A-site substitution of SrRuO\u3csub\u3e3\u3c/sub\u3e using La, K and Pb

We have investigated Sr1−xLax/2Kx/2RuO3 and Sr1−xPbxRuO3, which have a larger average size of the A-site cations. They manifest a gradual loss of ferromagnetism in a similar way as their counterparts with smaller A-site cations. There is also evidence for a magnetism-suppressing disorder effect similar to that observed in Sr1−xLax/2Nax/2RuO3. Therefore, the Stoner ferromagnetism in SrRuO3 is rather unique and cannot be easily tuned by lattice distortion to yield a higher Curie temperature

Magnetic impurities in conducting oxides. II. (Sr\u3csub\u3e1-x\u3c/sub\u3eLa\u3csub\u3ex\u3c/sub\u3e)(Ru\u3csub\u3e1-x\u3c/sub\u3eCo\u3csub\u3ex\u3c/sub\u3e)O\u3csub\u3e3\u3c/sub\u3e system

The perovskite solid solution between ferromagnetic SrRuO3 and antiferromagnetic LaCoO3 is studied and its structural, electronic,and magnetic properties are compared with (Sr1-xLax)(Ru1-xFex)O3. The lower 3d energy levels of Co3+ cause a local charge transfer from 4d Ru4+, a reaction that has the novel feature of being sensitive to the local atomic structure such as cation order. Despite such a complication, Co, like Fe, spin-polarizes the itinerant electrons in SrRuO3 to form a large local magnetic moment that is switchable at high fields. In the spin glass regime when Anderson localization dominates, a large negative magnetoresistance emerges as a result of spin polarization of mobile electronic carriers that occupy states beyond the mobility edge. A phenomenological model predicting an inverse relation between magnetoresistance and saturation magnetization is proposed to explain the composition dependence of magnetoresistance for both (Sr1-xLax)(Ru1-xCOx)O3 and (Sr1-xLax)(Ru1-xFex)O3 systems

Dynamic Kerr Effect and Spectral Weight Transfer in the Manganites

We perform pump-probe Kerr spectroscopy in the colossally magnetoresistive manganite Pr0.67Ca0.33MnO3. Kerr effects uncover surface magnetic dynamics undetected by established methods based on reflectivity and optical spectral weight transfer. Our findings indicate the connection between spin and charge dynamics in the manganites may be weaker than previously thought. Additionally, important differences between this system and conventional ferromagnetic metals manifest as long-lived, magneto-optical coupling transients, which may be generic to all manganites.Comment: 12 text pages, 4 figure

Optical evidence for transient photoinduced magnetization in La\u3csub\u3e0.7\u3c/sub\u3eCa\u3csub\u3e0.3\u3c/sub\u3eMnO\u3csub\u3e3\u3c/sub\u3e

Pump-probe Kerr spectroscopy reveals evidence for transient photoinduced magnetization (PIM) near Tc in the colossally magnetoresistive manganite La0.7Ca0.3MnO3. For temperatures above Tc, the PIM signature reaches full strength at the field-driven magnetic phase transition, while below Tc it exhibits a magnetic activation threshold of ~0.5 T. We compare the temperature dependence of the effect with diffuse spin scattering previously measured with neutrons and discuss these findings in the context of phase separation near Tc

Structure, Transport and Magnetic properties in La2x_{2x}Sr2−2x_{2-2x}Co2x_{2x}Ru2−2x_{2-2x}O6_{6}

The perovskite solid solutions of the type La$_{2x}$Sr$_{2-2x}$Co$_{2x}$Ru$_{2-2x}$O$_{6}$ with 0.25 $\leq$ x $\leq$ 0.75 have been investigated for their structural, magnetic and transport properties. All the compounds crystallize in double perovskite structure. The magnetization measurements indicate a complex magnetic ground state with strong competition between ferromagnetic and antiferromagnetic interactions. Resistivity of the compounds is in confirmation with hopping conduction behaviour though differences are noted especially for $x$ = 0.4 and 0.6. Most importantly, low field (50Oe) magnetization measurements display negative magnetization during the zero field cooled cycle. X-ray photoelectron spectroscopy measurements indicate presence of Co$^{2+}$/Co$^{3+}$ and Ru$^{4+}$/Ru$^{5+}$ redox couples in all compositions except $x$ = 0.5. Presence of magnetic ions like Ru$^{4+}$ and Co$^{3+}$ gives rise to additional ferromagnetic (Ru-rich) and antiferromagnetic sublattices and also explains the observed negative magnetization.Comment: Accepted for publication in J. Magn. Magn. Mate

Effect of B-site Dopants on Magnetic and Transport Properties of LaSrCoRuO6_6

Effect of Co, Ru and Cu substitution at B and B' sites on the magnetic and transport properties of LaSrCoRuO$_6$ have been investigated. All the doped compositions crystallize in the monoclinic structure in the space group $P2_1/n$ indicating a double perovskite structure. While the magnetization and conductivity increase in Co and Ru doped compounds, antiferromagnetism is seen to strengthen in the Cu doped samples. These results are explained on the basis of a competition between linear Co-O-Ru-O-Co and perpendicular Co-O-O-Co antiferromagnetic interactions and due to formation of Ru-O-Ru ferromagnetic networks

Doped perovskite-based ruthenates: Structure, electrical, magnetic and magnetoresistive properties

The electric and magnetic properties of ruthenium-containing ABO 3 oxides with perovskite structure are intimately connected with their structure and composition. Even a slight perturbation caused by doping can significantly modify the electrical conductivity and the magnetic ground state of these compounds. In this thesis the structural, electronic, and magnetic properties of several perovskite ruthenate solid solutions, based on SrRuO 3 and CaRuO3, and containing Fe or Co on the B-sites, are presented. In the Fe-containing compounds, Ru preserves its 4+ valence state, while in the Co-doped compounds there is an order-dependent charge transfer between Ru and Co, leading to some Ru in the 5+ state. Saturation magnetization of solid solutions initially increases with both Fe and Co concentration, indicating the formation of large local magnetic moments around these cations. At higher Fe and Co substitution level, a spin glass state develops and a gradual metal/insulator transition occurs. At the same time, a large negative magnetoresistance emerges. These solid solutions are analogous to Mn-doped diluted magnetic semiconductors that contain giant local moments around Mn impurities, which themselves interact antiferromagnetically. Similar magnetic and magnetoresistive behavior is expected in other conducting ruthenates, and possibly other 4d and 5d conducting oxides that are doped with 3d transition metals

Pertussis in the Voronezh Region: Epidemiology and Vaccination

Relevance. In recent years, the increase in the incidence of pertussis has been observed in many countries despite high vaccination coverage of the child population.Purpose: was to study the epidemiological features of whooping cough in the Voronezh region for the period from 2008 to 2018 years.Methods. The research material was data the annual form No. 2, 5, 6 of Rosstat for 2008 through 2018. Statistical data processing was performed using Microsoft Excel 2007.Results. The epidemiological features of pertussis in the Voronezh region for the period from 2008 to 2018 have been studied. Despite the high coverage of preventive vaccinations in children of the first years of life, in recent years, the incidence of pertussis increased the average Russian rates by 3,5 times. In the age structure of the diseased there was a tendency to increase the proportion of schoolchildren and adults. Analysis of the reports showed that half of the cases were vaccinated at the prescribed age, but the interval after vaccination before the illness was an average of 9 years.Conclusions. In recent years, there has been a tendency to an increase in the incidence of whooping cough in the Voronezh region. The incidence of vaccinated indicates the natural extinction of post-vaccination immunity to school age and requires a decision on the introduction of revaccination of schoolchildren with actual acellular vaccines

IT for the remediation of the geological environment poluted with the petroleum products: Experience of the Kazakh-Belarus Russian joint project

The objective of the poject is to create an expert system on rehabilitation of the geological environment polluted with petroleum products for the terriories of Kazakhstan, Russia and Belarus. Despite some specificity of the pollution (prevalence of certain sources) in all three countries, oil pollution is one of the most problematic. Thanks to the contacts between scientific teams is formed unified methodological basis for the development of the architecture of an expert system, filling its blocks, selecting optimal prediction models of pollution and effective methods of remediation. Analyzed the existing models and software systems on migration of oil and petroleum products; estimated the possibility of their use in an expert system. Estimated losses of petroleum products during handling on model objects. In the following steps are carried out "assembly" of blocks of the expert system and its testing with potential users - decision makers in elimination of accidents and rehabilitation of the geological environment, representatives of environmental agencies, enterprises and other polluters. Currently identified the problems of modeling of hydrocarbon pollution of the geological environment: underestimation of the detailed component composition and transformation processes of hydrocarbons, excessive simplification of their migration patterns; underestimation of self-organization processes in contaminated geological environment; insufficient accuracy of methods of chemical analysis of environmental pollution (such as extraction); fragmentation and the lack of justification for the content of oil products standards in soils. Formed architecture of the expert system. We select the models of pollution of geological environment for the territories of the participating countries, taking into account specificity of their areas (landscape features) and specific sources of pollution - model objects. The project creates an effective information base to solve the problem by reducing the time for the development of management decisions, the optimal use of information for modeling and forecasting of contamination of the geological environment. Provides a higher environmental and economic performance of works on the rehabilitation of the geological environment. Features of the project: focus on the potential recovery of the environment using its own reserves; selection of typical landscape conditions and model objects; Environmental expert system - an effective tool to support decision-making in crisis situations. The complexity of the simulation often doesn't allows you to select sufficiently effective recovery technology. The created expert system can solve this problem for a variety of natural conditions and man-made objects and sources of pollution. Creation and implementation of most projects on protection of the environment requires the use of specialized software, which would allow to reliably identify, predict and model the development of the processes of pollution of natural environments. Given the urgency of the problems of oil pollution in exploration, transport, storage and processing of petroleum products, the studies on the creation of software products, which facilitate management decisions on remediation of contaminated areas, are extremely relevant. Copyright 2015, Society of Petroleum Engineers