Co-based Amorphous Ribbons Research Articles

Amorphous ribbons for GMI detection of stray fields FeOx magnetic filler of epoxicomposites

Magnetoimpedance (MI) effect in stress-annealed Co-based amorphous ribbon was studied in the states without and in presence of the magnetic epoxy composite of cylindrical shape. Iron oxide FeOx magnetic microparticles of different concentrations (0–70 wt.%) were used as a magnetic filler. The condition of stress annealing (350 °C, 1 h and 250 MPa specific load) were selected in order to insure the high MI sensitivity with respect to external magnetic field in the field of a few Oersted. The MI responses were modified in the presence of the magnetic epoxy composites due to the contribution of the stray fields of embedded microparticles. It was experimentally found that degree of the MI curves modification depended on the microparticles concentration. The MI characteristics were also dependent on the length-to-width ratio of the MI element. The most sensitive MI element under study showed a linear dependence with a 1 %/weightpercent microparticle concentration slope. Mathematical modeling using finite elements (FEM) protocol for the properties of short MI elements confirmed the results and highlighted the non-monotonic contribution of high-concentration composites to the MI responses.

A multidimensional integrated micro three-component fluxgate sensor based on microelectromechanical system technology

In this paper, a miniature three-component fluxgate sensor with U-shaped structure is fabricated by the multidimensional integration technology. We manufacture a batch of single axis solenoid fluxgate chips based on Micro Electromechanical System （MEMS） technology, which possesses the Co-based amorphous ribbon core and solenoid excitation-detection coil. According to multidimensional integration theory, a full integrated three-component fluxgate sensors is achieved through orthogonal linking of printed circuit board （PCB） substrates and bonding between single axis fluxgate chip and substrate. The chips used in the X-Y-Z axis have a sensitivity of 1947 V/T, 1951 V/T, and 1949 V/T, and noise power spectral density of 0.061 nT√Hz@1HZ, 0.077 nT√Hz@1HZ, and 0.087 nT√Hz@1HZ, and time-drift peaks of 21 nT, 17.4 nT, and 14.8 nT, respectively. The linear range of three chips is 0–70μT. After least square error correction, the peak-to-peak value of the in-situ total magnetic field decreases from 2.4 μT to 0.22 μT.

Nonuniformity of Magnetization Processes of a Co-Based Amorphous Alloy Ribbon in the As-Quenched State

Nonuniformity of Magnetization Processes of a Co-Based Amorphous Alloy Ribbon in the As-Quenched State

Optimization of temperature stability and sensitivity of the giant magnetoimpedance effect in meander shaped Co-based amorphous ribbon using DC-biased current for sensor application

The influence of DC-biased current (I DC) on the longitudinal giant magnetoimpedance (GMI) effect in Co-based amorphous ribbon with a meander structure, taken from room temperature to 120 °C, has been investigated. The results show that I DC increases the temperature stability of the impedance of amorphous ribbon at 20 MHz. By deriving the expression of the transverse permeability according to a magnetization rotation model, we attributed the improved temperature stability to the combined effect of temperature and bias field H DC generated by I DC on the transverse permeability. It is also shown that I DC not only effectively inhibits the weakening of the GMI ratio at high temperature, but also significantly improves the GMI sensitivity. This will help to achieve sensitive low magnetic field measurement under large temperature fluctuation.

Anomalous Nernst Effect in Flexible Co-Based Amorphous Ribbons.

Fe3Co67Cr3Si15B12 ribbons with a high degree of flexibility and excellent corrosion stability were produced by rapid quenching technique. Their structural, magnetic, and thermomagnetic (Anomalous Nernst Effect) properties were studied both in an as-quenched (NR) state and after stress annealing during 1 h at the temperature of 350 °C and a specific load of 230 MPa (AR). X-ray diffraction was used to verify the structural characteristics of our ribbons. Static magnetic properties were explored by inductive technique and vibrating sample magnetometry. The thermomagnetic curves investigated through the Anomalous Nernst Effect are consistent with the obtained magnetization results, presenting a linear response in the thermomagnetic signal, an interesting feature for sensor applications. Additionally, Anomalous Nernst Effect coefficient SANE values of 2.66μV/K and 1.93μV/K were estimated for the as-quenched and annealed ribbons, respectively. The interplay of the low magnetostrictive properties, soft magnetic behavior, linearity of the thermomagnetic response, and flexibility of these ribbons place them as promising systems to probe curved surfaces and propose multifunctional devices, including magnetic field-specialized sensors.

Giant magneto-impedance effect adjusted by electrolytic polishing and thinning of Co-based amorphous ribbons

The giant magneto-impedance (GMI) effect of Co-based ribbons treated by using electrochemical polishing method has been investigated. The initial susceptibility (χi ) and the longitudinal GMI ratio (L-GMI) as a function of the polishing time (t poli) were measured and discussed. The L-GMI firstly increases and then decreases with the increasing of t poli. At t poli = 30 s, the maximum GMI of ∼270% is obtained. This L-GMI trend as a function of t poli is mainly attributed to the variation of effective magnetic anisotropy (H k,eff). The variation of H k,eff comes from the optimization of surface qualities as well as the thinning of the thickness. The thinning of the Co-based ribbons results in the changing of demagnetization effect and, more importantly, the variation in the residual stress distributions. The latter effect will strongly affect the magnetization conditions for the samples with longer t poli: stress variation here is dominant over the influence of surface qualities in the final GMI effect. Furthermore, another factor that may influence GMI is the current density variation related to thickness decrease. At the same time, reducing of stray fields, closely related to surface qualities, is the dominant factor affecting GMI for the samples with shorter t poli.

Magnetoimpedance of CoFeCrSiB Ribbon-Based Sensitive Element with FeNi Covering: Experiment and Modeling.

Soft magnetic materials are widely requested in electronic and biomedical applications. Co-based amorphous ribbons are materials which combine high value of the magnetoimpedance effect (MI), high sensitivity with respect to the applied magnetic field, good corrosion stability in aggressive environments, and reasonably low price. Functional properties of ribbon-based sensitive elements can be modified by deposition of additional magnetic and non-ferromagnetic layers with required conductivity. Such layers can play different roles. In the case of magnetic biosensors for magnetic label detection, they can provide the best conditions for self-assembling processes in biological experiments. In this work, magnetic properties and MI effect were studied for the cases of rapidly quenched Co67Fe3Cr3Si15B12 amorphous ribbons and magnetic Fe20Ni80/Co67Fe3Cr3Si15B12/Fe20Ni80 composites obtained by deposition of Fe20Ni80 1 μm thick films onto both sides of the ribbons by magnetron sputtering technique. Their comparative analysis was used for finite element computer simulations of MI responses with different types of magnetic and conductive coatings. The obtained results can be useful for the design of MI sensor development, including MI biosensors for magnetic label detection.

Design of a Low-Cost Small-Size Fluxgate Sensor.

Traditional fluxgate sensors used in geomagnetic field observations are large, costly, power-consuming and often limited in their use. Although the size of the micro-fluxgate sensors has been significantly reduced, their performance, including indicators such as accuracy and signal-to-noise, does not meet observational requirements. To address these problems, a new race-track type probe is designed based on a magnetic core made of a Co-based amorphous ribbon. The size of this single-component probe is only Φ10 mm × 30 mm. The signal processing circuit is also optimized. The whole size of the sensor integrated with probes and data acquisition module is Φ70 mm × 100 mm. Compared with traditional fluxgate and micro-fluxgate sensors, the designed sensor is compact and provides excellent performance equal to traditional fluxgate sensors with good linearity and RMS noise of less than 0.1 nT. From operational tests, the results are in good agreement with those from a standard fluxgate magnetometer. Being more suitable for modern dense deployment of geomagnetic observations, this small-size fluxgate sensor offers promising research applications at lower costs.

High-frequency GMI hysteresis effect analysis by first-order reversal curve (FORC) method

In this work, we investigate the giant magnetoimpedance (GMI) hysteresis at high-frequency (10 MHz – 1 GHz) of Co-based amorphous magnetic ribbons. The first-order reversal curve (FORC) method was used to analyze their hysteretic behavior present at a low magnetic field (below 7 Oe). Results show that the GMI hysteresis is related to both the system magnetic anisotropy and the current frequency (through the skin depth). The GMI hysteresis gradually decreases upon frequency increase before disappearing, while a clockwise rotation of the FORC distributions is observed. These results are attributed to a heterogeneous magnetic structure in the magnetic ribbon volume. On the other side, while the cut-off frequency depends on the magnetic anisotropy strength, an inverted GMI hysteresis revives for the higher anisotropy ribbon. Above this frequency inversion, FORC results indicate a hardening of the effective switching field as a thicker region is probed. We propose that in this case, the stronger perpendicular anisotropy creates important differences between the superficial and volumetric anisotropy, enough to induce interaction between the two regions of different magnetization directions. This sensitive FORC protocol can be applied for investigating the GMI hysteresis, and thus the complex magnetic structure of several soft magnetic systems.

Influence of Joule-Annealing on Double-Peak GMI Effect in Co-Based Amorphous Ribbons

Influence of Joule-Annealing on Double-Peak GMI Effect in Co-Based Amorphous Ribbons

Improved Performance of Fundamental Mode Orthogonal Fluxgate Using a Micro-Patterned Meander-Shaped Ribbon Core.

In this paper, the performance of orthogonal fluxgate sensors with meander-shaped cores is studied in fundamental mode. The meander-shaped cores are made by micro-patterning technology based on a Co-based amorphous ribbon. The main advantage of this structure is that the linear operating range of the sensor can be adjusted simply by changing the number of strips, without affecting the excitation mechanism. Experiments show that a linear range of 560 μT is obtained by a meander-shaped core sensor with 12 strips. The changes in the number of strips can also increase sensitivity and reduce noise of the sensor. We can achieve a sensitivity of 600 V/T and a noise level of 0.64 nT/√Hz at 1 Hz for a meander-shaped core sensor with eight strips. Compared with the performance of the sensors built using a single strip core having the same equivalent cross-sectional area, the use of meander-shaped core can provide a higher sensitivity and linearity, and a lower noise level. We also compare the performance of an eight-strip meander-shaped core orthogonal fluxgate operated in the fundamental and second-harmonic modes. Similar sensitivity for the two modes can be obtained by adjusting the excitation current. In this case, we find that the noise of sensor operating in fundamental mode is about five times lower than that of the sensor operating in second-harmonic mode. This can be interpreted as the suppression of Barkhausen noise by unipolar bias in the fundamental mode.

Influence of current annealing on the magneto-impedance response of co-based ribbons arising from surface structural improvement

In this paper, influence of current annealing on the magneto-impedance (MI) response of the Co-based amorphous ribbons with chemical composition of Co68.15Fe4.35Si12.5B15 was investigated. In order to achieve a maximum MI ratio, ribbon samples were annealed under two different conditions: the atmospheric pressure and a vacuum pressure of 5 × 10−3 mbar. During the annealing process, the dc electric current passing through the ribbons improved the surface structure while also changing the magnetic properties, arising from heating of the samples under proper conditions. The annealing process not only induced transverse magnetic anisotropy in the ribbon but also decreased stresses generated during melt spinning processes, thus enhancing the corresponding MI response. Annealing at different times and currents were performed in order to achieve optimum conditions and reach the maximum MI. Our results showed that the MI ratio increased for the annealed samples at both vacuum and atmospheric pressures so that the maximum MI (288%) was obtained for current annealing (at 200 mA for 65 s) in the vacuum, being promising for sensor applications. On the other hand, AFM and XRD results confirmed that less surface roughness would provide a smaller stray field, which in turn would increase the MI ratio.

The Step-Current Annealing: An Easy Method to Improve the Magnetoimpedance in Co-Rich Ribbons

The magnetoimpedance (MI) response of Co-based amorphous ribbons, thermally treated by a dc step-current annealing, was studied. In this annealing method, a certain dc current value is passed through a ribbon at a fixed time, followed by a step-by-step increase in the current while also repeating the annealing. In this way, the growth of Co nanocrystalline grains on the surface of the ribbon slowly starts during the annealing. The nanocrystalline formation of Co layers on the surface was confirmed by X-ray diffraction patterns and field-emission scanning electron microscopy images. The current annealing under the optimum conditions of current and time leads to a higher induced anisotropy, thereby increasing the MI ratio. The step-current annealing is considered a simple and efficient technique to enhance the MI effect of amorphous ribbons, providing a tool for detecting weak magnetic fields at a relatively wider working range.

Investigation of magnetic field anneal in micro-patterned amorphous ribbon on giant magneto-impedance effect enhancement

PurposeThis paper aims to investigate magnetic field anneal in micro-patterned Co-based amorphous ribbon on giant magneto-impedance (GMI) effect enhancement.Design/methodology/approachThe amorphous ribbons were annealed in transverse and longitudinal magnetic field. The influence of different field annealing directions on GMI effect and impedance Z, resistance R and reactance X with a series of line width have been deeply analyzed.FindingsIn comparison with GMI sensors microfabricated by unannealed and transversal field annealed ribbons, GMI sensor which was designed and microfabricated by longitudinal field anneal ribbon performs better. The results can be explained by the domain wall motion and domain rotation during annealing process and the geometric structure of Co-based GMI sensor. In addition, shrinking the line width of GMI sensor can promote GMI effect significantly because of the effect of demagnetizing field, and the optimum GMI ratio is 209.7 per cent in longitudinal field annealed GMI sensor with 200 μm line width.Originality/valueIn conclusion, annealing in longitudinal magnetic field and decreasing line width can enhance GMI effect in micro-patterned Co-based amorphous ribbon.

Electrophoretic deposition of graphene oxide on magnetic ribbon: Toward high sensitive and selectable magnetoimpedance response

Graphene oxide (GO) layers have shown to be fascinating elements for application in high performance sensors. They can be applied in multi-disciplinary designs based on surface selective sensing mechanisms. One immediate application of such surface sensitive elements is implementing of GO layer in magnetoimpedance (MI) sensors to improve their multi-functionality. In this paper, deposition of GO on the surface of Co-based amorphous ribbons (Co68.15Fe4.35Si12.5B15) is performed using electrophoretic deposition (EPD) method to evaluate the MI response. MI ratio increased from 271% (bare ribbon) up to 281% and 301% EPD GO deposited within 4 and 8 min, respectively. Similar experiment for the ribbon drop coated with GO was carried out while no enhancement in MI response was seen. Vertical growth of GO on the surface of the ribbon in EPD and drop coated layers observed by topographical measurements. We explained the difference between the MI responses based on layers verticality and surface coverage. UV–Visible absorption and Raman spectroscopy were used to study the nature of GO. Gaining a high surface area of GO along with their biocompatible and anticorrosive properties atop the MI sensors can open pathways towards increasing applications of surface selective and high sensitive MI sensors.

Analysis of the off-diagonal component of giant magnetoimpedance effect in Co-based (as-cast and stress-annealed) amorphous ribbons

We investigated the effect of the application of dc bias current IB on the off-diagonal magnetoimpedance (MI) components at 50 MHz in nearly-zero magnetostrictive Co66.5Fe3.5Si12.0B18.0 amorphous ribbons in as-cast and stress-annealed state. The off-diagonal MI component is anti-symmetrical with near-linear behavior within a certain field interval. For the off-diagonal response, the dc bias current is necessary to eliminate transverse domains present in the ribbon. A highly asymmetry of the off-diagonal dependence with the axial magnetic field was obtained when the bias current is applied along the ribbon. A rather high slope at the zero-field point was obtained, being more pronounced in the stress-annealed samples. This is probably related with the domain structure reorganization under the effect of the bias current. This behavior is ideal for a practical sensor circuit design.

Magnetic properties and giant magnetoimpedance effect for CoFeMoSiB surface modified amorphous ribbons covered by water based ferrofluid

Giant magnetoimpedance (GMI) effect is a powerful technique for magnetic label detection. Co-based amorphous ribbons are cheap materials showing high GMI effect at low operation frequencies for close to zero magnitostriction compositions. In this work magnetic properties and GMI were studied for CoFeMoSiB amorphous ribbons in as-quenched and surface modified states without and in the presence of water-based ferrofluid with electrostatic stabilization of γ-Fe2O3 nanoparticles. Surface modification by ultrasound treatment resulted in appearance of round defects with average diameter of about 150 micrometers. The GMI difference for as-quenched ribbons in absence and in the presence of ferrofluid was measured for the frequency range of 0.5 to 10 MHz. Although proposed surface modification by the ultrasound treatment did not improve the sensitivity limit for ferrofluid detection, it did not decrease it either. Observed changes of GMI are useful for understanding of functionality of GMI biosensors.

Magnetic properties and giant magnetoimpedance of surface modified Co-based amorphous ribbons with carbon covering

Fe3Co66Cr3Si16B12and Fe6Co60Ni10Si14B10amorphous ribbons were surface modified in toluene at room temperature. Such a treatment resulted in deposition of thin carbon-based layer. As a result of the carbon covering deposition the stress distribution in the near-surface layers was changed due to partial compensation of the initial quenching stresses. Comparative analysis of magnetic and magnetoimpedance properties of as-quenched and surface modified ribbons confirms changes in effective magnetic anisotropy as a result of surface treatment. An increase of the corrosion resistance of the ribbons with carbon covering can be useful for the development amorphous ribbon based magnetic biosensor.

Investigation of a novel MEMS orthogonal fluxgate sensor fabricated with Co-based amorphous ribbon core

In this paper, we present a novel MEMS orthogonal fluxgate sensor fabricated by standard micro fabricated technology. The sensor mainly consists of a three-dimensional solenoid pick-up coil and a meander-shaped Co-based amorphous ribbon core. The experimental results demonstrate that the sensitivity and noise can be optimized by tuning operation conditions with excitation current amplitude and frequency. The fabricated sensor exhibits a maximum sensitivity of 575V/T, a wide linear range of ±480μT, and a perming below 0.8μT for 90mA rms sinusoidal excitation current at 500kHz frequency. The equivalent magnetic noise is 0.20 nT/√Hz at 1Hz, and the RMS noise is 1.09nT in the frequency range of 0.1–10Hz under the same excitation. In comparison with other micro fabricated fluxgates in similar dimensions, this device possesses relatively high sensitivity and low noise spectral density.

Cycle rapid cooling treatment effect on the magnetic properties and giant magnetoimpedance properties of Co-based amorphous alloy ribbons

The influence of cycle rapid cooling treatment on the giant magnetoimpedance (GMI) properties in Co-based amorphous alloys was investigated. Hysteresis loops show that the saturation magnetization of ribbons has been improved by cycle treatment. It can be found that the GMI ratio was increased from 89% to 130% at 1MHz by the thermal cycle (TC) treatment. Moreover, GMI ratio of TC treatment sample increased up to 321% at 5MHz. It is considered that internal thermoelastic stress leads to surface roughness, magnetic domain structures and saturation magnetization changes of the ribbons during different cycle processes. It was also found that the asymmetric GMI (AGMI) phenomenon occurred in the Co-based alloys with TC treatment after annealing, which can be regarded as a new method to get GMI-valve to improve GMI sensitivity.