Magnetic ordering and structural phase transitions in strained ultrathin SrRuO3_{3}/SrTiO3_{3} superlattice

Ruthenium-based perovskite systems are attractive because their Structural, electronic and magnetic properties can be systematically engineered. SrRuO$_3$/SrTiO$_3$ superlattice, with its period consisting of one unit cell each, is very sensitive to strain change. Our first-principles simulations reveal that in the high tensile strain region, it transits from a ferromagnetic (FM) metal to an antiferromagnetic (AFM) insulator with clear tilted octahedra, while in the low strain region, it is a ferromagnetic metal without octahedra tilting. Detailed analyses of three spin-down Ru-t$_{2g}$ orbitals just below the Fermi level reveal that the splitting of these orbitals underlies these dramatic phase transitions, with the rotational force constant of RuO$_6$ octahedron high up to 16 meV/Deg$^2$, 4 times larger than that of TiO$_6$. Differently from nearly all the previous studies, these transitions can be probed optically through the diagonal and off-diagonal dielectric tensor elements. For one percent change in strain, our experimental spin moment change is -0.14$\pm$0.06 $\mu_B$, quantitatively consistent with our theoretical value of -0.1 $\mu_B$.Comment: 3 figures, 1 supplementary material, accepted by Phys. Rev. Let

The link between diabetic retinal and renal microvasculopathy is associated with dyslipidemia and upregulated circulating level of cytokines

PurposeTo investigate the mechanisms underlying the correlations between diabetic retinopathy (DR) and diabetic nephropathy (DKD) and examine whether circulating cytokines and dyslipidemia contribute to both DR and DKD in patients with 2 diabetes mellitus (T2DM).MethodsA total of 122 patients with T2DM were enrolled and categorized into the DM group (without no DR and DKD), DR group [non-proliferative DR (NPDR), and proliferative DR (PDR)] with no DKD), DR complicated with DKD groups (DR+DKD group). The biochemical profile, including fasting blood glucose (FBG), glycated hemoglobin (HbA1c), and lipid profile were estimated, and plasma inflammatory and angiogenic cytokines [monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6, IL-8, vascular endothelial growth factor (VEGF)-A, C, D, and placental growth factor (PlGF)] were analyzed by protein microarrays. The atherogenic plasma index (API) was defined as low-density lipoprotein cholesterol (LDL-C)/high-density lipoprotein-cholesterol (HDL-C); atherogenic index (AI) was calculated as [(total cholesterol (TC) -HDL-C)/HDL-C], and atherogenic index of plasma (AIP) was defined as log (TG/HDL-C).ResultsBy multivariable disordered regression analysis, after controlling for duration of DM and hypertension, LDL-C (p = 0.019) and VEGF-D (p = 0.029) resulted as independent risk factors for DR. Albumin-to-creatinine ratio (uACR) (p = 0.003) was an independent risk factor for DR with DKD. In DR, NPDR, and PDR groups, grades of A1, A2, and A3 of albuminuria increased with the severity of DR. In A1, A2, and A3 grade groups, the severity of DR (DM, NPDR, and PDR) increased with higher albuminuria grades. Kendall's tau-b correlation coefficient analysis revealed that FBG (p = 0.019), circulating level of PlGF (p = 0.002), and VEGF-D (p = 0.008) were significantly positively correlated with the grades of uACR (p < 0.001), and uACR grades were significantly correlated with DR severity (p < 0.001).ConclusionsThe occurrence and severity of DR are closely correlated with kidney dysfunction. Among the three kidney functional parameters, uACR resulted as the better indicator of DR severity and progression than glomerular filtration (eGFR) and serum creatinine (Scr). Impaired FBG was associated with microalbuminuria, emphasizing that well-controlled FBG is important for both DR and DKD. The link between diabetic retinal and renal microvasculopathy was associated with dyslipidemia and upregulated circulating level of angiogenic cytokines

Probing surface states: A study of UCF and WAL in Bi1.9Sb0.1Te2Se topological insulator

In the exploration of three-dimensional quaternary topological insulators, understanding surface states has become pivotal for unraveling the underlying physics and tapping into potential applications. Our study delves into the temperature and magnetic field-angle dependence of universal conductance fluctuations (UCF) and weak anti-localization (WAL) effects in a Bi1.9Sb0.1Te2Se topological insulator-based mesoscopic device. Conventionally, other low-temperature transport phenomena in probing surface states may inevitably face interference from three-dimensional bulk conductance. However, we experimentally demonstrate that, at low temperatures, UCF reflects the properties of two-dimensional topological surface states more accurately, thereby providing a more reliable and distinct way to confirm their existence. Moreover, we carefully analyze the temperature-dependent WAL using the Hikami–Larkin–Nagaoka model, proposing a crucial role for charge puddles associated with electrostatic fluctuations in the electron dephasing process. Our findings not only emphasize the key role of UCF in unveiling the underlying behavior of topological surface states but also offer a deeper understanding of phase-coherent transport in quaternary topological insulators

Enhanced physical compatibility in manganite/cuprate multilayer with high-quality interface

A systematical study of the relationship between microstructure of interface and physical properties is performed on La(0.67)Ca(0.33)MnO(3)(LCMO)/YBa(0.85)En(0.15)Cu(3)O(7) (YEBCO) multilayer. Flat and chemically well-defined interface is found for the film grown on (001) oriented SrTiO(3) (STO) substrate. High resolution transmission electron microscopy observations reveal that nano-scale periods of multilayer structure can effectively suppress the second phase inclusions that are commonly seen in superconducting single layer. The coexistence of ferromagnetism and superconducting behavior is evidenced in [(LCMO)/(YEBCO)](6)/STO multilayer. In contrast, when using Y stabilized ZrO(2) single crystals (YSZ) as substrate, pyramid-like defects and disordering layer form because of the lattice mismatch between the film and the substrate. The superconducting transition response is lost in this case but large magnetoresistance is obtained. These results indicate an extensive rearrangement of ferromagnetic domain under applied magnetic field at extended defects dominated [(LCMO)/(YEBCO)](6)/YSZ multilayer. The decoupling of ferromagnetism and superconductivity in [(LCMO)/(YEBCO)](6)/YSZ multilayer is ascribed to the missing high-quality interface nature that otherwise present in [(LCMO)/(YEBCO)](6)/STO multilayer. (C) 2011 Elsevier B.V. All rights reserved

Magnetic and transport properties of Ba and Co co-doped SrRuO3

The microstructure and electro-magnetic properties of simultaneous Ba doping for Sr and Co doping for Ru in SrRuO3 have been carefully investigated. All the doped samples exhibit the same orthorhombic Pnma structure as the pure bulk SrRuO3, although introducing some local structural modifications due to the ionic radius mismatch at Sr/Ru-site. A maximum of 2.2% negative magnetoresistance and much suppressed Curie temperature are found for the most insulating Ba and Co co-doped Sr0.88Ba0.12Ru0.88Co0.12O3 sample. The substitution induced A-site disorder, B-site ion dilution, structural distortion and the intrinsic nature of cobalt ion etc. are jointly considered to explain the observed interesting phenomena

Composition and Development Prospects of Scented Rice

Containing higher aromatic composition, scented rice is better than ordinary rice varieties in taste and nutrition. Major composition of scented rice is 2-acetyl-1-pyrroline (2-AP). Different scented rice varieties have different content of 2-AP. The content of 2-AP is not only influenced by genetic substances, but also closely connected with types and content of nutrition elements in soil, soil moisture management, ambient temperature, and storage. 2-AP synthesis and regulation are possibly connected with Proline and enzyme

The microstructural changes of Ge2Sb2Te5 thin film during crystallization process

Phase change memory is known as the most promising candidate for the next generation nonvolatile memory technology. In this paper, the microstructural changes of Ge2Sb2Te5 film, which is the most common choice of phase change memory material, has been carefully studied by the combination of several characterization techniques. The combination of resistance measurements, X-ray diffraction, Raman spectroscopy and X-ray reflectivity allows us to simultaneously extract the characteristics of microstructural changes during crystallization process. The existence of surface/interface Ge2Sb2Te5 layer has been proposed here based on X-ray reflectivity measurements. Although the total film thickness decreases, as a result of the phase transition from amorphous to metastable crystalline cubic and then to the stable hexagonal phase, the surface/interface thickness increases after crystallization. Moreover, the increase of average grain size, density and surface roughness has been confirmed during thermal annealing process

The flexoelectric effect associated size dependent pyroelectricity in solid dielectrics

A phenomenological thermodynamic theory is used to investigate the effect of strain gradient on the pyroelectric effect in centrosymmetric dielectric solids. Direct pyroelectricity can exist as external mechanical stress is applied to non-pyroelectric dielectrics with shapes such as truncated pyramids, due to elastic strain gradient induced flexoelectric polarization. Effective pyroelectric coefficient was analyzed in truncated pyramids. It is found to be controlled by size, ambient temperature, stress, and aspect ratio and depends mainly on temperature sensitivity of flexoelectric coefficient (TSFC) and strain gradient of the truncated pyramids dielectric solids. These results show that the pyroelectric property of Ba0.67Sr0.33TiO3 above Tc similar to PZT and other lead-based ferroelectrics can be obtained. This feature might widely broaden the selection of materials for infrared detectors with preferable properties

Microstructures of YBa1.85Eu0.15Cu3O7-delta superconducting films grown on SrTiO3 and YSZ substrates

A detailed atomic scale microstructure analysis of Eu-doped YBa1.85Eu0.15Cu3O7-delta (YEBCO) thin films with 100 nm in thickness has been carried out by a combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Interesting regular-like arranged network of nanoscale undulations is observed on the surface of YEBCO film on (0 0 1) SrTiO3 substrate. TEM image clearly indicates that the film is always c-axis oriented, but lots of natural precipitates of Y2O3 are involved both at the interface and deep in the film. Desirable size and number density of Y2O3 are thought to be important for acting as efficient flux pinning centers. In the case of YEBCO film on (0 0 1) yttrium stabilized ZrO2 (YSZ) substrate, few cracks and outgrowths appear due to much larger lattice mismatch and dissimilar crystal structure between the film and substrate, but surface quality is still much better compared to the parent YBaCu3O7-delta film. Besides, highly textured BaZrO3 layer at the interface and alpha-axis grains with small dimensions in the film are formed. Interface stability of two kinds of films studied, namely YEBCO/STO and YEBCO/YSZ, is also assessed comprehensively by first principle calculations. (C) 2010 Elsevier B.V. All rights reserved