]