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ABSTRACT: A new method for magnetic thin-film characterization is presented. New microwave electronic technology challenges require integration of many passive components on chips. Among them, isolators and circulators are nonreciprocal passive devices which contain magnetic materials. The use of thin magnetic films in place of bulk materials seems to be a solution to integrate these components on chips. Hence, it is important to know the magnetic properties of thin films in the microwave range. An isolator is obtained by locating the thin magnetic film in a coplanar line; however, it is often difficult to measure the constitutive parameters of the film before the end of its production. The method described allows in situ measurement of two parameters of the film permeability tensor.
IEEE Transactions on Microwave Theory and Techniques 05/2005; · 1.85 Impact Factor
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ABSTRACT: New passive components for microwave applications above 30 GHz currently have the major defect not to be compatible with industrial integration. Their performances are often ruined either when it is needed to reduce their dimensions or when some of their materials cannot be deposited in the requested conditions. This study takes a coplanar isolator working at 50 GHz and with barium hexaferrite thin film as an illustration of this problem. The component, which has been fabricated at the laboratory by RF sputtering of the different layers which stacks it up, shows very interesting characteristics. However, much work remains on the increasing of its isolation capacity as well as on its miniaturization. All of the component's dealings are here presented. Its behaviour has been revealed experimentally performing on-wafer measurements with a probe system coupled with a vector network analyser. The measurement technique is explained beforehand and then validated by further simulation results. The modelling of the component is tackled also and the obtained model serves as a basis for optimization investigations. In that matter, an innovative approach is introduced which leads to the use of currently emerging metamaterials technology. Finally, conclusions are drawn on the real opportunity that such new composite materials can be.
Industrial Electronics, 2004 IEEE International Symposium on; 06/2004
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IBCE'04 IFAC Workshop Internet Based Control Education, Grenoble; 01/2004
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ABSTRACT: An issue of current research is the integration of microwave ferrite devices with semiconductor technologies by using vacuum deposition techniques. Thin magnetic films may be used in commercial products and they can be more easily involved in the development of magnetic devices if we are able to extract their magnetic properties. One of the interesting points of this paper is to highlight the properties of a thin film, such as anisotropic behavior to release non reciprocal devices. A study of physicochemical and magnetic properties is tackled and experimental results are discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (c) 01/2004; 1(12):3744-3747.
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ABSTRACT: The transmission coefficient of a nonreciprocal coplanar waveguide (CPW) using ferrite rods is studied. A new approximate method is proposed to evaluate the propagation constant of such a perturbed waveguide, which is based on the use of numerical data referring to the nonperturbed waveguide. We have estimated the value of the nonreciprocity effect and settled the condition of the validity of our theory. Some experimental data of a CPW with ferrite inclusions are also presented.
IEEE Transactions on Microwave Theory and Techniques 08/2003; · 1.85 Impact Factor
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ABSTRACT: The transmission coefficients of a non-reciprocal coplanar waveguide using ferrite rods is computed. A new approximate method is proposed to evaluate the direct and reverse propagation constant of such a perturbed waveguide. The propagation constant of the non-perturbed waveguide or coplanar line is calculated using the Spectral Domain Approach method. From these numerical data we have estimated the value of the non-reciprocity effect and settled the condition of the validity of our theory. The first experimental data are presented when ferrofluids or magnetic powders are deposited on the coplanar waveguide.
Microwave Conference, 2001. 31st European; 10/2001
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ABSTRACT: We present a magneto-optical method using Brown's relaxation in ferrofluids. This method permits one to make some viscosimetric measurements by putting a drop of miscible ferrofluid into a test liquid, glycerol or diethylene glycol (DEG). To test this method we have compared our results obtained for glycerol with those obtained from a more conventional method and we observed good agreement. After this validation, we were able to study the viscosity of DEG between -20 and +90 °C by using our magneto-optical method. The comparison of these results with those obtained in standard ways (in the temperature range from -10 to +20 °C) revealed very slight deviations.
Measurement Science and Technology 09/1999; 10(11):1054. · 1.49 Impact Factor
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ABSTRACT: A magneto-optical method, conceived in our laboratory to measure
Brown's relaxation frequency of ferrofluids, is compared with Fannin's
technique based on impedance measurements (slit toroid). We have
developed a complete theory and an experimental setup of the first
method and have briefly described the second one. We present a study of
Brown's relaxation of cobalt ferrite Fe<sub>2</sub>CoO<sub>4</sub> in
different carrier liquids (glycerol, diethylene glycol, dibutyl
phthalate, and water). The two methods show very close results, proving
the high sensitivity of both. The relation between the viscosity η
and Brown's relaxation frequency f<sub>B</sub> has been verified.
Moreover the analysis of relaxation and viscosity versus temperature has
enabled us to estimate the hydrodynamic diameter of particles
IEEE Transactions on Magnetics 06/1999; · 1.36 Impact Factor
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ABSTRACT: A simple, fast method of characterization of anisotropic magnetic
materials uses a nonreciprocal X-band rectangular cell. The material may
be a solid, powder, or magnetic liquid. A network analyzer measures the
scattering parameters, and an original numerical processing routine
computes the permeability tensor components. Two anisotropic magnetic
materials have been characterized: a ferrofluid made with magnetite
particles suspended in a hydrocarbon and a barium iron oxide powder. The
knowledge of permeability behavior of magnetic liquids is important in
designing specific nonreciprocal microwave devices. Experimental results
are in good agreement with the proposed theoretical simulated
model
IEEE Transactions on Magnetics 02/1999; · 1.36 Impact Factor
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ABSTRACT: We propose an appropriate calculation method, giving both the complex permittivity epsilon * and permeability mu * of a liquid sample, from transmission/reflection measurements obtained from a network analyser working on a coaxial line between 0.1 and 20 GHz. A 20 mm long specific coaxial cell has been constructed using two polytetrafluoroethylene joints to ensure air tightness. Its small length allows rejection towards the upper frequencies of the measurement anomalies given by the Nicolson-Ross equations. Positions and thickness of the joints are taken into account by the calculus. The whole system has been tested with the empty cell and then on several alcohols and ferrofluids. The results on alcohols are in excellent agreement with all previous results; measurement on one of the magnetic fluids (Fe2MnO4 in CCl4) has shown a Neel relaxation and also a gyromagnetic resonance.
Measurement Science and Technology 12/1998; 5(8):990. · 1.49 Impact Factor
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ABSTRACT: We present susceptibility measurements on a ferrofluid in the
microwave frequency range with three different measurement cells: a
coaxial line, an X-band rectangular waveguide, and an X-band slab-loaded
rectangular waveguide. We use the reflection/transmission method to
obtain the complex susceptibility χ<sup>*</sup>. We have subjected
the cells to a constant magnetic field applied parallel or transversal
to the propagation direction. We observe an increase of the gyromagnetic
resonance phenomenon and some discrepancies between the consequences of
a parallel or transverse applied field. Nonreciprocal phenomenon has
been observed for the first time in a ferrofluid when a transversal
field is applied to an X-band slab-loaded rectangular waveguide
IEEE Transactions on Magnetics 06/1998; · 1.36 Impact Factor
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ABSTRACT: This work presents the dielectric behaviour in the primary amines
for the importance of NH<sub>2</sub> group it bears in the interaction
of amino acids and proteins and their influence in the electric
conduction process. Therefore, we have studied the dielectric properties
for 1-propylamine, 1-butylamine and 1-pentylamine. Measurements were
performed, between room temperature and -200°C, in the low frequency
range. The isofrequency recordings of dispersion ε' and absorption
ε'', for these three primary amines, show clearly the liquid-solid
phase transitions and the effect of the aliphatic chain length
Dielectric Materials, Measurements and Applications, Seventh International Conference on (Conf. Publ. No. 430); 10/1996
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ABSTRACT: We report on the dielectric and magnetodielectric effects in the
different phases of an ionic ferrofluid made of nanometric particles of
manganese ferrite (Fe<sub>2</sub>MnO<sub>4</sub>) diluted at different
volume concentration in carbon tetrachloride (CCl<sub>4</sub>) used as
carrier liquid. To obtain a fast recording of experimental data we have
used an automated spectrometer working in the frequency range 1 mHz-10
MHz and from -200°C up to 50°C. This study shows the presence of
three phases (liquid, plastic and solid) for pure CCl<sub>4</sub>, these
phases remain for the ferrofluid. Our experimental results allow an
investigation of homogeneity and stability of these ionic dispersions at
different concentrations and phases. Finally, a magnetodielectric
anisotropy is observed when a continuous magnetic field (parallel or
perpendicular to the electric field) is applied. This anisotropy
observed at room temperature remains at very low temperature, in
particular in the plastic phases
Conduction and Breakdown in Dielectric Liquids, 1996, ICDL '96., 12th International Conference on; 08/1996
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ABSTRACT: We propose an appropriate method giving the complex permittivity
of a liquid sample from transmission/ reflection measurements obtained
from a network analyzer working on a coaxial line between 0.1 and 20
GHz. A specific coaxial cell was made with two etancheity joints in
teflon encased at its extremities, Positions and thickness of this
joints are taken into account by the calculus. This technique has been
tested with the empty cell and then on several dielectric liquids. The
results are in excellent agreement with all previous measurements, This
method allows also to obtain complex permittivity and permeability of
the liquid sample (ferrofluids), but then we have the “length
resonance” problem which may be solved with an appropriate
algorithm
Conduction and Breakdown in Dielectric Liquids, 1996, ICDL '96., 12th International Conference on; 08/1996
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ABSTRACT: This paper presents an experimental dielectric study of a
ferrofluid, magnetic particles of CoFe<sub>2</sub>O<sub>4</sub>
dispersed in dibutylphthalate at different volume concentrations over a
large temperature range (40 to -100°C), between 1 mHz and 10 MHz,
with and without a continuous axial or radial magnetic field. The
analysis of static permittivity indicates that the magnetodielectric
anisotropy which exists at room temperature, persists at lower
temperature, near the glass transition temperature of the carrier
liquid. Moreover these results show a possible existence and growth of
aggregates at the upper concentrations of ferrites. The position of the
relaxation peaks of different solutions is modified by the presence of
an axial continuous magnetic field
IEEE Transactions on Dielectrics and Electrical Insulation 07/1994; · 1.09 Impact Factor
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ABSTRACT: The authors present a dielectric study of ferrofluid, magnetic
particles of Fe<sub>2</sub>CoO<sub>4</sub> dispersed in dibutyl
phthalata, at different volume concentrations in a large temperature
range (from 40°C down to -100°C) between 1 MHz and 10 MHz, with
and without a continuous axial or radial magnetic field. The analysis of
static permittivity shows a small magnetodielectric anisotropy, even at
low temperature, and the possible existence and growth of aggregates at
higher concentrations. It is shown that, in the given experimental
conditions, and under a continuous longitudinal or transverse magnetic
field, this ionic colloidal suspension does not remain well-dispersed
above a limit volume concentration (x ≈ 0.05) when temperature is
decreasing
Conduction and Breakdown in Dielectric Liquids,1993., ICDL '93., IEEE 11th International Conference on; 08/1993
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ABSTRACT: Temperature dependence of the viscosity of many glass-forming liquids is investigated over a wide range of temperatures (100 to 1700 K). It is shown that the three Vogel-Fulcher coefficients are not constant but exhibit regular variations versus temperature over the entire range 10<sup>-3</sup> to 10<sup>12</sup> Pl. This property is consistent with the nonlinear variations of the free-volume in the Cohen and Grest percolation model (1981, 1984). A similar result is found for the dielectric relaxation time in glycerol-water mixtures and in propylene carbonate.
IEEE Transactions on Electrical Insulation 09/1988;
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ABSTRACT: The dielectric relaxation times and static permittivity of the binary mixtures of water and methylhydrazine, CH3N H N H2 or 1,1-dimethylhydrazine (CH3)2NNH2 are determined in supercooled conditions down to 150K. For each system, these properties can be modeled using chemical associations of the type (H2O)m(RR'NNH2)p and, also, self associations for pure hydrazines.
Fluid Phase Equilibria 85:239-255. · 2.14 Impact Factor
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ABSTRACT: This work concerns the research on ferrofluids or magnetic liquids. Fast changes of their dielectric properties, which may be induced by phase transitions of the carrier liquid or by aggregates or multi-layers forming, require the whole automation of the measurement process. Therefore, we have used a high impedance programmable adaptor working on shunt mode in the frequency range 1 mHz-10 kHz. It allowed us to characterize, between +50°C and −200°C, an ionic ferrofluid made from nanometric particles of manganese ferrite (Fe2MnO4) diluted at different concentrations in carbon tetrachloride (CC14) used as carrier liquid. We have pointed out the different phases of pure CCI4 (liquid, plastic and solid). In our experimental conditions, we have shown the lack of the ferrofluid stability at low temperature and high concentration. In addition, a magneto dielectric anisotropy is observed when a continuous magnetic field (parallel or perpendicular to the electric field) is applied.
Journal of Magnetism and Magnetic Materials.
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ABSTRACT: This paper presents a dielectric and magneto-dielectric study of magnetic fluids made of three different, partially substituted, manganese ferrite particles dispersed in kerosene. Measurements were performed using a wholly automated spectrometer in the frequency range 1 mHz–10 MHz and a temperature range from −200°C up to 100°C. We can distinguish the two phases (solid and liquid) in pure kerosene and three phases for all the magnetic fluid samples. We observed the effect of anisotropy constant and domain magnetization of the particles on magneto-dielectric measurements. We also observed the temperature sensitivity of these fluids.
Journal of Magnetism and Magnetic Materials.
