Amorphous Magnetic Ribbons Research Articles

Improved micro fluxgate sensor with double-layer Fe-based amorphous core

A rapid manufacturing process for the micro solenoid fluxgate sensor integrating multilayer amorphous ribbon core has been established, which combines the micro assembling method and the MEMS technologies. We select Fe-based amorphous soft magnetic ribbons for core materials and have fabricated the micro fluxgate sensors by MEMS technologies, with single-layer core and double-layer core respectively. The micro fluxgate sensors with double-layer core show the advantageous to that with single-layer core and exhibit sensitivity of 1089.2 V/T at excitation current of 120 mA rms, wide linear range of ź900 to 900 μT and power consumption of 24.48 mW. The noise power density of the single core fluxgate sensor is 2.48nT/Hz1/2@1 Hz.

Continuous-annealing method for producing a flexible, curved, soft magnetic amorphous alloy ribbon

A method has been developed for continuous annealing of an amorphous alloy ribbon moving forward at several meters per second, giving a curved shape to the ribbon that remains flexible afterward and can be easily wound into a toroidal core with excellent soft magnetic properties. A heat pulse was applied by a compact system on a Metglas 2605HB1 ribbon moving forward at 5 m/s to initiate a thermal treatment at 460 °C, near crystallization onset. The treatment duration was less than 0.1 s, and the heating and cooling rates were above 10 000 °C/s, which helped preserve most of the alloy as-cast ductility state. Such high temperature rates were achieved by forcing a static contact between the moving ribbon and a temperature-controlled roller. A tensile stress and a series of bending configurations were applied on the moving ribbon during the treatment to induce the development of magnetic anisotropy and to obtain the desired natural curvature radius. The core losses at 60 Hz of a toroidal test core wound with the resulting ribbon are lower than the specific values reported by the alloy manufacturer. This method can be implemented at the casting plant for supplying a low-cost, ready-to-use ribbon, easy to handle and cut, for mass production of toroidal cores for distribution transformer kernels (core and coil only), pulse power cores, etc.

Hysteretic giant magnetoimpedance effect analyzed by first-order reversal curves

We applied the first-order reversal curve method to hysteretic giant magnetoimpedance (GMI) of soft magnetic amorphous ribbons with a well-defined transversal domain structure and quasi-anhysteretic magnetization behavior. In opposition to major curve, it gives access to the distribution of local irreversible changes of the transverse permeability, which undergo a gradual transition. Results show that hysteretic GMI effect consists of three distinct regimes depending on the applied field. An interlinked hysteron/anti-hysteron model is proposed to analyze the obtained results, which allows one to follow the influence of frequency and anisotropy upon the irreversible switches probed by GMI.

Time of isothermal holding in the course of in-air heat treatment of soft magnetic Fe-based amorphous alloys and their magnetic properties

On the example of soft magnetic Fe81B13Si4C2 and Fe77Ni1Si9B13 amorphous alloys, the relation between the level of magnetic properties and duration of isothermal holding in the course of heat treatment in air has been studied. The optimum temperature-dependent time τ of isothermal holding has been shown to be related to the volume fraction of domains (Vorth) with orthogonal magnetization in the initial (quenched) ribbon by equation Vorth = ττ1/3. A temperature dependence of the proportionality coefficient α, which determines the degree of diffusion-process activity, has been determined. The results obtained allow us to substantially simplify the choice of optimum conditions of atmospheric heat treatment of soft magnetic Fe-based amorphous ribbons.

Influence of the Corrosion on the Surface Magnetic Properties in Amorphous and Nanocrystalline Materials

In this review article recent studies about the corrosion and the influence of corrosion on the surface magnetic properties of amorphous and nanocrystalline magnetic ribbons are presented. The studies have been performed in Febased and Co-based amorphous ribbons, because these ribbons are used in different magnetic sensors. In the first case the investigation has been focused on the corrosion, the influence of corrosion in the surface magnetic properties and the influence of the nickel content on the electrochemical behaviour. The results show that in the amorphous samples, when the oxidized layer increases, the surface saturation magnetization decreases. However, in the nanocrystalline samples the surface saturation magnetization does not change significantly. The values of the surface coercive field for the oxidized and non oxidized samples with the same Ni content are practically the same. In the case of Co-based ribbons the study has been focused in the corrosion process and how the corrosion affects the magnetoimpedance response of the ribbons. The results indicate that FeCoCrSiB ribbons show an excellent corrosion stability and high magnetoimpedance response, meanwhile FeCoSiB ribbons show low corrosion resistance but high magnetoimpedance response. The relevant patents discussed in this article cover the areas connected with the application, magnetic behaviour and corrosion of amorphous and nanocrystalline materials. Keywords: Metallic glasses, nanocrystalline, corrosion, magnetic properties, biocorrosion, biosensors, magnetoimpedance

Field-Concentrator-Based Resonant Magnetic Sensor With Integrated Planar Coils

This paper reports on a highly sensitive resonant magnetic microsensor with a shift of the mechanical resonance frequency f res depending quadratically on the magnetic flux density B to be measured. The sensor combines an electrostatically driven micromechanical resonator with a geometrically optimized planar magnetic concentrator with two narrow gaps. Sensitivities df res/dB of several megahertz per tesla are achieved without complex feedback and modulation electronics. When the device is operated in a switched auxiliary magnetic field using two integrated planar coils, the raw parabolic response of the sensor is translated into a resonance frequency difference proportional to B . For a coil current of plusmn120 mA, the device offers a sensitivity of 1.91 MHz/T and a resolution of 1.3 muT . In vacuum, a resolution of 400 nT is demonstrated. With these performance numbers, applications such as a microelectromechanical (MEM) compass for the measurement of the Earth's magnetic field can be envisaged. The fabrication process of the microsensor combines the following: 1) the micromachining of a silicon-on-insulator substrate for the MEM structure; 2) the attachment and structuring of a thin amorphous soft magnetic ribbon for the magnetic concentrator; and 3) the UV-laser ablation for the micropatterning of the concentrator gaps. Thermal effects due to high coil currents were analyzed in detail, as they play an important role in the reported microsensor design.

Enhancement of the giant magnetoimpedance effect and its magnetic response in ion-irradiated magnetic amorphous ribbons

The influences of N and Xe ion irradiation on the giant magnetoimpedance (GMI) effect and its magnetic response in Co 69Fe 4.5Al 1.5Si 10B 15 amorphous ribbons were systematically investigated. A large enhancement of the GMI effect and its magnetic response were achieved in N and Xe ion-irradiated amorphous ribbons. At a frequency of 3 MHz, the GMI ratio and magnetic response for an N-ion-irradiated amorphous ribbon respectively reached the highest values of 130% and 13%/Oe, while for a non-irradiated amorphous ribbon they were only about 53% and 8%/Oe. The enhancement of the GMI effect and magnetic response in the ion-irradiated amorphous ribbons resulted from the enhancement of the permeability due to rotational magnetization. Our studies indicate that low energy ion irradiation is useful for improving the magnetic softness, GMI and magnetic response of amorphous alloys, which is of practical importance for the development of high-performance magnetic sensors.

Study of magnetoimpedance effect of Co-based amorphous ribbons after current annealing at various kinds of ambient pressure

The physical properties of magnetic amorphous alloys can be improved by using different annealing processes. In this paper, for annealing purposes, different driving currents were flowed through Co-based magnetic amorphous ribbons at different ambient air pressures between 5 × 10 −5 mbar and 10 3 mbar. The magnetoimpedance effect in the annealed samples was studied at a frequency interval between 250 kHz and 10 MHz. Magnetic properties and microstructures of samples were investigated by means of alternative gradient force magnetometers and X-ray diffraction. Regarding the giant magnetoimpedance (GMI) effect, annealing at different ambient pressures with the same current can lead to various responses. For annealing at higher pressures such as in air, higher current is necessary for crystallization of samples which results in the development of greater transverse magnetic anisotropy.

Magnetoelectric effects in piezoelectric/soft magnetic amorphous FeCo-based ribbon composites

Magnetoelectric effect has been investigated in several multiferroic laminates generated by inserting a lead-zirconate titanate PZT plate between sheets of highly soft magnetic amorphous FeCo-based alloy ribbon. The results show that the magnetoelectric coefficient αE (= dE/dH) depends on the rest glass-forming elements as well as the concentration of Co substitution. Giant magnetoelectric is found for the composite of Fe73.5Cu1Nb3B9Si13.5 ribbon, where αE as high as 1000 mV/cmOe at low field of 50 Oe. aE can be further improved up to 1170 mV/cmOe at 20% Fe substituted by Co. The higher the Co concentration, the lower magnetoelectric effect is observed. High magnetoelectricty at low field makes these composites suitable for special applications such as smart sensors for detecting microtesla magnetic fields and especially biosensor for magnetic label detection.

Influence of the demagnetizing field on the determination of the magnetocaloric effect from magnetization curves

The influence of the demagnetizing factor (N) on the magnetic entropy change (ΔSM) curves is studied for materials with a second order phase transition. For this purpose, a soft magnetic amorphous ribbon is measured for different orientations of the magnetic field with respect to the plane of the sample. For temperatures below the Curie temperature (TC), the increase in N causes a decrease in ΔSM, while for temperatures above TC no change in the shape of the curves has been found for the different orientations, as expected. In order to eliminate this influence of N and compare the ΔSM(T) curves for samples with different shapes, the recently proposed universal curve for the magnetocaloric effect can be used.

Study of Magnetic Inhomogeneity on the Magnetoimpedance Effect of Soft Magnetic Alloys

There are various annealing techniques to influence the magnetic anisotropy of amorphous soft magnetic alloys, applicable for magnetic sensing elements. Laser irradiation of amorphous magnetic ribbons is a kind of annealing method to affect their magnetic moment orientations and consequently change their magnetic anisotropy and magnetoimpedance effect. In this paper, we have studied the role of magnetic anisotropy in the magnetoimpedance effect of laser annealed amorphous ribbons. In our theoretical study, we took into account the variations of magnetic anisotropy constants of local magnetic moments after annealing process. We showed that the flatten magnetoimpedance response which was observed in the experiments can be justified by averaging different local anisotropies induced by laser processing.

Large magnetic entropy changes in Gd–Co amorphous ribbons

A series of magnetic amorphous ribbons with different Gd/Co ratios was prepared by melt-spun method. With the decrease in Gd/Co ratio, Curie temperatures increase gradually from 166 to 193 K. The maximum values of magnetic entropy changes under a magnetic field of 10 kOe are −3.1, −3.0, −2.9, and −2.8 J/kg K for Gd71Co29, Gd68Co32, Gd65Co35, and Gd62Co38 samples, respectively. The approximately constant peak values of ΔSM at different working temperatures indicate that they are advantageous for an Ericsson refrigeration cycle. In addition, these samples have large resistivity and greatly reduced magnetic hysteresis losses, which could increase the refrigeration efficiency. These advantages make the Gd–Co amorphous ribbons good candidates for the practical magnetic refrigeration.

Optimization of the magnetic properties of materials for fluxgate sensors

A study was made of the variation of the magnetic properties of cobalt-based alloys using different compositions of CoFeSiB and CoFeSiBCr systems, which were produced by the melt-spinning technique and some of them subjected to a stress annealing treatment. A comparative study of core geometry and supporting material was also performed in order to obtain low noise fluxgate sensor core using amorphous magnetic ribbons of these alloys. The best alloy was a stress annealed Co67.5Fe3.5Si17.4B11.6 sample, which yielded fluxgate sensors with lower noise levels than those of commercial crystalline materials.

Failure Behaviour of Fe- and Co-Based Amorphous Soft Magnetic Ribbons

Failure Behaviour of Fe- and Co-Based Amorphous Soft Magnetic Ribbons

Remote temperature sensor composed of an amorphous magnetic ribbon and a low Curie temperature ferrite tube

AbstractThis paper describes the application of remote temperature sensors made of an amorphous magnetic ribbon and a low Curie temperature ferrite tube to the measurement of temperature in an arbitrary range. By combining an amorphous magnetic ribbon and a ferrite tube with a Curie temperature of 40 °C, a resonant frequency change rate of 6.3%/°C was realized in the 35 to 40 °C temperature range. Similarly, by combining an amorphous magnetic ribbon and a ferrite tube with a Curie temperature of 47 °C, a resonant frequency change rate of 4.9%/°C was achieved in the 41 to 47 °C temperature range. These values are ∼100 times larger than that of the previously reported remote temperature sensor made only of an amorphous ribbon. Therefore, this confirms that a highly sensitive remote temperature sensor can be realized in an arbitrary temperature range. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Wide-angle magnetoimpedance field sensor based on two crossed amorphous ribbons

Soft magnetic amorphous ribbons have been exhaustively studied in order to use them as magnetic field sensitive elements based on the magnetoimpedance effect, MI. In comparison with other materials they exhibit some disadvantages like double-peak response for small values of the applied magnetic field due to the peculiarities of the surface anisotropy. In this work, magnetic properties, MI effect, and the angular dependence of the impedance on the applied magnetic field direction have been studied for CoFeMoSiB amorphous ribbon based sensitive elements in two configurations. The first one is a classic MI prototype with one amorphous ribbon sensitive element installed on a printed circuit board. In the second configuration two amorphous ribbons with the same size are placed in the board forming an angle of 15° between them. MI effect is measured in a frequency range from 0.4 to 10 MHz for exciting current amplitudes ranging from 2 to 20 mA. For this prototype of sensor device formed by two crossed amorphous ribbons, it is possible to obtain single-peak MI response and independent on the orientation of the external field output signal in a wide range of the angles from 0 to 45°, in contrast with the double peak and angle dependent response obtained for single ribbon sensitive element.

Energy Recover Device Based on Magnetostrictive Amorphous Magnetic Ribbons

Energy Recover Device Based on Magnetostrictive Amorphous Magnetic Ribbons

Effect of magnetic field–current annealing on the magnetoimpedance of Co-based ribbons

The roles of applied magnetic field during the current annealing of Co68.15Fe4.35Si12.5B15 soft magnetic amorphous ribbons have been studied. The Joule heating process causes a complex domain structure which is related to the circular field generated by the current. We have shown that magnetic field–current annealing modifies the transverse permeability and under suitable conditions, enhances the GMI response.

Novel Fabrication Process for the Integration of MEMS Devices with Thick Amorphous Soft Magnetic Field Concentrators

AbstractThis paper reports a novel fabrication process enabling the integration of mechanical MEMS devices with thick amorphous soft magnetic field concentrators. The integration process combines silicon on insulator technology for the MEMS device fabrication and epoxy-resin-based attachment of 18-µm-thick amorphous soft magnetic ribbons followed by a wet chemical structuring process. The fabrication process is reported on the basis of a field-concentrator-based resonant magnetic sensor combining an electrostatically driven micromechanical resonator and a planar magnetic field concentrator with two narrow gaps. For realization of the concentrator gaps, the integration process is extended by micro-patterning of the soft magnetic ribbons via UV-laser ablation using an excimer laser system. The characterization of the fabricated resonant magnetic sensor using a stroboscopic video microscope for in-plane motion measurement shows a high sensitivity of 390 kHz/T at a magnetic flux density of 158 µT.

A Micro Fluxgate Magnetic Sensor Using New Printed Circuit Board Technology

We have developed a micro fluxgate magnetic sensor using new printed circuit board (PCB) technology. The fluxgate sensor consisted of five PCB stack layers including one layer of magnetic core and four layers of excitation and pick-up coils. The center layer as a magnetic core was made of micro patterned amorphous magnetic ribbon with an extremely high DC permeability of ~100,000, and the core had a rectangular ring shape. Four outer layers as an excitation and pickup coils had a planar solenoid structure. The amorphous magnetic core was easily saturated due to the high permeability, low coercive field, and closed magnetic path for the excitation field. The chip size of the fabricated sensing element was 7.3 × 5.7 mm2. Excellent linear response over the range of –100 μT to +100 μT was obtained with sensitivity of 780 V/T at excitation sine wave of 3 Vp-p and 360 kHz. A very low power consumption of ~8 mW was measured. This low power, small size, and high sensitive fluxgate sensor to measure a low magnetic field is very useful for various applications.