Negative Magnetoresistance in Amorphous Indium Oxide Wires

We study magneto-transport properties of several amorphous Indium oxide nanowires of different widths. The wires show superconducting transition at zero magnetic field, but, there exist a finite resistance at the lowest temperature. The $R(T)$ broadening was explained by available phase slip models. At low field, and far below the superconducting critical temperature, the wires with diameter equal to or less than 100 nm, show negative magnetoresistance (nMR). The magnitude of nMR and the crossover field are found to be dependent on both temperature and the cross-sectional area. We find that this intriguing behavior originates from the interplay between two field dependent contributions.Comment: 11 pages, 7 figure

Veterinary Ethnomedicinal Plants in Uttarakhand Himalayan Region, India

Drug research has enriched human life in many ways. The health care and resulting social and economic benefits of new drugs to society are most remarkable, are quite well recognized. Drug research has been the driving force for many basic scientific developments, such as that of many new synthetic methods, of the understanding of the physiology and pharmacology of biological systems and has contributed much too molecular recognition. The Uttarakhand Himalayas have a great wealth of medicinal plants and traditional medicinal knowledge. The medicinal plant that has been widely used as veterinary ethno-medicine in Uttarakhand region has been studied. These do not either occur elsewhere or have not so far been exploited commercially. Attempts have been made to explore the new possible species having medicinal importance especially for veterinary and to grow them in suitable areas so as to meet national industrial demands. The present paper deals with the traditional uses of 100 plant species employed in ethno-medicine and ethno-veterinary practice in Uttarakhand

Quantitative assessment and antibacterial activity of Origanum vulgare L.

Biodiversity, which twenty years ago was considered unimportant by most ecologists, has now been shown to impact significantly upon many aspects of ecosystem functioning. Diversity must now be added to the list of factors — including species composition, disturbance regime, soil type and climate — that influence ecosystem functioning. The recent knowledge of the importance of biodiversity highlights an under-appreciated truth — although society is dependent on natural and managed ecosystems for goods and services that are essential for human survival, we know all too little about how ecosystems work. Origanum vulgare L. is one of the important ethno medicinal plants, are found spread over to sub-temperate forest zone. They are of Ayurvedic importance and have trade value as well. Due to over exploitation and habitat degradation they are now turning into a rare species. Threat assessments of this species revealed that they are vulnerable in study area under reference. Their dominance too was found less as compare to other species. Their diversity profile in study areas also went down. Origanum vulgare L. has antimicrobial activities but Becillus subtillis, Pseudomonas aereuguinosa, Staphylococcus aureus and Escherchia coli bacteria were shown to be proactive. Due to fast growing urbanization of life, people are being attracted towards use of natural products and as such utility of such plants are gaining ground. Thus the need is to protect, promote and conserve such natural resources to have advantage of biodiversity conservation.Â

Fe3Se4: A Possible Ferrimagnetic Half-Metal?

Half-metallic ferromagnets show 100% spin-polarization at the Fermi level and are ideal candidates for spintronic applications. Despite the extensive research in the field, very few materials have been discovered so far. Here we present results of electronic band structure calculations based on density functional theory and extensive physical-property measurements for Fe3Se4 revealing signatures of half-metallicity. The spin-polarized electronic band structure calculations predict half-metallic ferrimagnetism for Fe3Se4. The electrical resistivity follows exponentially suppressed electron-magnon scattering mechanism in the low-temperature regime and show a magnetoresistance effect that changes the sign from negative to positive with decreasing temperature around 100 K. Other intriguing observations include the anomalous behavior of Hall resistance below 100 K and an anomalous Hall coefficient that roughly follows the \r{ho}2 behavior.Comment: Accepte

Transport properties of Layer-Antiferromagnet CuCrS2: A possible thermoelectric material

The electrical, thermal conductivity and Seebeck coefficient of the quenched, annealed and slowly cooled phases of the layer compound CuCrS2 have been reported between 15K to 300K. We also confirm the antiferromagnetic transition at 40K in them by our magnetic measurements between 2K and 300K. The crystal flakes show a minimum around 100K in their in-plane resistance behavior. For the polycrystalline pellets the resistivity depends on their flaky texture and it attains at most 10 to 20 times of the room temperature value at the lowest temperature of measurement. The temperature dependence is complex and no definite activation energy of electronic conduction can be discerned. We find that the Seebeck coefficient is between 200-450 microV/K and is unusually large for the observed resistivity values of between 5-100 mOhm-cm at room temperature. The figure of merit ZT for the thermoelectric application is 2.3 for our quenched phases, which is much larger than 1 for useful materials. The thermal conductivity K is mostly due to lattice conduction and is reduced by the disorder in Cu- occupancy in our quenched phase. A dramatic reduction of electrical and thermal conductivity is found as the antiferromagnetic transition is approached from the paramagnetic region, and K subsequently rises in the ordered phase. We discuss the transport properties as being similar to a doped Kondo-insulator

Organic-Component Dependent Crystal Orientation and Electrical Transport Properties in ALD/MLD Grown ZnO-Organic Superlattices

| openaire: EC/H2020/765378/EU//HYCOATTwo series of ZnO-organic superlattice thin films are fabricated with systematically controlled frequencies of monomolecular hydroquinone (HQ) or terephthalic acid (TPA) based organic layers within the ZnO matrix using the atomic/molecular layer deposition (ALD/MLD) technique. The two different organic components turn the film orientation to different directions and affect the electrical transport properties differently. While the TPA layers enhance the c-axis orientation of the ZnO layers and act as electrical barriers depressing the electrical conductivity even in low concentrations, adding the HQ layers enhances the a-axis orientation and initially increases the carrier concentration, effective mass, and electrical conductivity. The work thus demonstrates the intriguing but little exploited role of the organic component in controlling the properties of the inorganic matrix in advanced layer-engineered inorganic-organic superlattices.Peer reviewe

Investigating the vibrational lattice anisotropy in FeTe0.5Se0.5 using magnetically oriented crystallites

An iron chalcogenide sample with nominal composition FeTe0.5Se0.5 was synthesized following a solid-state reaction route. X-ray diffraction followed by Rietveld analysis were used for verifying the phase content. Using the field of an 11.7 T magnet textured samples, having the c axes parallel with and normal to the sample surface, were made. 57Fe Mössbauer spectroscopy in transmission geometry was used for characterizing the hyperfine parameters of the iron site. Clear indications of vibrational anisotropy, i.e. the Goldanskii-Karyagin effect, were observed. Fitting spectral absorption with the Debye model yielded rather low Debye temperatures of 255(3) and 303(3) K, for samples texturized with the c axis parallel with and perpendicular to the Mössbauer γ beam, respectively. Also the second-order Doppler shift of the isomer shift data exhibited a similar, although weaker, anisotropy.Peer reviewe

Tunable Low-Temperature Thermoelectric Transport Properties in Layered CuCr(S1-xSex)2 System

Funding Information: HSK would like to acknowledge Jenny Ja Antti Wihuri foundation for research grant (2021‐2023). The authors would also like to acknowledge Academy of Finland (Profi3 and PREIN). This work made use of the RawMatters Finland infrastructure (RAMI) facilities at Aalto University. Publisher Copyright: © 2023 The Authors. Zeitschrift für anorganische und allgemeine Chemie published by Wiley-VCH GmbH.We have characterized the layered CuCr(S,Se)2 system for the spin-polarized electronic band structures and low-temperature thermoelectric transport properties. The electronic band structure calculations reveal semiconducting behavior for CuCrS2, CuCr(S0.5Se0.5)2 and CuCrSe2 with an indirect bandgap of 0.42, 0.30 and 0.10 eV, respectively. The systematically decreased bandgap with increasing Se content is in line with the experimental observations showing a semiconductor-to-metal transition with increasing Se-substitution level in the CuCr(S1-xSex)2 system because of an increase in the charge carrier density. The p-type Seebeck coefficient shows a linear temperature dependence for the samples, like in degenerate semiconductors or metals. The remarkably large Seebeck coefficient even in metallic samples is due to a relatively large effective mass of charge carriers. As the thermal conductivity is intrinsically low owing to the layered crystal structure and is further decreased for the Se-substituted samples because of the increased phonon scattering from point defects, the thermoelectric characteristics are promising. The highest dimensionless figure-of-merit values were seen for the x=0.5 sample, e. g., 0.04 at 400 K.Peer reviewe

Optically transparent pectin/poly(methyl methacrylate) composite with thermal insulation and UV blocking properties based on anisotropic pectin cryogel

Funding Information: This work was supported by the Academy of Finland projects “SUBSTAINABLE” (Decision number 334818) and "SUPER-WEAR" (decision number: 322214). We acknowledge BioEconomy and RawMatTERS Finland infrastructure (RAMI) facilities based at Aalto University for measurements. Funding Information: This work was supported by the Academy of Finland projects ?SUBSTAINABLE? (Decision number 334818) and ?SUPER-WEAR? (decision number: 322214). We acknowledge BioEconomy and RawMatTERS Finland infrastructure (RAMI) facilities based at Aalto University for measurements. Publisher Copyright: © 2022 The AuthorsBioderived polysaccharide-based cryogels prepared via freeze-casting method not only mimic the highly aligned anisotropic pore structure of plant stems but also offer other benefits as compared to biological structures, such as lower density, higher porosity, better permeability, and lower thermal conductivity. However, the application of polysaccharide cryogels to fabricate multifunctional composites is still at its infancy. In this study, a novel class of optically transparent pectin/poly(methyl methacrylate) (PMMA) composite (with optical transmittance as high as 84% and haze of 38% ∼ 73%) combined with thermal insulation outperforming conventional glass has been prepared by using freeze-casted pectin cryogel as template. The final pectin/PMMA has comparable optical transmittance and comparable or lower haze as contrasted with most reported studies on transparent wood/bamboo. Astonishingly, this type of composite has very good UV blocking ability both as compared to glass and nanocellulose-based polymer composites. Overall, the optical properties of these composites can be optimized via controlling the pectin concentration and freeze-casting temperature. Furthermore, pectin/PMMA composites can reach much lower thermal conductivity (0.110 ∼ 0.126 W/(m·K)) than glass. Therefore, these multifunctional pectin/PMMA composites could be beneficial in many applications, such as optically transparent materials, solar cell substrates, and UV protective displays.Peer reviewe