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CONTENTS
Volume 1, Number 4, December 2013
 

Abstract
One-dimensional multiferroic nanostructured composites have drawn increasing interest as they show tremendous potential for multifunctional devices and applications. Herein, we report the synthesis, structural and dielectric characterization of barium titanate (BaTiO3)-bismuth ferrite (BiFeO3) composite fibers that were obtained using a novel sol-gel based electrospinning technique. The microstructure of the fibers was investigated using scanning electron microscopy and transmission electron microscopy. The fibers had an average diameter of 120 nm and were composed of nanoparticles. X-ray diffraction (XRD) study of the composite fibers demonstrated that the fibers are composed of perovskite cubic BaTiO3-BiFeO3 crystallites. The magnetic hysteresis loops of the resultant fibers demonstrated that the fibers were ferromagnetic with magnetic coercivity of 1500 Oe and saturation magnetization of 1.55 emu/g at room temperature (300 K). Additionally, the dielectric response of the composite fibers was characterized as a function of frequency. Their dielectric permittivity was found to be 140 and their dielectric loss was low in the frequency range from 1000 Hz to 107 Hz.

Key Words
electrospinning; multiferroic; multifunctional; sol-gel; dielectric property; nano-fiber

Address
Avinash Baji: Engineering Product Development (EPD) Pillar, Singapore University of Technology and Design (SUTD), Singapore 138682, Singapore
Mojtaba Abtahi: Centre for Advanced Materials Technology (CAMT), School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, Sydney, NSW 2006, Australia

Abstract
In this article, we present the effects of Ag doping and after-growth thermal annealing on the photoluminescence (PL) and thermoluminescence (TL) behaviors of SnO2 nanoparticles. SnO2 nanoparticles of 4-7 nm size range containing different Ag contents were synthesized by hydrothermal process. It has been observed that the after-growth thermal annealing process enhances the crystallite size and stabilizes the TL emissions of SnO2 nanostructures. Incorporated Ag probably occupies the interstitial sites of the SnO2 lattice, affecting drastically their emission behaviors on thermal annealing. Both the TL response and dose-linearity of the SnO2 nanoparticles improve on 1.0% Ag doping, and subsequent thermal annealing. However, a higher Ag content causes the formation of Ag clusters, reducing both the TL and PL responses of the nanoparticles.

Key Words
tin oxide; nanoparticle;Ag-doping; photoluminescence; thermoluminescence

Address
R. Sánchez Zeferino and U. Pal: Instituto de Física, Universidad Autónoma de Puebla, Apdo. Postal J-48, Puebla, Pue. 72570, Mexico
R. Meléndrez and M. Barboza Flores: Centro de Investigación en Física, Universidad de Sonora, Apartado Postal 5-088, Hermosillo, Sonora 83190, Mexico

Abstract
So far, all reviews and control approaches of spin relaxation have been done on lateral single electron quantum dots. In such structures, many efforts have been done, in order to eliminate spin-lattice relaxation, to obtain equal Rashba and linear Dresselhaus parameters. But, ratio of these parameters can be adjustable up to 0.7 in a material like GaAs under high- electric field magnitudes. In this article we have proposed a single electron QD structure, where confinements in all of three directions are considered to be almost identical. In this case the effect of cubic Dresselhaus interaction will have a significant amount, which undermines the linear effect of Dresselhaus while it was destructive in lateral QDs. Then it enhances the ratio of the Rashba and Dresselhaus parameters in the proposed structure as much as required and decreases the spin states up and down mixing and the deviation angle from the net spin-down As a result to the least possible value.

Key Words
spin relaxation; spin orbit interaction; Rashba spin-orbit interaction; Dresselhaus spin-orbit interaction; lateral quantum dot

Address
M.Z. Mashayekhi, K. Abbasian and S. Shoar-Ghaffari: School of Engineering Emerging-Technologies, University of Tabriz, Tabriz 51666, Iran

Abstract
A low-cost, green and reproducible citric acid assisted synthesis of nanocrystalline Al0.5Ag0.5TiO3 (n-AAT) powder is reported. X-ray, FTIR, energy dispersive X-ray, transmission electron microscopy and scanning electron microscopy analyses are performed to ascertain the formation of n-AAT. X-ray diffraction data analysis indicated the formation of monoclinic structure. Spherical shaped particles having the sizes of 3-15 nm are found. The mechanism of nano-transformation for the soft-chemical synthesis of n-AAT has been explained using simple organic chemistry rules and nucleation and growth theory. Dielectric study revealed that AAT ceramic might be a suitable candidate for capacitor applications.

Key Words
green synthesis; citric acid gel method; nanoparticle; dielectric properties; Al0.5Ag0.5TiO3

Address
Sandeep Kumar and L.K. Sahay: University Department of Chemistry, T.M. Bhagalpur University, Bhagalpur 812 007, India
Anal K. Jha: Aryabhatta Centre for Nanoscience and Nanotechnology, Aryabhatta Knowledge University, Patna 800 001, India
K. Prasad: Aryabhatta Centre for Nanoscience and Nanotechnology, Aryabhatta Knowledge University, Patna 800 001, India; University Department of Physics, T.M. Bhagalpur University, Bhagalpur 812 007, India

Abstract
We report on the preparation of iron pyrite (FeS2) using pulsed electron ablation of two targets, namely, a mixture of sulfur and iron compound target, and a natural iron pyrite target. Thin films of around 50 nm in thickness have been deposited on glass substrates under Argon background gas at 3 mTorr, and at a substrate temperature of up to 450oc. The thin films have been analyzed chemically and examined structurally using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and visible Raman spectroscopy. The morphology and thickness of the films have been assessed using scanning electron microscopy (SEM) and visible spectroscopic reflectance. The preliminary findings, using a synthetic target, show the presence of iron pyrite with increasing proportion as substrate temperature is increased from 150oc to 250oc. The data have not shown any evidence of pyrite in the deposited films from a natural target.

Key Words
iron pyrite; pulsed electron beam ablation; thin films; photovoltaics

Address
Omar Al-Shareeda and Redhouane Henda: School of Engineering, Laurentian University, Sudbury, P3E 2C6, Canada
Allan Pratt: CANMET Mining and Mineral Sciences Laboratories, Natural Resources Ottawa, K1A 0G1, Canada
Andrew M. McDonald: Earth Science Dept., Laurentian University, Sudbury, P3E 2C6, Canada


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