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Nor Saadah Mohd Yusof - One of the best experts on this subject based on the ideXlab platform.
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The effect of sonication on the ion Exchange Constant, KXBr of CTABr/chlorobenzoates micellar systems.
Ultrasonics sonochemistry, 2020Co-Authors: Nor Saadah Mohd YusofAbstract:Abstract The ion Exchange Constant, K X Br (for the case of cetyltrimethylammonium bromide, CTABr, in this study) is a method dependant characterization of ion Exchange process by counterions, X and Br with different relative binding ratios. In this report, the ion Exchange Constant, K X Br values for micelle systems irradiated under 2 minutes of sonication at 120 W power using a probe sonicator with 1 cm tip were determined to be 85.2, 125.6 and 122.4 when X = o-, m- and p-chlorobenzoates, respectively. The values were quantified using a semiempirical kinetic method coupled with Pseudophase Micellar model, and later compared to the same system in the absence of sonication. The sonication was found to amplify the K X Br values by ∼13-fold for X = o-chlorobenzoate and ∼2.5-fold for X = m- and p-chlorobenzoates. This is due to the improvement of ion Exchange process by the oscillation of bubbles generated by acoustic cavitation. An active ion Exchange process indicates better stabilization of the micelle aggregational structure by the penetration of the introduced counterions, X into the micelle Stern layer leading to the growth of the micelle. This is supported by the remarkable increase in the viscosity of the micelle system by > 7-fold for X = o-chlorobenzoate and by > 2-folds for X = m- and p-chlorobenzoates. Sonication was also found to induce maximum viscoelasticity at lower concentration ratio of [CTABr]:[X]. The ability of ultrasound to induce micelle growth and exhibiting viscoelasticity at lower concentration of counterionic additive will be very useful in technologies where viscoelastic solution is desired such as in oil drilling and centralized heating and cooling system.
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Determination of an Ion Exchange Constant by the Use of a Kinetic Probe: A New Semiempirical Kinetic Approach Involving the Effects of 3-F- and 4-F-Substituted Benzoates on the Rate of Piperidinolysis of Anionic Phenyl Salicylate in Aqueous Cationic
Langmuir : the ACS journal of surfaces and colloids, 2010Co-Authors: Nor Saadah Mohd Yusof, M. Niyaz KhanAbstract:Pseudo-first-order rate Constants (k(obs)) for the nucleophilic substitution reaction of piperidine (Pip) with ionized phenyl salicylate (PS(-)), obtained at a Constant [Pip](T) (= 0.1 M), [PS(-)](T) (= 2 x 10(-4) M), [CTABr](T) (cetyltrimethylammonium bromide), < or = 0.06 M NaOH, and a varying concentration of MX (= 3-FC(6)H(4)CO(2)Na, 3-FBzNa and 4-FC(6)H(4)CO(2)Na, 4-FBzNa), follow the kinetic relationship k(obs) = (k(0) + thetaK(X/S)[MX])/(1 + K(X/S)[MX]) which is derived by the use of the pseudophase micellar (PM) model coupled with an empirical equation. The empirical equation explains the effects of [MX] on CTABr micellar binding Constant (K(S)) of PS(-) that occur through X(-)/PS(-) ion Exchange. Empirical Constants theta and K(X/S) give the parameters F(X/S) and K(X/S), respectively. The magnitude of F(X/S) gives the measure of the fraction of micellized PS(-) transferred to the aqueous phase by the limiting concentration of X(-) through X(-)/PS(-) ion Exchange. The values of F(X/S) and K(X/S) have been used to determine the usual thermodynamic ion Exchange Constant (K(X)(Y)) for ion Exchange process X(-)/Y(-) on the CTABr micellar surface. The values of K(X)(Br) (where Br = Y) have been calculated for X = 3-FBzNa and 4-FBzNa. The mean values of K(X)(Br) are 12.8 +/- 0.9 and 13.4 +/- 0.6 for X(-) = 3-FBz(-) and 4-FBz(-), respectively. Nearly 3-fold-larger values of K(X)(Br) for X = 3-FBz(-) and 4-FBz(-) than those for X = Bz(-), 2-ClBz(-), 2-CH(3)Bz(-), and the 2,6-dichlorobenzoate ion (2,6-Cl(2)Bz(-)) are attributed to the presence of wormlike micelles in the presence of > 50 mM 3-FBz(-) and 4-FBz(-) in the [CTABr](T) range of 5-15 mM. Rheological properties such as shear thinning behavior of plots of shear viscosity versus the shear rate at a Constant [3-FBz(-)] or [4-FBz(-)] as well as shear viscosity (at a Constant shear rate) maxima as a function of the concentrations of 3-FBz(-) and 4-FBz(-) support the conclusion, derived from the values of K(X)(Br), for the probable presence of wormlike/viscoelastic micellar solutions under the conditions of the present study.
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determination of an ion Exchange Constant by the use of a kinetic probe a new semiempirical kinetic approach involving the effects of 3 f and 4 f substituted benzoates on the rate of piperidinolysis of anionic phenyl salicylate in aqueous cationic mi
Langmuir, 2010Co-Authors: Nor Saadah Mohd Yusof, Niyaz M KhanAbstract:Pseudo-first-order rate Constants (kobs) for the nucleophilic substitution reaction of piperidine (Pip) with ionized phenyl salicylate (PS−), obtained at a Constant [Pip]T (= 0.1 M), [PS−]T (= 2 × 10−4 M), [CTABr]T (cetyltrimethylammonium bromide), ≤0.06 M NaOH, and a varying concentration of MX (= 3-FC6H4CO2Na, 3-FBzNa and 4-FC6H4CO2Na, 4-FBzNa), follow the kinetic relationship kobs = (k0 + θKX/S[MX])/(1 + KX/S[MX]) which is derived by the use of the pseudophase micellar (PM) model coupled with an empirical equation. The empirical equation explains the effects of [MX] on CTABr micellar binding Constant (KS) of PS− that occur through X−/PS− ion Exchange. Empirical Constants θ and KX/S give the parameters FX/S and KX/S, respectively. The magnitude of FX/S gives the measure of the fraction of micellized PS− transferred to the aqueous phase by the limiting concentration of X− through X−/PS− ion Exchange. The values of FX/S and KX/S have been used to determine the usual thermodynamic ion Exchange Constant (KX...
Burkard Hillebrands - One of the best experts on this subject based on the ideXlab platform.
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Annealing influence on the Gilbert damping parameter and the Exchange Constant of CoFeB thin films
Applied Physics Letters, 2014Co-Authors: A. Conca, T. Sebastian, E. Th. Papaioannou, Stefan Klingler, Jochen Greser, B. Leven, J. Lösch, Burkard HillebrandsAbstract:We present a study of the influence of the annealing temperature Ta on the magnetic properties of Co40Fe40B20 thin films. Using a vector network analyzer ferromagnetic resonance (VNA-FMR) setup and the magneto-optical Kerr effect, the dependence of the Gilbert damping parameter α, the Exchange Constant A, the saturation magnetization as well as the coercive field and the Kerr signal on Ta is reported. Additionally, the correlation with the crystalline properties of the films studied by X-ray diffractometry is discussed. We found that while the damping parameter α and the coercive field show sharp changes starting at a certain Ta value, the Exchange Constant A and the Kerr signal show a steady evolution. A differential modification of the film surface compared to the bulk is discussed as a possible reason. In any case, we found that the low damping values are preserved at the first onset of crystallization.
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Exchange stiffness in the Co2FeSi Heusler compound
Journal of Physics D: Applied Physics, 2009Co-Authors: O Gaier, Jaroslav Hamrle, Burkard Hillebrands, Simon Trudel, H. Schneider, Gerhard JakobAbstract:Using Brillouin light scattering spectroscopy, we determine the spin-wave Exchange stiffness D and the Exchange Constant A for thin films of the full Heusler compound Co2FeSi prepared by pulsed laser deposition. The thermal spin-wave spectra were measured in various magnetic fields, for different transferred spin-wave momenta, and for different film thicknesses. Fitting the observed spin-wave frequencies, we find an extraordinarily large value of
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Determination of Exchange Constants of Heusler compounds by Brillouin light scattering spectroscopy: application to Co$_2$MnSi
Journal of Physics D: Applied Physics, 2009Co-Authors: Jaroslav Hamrle, O Gaier, Burkard Hillebrands, Seong-gi Min, Yuya Sakuraba, Yasuo AndoAbstract:Brillouin light scattering spectroscopy from so-called standing spin waves in thin magnetic films is often used to determine the magnetic Exchange Constant. The data analysis of the experimentally determined spin-wave modes requires an unambiguous assignment to the correct spin wave mode orders. Often additional investigations are needed to guarantee correct assignment. This is particularly important in the case of Heusler compounds where values of the Exchange Constant vary substantially between different compounds. As a showcase, we report on the determination of the Exchange Constant (Exchange stiffness Constant) in Co$_2$MnSi, which is found to be $A=2.35\pm0.1$ $\mu$erg/cm ($D=575\pm20$ meV \AA$^2$), a value comparable to the value of the Exchange Constant of Co.
T. Sebastian - One of the best experts on this subject based on the ideXlab platform.
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Parameter-free determination of the Exchange Constant in thin films using magnonic patterning
Applied Physics Letters, 2016Co-Authors: M Langer, T. Sebastian, Kai Wagner, Rene Hubner, J Grenzer, Yutian Wang, Takahide Kubota, T Schneider, S. Stienen, Kilian LenzAbstract:Artículo de publicación ISISin acceso a texto completoAn all-electrical method is presented to determine the Exchange Constant of magnetic thin films using ferromagnetic resonance. For films of 20 nm thickness and below, the determination of the Exchange Constant A, a fundamental magnetic quantity, is anything but straightforward. Among others, the most common methods are based on the characterization of perpendicular standing spin-waves. These approaches are however challenging, due to (i) very high energies and (ii) rather small intensities in this thickness regime. In the presented approach, surface patterning is applied to a permalloy (Ni80Fe20) film and a Co2Fe0.4Mn0.6Si Heusler compound. Acting as a magnonic crystal, such structures enable the coupling of backward volume spin-waves to the uniform mode. Subsequent ferromagnetic resonance measurements give access to the spin-wave spectra free of unquantifiable parameters and, thus, to the Exchange Constant A with high accuracy
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parameter free determination of the Exchange Constant in thin films using magnonic patterning
Applied Physics Letters, 2016Co-Authors: T. Sebastian, M Langer, Kai Wagner, Rene Hubner, J Grenzer, Yutian Wang, Takahide Kubota, T SchneiderAbstract:An all-electrical method is presented to determine the Exchange Constant of magnetic thin films using ferromagnetic resonance. For films of 20 nm thickness and below, the determination of the Exchange Constant A, a fundamental magnetic quantity, is anything but straightforward. Among others, the most common methods are based on the characterization of perpendicular standing spin-waves. These approaches are however challenging, due to (i) very high energies and (ii) rather small intensities in this thickness regime. In the presented approach, surface patterning is applied to a permalloy (Ni80Fe20) film and a Co2Fe0.4Mn0.6Si Heusler compound. Acting as a magnonic crystal, such structures enable the coupling of backward volume spin-waves to the uniform mode. Subsequent ferromagnetic resonance measurements give access to the spin-wave spectra free of unquantifiable parameters and, thus, to the Exchange Constant A with high accuracy.
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All-optical characterisation of the spintronic Heusler compound Co2Mn0.6Fe0.4Si
Journal of Physics D: Applied Physics, 2015Co-Authors: T. Sebastian, Yuki Kawada, Björn Obry, Thomas Brächer, Philipp Pirro, Dmytro A. Bozhko, Alexander A. Serga, Hiroshi Naganuma, Mikihiko Oogane, Yasuo AndoAbstract:This article is devoted to the evaluation of the material parameters of the Heusler compound Co2Mn0.6Fe0.4Si via Brillouin light scattering spectroscopy. Recently, cobalt-based Heusler compounds and, in particular, the compound Co2Mn0.6Fe0.4Si have attracted huge interest in the fields of spintronics and magnon spintronics. Thus, evaluation of the material parameters that govern spin dynamics in the gigahertz regime is essential to develop and understand advanced experimental scenarios as well as potential technical applications. We demonstrate the evaluation of these parameters based on wavevector as well as time-resolved Brillouin light scattering spectroscopy. The focus of our study is the determination of the spin-wave damping in an individual microstructure as wells as of the Exchange Constant of Co2Mn0.6Fe0.4Si—parameters, that are difficult to estimate with alternative techniques.
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Annealing influence on the Gilbert damping parameter and the Exchange Constant of CoFeB thin films
Applied Physics Letters, 2014Co-Authors: A. Conca, T. Sebastian, E. Th. Papaioannou, Stefan Klingler, Jochen Greser, B. Leven, J. Lösch, Burkard HillebrandsAbstract:We present a study of the influence of the annealing temperature Ta on the magnetic properties of Co40Fe40B20 thin films. Using a vector network analyzer ferromagnetic resonance (VNA-FMR) setup and the magneto-optical Kerr effect, the dependence of the Gilbert damping parameter α, the Exchange Constant A, the saturation magnetization as well as the coercive field and the Kerr signal on Ta is reported. Additionally, the correlation with the crystalline properties of the films studied by X-ray diffractometry is discussed. We found that while the damping parameter α and the coercive field show sharp changes starting at a certain Ta value, the Exchange Constant A and the Kerr signal show a steady evolution. A differential modification of the film surface compared to the bulk is discussed as a possible reason. In any case, we found that the low damping values are preserved at the first onset of crystallization.
E Chikoidze - One of the best experts on this subject based on the ideXlab platform.
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Zn1-xMnxO: A typical member of the II-VI : Mn DMS family
Superlattices and Microstructures, 2007Co-Authors: E Chikoidze, Jurgen Von Bardeleben, Y Dumont, W. Pacuski, O. GorochovAbstract:ZnO:Mn thin films are grown by MOCVD technique. Mn(x) varies in 0 < x < 0.44 range. Vegrad's law has been verified for the lattice parameters. EPR measurements prove the substitution incorporation of Mn2+ on zinc sites. The behavior of EPR line-width regarding temperature is discussed. All ZnO:Mn layers show antiferromagnetic interaction and a J(1)/k(B) = -15 K effective Exchange Constant. Observation of excitons, giant Zeeman effect, and trace of the Brillouin function is evidence for high quality of the crystal lattice and of substitutional incorporation of manganese ions in place of Zn, as Mn2+. (c) 2007 Elsevier Ltd. All rights reserved.
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ZnO : Mn as a member of II-VI : Mn family
Applied physics. A Materials science & processing, 2007Co-Authors: E Chikoidze, Jurgen Von Bardeleben, Y Dumont, J. Gleize, F. Jomard, E. Rzepka, G. Berrerar, D. Ferrand, O. GorochovAbstract:ZnO:Mn thin films are grown by the metal organic chemical vapor deposition technique. Mn (x) varies in the 0 < x < 0.44 range. Vegard's law has been verified for the lattice parameters. Electron paramagnetic resonance (EPR) measurements prove the substitutional incorporation of Mn2+ on zinc sites. The behavior of the EPR line width regarding temperature is discussed. All ZnO:Mn layers show antiferromagnetic interaction and a J(1)/k(B)=-15 K effective Exchange Constant. The optical band gap of ZnO:Mn increases with the manganese concentration. Raman spectroscopy reveals a Mn-related scattering band.
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Magnetic interactions in Zn1-xMnxO studied by electron paramagnetic resonance spectroscopy
Journal of Applied Physics, 2005Co-Authors: E Chikoidze, Jurgen Von Bardeleben, Y Dumont, P Galtier, Jean-louis CantinAbstract:Zn1-xMnxO layers with x varying between 0.006 and 0.22, have been prepared by metal-organic chemical-vapor deposition technique and analyzed by electron paramagnetic 2, resonance spectroscopy. The layers show an Exchange narrowed single line spectrum of Mn2+ ions; its temperature dependence demonstrates antiferromagnetic coupling with an effective Exchange Constant of J1/k(B)=-14.9 K. (c) 2005 American Institute of Physics.
M. Niyaz Khan - One of the best experts on this subject based on the ideXlab platform.
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Determination of an Ion Exchange Constant by the Use of a Kinetic Probe: A New Semiempirical Kinetic Approach Involving the Effects of 3-F- and 4-F-Substituted Benzoates on the Rate of Piperidinolysis of Anionic Phenyl Salicylate in Aqueous Cationic
Langmuir : the ACS journal of surfaces and colloids, 2010Co-Authors: Nor Saadah Mohd Yusof, M. Niyaz KhanAbstract:Pseudo-first-order rate Constants (k(obs)) for the nucleophilic substitution reaction of piperidine (Pip) with ionized phenyl salicylate (PS(-)), obtained at a Constant [Pip](T) (= 0.1 M), [PS(-)](T) (= 2 x 10(-4) M), [CTABr](T) (cetyltrimethylammonium bromide), < or = 0.06 M NaOH, and a varying concentration of MX (= 3-FC(6)H(4)CO(2)Na, 3-FBzNa and 4-FC(6)H(4)CO(2)Na, 4-FBzNa), follow the kinetic relationship k(obs) = (k(0) + thetaK(X/S)[MX])/(1 + K(X/S)[MX]) which is derived by the use of the pseudophase micellar (PM) model coupled with an empirical equation. The empirical equation explains the effects of [MX] on CTABr micellar binding Constant (K(S)) of PS(-) that occur through X(-)/PS(-) ion Exchange. Empirical Constants theta and K(X/S) give the parameters F(X/S) and K(X/S), respectively. The magnitude of F(X/S) gives the measure of the fraction of micellized PS(-) transferred to the aqueous phase by the limiting concentration of X(-) through X(-)/PS(-) ion Exchange. The values of F(X/S) and K(X/S) have been used to determine the usual thermodynamic ion Exchange Constant (K(X)(Y)) for ion Exchange process X(-)/Y(-) on the CTABr micellar surface. The values of K(X)(Br) (where Br = Y) have been calculated for X = 3-FBzNa and 4-FBzNa. The mean values of K(X)(Br) are 12.8 +/- 0.9 and 13.4 +/- 0.6 for X(-) = 3-FBz(-) and 4-FBz(-), respectively. Nearly 3-fold-larger values of K(X)(Br) for X = 3-FBz(-) and 4-FBz(-) than those for X = Bz(-), 2-ClBz(-), 2-CH(3)Bz(-), and the 2,6-dichlorobenzoate ion (2,6-Cl(2)Bz(-)) are attributed to the presence of wormlike micelles in the presence of > 50 mM 3-FBz(-) and 4-FBz(-) in the [CTABr](T) range of 5-15 mM. Rheological properties such as shear thinning behavior of plots of shear viscosity versus the shear rate at a Constant [3-FBz(-)] or [4-FBz(-)] as well as shear viscosity (at a Constant shear rate) maxima as a function of the concentrations of 3-FBz(-) and 4-FBz(-) support the conclusion, derived from the values of K(X)(Br), for the probable presence of wormlike/viscoelastic micellar solutions under the conditions of the present study.
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A new semi-empirical kinetic method for the determination of ion Exchange Constants for the counterions of cationic micelles.
Advances in colloid and interface science, 2010Co-Authors: M. Niyaz KhanAbstract:A new method, based upon semi-empirical kinetic approach, for the determination of ion Exchange Constant for ion Exchange processes occurring between counterions at the cationic micellar surface is described in this review article. Basically, the method involves a reaction kinetic probe which gives observed pseudo-first-order rate Constants (k(obs)) for a nucleophilic substitution reaction between the nonionic and anionic reactants (R and S) in the presence of a Constant concentration of both reactants as well as cationic micelles and varying concentrations of an inert inorganic or organic salt (MX). The observed data (k(obs), versus [MX]) fit satisfactorily (in terms of residual errors) to an empirical equation which could be derived from an equation explaining the mechanism of the reaction of the kinetic probe in terms of pseudophase micellar (PM) model coupled with another empirical equation. This (another) empirical equation explains the effect of [MX] on cationic micellar binding Constant (K(S)) of the anionic reactant (say S) and gives an empirical Constant, K(X/S). The magnitude of K(X/S) is the measure of the ability of X(-) to expel S(-) from a cationic micellar pseudophase to the bulk aqueous phase through ion Exchange X(-)/S(-). The values of K(X/S) and K(Y/S) (where Y(-) is another inert counterion) give the ion Exchange Constant, K(X)(Y) (=K(X)/K(Y) where K(X) and K(Y) represent cationic micellar binding Constants of X(-) and Y(-), respectively). The suitability of this method is demonstrated by the use of three different reaction kinetic probes and various MX.
