Effect of Pt doping on the critical temperature and upper critical field in YNi2-xPtxB2C (x=0-0.2)

We investigate the evolution of superconducting properties by doping non-magnetic impurity in single crystals of YNi2-xPtxB2C (x=0-0.2). With increasing Pt doping the critical temperature (Tc) monotonically decreases from 15.85K and saturates to a value ~13K for x>0.14. However, unlike conventional s-wave superconductors, the upper critical field (HC2) along both crystallographic directions a and c decreases with increasing Pt doping. Specific heat measurements show that the density of states (N(EF)) at the Fermi level (EF) and the Debye temperatures (Theta_D) in this series remains constant within the error bars of our measurement. We explain our results based on the increase in intraband scattering in the multiband superconductor YNi2B2C.Comment: ps file with figure

Temperature dependence of transport spin polarization in NdNi5 measured using Point Contact Andreev reflection

We report a study in which Point contact Andreev reflection (PCAR) spectroscopy using superconducting Nb tip has been carried out on NdNi5, a ferromagnet with a Curie temperature of TC~7.7K. The measurements were carried out over a temperature range of 2-9K which spans across the ferromagnetic transition temperature. From an analysis of the spectra, we show that (i) the temperature dependence of the extracted value of transport spin polarization closely follows the temperature dependence of the spontaneous magnetization; (ii) the superconducting quasiparticle lifetime shows a large decrease close to the Curie temperature of the ferromagnet. We attribute the latter to the presence of strong ferromagnetic spin fluctuations in the ferromagnet close to the ferromagnetic transition temperature.Comment: pdf file including figures-Typographical error and errors in references correcte

Phytochemical, antioxidant and in-vitro anti-inflammatory studies of peels of sweet potato (Ipomea batatas) have shown a promising natural cure against antibiotic resistant bacteria and opportunistic fungus

Background- Multidrug-resistance has become an emerging health concern worldwide mostly in the immune-compromised patients. This indicates the need to search for alternative methods of controlling antibiotic-resistant pathogens. Ethono-medicinal data indicated sweet potato (Ipomoea batatas), a widely consumed vegetable as a potent remedy in inflammatory and infectious diseases. The present study evaluated the phytochemical, antioxidant and anti-bacterial action of the ethanolic extract of Ipomoea batatas peels against some drug-resistant pathogens like Pseudomonas aeruginosa, Staphylococcus aureus and anti-fungal action against Aspergilus niger responsible for most of the infections leading to the treatment failure. There is inflammation induced disorders like cardiovascular diseases, atherosclerosis, type 2 diabetes, etc. where the peels of Ipomoea batatas have very much potent anti-inflammatory activity. Methods- The peels of sweet potato were authenticated and macerated ethanolic extract was used for the Phytochemical analysis, antioxidant, in-vitro anti-inflammatory studies were performed. The antifungal activity was studied against Aspergilus niger and antimicrobial action was evaluated against two most commonly found resistant strains like Pseudomonas aeruginosa and Staphylococcus aureus. Results- The phytochemical analysis the ethanolic extract of the peels of Ipomoea batatas has shown the presence of alkaloid, glycoside, phenol and tannin. Antioxidant activity in terms of total phenolic & total flavonoid contents has shown a significantly good value, less than 50µg/ml. The anti-bacterial activity against two antibiotic resistant bacteria Pseudomonas aeruginosa and Staphylococcus aureous were prominently good with the MIC (Minimum Inhibitory Concentration) 25 mg/ml and for the fungal strain Aspergilus niger, the MIC was 50 mg/ml. The various in-vitro anti-inflammatory studies like heat induced haemolysis, protein denaturation study etc. have proved that the sweet potato leaves have potent anti-inflammatory activity with an IC50 value less than 400 µg/ml. Conclusion- The present study indicated the ethanolic extract of Ipomoea batatas peel can be beneficial to develop a cost-effective natural source of antimicrobial agent against drug resistant pathogen and also source of cure for various inflammation induced disorders. Further study will lead to a sustainable source in pharmaceutical industries also helpful to maintain an eco-friendly environment

Non-intrinsic superconductivity in InN epilayers: role of Indium Oxide

In recent years there have been reports of anomalous electrical resistivity and the presence of superconductivity in semiconducting InN layers. By a careful correlation of the temperature dependence of resistivity and magnetic susceptibility with structural information from highresolution x-ray diffraction measurements we show that superconductivity is not intrinsic to InN and is seen only in samples that show traces of oxygen impurity. We hence believe that InN is not intrinsically a superconducting semiconductor.Comment: pdf file with figure

Point contact Andreev reflection studies on the low TCurie ferromagnet NdNi5 using a superconducting Nb tip

We report measurement of transport spin polarization (Pt) using point contact Andreev reflection (PCAR) spectroscopy on NdNi5, a ferromagnet with Curie temperature of View the MathML source, using superconducting Nb tip View the MathML source. Detail analysis of the spectra shows that the normalized value of Pt(=Pt(T)/Pt(T=0)) for contacts with different Z follows closely the temperature variation of spontaneous magnetization, though the value of Pt decreases with increasing Z. We also observe a large decrease in superconducting quasiparticle lifetime arising from critical spin fluctuations close to the Curie temperature of the ferromagnet.© Elsevie

Study of spin fluctuations in Ni<SUB>3±x</SUB>Al<SUB>1∓x</SUB> using point contact Andreev reflection spectroscopy

We report point contact Andreev reflection (PCAR) spectroscopy studies on Ni3±xAl1∓x with composition range spanning the ferromagnetic to paramagnetic phase boundary. PCAR studies performed using Nb tip as counterelectrode reveal that the superconducting quasiparticle lifetime (τ) and superconducting energy gap (Δ) decrease with increasing spin fluctuation in the normal metal electrode. Our study reveals that PCAR could be a useful probe to study spin fluctuations in systems that are on the verge of magnetic instability

Evidence of multiband superconductivity in the quaternary borocarbide superconductor YNi<SUB>2</SUB>B<SUB>2</SUB>C using directional point-contact spectroscopy

In this paper, we review our recent investigations on the gap anisotropy of the quaternary borocarbide superconductor YNi<SUB>2</SUB>B<SUB>2</SUB>C using directional point-contact spectroscopy. Through a detailed study of the temperature and magnetic field dependence of the superconducting energy gaps we show that the gap anisotropy in this material originates from electrons on different Fermi sheets having very different Fermi velocities. The gap anisotropy in this material is therefore well explained through a multiband scenario where electrons in different k-directions have very different electron–phonon coupling strength