Superconductivity over 30 K of Nd2CuO4 Films on CaF2 Substrates

Nd2CuO4 has a crystal structure called the Nd2CuO4 (T’) structure in which fluorite-like Nd2O2 slabs and CuO2 planes stack alternately. Nd2CuO4 is known to show superconductivity by carrier doping via anion/cation substitution, or making the oxygen sublattice highly ordered via a stringent control of thermodynamic conditions during crystal growth. In this study, CaF2 is used for growing Nd2CuO4 films, as a substrate material which contains fluorine atoms. The films show superconducting onset (Tonc) beyond 30 K. Furthermore, in contrast to reported superconductivity in this system, the emergence of superconductivity is found to be insensitive to post annealing procedures.PostprintPeer reviewe

Superconductivity in undoped T' cuprates with Tc over 30 K

Undoped cuprates have long been considered to be antiferromagnetic insulators. In this article, however, we report that superconductivity is achieved in undoped T'-RE2CuO4 (RE = Pr, Nd, Sm, Eu, and Gd). Our discovery was performed by using metal-organic decomposition (MOD), an inexpensive and easy-to-implement thin-film process. The keys to prepare the superconducting films are firing with low partial-pressure of oxygen and reduction at low temperatures. The highest Tc of undoped T'-RE2CuO4 is over 30 K, substantially higher than "electron-doped" analogs. Remarkably, Gd2CuO4, even the derivatives of which have not shown superconductivity so far, gets superconducting with Tconset as high as ~ 20 K. The implication of our discovery is briefly discussed.Comment: 22 pages, 5 figures, submitted to Physical Review Letter

Superconducting weak bonds at grain boundaries in MgB2

The possibility of preparing bicrystalline Josephson junctions and bolometers based on superconducting MgB2 on specially prepared bicrystalline MgO substrates is investigated. Microbridges 0.85–6.00 μm in width, intersecting the bicrystalline interface, are formed in epitaxial bicrystalline MgB2 films grown on these substrates. It is found that annealing of bicrystalline samples in oxygen leads to a systematic decrease in the critical current, an increase in the temperature width of the superconducting transition region, and to an improvement of the current-voltage (IV) characteristic, which becomes close in shape to the IV characteristic of a Josephson junction. The response of such a junction to radiation at a frequency of 110 GHz with an amplitude attaining 0.5 mV is measured

K-doped Ba122 epitaxial thin film on MgO substrate by buffer engineering

Molecular beam epitaxy of K-doped Ba122 (Ba$_{1-x}$K$_x$Fe$_\text{2}$As$_\text{2}$) superconductor was realized on a MgO substrate. Microstructural observation revealed that the undoped Ba122 served as a perfect buffer layer for epitaxial growth of the K-doped Ba122. The film exhibited a high critical temperature of 39.8 K and a high critical current density of 3.9 MA/cm$^\text{2}$ at 4 K. The successful growth of epitaxial thin film will enable artificial single grain boundary on oxide bicrystal substrates and reveal the grain boundary transport nature of K-doped Ba122.Comment: 5 pages, 4 figures, accepted manuscript Supercond. Sci. Technol 202

Morphologic studies of bone marrow cells exposed to the phospholipid fraction from the liver of irradiated animal, an experiment in vitro

With the purpose of revealing the biological effects of the X-ray irradiation the authors extracted phospholipids from the liver of irradiated animals and proved that this substance has the action to inhibit the growth of the bone marrow cells, the motility of pseudo-eosinophilis and the erythropoiesis in tissue culture, suggesting that the injury will mainly be induced by the toxic substances produced by irradiation.</p

Effect of Radiological Countermeasures on Subjective Well-Being and Radiation Anxiety after the 2011 Disaster: The Fukushima Health Management Survey

After the Fukushima Daiichi Nuclear Power Station accident in 2011, concerns about radiation exposure and decline in subjective well-being have been reported. To tackle these problems, various countermeasures in relation to radiation have been implemented. In this study, we comprehensively evaluated the effects of radiological countermeasures on subjective well-being (e.g., satisfaction with life (SWL) and emotional well-being) and radiation anxiety, through a questionnaire survey targeting Fukushima residents (N = 1023). Propensity scores matching was applied to evaluate significant effects of radiological countermeasures on subjective well-being and radiation anxiety. Among the radiological countermeasures, thyroid examination, whole body counter, and air dose monitoring showed the highest proportions of participation, utilization, and useful evaluation, suggesting a high degree of public attention focused on these countermeasures. The basic survey was associated with significant increases in SWL and self-rated health (SH). Thyroid examination was significantly associated with not only a reduction in radiation anxiety but also an increase of emotional stress, suggesting the importance of careful design of system and detailed communication. Food inspection was associated with deterioration in SH. Those who utilized explanatory meetings showed increases in sadness, worry, and radiation anxiety, indicating that additional attention is required of the experts and authorities involved in explanatory meetings

Universal scaling behavior of the upper critical field in strained FeSe0.7Te0.3 thin films

open15Revealing the universal behaviors of iron-based superconductors (FBS) is important to elucidate the microscopic theory of superconductivity. In this work, we investigate the effect of in-plane strain on the slope of the upper critical field H c2 at the superconducting transition temperature T c (i.e. -dH c2/dT) for FeSe0.7Te0.3 thin films. The in-plane strain tunes T c in a broad range, while the composition and disorder are almost unchanged. We show that -dH c2/dT scales linearly with T c, indicating that FeSe0.7Te0.3 follows the same universal behavior as observed for pnictide FBS. The observed behavior is consistent with a multiband superconductivity paired by interband interaction such as sign change s ± superconductivity.openYuan, Feifei; Grinenko, Vadim; Iida, Kazumasa; Richter, Stefan; Pukenas, Aurimas; Skrotzki, Werner; Sakoda, Masahito; Naito, Michio; Sala, Alberto; Putti, Marina; Yamashita, Aichi; Takano, Yoshihiko; Shi, Zhixiang; Nielsch, Kornelius; Hühne, RubenYuan, Feifei; Grinenko, Vadim; Iida, Kazumasa; Richter, Stefan; Pukenas, Aurimas; Skrotzki, Werner; Sakoda, Masahito; Naito, Michio; Sala, Alberto; Putti, Marina; Yamashita, Aichi; Takano, Yoshihiko; Shi, Zhixiang; Nielsch, Kornelius; Hühne, Rube

The influence of the in-plane lattice constant on the superconducting transition temperature of FeSe0.7Te0.3 thin films

Epitaxial Fe(Se,Te) thin films were prepared by pulsed laser deposition on (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT), CaF2-buffered LSAT and bare CaF2 substrates, which exhibit an almost identical in-plane lattice parameter. The composition of all Fe(Se,Te) films were determined to be FeSe0.7Te0.3 by energy dispersive X-ray spectroscopy, irrespective of the substrate. Albeit the lattice parameters of all templates have comparable values, the in-plane lattice parameter of the FeSe0.7Te0.3 films varies significantly. We found that the superconducting transition temperature (Tc) of FeSe0.7Te0.3 thin films is strongly correlated with their a-axis lattice parameter. The highest Tc of over 19 K was observed for the film on bare CaF2 substrate, which is related to unexpectedly large in-plane compressive strain originating mostly from the thermal expansion mismatch between the FeSe0.7Te0.3 film and the substrate.Comment: Accepted in AIP Advances, 4 figure