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Agrawal N.,M. S. University of Baroda | Sarkar M.,M. S. University of Baroda | Chawda M.,M. S. University of Baroda | Ganesan V.,UGCDAE Consortium for Scientific Research | Bodas D.,Agharkar Research Institute
Materials Research Express | Year: 2015

The magnetism was observed in very dilute Fe doped alloy thin film Fe0.008Sb1-xSex, for x = 0.01 to 0.10. These thin films were grown on silicon substrate using thermal evaporation technique. Structural, electrical, optical, charge carrier concentration measurement, surface morphology and magnetic properties were observed using glancing incidence x-ray diffraction (GIXRD), four probe resistivity, photoluminescence, Hall measurement, atomic force microscopy (AFM) and magnetic force microscopy (MFM) techniques, respectively. No peaks of iron were seen in GIXRD. The resistivity results show that activation energy increases with increase in selenium (Se) concentration. The Arrhenius plot reveals metallic behavior below room temperature. The low temperature conduction is explained by variable range-hopping mechanism, which fits very well in the temperature range 150-300 K. The decrease in density of states has been observed with increasing selenium concentration (x = 0.01 to 0.10). There is a metal-to-semiconductor phase transition observed above room temperature. This transition temperature is Se concentration dependent. The particle size distribution ∼47-61 nmis evaluated usingAFMimages. These thin films exhibit ferromagnetic interactions at room temperature. © 2015 IOP Publishing Ltd.

De D.,Indian Institute of Technology Kharagpur | Ram S.,Indian Institute of Technology Kharagpur | Banerjee A.,UGCDAE Consortium for Scientific Research | Roy S.K.,Indian Institute of Technology Kharagpur
Journal of Magnetism and Magnetic Materials | Year: 2012

(La 0.6Eu 0.4) 0.67Ca 0.33MnO 3 has been prepared in the shape of nanoplates of single crystallites (an orthorhombic structure) through polymer templates. HRTEM images reveal 18, 25, and 30 nm thicknesses of plates after heating a precursor powder at 873, 1073, and 1273 K in air for 2 h. These values present average crystallite size determined from broadening of the X-ray diffraction peaks. A spin-glass-like surface (GS) overlayer (35 nm thickness) in such plates facilitates a ferromagnetic→ferrimagnetic reordering with markedly suppressed Curie point T C, i.e., as small as 90 K in a 873 K heated sample, from the parent value 268 K. The T C point increases to 103 K (or 120 K) when heating at higher temperature 1073 (or 1273 K), during which the core grows at the expense of the overlayer. The GS tailors as high coercivity H c as 617 Oe in the zero field cooled (ZFC) sample that is decreased to 500 Oe in the field cooled (FC) sample in the surface spin-freezing along the field direction. The H c-value (ZFC) that steps down successively to 252 Oe on the overlayer is thinned down by heating at 1273 K. Samples heated at 873, 1073, or 1273 K have regularly increased saturation magnetization 35.3, 63.9, or 69.6 emu/g in ZFC, while 43.7, 70.2, or 75.5 emu/g in FC measured at 10 K. The ferrimagnetic reordering are described based on the scenario of an antiferromagnetic exchange coupling between the Eu 3 and Mn 3 (or Mn 4) sublattices. © 2011 Elsevier B.V. All rights reserved.

Vachhani P.S.,Saurashtra University | Solanki P.S.,Saurashtra University | Doshi R.R.,Saurashtra University | Shah N.A.,Saurashtra University | And 2 more authors.
Physica B: Condensed Matter | Year: 2011

We report magnetotransport properties of La0.5Pr 0.2Sr0.3MnO3 (LPSMO) {5 layers}/La 0.5Pr0.2Ba0.3MnO3 (LPBMO) {4 layers} manganite multilayers grown on single crystalline STO (h 0 0) and NGO (h 0 0) substrates using pulsed laser deposition (PLD) technique. An appreciable magnetoresistance (MR) ∼56% (80 kOe field) at room temperature (RT) is exhibited by the heterostructure deposited on STO substrate having field coefficient of resistance (FCR) ∼35% (100 Oe) while the multilayer deposited on NGO substrate exhibits MR∼61% (80 kOe field) and FCR∼18% (5 kOe) at RT. The observed values of temperature coefficient of resistance (TCR) are ∼3.15% and 2.77% at RT for the multilayers grown on STO and NGO substrates, respectively. A comparison of the field sensitivity of the multilayered structure studied with those reported for LPSMO/Al2O 3/LPSMO (FCR∼20% at 220 K) and LPSMO/STO film (FCR∼13% at 250 K) shows that the multilayer exhibits higher field sensitivity, which can be attributed to the improved LPSMOLPBMO interfaces. In this communication, the results of the structural, transport and magnetotransport studies on LPSMO/LPBMO multilayered systems have been discussed. © 2011 Elsevier B.V. All rights reserved.

Bagchi S.,CSIR - Institute of Minerals And Materials Technology | Bagchi S.,UGCDAE Consortium for Scientific Research | Jani S.,Mohanlal Sukhadia University | Anwar S.,CSIR - Central Electrochemical Research Institute | And 2 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2010

The present study reports the effect of swift heavy ion irradiation on structural and magnetic properties of sputtered W/Fe multilayer structure (MLS) having bilayer compositions of [W(10 )/Fe(20 )]10BL. The MLS is irradiated by 120 MeV Au9 ions of fluences 1×1013 and 4×1013 ions/cm2. Techniques like X-ray reflectivity (XRR), cross-sectional transmission electron microscopy (X-TEM) and DC magnetization with a vibrating sample magnetometer (VSM) are used for structural and magnetic characterization of pristine and irradiated MLS. Analysis of XRR data using Parratt's formalism shows a significant increase in W/Fe layer roughness. X-TEM studies reveal that intra-layer microstructure of Fe layers in MLS becomes nano-crystalline on irradiation. DC magnetization study shows that with spacer layer thickness interlayer coupling changes between ferromagnetic to antiferromagnetic. © 2010 Elsevier B.V. All rights reserved.

Chatterjee A.,UGCDAE Consortium for Scientific Research | Priyam A.,UGCDAE Consortium for Scientific Research | Ghosh D.,UGCDAE Consortium for Scientific Research | Mondal S.,UGCDAE Consortium for Scientific Research | And 2 more authors.
Journal of Luminescence | Year: 2012

Interactions of luminescence, water soluble ZnS nanoparticles (NPs) with flavins and glucose oxidase have been thoroughly investigated through optical spectroscopy. The photoluminescence of ZnS nanoparticles was quenched severely (∼60%) by riboflavin while other flavins such as flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) show quenching to different extents under analogous conditions. However, interestingly no effect in luminescence intensity of ZnS NPs was observed with protein bound flavins such as in glucose oxidase. Fluorescence lifetime measurement confirmed the quenching to be static in nature. Scavenging of photo-generated electron of ZnS nanoparticles by the flavin molecules may be attributed to the decrease in luminescence intensity. Quenching of ZnS nanoparticles with flavins follows the linear SternVolmer plot. The SternVolmer constants decreased in the following order: K S-V (Riboflavin)> K S-V (FAD)> K S-V (FMN). This interaction study could generate useful protocol for the fluorimetric determination of riboflavin (vitamin B 2) content and also riboflavin status in biological systems. © 2011 Elsevier B.V. All rights reserved.

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