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In the present study, we demonstrate the frequency-bias-temperature-dependent dielectric studies of ferrofluid (FF) mixed ferroelectric liquid crystals (FLCs; SCE13 and Felix017/100). Here, Cobalt ferrite NPs of the order of 9 nm size and... more
In the present study, we demonstrate the frequency-bias-temperature-dependent dielectric studies of ferrofluid (FF) mixed ferroelectric liquid crystals (FLCs; SCE13 and Felix017/100). Here, Cobalt ferrite NPs of the order of 9 nm size and a very homogeneous size distribution, used as FF, were prepared by using chemical method. In these FLCs-nanocomposites, memory (dielectric) effect is observed at room temperature, which further becomes more pronounced as temperature tends towards Sm C*-Sm A* phase transitions. Such fascinating memory effects are of potential interest for next generation FLCs-based electro-optical devices. Moreover, the physical parameters such as dielectric permittivity (ε′), spontaneous polarization (Ps), rotational viscosity (η), and switching response (τ) have also been critically investigated in order to explore the physical mechanism behind memory effect and the optimization of memory-based devices.
Finite size effect on Gd 3 + doped CoGd x Fe 2 À x O 4 (0.0 rx r0. a b s t r a c t Nanoparticles of CoGd x Fe 2 À x O 4 (where x ¼ 0.0, 0.1, 0.3, 0.5) series have been prepared by chemical co-precipitation. The effect of Gd 3 + ion... more
Finite size effect on Gd 3 + doped CoGd x Fe 2 À x O 4 (0.0 rx r0. a b s t r a c t Nanoparticles of CoGd x Fe 2 À x O 4 (where x ¼ 0.0, 0.1, 0.3, 0.5) series have been prepared by chemical co-precipitation. The effect of Gd 3 + ion concentration on crystalline phase, crystallinity, crystallite size, molecular vibrations and magnetic resonance has been investigated in detail. The crystallinity decreases with an increase in Gd 3 + ion concentration and changes the structural parameters. The spin lattice relaxation has been correlated with the doping ion concentration. Similarly, the super-paramagnetic behavior of these particles has been observed with EPR spectroscopy.
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Nanocrystalline nickel ferrite with different concentration of Ni and Zn (Ni x Zn 1 − x Fe 2 O 4 where x = 0.1, 0.3, 0.5) were synthesized using chemical co-precipitation method. The effect of doping ion concentration on physical... more
Nanocrystalline nickel ferrite with different concentration of Ni and Zn (Ni x Zn 1 − x Fe 2 O 4 where x = 0.1, 0.3, 0.5) were synthesized using chemical co-precipitation method. The effect of doping ion concentration on physical properties like crystalline phase, crystallite size, particle size, and saturation magnetization are investigated. The X-ray diffraction pattern confirms the synthesis of single crystalline Ni x Zn 1 − x Fe 2 O 4 nanoparticles. The lattice parameter decreases with increase Ni content resulting in reduction of lattice strain. HRTEM images revealed that the as-prepared nanoparticles were crystalline with particle size distribution in 10–30 nm range. The saturation magnetization show the superparamagnetic nature of sample for x = 0.1 and x = 0.3 whereas for x = 0.5, the material is ferromagnetic. The saturation magnetization value is 23.95 emu/gm for Ni 0.1 Zn 0.9 Fe 2 O 4 sample and it increases with increase in Ni content.
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Mn2+ substituted Zn ferrite nano particles have been synthesized using two different wet methods, sol-gel and co-precipitation. The doping effect of Mn2+ ion concentration on physical properties like structural and magnetic properties is... more
Mn2+ substituted Zn ferrite nano particles have been synthesized using two different wet methods, sol-gel and co-precipitation. The doping effect of Mn2+ ion concentration on physical properties like structural and magnetic properties is investigated. The crystallite size and lattice parameter increases with increasing Mn2+ concentration. EPR study reveals that the line width and g-factor increases with increasing Mn2+ concentration for co-precipitated particles whereas the reverse trend for sol-gel technique is observed. However, in both the processes the saturation magnetization (Ms) and coercivity (Hc) increase with increasing Mn2+ concentration. In a comparative study, the nano particles synthesized by sol-gel are more crystalline in nature as compared to co-precipitated particles.
Nano particles of CoGdxFe(2-x)O4, with x = 0.0, 0.1, 0.3, 0.5 have been prepared by chemical co-precipitation method. The as synthesized particles are annealed at 300 degrees C for two hours to improve crystallinity. The X-ray diffraction... more
Nano particles of CoGdxFe(2-x)O4, with x = 0.0, 0.1, 0.3, 0.5 have been prepared by chemical co-precipitation method. The as synthesized particles are annealed at 300 degrees C for two hours to improve crystallinity. The X-ray diffraction patterns reveal the single cobalt ferrite phase formation and the average crystallite size decreases to 7 nm in the Gd3+ ion doped sample (with x = 0.5) compared to 27 nm in case of un-doped cobalt ferrite sample. The electrical properties for the different compositions of Gd3+ ion substituted cobalt ferrite material were studied in the frequency range 100 Hz to 10 MHz at room temperature using WK impedance analyzer. It is found that the electrical conductivity of the samples increases with increasing Gd3+ ion concentration. The results of our investigations reveal a strong dependence of material properties on Gd3+ ion doping. PMID: 22962748 [PubMed]
Gd 3+ ions substituted in Ni 0.5 Zn 0.5 Gd x Fe 2-x O 4 (where x = 0.1, 0.2, 0.3) ferrite nanoparticles in the size range from 15 to 25 nm were prepared by chemical method. The effect of Gd 3+ ions in spinel structure in correlation to... more
Gd 3+ ions substituted in Ni 0.5 Zn 0.5 Gd x Fe 2-x O 4 (where x = 0.1, 0.2, 0.3) ferrite nanoparticles in the size range from 15 to 25 nm were prepared by chemical method. The effect of Gd 3+ ions in spinel structure in correlation to structural and magnetic properties has been studied in detail using XRD, HRTEM and EPR techniques. The spin resonance confirms the ferromagnetic behaviour of these nanoparticles and higher order of dipolar-dipolar interaction. On increasing Gd 3+ ions concentrations, the super exchange interaction i.e. increase in movement of electron among Gd 3+ -O -Fe 3+ in the core group and the spin biasing in the glass layer has been interpreted. The decrease in 'g' value and increase in relaxation time is well correlated with the change of particle size on different concentrations of Gd 3+ ions in Ni-Zn ferrite.
Research Interests: Mechanical Engineering, Condensed Matter Physics, Nanomaterials, Magnetism, Ferrofluid, and 10 moreMagnetic Properties, Zinc, Nickel, Ac Susceptibility, Crystallite Size, Lattice Parameter, X ray diffraction, Fourier transform infrared spectroscopy, Magnetism and Magnetic Materials, and Electron Paramagnetic Resonance
Carbon nanotube and Fe3O4 based magnetic composites have been prepared by dispersing acid treated CNTs in the precursor solution required for the synthesis of Fe3O4. The different weight percentage of CNTs has been mixed in ionic solution... more
Carbon nanotube and Fe3O4 based magnetic composites have been prepared by dispersing acid treated CNTs in the precursor solution required for the synthesis of Fe3O4. The different weight percentage of CNTs has been mixed in ionic solution of Fe3O4. The various properties like crystalline nature, morphology and free electron spin concentration have been investigated to characterize the composites. The XRD pattern and SEM images of composites confirmed that the composites have been synthesized successfully by chemical co-precipitation technique. The free electron spin concentrations have increased with the increasing weight percentage of CNTs. The varying free electron concentration confirmed the varying weight percent of CNTs and enhanced magnetic nature of composites.
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ABSTRACT Some existence and convergence theorems for a class of nonexpansive type mappings are obtained in a normed space. The results obtained herein generalize certain known results.
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ABSTRACT Using some new notions of convergence, Barbet and Nachi [Barbet L, Nachi K. Sequences of contractions and convergence of fixed points. Monografias del Seminario Matemático García de Galdeano 2006;33:51–58.] obtained several... more
ABSTRACT Using some new notions of convergence, Barbet and Nachi [Barbet L, Nachi K. Sequences of contractions and convergence of fixed points. Monografias del Seminario Matemático García de Galdeano 2006;33:51–58.] obtained several interesting results on the stability of fixed points in a metric space. These results are extended to 2-metric spaces which differ topologically from metric spaces in many ways.
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Nickel zinc ferrite nanoparticles NixZn1−xFe2O4 (x=0.1, 0.3, 0.5) have been synthesized by a chemical co-precipitation method. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, electron... more
Nickel zinc ferrite nanoparticles NixZn1−xFe2O4 (x=0.1, 0.3, 0.5) have been synthesized by a chemical co-precipitation method. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, electron paramagnetic resonance, dc magnetization and ac susceptibility measurements. The X-ray diffraction patterns confirm the synthesis of single crystalline NixZn1−xFe2O4 nanoparticles. The lattice parameter decreases with increase in Ni content resulting in a
Research Interests: Mechanical Engineering, Condensed Matter Physics, Nanomaterials, Magnetism, Ferrofluid, and 10 moreMagnetic Properties, Zinc, Nickel, Ac Susceptibility, Crystallite Size, Lattice Parameter, X ray diffraction, Fourier transform infrared spectroscopy, Magnetism and Magnetic Materials, and Electron Paramagnetic Resonance
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ABSTRACT Superparamagnetic (SP) crystalline cobalt ferrite (CoFe2O4) nanoparticles are synthesized by chemical co-precipitation method. Grown nanoparticles are annealed in air at various temperatures in the range 373 K to 1173 K to... more
ABSTRACT Superparamagnetic (SP) crystalline cobalt ferrite (CoFe2O4) nanoparticles are synthesized by chemical co-precipitation method. Grown nanoparticles are annealed in air at various temperatures in the range 373 K to 1173 K to understand the variation in properties in nanoregion. Physical properties are analyzed for crystalline phase, crystallite size, particle size, shape, magnetization and relaxation behavior by using various characterization techniques viz. X-ray diffractometer (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR). Annealing effect on various physical properties of particles are investigated. Particles are used in the development of stable ferrofluid.
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... 1 pp. 119, 1992. [4] G. Skandan, H. Hahn, M. Roddy, WR Cannon, J. Am. Ceram. Soc. vol. 77 pp. 1706, 1994. [5] RP Pant, RM Krishna, DP Singh, D. Srinivas, RV Mehta, J. Magn. Magn. Mater. vol. 164 pp. 143, 1996. [6] K. Raj, B.... more
... 1 pp. 119, 1992. [4] G. Skandan, H. Hahn, M. Roddy, WR Cannon, J. Am. Ceram. Soc. vol. 77 pp. 1706, 1994. [5] RP Pant, RM Krishna, DP Singh, D. Srinivas, RV Mehta, J. Magn. Magn. Mater. vol. 164 pp. 143, 1996. [6] K. Raj, B. Moskowitz, S. Tsuda, Indian J. Eng. Mater. Sci. ...
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ABSTRACT A stable kerosene based ferrofluid having magnetite nanoparticles (∼10 nm) coated with oleic acid as primary was synthesized by coprecipitation route. The Rietveld refinement of XRD pattern of Fe3O4 nanoparticles was carried out... more
ABSTRACT A stable kerosene based ferrofluid having magnetite nanoparticles (∼10 nm) coated with oleic acid as primary was synthesized by coprecipitation route. The Rietveld refinement of XRD pattern of Fe3O4 nanoparticles was carried out using Fullprof. The Williamson-Hall method gives 10.2(3) m and 0.002(1) as average crystallite size and strain respectively. The HRTEM image shows that particles are nearly spherical in shape. The room temperature magnetic measurements shows the superparamagnetic nature of the fluid. Using modified Langevin function, the average particle size was found to be 9.8(2) nm with 0.5 as standard deviation. The low temperature ESR measurements were performed in the temperature range 4 K–300 K using zero-field cooled (ZFC) protocol. The deconvolutions of the spectra suggest coexistence of two different resonance modes; i.e., a broad resonance signal superimposed by a sharp signal. This observation is consistent for temperature range 200 K– 300 K. The behavior of resonance field, linewidth and intensity shows a characteristic spin-glass state near to 190 K.
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ABSTRACT We have investigated the influence of nanosized particle concentration on rheological properties when mixed with Magneto-rheological (MR) fluid. We have also studied the structural, morphological and magnetic properties of... more
ABSTRACT We have investigated the influence of nanosized particle concentration on rheological properties when mixed with Magneto-rheological (MR) fluid. We have also studied the structural, morphological and magnetic properties of ferrofluid based MR fluids (F-MRFs). Field induced rheological and viscoelastic properties of F-MRFs with varying shear rate and strain amplitude have been performed. The Herschel–Bulkley model was found to be fit well with the flow behaviour of F-MRFs. In the oscillatory strain sweep test, F-MRFs show linear viscoelasticity at small strain and storage modulus (G′) is higher than the viscous modulus (G′′), which indicate the existence of strong links among the particles that form the microscopic structures. The storage modulus increases with increasing weight fraction of nanosized particles. Further, the loss factor, ratio of G" and G' was also investigated as a function of magnetic field strength. In addition, time dependent relaxation behaviour for magnetically induced chain like structures has also been described. The study reveals that the addition of nanoparticles in MR fluids increases the viscosity as well as fluid stability under magnetic field
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We demonstrate here the frequency-bias-temperature-dependent dielectric studies of ferrofluid (FF) mixed ferroelectric liquid crystals (FLCs; SCE13 and Felix017/100). As a FF, cobalt ferrite nanoparticles (∼9 nm) synthesised through... more
We demonstrate here the frequency-bias-temperature-dependent dielectric studies of ferrofluid (FF) mixed ferroelectric liquid crystals (FLCs; SCE13 and Felix017/100). As a FF, cobalt ferrite nanoparticles (∼9 nm) synthesised through chemical co-precipitation were used in the study. In these FF–FLCs nanocomposites, a memory (dielectric) effect is observed at room temperature, which becomes more pronounced as the temperature tends towards the smectic C*
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Nano particles of CoGdxFe(2-x)O4, with x = 0.0, 0.1, 0.3, 0.5 have been prepared by chemical co-precipitation method. The as synthesized particles are annealed at 300 degrees C for two hours to improve crystallinity. The X-ray diffraction... more
Nano particles of CoGdxFe(2-x)O4, with x = 0.0, 0.1, 0.3, 0.5 have been prepared by chemical co-precipitation method. The as synthesized particles are annealed at 300 degrees C for two hours to improve crystallinity. The X-ray diffraction patterns reveal the single cobalt ferrite phase formation and the average crystallite size decreases to 7 nm in the Gd3+ ion doped sample (with x = 0.5) compared to 27 nm in case of un-doped cobalt ferrite sample. The electrical properties for the different compositions of Gd3+ ion substituted cobalt ferrite material were studied in the frequency range 100 Hz to 10 MHz at room temperature using WK impedance analyzer. It is found that the electrical conductivity of the samples increases with increasing Gd3+ ion concentration. The results of our investigations reveal a strong dependence of material properties on Gd3+ ion doping.
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Proglacial lake sediments at Goting in the Higher Central Himalaya were analyzed to reconstruct the summer monsoon variability during the Last Glacial to early Holocene. Sedimentary structures, high resolution mineral magnetic and... more
Proglacial lake sediments at Goting in the Higher Central Himalaya were analyzed to reconstruct the summer monsoon variability during the Last Glacial to early Holocene. Sedimentary structures, high resolution mineral magnetic and geochemical data suggest ...
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Research Interests: Materials Engineering, Condensed Matter Physics, Quantum Physics, Analytical Chemistry, Inorganic Chemistry, and 14 moreNanotechnology, Magnesium, Non crystalline solids, Zinc, Potassium, Optical physics, Fine Structure Constant, Spectrum, Room Temperature, Single Crystal, Fresh water, Optical Materials, Electron Paramagnetic Resonance, and Crystal field
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Gd3+ substituted MnZn ferrites [Mn0. 5Zn0. 5GdxFe2− xO4 (x= 0.1, 0.2, 0.3, 0.4)] nanoparticles have been explored for ferrofluid applications. The oleic acid coated water base ferrofluids of these ferrites are prepared by chemical... more
Gd3+ substituted MnZn ferrites [Mn0. 5Zn0. 5GdxFe2− xO4 (x= 0.1, 0.2, 0.3, 0.4)] nanoparticles have been explored for ferrofluid applications. The oleic acid coated water base ferrofluids of these ferrites are prepared by chemical co-precipitation. The effect of ...