Britel Mohammed Reda | Université Abdelmalek Essaâdi (original) (raw)

Papers by Britel Mohammed Reda

Research paper thumbnail of A Low-Cost Elliptical Triple-Band Antenna for RF Energy Harvesting Applications

This paper presents the design, optimization, simulation and fabrication of a novel single layer,... more This paper presents the design, optimization, simulation and fabrication of a novel single layer, single-feed triple-band elliptical microstrip patch antenna. The proposed antenna effectively operates at three frequency bands to harvest RF energy from cellular network frequency bands (900 MHz and 1800 MHz) and Wi-Fi sources (2.45 GHz) available in our surrounding ambience. The antenna is printed on a low cost commercial FR4 substrate, has a compact size, and easy fabricate. The overall dimensions of this multiband antenna unit are 95 mm times95\times 95times95 mm times1.6\times 1.6times1.6 mm. The simulations and experimental results of the proposed antenna are presented, and a good agreement is observed between the simulated and measured results.

Research paper thumbnail of A Sensitive Triple-Band Rectifier for Energy Harvesting Applications

IEEE Access

This paper presents a novel sensitive triple-band power rectifier for RF energy harvesting system... more This paper presents a novel sensitive triple-band power rectifier for RF energy harvesting systems. The proposed rectifier can simultaneously harvest RF energy from GSM-900, GSM-1800, and Wi-Fi-2450 bands at relatively low and medium ambient power densities. Previously, a few multi-band rectennas have been reached a stable conversion efficiency overall frequency bands of interest because of the nonlinearity and the distinct input impedance of the rectifying circuit at these frequencies. The originality of this paper is on the improved impedance matching technique that enhances the efficiency and performance of the rectifier. The proposed high-efficiency triple-band rectifier consists of three parallel branches. Each branch comprises an input matching circuit designed to provide maximum RF power transferred to rectifying diodes, a single voltage doubler using Schottky diode HSMS-2852, and a DC-pass filter to smooth the DC output voltage. A prototype of the proposed rectifier circuit is fabricated and tested to verify its performance against the simulation results. With an optimum load resistance of 3.8 k at-10 dBm input power level, the measured RF to DC conversion efficiency achieves 33.7%, 21.8%, and 20% at 0.9, 1.8 and 2.45 GHz respectively. The efficiency is above 46.5 % overall bands of interest under 0 dBm input power. INDEX TERMS RF energy harvesting, RF to DC conversion efficiency, Schottky diode, triple-bands rectifier.

Research paper thumbnail of Anisotropic behaviour of permalloy wires using the giant magnetoimpedance effect

Journal of Magnetism and Magnetic Materials, 1999

Magnetoimpedance spectra of soft magnetic wires are characterized by peaks of the real part of th... more Magnetoimpedance spectra of soft magnetic wires are characterized by peaks of the real part of the impedance at frequencies f0 which increase with the strength of the applied field, H0. In the high-field region, f20 varies linearly with H0, with a slope that depends on the saturation magnetization and the gyromagnetic ratio; in the low-field region, the plot f20-H0 shows a near-zero intercept at H0 = HK. Given the gyromagnetic ratio, both the saturation magnetization and the anisotropy field can be determined from the variation of f20 vs. H0.

Research paper thumbnail of Calculations of giant magnetoimpedance and of ferromagnetic resonance response are rigorously equivalent

Applied Physics Letters, 1996

... A. Yelon, D. Ménard, M. Britel, and P. Ciureanu Groupe de Recherches en Physique et Technolog... more ... A. Yelon, D. Ménard, M. Britel, and P. Ciureanu Groupe de Recherches en Physique et Technologie de Couches Minces and Département de génie ... Since the linear polariza-tion is the sum of the two, the reference impedance will be twice the impedance for the resonant ...

Research paper thumbnail of Investigation of the damping parameter in soft magnetic wires using the giant magnetoimpedance effect

Journal of Magnetism and Magnetic Materials, 1999

We construct a simple model of the high frequency impedance applicable to soft magnetic wires and... more We construct a simple model of the high frequency impedance applicable to soft magnetic wires and derive an expression which relates the Landau–Lifschitz damping parameter, λ, to the peak value of the wire impedance at ferromagnetic resonance. Measurements on a ferromagnetic Co68.15Fe4.35Si12.5B15 amorphous magnetic wire are characterized by resonance peaks which vary significantly in amplitude and width as a function of the applied field. These results can be accounted for by a near exponential field dependence of the damping parameter at high magnetic fields. We suggest that this behavior results from inhomogeneities in the sample properties.

Research paper thumbnail of High frequency behavior of soft magnetic wires using the giant magnetoimpedance effect

Journal of Applied Physics, 1998

We have investigated the high frequency properties of several amorphous and polycrystalline wires... more We have investigated the high frequency properties of several amorphous and polycrystalline wires mounted as inner conductors in coaxial lines. A static magnetic field was applied along the wire axis. The impedance spectra of the wires, measured using a network analyzer, show peaks in the real part of the impedance, which shift to higher frequency with the strength of the static field, a behavior typical of ferromagnetic resonance. The theoretical resonance condition predicts a straight line on an f02-H0 plot, where f0 is the resonance frequency and H0 is the resonant field, whose slope depends only on the saturation magnetization, Ms, of the material. All our wires obey this relation, and the values of Ms calculated from the slopes are in good agreement with those measured directly using a vibrating sample magnetometer.

Research paper thumbnail of Microwave behavior in CoFe-based single- and two-phase magnetic microwires

Physica Status Solidi (a), 2011

1 Materials Science Institute of Madrid, CSIC, 28049 Madrid, Spain 2 Laboratory of Chemical Engin... more 1 Materials Science Institute of Madrid, CSIC, 28049 Madrid, Spain 2 Laboratory of Chemical Engineering and Resource Development, FST, UAE, BP 418, Tangier, Morocco 3 Innovative Technologies Laboratory, ENSA of Tangier, UAE, BP 1818, Tangier, Morocco

Research paper thumbnail of Influence of AC magnetic field amplitude on the surface magnetoimpedance tensor in amorphous wire with helical magnetic anisotropy

IEEE Transactions on Magnetics, 2004

We have performed experimental and theoretical studies on the influence of ac magnetic field ampl... more We have performed experimental and theoretical studies on the influence of ac magnetic field amplitude on the magnetoimpedance tensor in an amorphous wire with helical magnetic anisotropy. For the experimental measurements, we used an amorphous wire of composition (Co 0 94 Fe 0 06 ) 72 5 Si 12 5 B 15 with negative, nearly zero magnetostriction constant, excited either by an ac circular or by an axial magnetic field created by an ac electric current. We changed the ac current amplitude from 7.5 to 40 mA and the current frequency from 1.5 to 20 MHz. The values of the asymmetric giant magnetoimpedance ratio associated with the sweeping direction of the dc field ex and the corresponding sensitivity were 211% and 0.64 V/Oe, respectively, for an ac current of 37.5 mA at 3 MHz. For the theoretical study based on the magnetization rotation, we obtained the second-order harmonic of the ac magnetization (2) induced by the relatively high ac magnetic field by solving the Landau-Lifshitz-Gilbert (LLG) equation. We also considered a second-order surface impedance tensor^( 2) , which allowed us to analyze quantitatively the influence of the ac magnetic field amplitude on the impedance tensor of the wire. We obtained the domain model of the wire with helical magnetic anisotropy having multidomains and the magnetization vector 0 directed in the easy direction, and the corresponding static magnetic configurations, by solving the static LLG equation. For the given magnetic configurations, we calculated the second-order impedance tensor^( 2) . The results can well explain the irregular field characteristics of the voltage responses at low dc field value, when the wire was excited at high frequency and at large ac magnetic field.

Research paper thumbnail of Origin of linear and nonlinear giant magnetoimpedance

Physica A-statistical Mechanics and Its Applications, 1997

It has gradually become clear that giant magnetoimpedance, which initially appeared very mysterio... more It has gradually become clear that giant magnetoimpedance, which initially appeared very mysterious, can be explained classically, as arising from the dependence of skin depth upon the magnetic permeability. As the permeability may vary with dc field or with frequency, the impedance will vary as a function of these parameters. Thus, a variety of circumstances may give rise to GMI. A number of these circumstances are considered. The equivalence of GMI and ferromagnetic resonance calculations is discussed. On the basis of this equivalence, some effects are predicted.

Research paper thumbnail of Analysis of the complex permeability of a ferromagnetic wire

Journal of Applied Physics, 1999

We have measured the magnetoimpedance of ferromagnetic wires placed as internal conductors in sho... more We have measured the magnetoimpedance of ferromagnetic wires placed as internal conductors in shorted coaxial lines. We have also modeled the impedance by simultaneously solving Maxwell's equations and the Landau-Lifshitz equation of motion for the magnetization in a cylindrical magnetic conductor under the appropriate boundary conditions. The permeability of Ni45Co25Fe6Si9B13Mn2 amorphous wires, deduced from the impedance, is compared with the model on plots of the imaginary part of the permeability versus the real part, with the dc magnetic field as implicit parameter. This approach emphasizes the region of ferromagnetic resonance and facilitates the investigation of the permeability locus. A number of intrinsic parameters of the magnetic wire, such as the exchange constant, the damping constant, and the gyromagnetic ratio, have been evaluated.

Research paper thumbnail of Rf and uhf giant magnetoimpedance effects in soft magnetic fibers and wires

IEEE Transactions on Magnetics, 1996

We have investigated the giant magnetoimpedance (GMI) effect in fibers of different soft magnetic... more We have investigated the giant magnetoimpedance (GMI) effect in fibers of different soft magnetic materials and in Permalloy wires. The fibers have been tested in the radio frequency (rf) range, by measuring the voltage drops in different parts of the circuit. The wires have been tested in the ultra high frequency (uhf) range, by measuring the transmission coefficient s21 of coaxial lines having as central conductor a HyMu80 wire. The two methods provided quite similar results showing a strong GMI effect for very different magnetic samples

Research paper thumbnail of Anisotropy and magnetization processes in Co-rich amorphous wires

Journal of Applied Physics, 1999

Longitudinal magnetization curves and giant magnetoimpedance (GMI) analyses are combined to inves... more Longitudinal magnetization curves and giant magnetoimpedance (GMI) analyses are combined to investigate the anisotropy and magnetization processes of dc-current-self-annealed Co68.15Fe4.35Se12.5B15 wires. The magnetization curves show an almost anhysteretic behavior with small Barkhausen jumps occurring at a critical field H*. This unusual shape is in very good agreement with the high resolution GMI response to the field, which reflects the circumferential bias permeability. Magnetization curves yield information on the bulk properties, while GMI allows the investigation of the surface region of the sample. The anisotropy constant is calculated using initial-magnetization curves and the resonance condition, yielding interesting conclusions concerning the inhomogeneity of the wires.

Research paper thumbnail of Giant magnetoimpedance in a cylindrical magnetic conductor

Journal of Applied Physics, 1998

Giant magnetoimpedance in a cylindrical magnetic conductor. [Journal of Applied Physics 84, 2805 ... more Giant magnetoimpedance in a cylindrical magnetic conductor. [Journal of Applied Physics 84, 2805 (1998)]. D. Ménard, M. Britel, P. Ciureanu, A. Yelon. Abstract. ... Accordingly, any phenomenon which produces a large change in the permeability will give rise to a GMI effect. ...

Research paper thumbnail of Study of microwave magnetoimpedance effect in amorphous FeSiB wires

Journal of Magnetism and Magnetic Materials, 2007

Measurements of microwave magnetoimpedance of melt-extracted Fe-rich amorphous wires are presente... more Measurements of microwave magnetoimpedance of melt-extracted Fe-rich amorphous wires are presented. These wires were simultaneously submitted to a microwave electromagnetic wave propagating at the wire surface, Joule heating and circumferential static magnetic field. This field is generated by a DC electric current flowing through the wire with maximum strength of 90 mA in order not to reach the recrystallization temperature of the amorphous alloy. The impedance was measured up to 6 GHz using a technique based on the s-parameters measurement of a custom-designed coaxial line by means of a vectorial network analyzer. The real part of the impedance spectra we obtained show peaks, which characterize the magnetic losses occurring in the amorphous material. These peaks shift toward lower frequency for stronger DC currents. Theoretically, these results can be accounted for by the fact that the peaks frequency represents the ferromagnetic resonance occurring in the magnetic material. Its magnitude depends on the saturation magnetization. Since this magnetization decreases with temperature following the Curie law, the resonance frequency also decreases and the impedance peaks shift towards lower frequency. r 2007 Published by Elsevier B.V.

Research paper thumbnail of High frequency impedance spectra of soft amorphous fibers

Journal of Applied Physics, 1997

Giant magnetoimpedance ͑GMI͒ spectra of soft amorphous magnetic fibers, measured in the 1 kHz-1.2... more Giant magnetoimpedance ͑GMI͒ spectra of soft amorphous magnetic fibers, measured in the 1 kHz-1.2 GHz frequency range, and GMI responses, measured in the field range of Ϯ120 Oe, have reinforced the assumption that linear giant magnetoimpedance and ferromagnetic resonance ͑FMR͒ have the same physical origin. The samples, NiCo-rich, CoFe-rich, and Metglas-type fibers, 30-40 m in diameter, were cast by melt extraction. Their impedance has been measured up to 13 MHz, in the presence of a magnetic field, using an impedance analyzer. These measurements have been extended up to 1.2 GHz by using a network analyzer. The reflection coefficient of a shorted coaxial line whose inner conductor was replaced by a magnetic fiber was measured, and the input impedance per unit length of this line was then calculated. The two impedances above are equivalent and their spectra show a behavior associated with FMR: the real part of the impedance peaks at a frequency where the imaginary part passes through zero.

Research paper thumbnail of Anisotropic magnetoresistance and giant magnetoimpedance effects in soft magnetic fibers

Journal of Magnetism and Magnetic Materials, 1996

Soft magnetic fibers with different compositions have been cast by melt extraction. An anisotropi... more Soft magnetic fibers with different compositions have been cast by melt extraction. An anisotropic magnetoresistance effect (AMR) of about 3% was measured in NiFe fibers and employed to propose a model for their anisotropy and magnetization process. A giant magnetoimpedance effect (GMI) of about 60% was measured in the same fibers driven by a sinusoidal rf current at frequencies up to 100 MHz. Permalloy fibers were then compared in terms of GMI with (NiCo)v0FeSiBMn amorphous fibers, which presumably have an analogous quenched-in stress distribution. Quite similar results have been obtained for fibers with similar geometry irrespective of their composition.

Research paper thumbnail of Magnetoimpedance measurements of ferromagnetic resonance and antiresonance

Applied Physics Letters, 2000

... Centre-ville, Montréal (Québec) H3C 3A7, Canada RW Cochrane and M. Rouabhi Groupe de Recherch... more ... Centre-ville, Montréal (Québec) H3C 3A7, Canada RW Cochrane and M. Rouabhi Groupe de Recherche en Physique et Technologie des Couches Minces ... GHz at constant magnetic fields ranging up to 1.1 kOe (88 kA/m). The sample was an amorphous NiCo-rich soft-magnetic ...

Research paper thumbnail of Anisotropic behaviour of permalloy wires using the giant magnetoimpedance effect

Journal of Magnetism and Magnetic Materials, 1999

Magnetoimpedance spectra of soft magnetic wires are characterized by peaks of the real part of th... more Magnetoimpedance spectra of soft magnetic wires are characterized by peaks of the real part of the impedance at frequencies f0 which increase with the strength of the applied field, H0. In the high-field region, f20 varies linearly with H0, with a slope that depends on the saturation magnetization and the gyromagnetic ratio; in the low-field region, the plot f20-H0 shows a near-zero intercept at H0 = HK. Given the gyromagnetic ratio, both the saturation magnetization and the anisotropy field can be determined from the variation of f20 vs. H0.

Research paper thumbnail of Giant magnetoimpedance effect in soft and ultrasoft magnetic fibers

Journal of Applied Physics, 1996

ABSTRACT Soft NiFe‐Permalloy fibers and ultrasoft NiCo‐based amorphous fibers, having a circular ... more ABSTRACT Soft NiFe‐Permalloy fibers and ultrasoft NiCo‐based amorphous fibers, having a circular cross section with 30–40 μm in diameter, have been cast by melt extraction. The fibers have been driven by a sinusoidal current with 20 mA pp constant amplitude and frequencies from 0.1 to 100 MHz. Both longitudinal and transverse giant magnetoimpedance effects have been observed in these fibers. The longitudinal GMI effect at 30 MHz was 60% in ultrasoft (NiCo) 70 FeSiBMn fibers for a saturating field of about 7 kA/m. The same effect was found at 10 MHz frequency for Permalloy fibers for a larger saturating field (20 kA/m). The transverse GMI effect was smaller (≊35% for NiCo and ≊20% for NiFe), and showed a maximum at low frequency (3 MHz). The magnetic field responses of the fibers are quadratic. An inverse effect of 10%–30% was observed for both types of fibers in longitudinal as well as in transverse field responses at high current frequency and low field strength. All of the observed effects could prove to be very useful for a new generation of high‐sensitivity magnetic field sensors. © 1996 American Institute of Physics.

Research paper thumbnail of A Low-Cost Elliptical Triple-Band Antenna for RF Energy Harvesting Applications

This paper presents the design, optimization, simulation and fabrication of a novel single layer,... more This paper presents the design, optimization, simulation and fabrication of a novel single layer, single-feed triple-band elliptical microstrip patch antenna. The proposed antenna effectively operates at three frequency bands to harvest RF energy from cellular network frequency bands (900 MHz and 1800 MHz) and Wi-Fi sources (2.45 GHz) available in our surrounding ambience. The antenna is printed on a low cost commercial FR4 substrate, has a compact size, and easy fabricate. The overall dimensions of this multiband antenna unit are 95 mm times95\times 95times95 mm times1.6\times 1.6times1.6 mm. The simulations and experimental results of the proposed antenna are presented, and a good agreement is observed between the simulated and measured results.

Research paper thumbnail of A Sensitive Triple-Band Rectifier for Energy Harvesting Applications

IEEE Access

This paper presents a novel sensitive triple-band power rectifier for RF energy harvesting system... more This paper presents a novel sensitive triple-band power rectifier for RF energy harvesting systems. The proposed rectifier can simultaneously harvest RF energy from GSM-900, GSM-1800, and Wi-Fi-2450 bands at relatively low and medium ambient power densities. Previously, a few multi-band rectennas have been reached a stable conversion efficiency overall frequency bands of interest because of the nonlinearity and the distinct input impedance of the rectifying circuit at these frequencies. The originality of this paper is on the improved impedance matching technique that enhances the efficiency and performance of the rectifier. The proposed high-efficiency triple-band rectifier consists of three parallel branches. Each branch comprises an input matching circuit designed to provide maximum RF power transferred to rectifying diodes, a single voltage doubler using Schottky diode HSMS-2852, and a DC-pass filter to smooth the DC output voltage. A prototype of the proposed rectifier circuit is fabricated and tested to verify its performance against the simulation results. With an optimum load resistance of 3.8 k at-10 dBm input power level, the measured RF to DC conversion efficiency achieves 33.7%, 21.8%, and 20% at 0.9, 1.8 and 2.45 GHz respectively. The efficiency is above 46.5 % overall bands of interest under 0 dBm input power. INDEX TERMS RF energy harvesting, RF to DC conversion efficiency, Schottky diode, triple-bands rectifier.

Research paper thumbnail of Anisotropic behaviour of permalloy wires using the giant magnetoimpedance effect

Journal of Magnetism and Magnetic Materials, 1999

Magnetoimpedance spectra of soft magnetic wires are characterized by peaks of the real part of th... more Magnetoimpedance spectra of soft magnetic wires are characterized by peaks of the real part of the impedance at frequencies f0 which increase with the strength of the applied field, H0. In the high-field region, f20 varies linearly with H0, with a slope that depends on the saturation magnetization and the gyromagnetic ratio; in the low-field region, the plot f20-H0 shows a near-zero intercept at H0 = HK. Given the gyromagnetic ratio, both the saturation magnetization and the anisotropy field can be determined from the variation of f20 vs. H0.

Research paper thumbnail of Calculations of giant magnetoimpedance and of ferromagnetic resonance response are rigorously equivalent

Applied Physics Letters, 1996

... A. Yelon, D. Ménard, M. Britel, and P. Ciureanu Groupe de Recherches en Physique et Technolog... more ... A. Yelon, D. Ménard, M. Britel, and P. Ciureanu Groupe de Recherches en Physique et Technologie de Couches Minces and Département de génie ... Since the linear polariza-tion is the sum of the two, the reference impedance will be twice the impedance for the resonant ...

Research paper thumbnail of Investigation of the damping parameter in soft magnetic wires using the giant magnetoimpedance effect

Journal of Magnetism and Magnetic Materials, 1999

We construct a simple model of the high frequency impedance applicable to soft magnetic wires and... more We construct a simple model of the high frequency impedance applicable to soft magnetic wires and derive an expression which relates the Landau–Lifschitz damping parameter, λ, to the peak value of the wire impedance at ferromagnetic resonance. Measurements on a ferromagnetic Co68.15Fe4.35Si12.5B15 amorphous magnetic wire are characterized by resonance peaks which vary significantly in amplitude and width as a function of the applied field. These results can be accounted for by a near exponential field dependence of the damping parameter at high magnetic fields. We suggest that this behavior results from inhomogeneities in the sample properties.

Research paper thumbnail of High frequency behavior of soft magnetic wires using the giant magnetoimpedance effect

Journal of Applied Physics, 1998

We have investigated the high frequency properties of several amorphous and polycrystalline wires... more We have investigated the high frequency properties of several amorphous and polycrystalline wires mounted as inner conductors in coaxial lines. A static magnetic field was applied along the wire axis. The impedance spectra of the wires, measured using a network analyzer, show peaks in the real part of the impedance, which shift to higher frequency with the strength of the static field, a behavior typical of ferromagnetic resonance. The theoretical resonance condition predicts a straight line on an f02-H0 plot, where f0 is the resonance frequency and H0 is the resonant field, whose slope depends only on the saturation magnetization, Ms, of the material. All our wires obey this relation, and the values of Ms calculated from the slopes are in good agreement with those measured directly using a vibrating sample magnetometer.

Research paper thumbnail of Microwave behavior in CoFe-based single- and two-phase magnetic microwires

Physica Status Solidi (a), 2011

1 Materials Science Institute of Madrid, CSIC, 28049 Madrid, Spain 2 Laboratory of Chemical Engin... more 1 Materials Science Institute of Madrid, CSIC, 28049 Madrid, Spain 2 Laboratory of Chemical Engineering and Resource Development, FST, UAE, BP 418, Tangier, Morocco 3 Innovative Technologies Laboratory, ENSA of Tangier, UAE, BP 1818, Tangier, Morocco

Research paper thumbnail of Influence of AC magnetic field amplitude on the surface magnetoimpedance tensor in amorphous wire with helical magnetic anisotropy

IEEE Transactions on Magnetics, 2004

We have performed experimental and theoretical studies on the influence of ac magnetic field ampl... more We have performed experimental and theoretical studies on the influence of ac magnetic field amplitude on the magnetoimpedance tensor in an amorphous wire with helical magnetic anisotropy. For the experimental measurements, we used an amorphous wire of composition (Co 0 94 Fe 0 06 ) 72 5 Si 12 5 B 15 with negative, nearly zero magnetostriction constant, excited either by an ac circular or by an axial magnetic field created by an ac electric current. We changed the ac current amplitude from 7.5 to 40 mA and the current frequency from 1.5 to 20 MHz. The values of the asymmetric giant magnetoimpedance ratio associated with the sweeping direction of the dc field ex and the corresponding sensitivity were 211% and 0.64 V/Oe, respectively, for an ac current of 37.5 mA at 3 MHz. For the theoretical study based on the magnetization rotation, we obtained the second-order harmonic of the ac magnetization (2) induced by the relatively high ac magnetic field by solving the Landau-Lifshitz-Gilbert (LLG) equation. We also considered a second-order surface impedance tensor^( 2) , which allowed us to analyze quantitatively the influence of the ac magnetic field amplitude on the impedance tensor of the wire. We obtained the domain model of the wire with helical magnetic anisotropy having multidomains and the magnetization vector 0 directed in the easy direction, and the corresponding static magnetic configurations, by solving the static LLG equation. For the given magnetic configurations, we calculated the second-order impedance tensor^( 2) . The results can well explain the irregular field characteristics of the voltage responses at low dc field value, when the wire was excited at high frequency and at large ac magnetic field.

Research paper thumbnail of Origin of linear and nonlinear giant magnetoimpedance

Physica A-statistical Mechanics and Its Applications, 1997

It has gradually become clear that giant magnetoimpedance, which initially appeared very mysterio... more It has gradually become clear that giant magnetoimpedance, which initially appeared very mysterious, can be explained classically, as arising from the dependence of skin depth upon the magnetic permeability. As the permeability may vary with dc field or with frequency, the impedance will vary as a function of these parameters. Thus, a variety of circumstances may give rise to GMI. A number of these circumstances are considered. The equivalence of GMI and ferromagnetic resonance calculations is discussed. On the basis of this equivalence, some effects are predicted.

Research paper thumbnail of Analysis of the complex permeability of a ferromagnetic wire

Journal of Applied Physics, 1999

We have measured the magnetoimpedance of ferromagnetic wires placed as internal conductors in sho... more We have measured the magnetoimpedance of ferromagnetic wires placed as internal conductors in shorted coaxial lines. We have also modeled the impedance by simultaneously solving Maxwell's equations and the Landau-Lifshitz equation of motion for the magnetization in a cylindrical magnetic conductor under the appropriate boundary conditions. The permeability of Ni45Co25Fe6Si9B13Mn2 amorphous wires, deduced from the impedance, is compared with the model on plots of the imaginary part of the permeability versus the real part, with the dc magnetic field as implicit parameter. This approach emphasizes the region of ferromagnetic resonance and facilitates the investigation of the permeability locus. A number of intrinsic parameters of the magnetic wire, such as the exchange constant, the damping constant, and the gyromagnetic ratio, have been evaluated.

Research paper thumbnail of Rf and uhf giant magnetoimpedance effects in soft magnetic fibers and wires

IEEE Transactions on Magnetics, 1996

We have investigated the giant magnetoimpedance (GMI) effect in fibers of different soft magnetic... more We have investigated the giant magnetoimpedance (GMI) effect in fibers of different soft magnetic materials and in Permalloy wires. The fibers have been tested in the radio frequency (rf) range, by measuring the voltage drops in different parts of the circuit. The wires have been tested in the ultra high frequency (uhf) range, by measuring the transmission coefficient s21 of coaxial lines having as central conductor a HyMu80 wire. The two methods provided quite similar results showing a strong GMI effect for very different magnetic samples

Research paper thumbnail of Anisotropy and magnetization processes in Co-rich amorphous wires

Journal of Applied Physics, 1999

Longitudinal magnetization curves and giant magnetoimpedance (GMI) analyses are combined to inves... more Longitudinal magnetization curves and giant magnetoimpedance (GMI) analyses are combined to investigate the anisotropy and magnetization processes of dc-current-self-annealed Co68.15Fe4.35Se12.5B15 wires. The magnetization curves show an almost anhysteretic behavior with small Barkhausen jumps occurring at a critical field H*. This unusual shape is in very good agreement with the high resolution GMI response to the field, which reflects the circumferential bias permeability. Magnetization curves yield information on the bulk properties, while GMI allows the investigation of the surface region of the sample. The anisotropy constant is calculated using initial-magnetization curves and the resonance condition, yielding interesting conclusions concerning the inhomogeneity of the wires.

Research paper thumbnail of Giant magnetoimpedance in a cylindrical magnetic conductor

Journal of Applied Physics, 1998

Giant magnetoimpedance in a cylindrical magnetic conductor. [Journal of Applied Physics 84, 2805 ... more Giant magnetoimpedance in a cylindrical magnetic conductor. [Journal of Applied Physics 84, 2805 (1998)]. D. Ménard, M. Britel, P. Ciureanu, A. Yelon. Abstract. ... Accordingly, any phenomenon which produces a large change in the permeability will give rise to a GMI effect. ...

Research paper thumbnail of Study of microwave magnetoimpedance effect in amorphous FeSiB wires

Journal of Magnetism and Magnetic Materials, 2007

Measurements of microwave magnetoimpedance of melt-extracted Fe-rich amorphous wires are presente... more Measurements of microwave magnetoimpedance of melt-extracted Fe-rich amorphous wires are presented. These wires were simultaneously submitted to a microwave electromagnetic wave propagating at the wire surface, Joule heating and circumferential static magnetic field. This field is generated by a DC electric current flowing through the wire with maximum strength of 90 mA in order not to reach the recrystallization temperature of the amorphous alloy. The impedance was measured up to 6 GHz using a technique based on the s-parameters measurement of a custom-designed coaxial line by means of a vectorial network analyzer. The real part of the impedance spectra we obtained show peaks, which characterize the magnetic losses occurring in the amorphous material. These peaks shift toward lower frequency for stronger DC currents. Theoretically, these results can be accounted for by the fact that the peaks frequency represents the ferromagnetic resonance occurring in the magnetic material. Its magnitude depends on the saturation magnetization. Since this magnetization decreases with temperature following the Curie law, the resonance frequency also decreases and the impedance peaks shift towards lower frequency. r 2007 Published by Elsevier B.V.

Research paper thumbnail of High frequency impedance spectra of soft amorphous fibers

Journal of Applied Physics, 1997

Giant magnetoimpedance ͑GMI͒ spectra of soft amorphous magnetic fibers, measured in the 1 kHz-1.2... more Giant magnetoimpedance ͑GMI͒ spectra of soft amorphous magnetic fibers, measured in the 1 kHz-1.2 GHz frequency range, and GMI responses, measured in the field range of Ϯ120 Oe, have reinforced the assumption that linear giant magnetoimpedance and ferromagnetic resonance ͑FMR͒ have the same physical origin. The samples, NiCo-rich, CoFe-rich, and Metglas-type fibers, 30-40 m in diameter, were cast by melt extraction. Their impedance has been measured up to 13 MHz, in the presence of a magnetic field, using an impedance analyzer. These measurements have been extended up to 1.2 GHz by using a network analyzer. The reflection coefficient of a shorted coaxial line whose inner conductor was replaced by a magnetic fiber was measured, and the input impedance per unit length of this line was then calculated. The two impedances above are equivalent and their spectra show a behavior associated with FMR: the real part of the impedance peaks at a frequency where the imaginary part passes through zero.

Research paper thumbnail of Anisotropic magnetoresistance and giant magnetoimpedance effects in soft magnetic fibers

Journal of Magnetism and Magnetic Materials, 1996

Soft magnetic fibers with different compositions have been cast by melt extraction. An anisotropi... more Soft magnetic fibers with different compositions have been cast by melt extraction. An anisotropic magnetoresistance effect (AMR) of about 3% was measured in NiFe fibers and employed to propose a model for their anisotropy and magnetization process. A giant magnetoimpedance effect (GMI) of about 60% was measured in the same fibers driven by a sinusoidal rf current at frequencies up to 100 MHz. Permalloy fibers were then compared in terms of GMI with (NiCo)v0FeSiBMn amorphous fibers, which presumably have an analogous quenched-in stress distribution. Quite similar results have been obtained for fibers with similar geometry irrespective of their composition.

Research paper thumbnail of Magnetoimpedance measurements of ferromagnetic resonance and antiresonance

Applied Physics Letters, 2000

... Centre-ville, Montréal (Québec) H3C 3A7, Canada RW Cochrane and M. Rouabhi Groupe de Recherch... more ... Centre-ville, Montréal (Québec) H3C 3A7, Canada RW Cochrane and M. Rouabhi Groupe de Recherche en Physique et Technologie des Couches Minces ... GHz at constant magnetic fields ranging up to 1.1 kOe (88 kA/m). The sample was an amorphous NiCo-rich soft-magnetic ...

Research paper thumbnail of Anisotropic behaviour of permalloy wires using the giant magnetoimpedance effect

Journal of Magnetism and Magnetic Materials, 1999

Magnetoimpedance spectra of soft magnetic wires are characterized by peaks of the real part of th... more Magnetoimpedance spectra of soft magnetic wires are characterized by peaks of the real part of the impedance at frequencies f0 which increase with the strength of the applied field, H0. In the high-field region, f20 varies linearly with H0, with a slope that depends on the saturation magnetization and the gyromagnetic ratio; in the low-field region, the plot f20-H0 shows a near-zero intercept at H0 = HK. Given the gyromagnetic ratio, both the saturation magnetization and the anisotropy field can be determined from the variation of f20 vs. H0.

Research paper thumbnail of Giant magnetoimpedance effect in soft and ultrasoft magnetic fibers

Journal of Applied Physics, 1996

ABSTRACT Soft NiFe‐Permalloy fibers and ultrasoft NiCo‐based amorphous fibers, having a circular ... more ABSTRACT Soft NiFe‐Permalloy fibers and ultrasoft NiCo‐based amorphous fibers, having a circular cross section with 30–40 μm in diameter, have been cast by melt extraction. The fibers have been driven by a sinusoidal current with 20 mA pp constant amplitude and frequencies from 0.1 to 100 MHz. Both longitudinal and transverse giant magnetoimpedance effects have been observed in these fibers. The longitudinal GMI effect at 30 MHz was 60% in ultrasoft (NiCo) 70 FeSiBMn fibers for a saturating field of about 7 kA/m. The same effect was found at 10 MHz frequency for Permalloy fibers for a larger saturating field (20 kA/m). The transverse GMI effect was smaller (≊35% for NiCo and ≊20% for NiFe), and showed a maximum at low frequency (3 MHz). The magnetic field responses of the fibers are quadratic. An inverse effect of 10%–30% was observed for both types of fibers in longitudinal as well as in transverse field responses at high current frequency and low field strength. All of the observed effects could prove to be very useful for a new generation of high‐sensitivity magnetic field sensors. © 1996 American Institute of Physics.