Homogeneity Range of ScMnO<Subscript>3</Subscript> in Air

Sc_cMn_{2 – c} O₃ (0.9 c 1.1) samples were prepared by reacting Sc₂O₃ and Mn₂O₃ in air between 800 and 1350°C and were characterized by x-ray diffraction. The results were used to determine the homogeneity range of ScMnO₃. The Mn- and Sc-rich phase boundaries of ScMnO₃ are at c 0.975 (800–1250°C) and c 1.025 (800–1200°C), respectively. At higher temperatures, the homogeneity range narrows down. At 1305 ± 5°C, stoichiometric ScMnO₃ dissociates to form Sc₂O₃- and Mn₃O₄-based solid solutions.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 5, 2005, pp. 608–610.Original Russian Text Copyright © 2005 by Golikov, Balakirev, Titova, Fedorova, Antonov.     

The Measurement of Contrast and Range in Air to Ground Viewing

In the previous paper of this series it has been shown that Photographic Detectors can be used very effectively to measure and study the atmospheric attenuation for air to ground viewing paths. The present paper considers the more general measurement of the contrast of objects on the ground against their immediate background. The problems of range measurement when studying range dependent brightness parameters in the air to ground viewing situation are also considered. It is shown that, whilst considerable errors must be accepted when using the simplest form of instrumentation, useful results can be obtained with no other equipment than a good quality kine camera mounted in an aircraft.     

Two-Phase Coexistence in CMR Manganite Thin Films

The consequence of the metal-insulator coexisting state in CMR manganite thin films in the macroscopic properties has been studied. Conventional transport measurement together with microcontact probe measurement and IR transmission spectroscopy revealed that the two phases coexist even far away from the transition temperature, that the coexistence is very robust, and that the inhomogeneity can be large scale. The use of untextured films allows us to show that the inhomogeneity is not pinned by defects and hence genuine thermodynamic phenomenon. N. Takubo’s current address: Institute of Solid State Physics, The University of Tokyo, Kashiwa 277-8561, Japan. K. Munakata’s current address: Department of Applied Physics, Stanford University, Stanford, California 49305, USA.     

Strain Effect in Cation Disorder Manganite Films

Y and Sr co-doped La_2/3Ca_1/3MnO₃ films with different A-site cation disorder were deposited on Yttrium-stabilized ZrO₂ (YSZ) single crystal substrate by modified off-axis rf magnetron sputtering technology. The influences of A-site cation disorder and biaxial strain on the surface morphologies and transport properties are discussed in detail. At high temperature, the mechanism of conduction is changed from the small polaron hopping model to the variable-range hopping model with increasing cation disorder, which reveals that cation disorder induces carrier localization. The Curie temperature and the magnetoresistance decrease with the increase of cation disorder. It reveals the variation of phase separation to be caused by the increasing cation disorder which suppresses the long-range FM metal state.     

Spin-Injection Quasiparticle Nonequilibrium in Cuprate/Manganite Heterostructures

Quasiparticle nonequilibrium due to spin-polarized current injection in perovskite superconductor/ferromagnet (S/F) thin-film heterostructures has been studied with the technique of cryogenic scanning tunneling spectroscopy. The spin-injection heterostructures consisted of epitaxial bilayers of the high-T _c superconductor YBa₂Cu₃O_{7 –} and the half-metallic ferromagnet La_0.7Ca_0.3MnO₃, with a spin-polarized quasiparticle current injected into the cuprate layer from the manganite layer. The tunneling conductance measured at 4.2 K on the cuprate layer showed a distinctly nonequilibrium quasiparticle spectrum as a result of the spin injection. Quantitative analysis of the tunneling spectral evolution versus the injection current yielded an estimate of the quasiparticle spin-diffusion depth and the spin-relaxation time in the superconducting cuprate.     

Electronic Phase Transition in Liquid Samarium

The irradiating of samples by a narrow beam of monochromatic gamma-rays with an energy of 662 keV is used to experimentally investigate the temperature and phase variations of the density of solid and liquid samarium (99.935%) in the temperature range from 293 to 1920 K. The results of measurements are presented in the form of tables. Density changes in structural transformations and melting are determined (1.70 ± 0.15%). The existence of a nonlinear dependence of the density of samarium in the liquid state is confirmed. Based on the obtained data and on the data available in the literature, a conclusion is made concerning the occurrence of electronic transformations in samarium during melting and thermal expansion in the liquid state.     

Samarium diffusion in polycrystalline samarium sulfide

The diffusion of samarium in polycrystalline samarium sulfide with a superstoichiometric composition of Sm_1.13S has been studied at T = 1000 and 1100°C. It is concluded that Sm atoms predominantly migrate over the boundaries of monocrystalline domains of the polycrystalline sample. The diffusion coefficient varies within D ≈ 10⁻²−10⁻³ cm²/s. In the temperature dependence of the diffusion coefficient, the diffusion activation energy is evaluated at E ∼ 4.6 eV and the preexponential term at D ₀ ≈ 1.8 × 10¹⁵ cm²/s.     

Interface and Bulk Charge Localization in Manganite Thin Films

Nuclear magnetic resonance (NMR) is utilized to map the hyperfine fields acting on ⁵⁵Mn nuclei of La_2/3Sr_1/3MnO₃ (LSMO) epitaxial thin films. In contrast to early thoughts, we show that phase separation (PS) in LSMO is not restricted to an interface‐related dead‐layer only a few nm thick. Instead, it propagates much deeper into the films, thus signalling different origins for the PS. These results indicate that both, surfaces and defects contribute to promote distinguishable PS effects. This view has been confirmed by detailed ⁵⁵Mn NMR analysis of LSMO films where engineered bulk‐like defects have been created by appropriate irradiation by energetic He⁺ ions. Moreover, from the analysis of the restoring fields sensed by the spins of the ⁵⁵Mn nuclei, we infer two sources of magnetic anisotropy. More specifically, a surface magnetic anisotropy –linked to the interfacial dead layer– is predominant for ultrathin samples (t < 10 nm), whereas structural film relaxation, provides a second mechanism for anisotropy. These findings provide guidelines for the growth of electric and magnetic homogeneous manganite films.     

Positive MR and Large Temperature--Field Sensitivity in Manganite Based Heterostructures

Studies on the ZnO/La0.5Pr0.2Sr0.3Mn03 （LPSMO）/SrNb0.002Ti0.99803 （SNTO） heterostructure having varying thickness of p-type LPSMO （100 nm - LP1） and （200 nm - LP2） manganite are carried out. ZnO/LPSMO （n-p） and LPSMO/SNTO （p-n） junctions of both the heterostructures exhibit good rectifying behavior in a wide range of temperature and applied field. Forward and reverse bias characteristics of both the junctions of heterostructures show opposite behavior. The observation of negative magnetoresistance （MR） at 5 K and positive MR at 300 K, in both the heterostructures, has been explained in the context of interface region effects and filling of energy bands of LPSMO manganite. Further, at high temperature, the heterostructures exhibit large temperature （46%K-1） and field （40%T-1） sensitivities. Dependence of transport, magnetotransport, I-V and sensing properties of the heterostructures, on the temperature, field and film thicknesses have been discussed in this communication.     

Non-Temperature-Sensitive and Large Low-Field Magnetoresistance in Bonded Perovskite Manganite Composites

Perovskite manganite composites containing polymer binder (epoxy resin) and additional metal (Sn) were prepared using a novel bonded method. The magnetoresistance (MR) for the sample containing 4 % polymer binder and 10 % metal was as high as 20 % and nonsensitive to temperature in the temperature range of 50–300 K under applied field of 3 kOe. The nontemperature-sensitive and large MR could be ascribed to the contribution of polymer and metal, respectively. When temperature was higher than 300 K, intrinsic colossal magnetoresistance effect was observed.     

Highly Efficient Clean Water Production from Contaminated Air with a Wide Humidity Range

The huge amount of moisture in the air is an unexplored and overlooked water resource in nature, which can be useful to solve the worldwide water shortage. However, direct water condensation from natural or even hazy air is always inefficient and inevitably contaminated by numerous impurities of dust, toxic gas, and microorganisms. In this regard, a drinkable and clean water harvester from complex contaminated air with a wide humidity range based on porous sodium polyacrylate/graphene framework (PGF), which can actively sorb moisture from common or even smoggy environments, efficiently grabs impurities, and then releases clean water with a high rejection rate of impurities under solar irradiation, is proposed. This PGF shows a superhigh equilibrium uptake of 5.20 g of water per gram of PGF at a relative humidity (RH) of 100% and 0.14 g g⁻¹ at a low RH of 15%. The rejection rate of impurities is up to 97% for the collected clean water. Moreover, a water harvesting system is established to produce over 25 L clean water per kilogram of PGF one day, enough to meet several people's drinking water demand. This work provides a new strategy for effective production of clean water from the atmosphere of practical significance.     

Homogeneity of triglycine sulphate crystals

Powder suspensions in silicone oil have been used for decorating slices of TGS grown from aqueous solutions by conventional means, and by a spinning disc technique. The method provides a quick means of assessment of crystal quality and uniformity and has helped in the interpretation of some of the phenomena observed in electrical measurements on both undoped and doped TGS crystals. Sections of crystals grown with alanine as dopant — which gives the crystals an internal polarization bias — show a markedly non-uniform decoration pattern, indicative of a variation of polarization in different growth sectors. Much improved uniformity is demonstrated in crystals grown on a single surface under controlled conditions of solution flow.     

真空处理炉炉温均匀性探讨

对影响真空热处理炉膛温度均匀性的各种因素进行了扼要的讨论与分析，并对保证炉膛温度均匀性的可行措施做了说明，所得结论得到了实践的证实。     

Voltage‐Controlled On/Off Switching of Ferromagnetism in Manganite Supercapacitors

The ever‐growing technological demand for more advanced microelectronic and spintronic devices keeps catalyzing the idea of controlling magnetism with an electric field. Although voltage‐driven on/off switching of magnetization is already established in some magnetoelectric (ME) systems, often the coupling between magnetic and electric order parameters lacks an adequate reversibility, energy efficiency, working temperature, or switching speed. Here, the ME performance of a manganite supercapacitor composed of a ferromagnetic, spin‐polarized ultrathin film of La_0.74Sr_0.26MnO₃ (LSMO) electrically charged with an ionic liquid electrolyte is investigated. Fully reversible, rapid, on/off switching of ferromagnetism in LSMO is demonstrated in combination with a shift in Curie temperature of up to 26 K and a giant ME coupling coefficient of ≈226 Oe V⁻¹. The application of voltages of only ≈2 V results in ultralow energy consumptions of about 90 µJ cm⁻². This work provides a step forward toward low‐power, high‐endurance electrical switching of magnetism for the development of high‐performance ME spintronics.     

Valence Change and Luminescence of Divalent Samarium in Strontium Borates

1.IlltroductionTheopticalspectraofSm2+inalkaliha1idesandothercrystalswerestudiedbyanumberofw.rk.r.I1~5].Sm2+has4rtconfigurationwhichisisoelectronicwithEu3+anditsluminescentspectrastructureareclosetothatoftheEu'+,therefore,theluminescenceofSm2+inhostwasusedasastructureprobeinmanyhosts[6~9].ItwasreportedthattheEu'+,Sm3+,Yb3+couldbereducedtothecorrespondingdivalentrareearthionsinSrB4O7bysolidstatereactionathightemper-atureinair[lo].TheyproposedthattherigidthIee-dimensionalnetworkofBO4tetrah…     

Homogeneity in a Metal Wire under Melting

Results of numerical simulations of the melting wave in a tungsten wire heated by a high-power nanosecond current pulse are presented. To take into account the hydrodynamic effects under melting, a semiempirical multiphase equation of state for tungsten is used. The structure of the melting wave at different parameters of the heating is studied, and a theoretical evaluation for the thickness of this wave, δ_m, is proposed. The homogeneity of the distribution of parameters over the wire can be expected in the case of δ_m >> a₀, where a₀ is the initial radius of the wire. The melting wave can be considered as a discontinuity of thermophysical properties of the solid and liquid phases at δ_m << a₀. Paper presented at the Seventh International Workshop on Subsecond Thermophysics, October 6–8, 2004, Orléans, France.