Zero-magnetostrictive Amorphous Wire Research Articles

Low-field hysteresis in the magnetoimpedance of amorphous microwires

The phenomena of low-field hysteresis of the magnetoimpedance (MI) in zero-magnetostrictive amorphous wires are studied theoretically and experimentally. We developed a mathematical model for magnetization reversal and impedance field dependence. The presented model considers the low-field hysteresis and the effect of circular bias magnetic field. It is demonstrated that the hysteresis originates from a nonzero angle $\ensuremath{\alpha}$ between the anisotropy easy axis and transversal plane. The bias field, which is produced by current running through the wire, considerably affects the MI dependence making it anhysteretic and highly asymmetric. The validity of the model is confirmed by the experiments. The main characteristics of the studied amorphous wire such as anisotropy field ${H}_{A}$, angle between the anisotropy easy axis with the transversal direction $\ensuremath{\alpha}$, and Gilbert damping constant ${\ensuremath{\alpha}}_{G}$ were obtained from the experiment in accordance with the presented model.

Amorphous wire and CMOS IC-based sensitive micromagnetic sensors utilizing magnetoimpedance (MI) and stress-impedance (SI) effects

New sensitive quick-response and low-power-consumption micromagnetic sensors, namely, the magnetoimpedance (MI) sensor utilizing the MI effect in zero-magnetostrictive amorphous wires and the stress-impedance (SI) sensor utilizing the SI effect in negative-magnetostrictive amorphous wires, are presented. The field detection resolution of the CMOS IC-type MI sensor is about I /spl mu/Oe for ac fields and 100 /spl mu/Oe for a dc field with the full scale of /spl plusmn/3 Oe using a 2- or 0.5-mm-long amorphous wire with 30- or 15-/spl mu/m diameter as a sensor head. The possible response speed is about 1 MHz, and the power consumption is about 10 mW. The magnetoimpedance integrated circuit (MIIC sensor was developed in 2002 by the Aichi Steel Company, Japan, for mass production. The stress detection resolution of the SI sensor is about 0.1 Gal in acceleration Sensing, which is suitable for detection of microdisplacement in the medical field. More than 100 themes are proposed for application of MI and SI sensors.

Amorphous wire and CMOS IC-based sensitive micro-magnetic sensors (MI sensor and SI sensor) for intelligent measurements and controls

New sensitive, quick response and low power consumption micro-magnetic sensors named the magnetoimpedance (MI) sensor utilizing the MI effect in zero-magnetostrictive amorphous wires and the stress impedance (SI) sensor utilizing the SI effect in negative-magnetostrictive amorphous wires are presented. The field detection resolution of the CMOS IC type MI sensor is about 1 μOe for AC fields and 100 μOe for a DC field with the full scale of ±3 Oe using a 2 mm long sensor head; the possible response speed is about 1 MHz, and the power consumption is about 10 mW. The high density fabricated MI sensor has just been developed by the Aichi Steel Co. for mass production. The stress detection resolution of the SI sensor is about 0.1 Gal in acceleration sensing which is suitable for detection of micro-displacement in the medical field. More than 100 themes are proposed for application of MI and SI sensors.

Improved pulse carrier MI effect by flash anneal of amorphous wires and FM wireless CMOS IC torque sensor

A figure of merit (FOM) for the magneto-impedance (MI) effect is defined by the product of the MI ratio and the cut-off frequency for ac field detection as (|/spl part/Z//spl part/Hex|/Z/sub 0/)/spl middot/f/sub cutoff/. The FOM for almost zero-magnetostrictive amorphous wire of 30 /spl mu/m diameter was about improved 2.5 times by twisting and flash annealing using a pulse current of 80 mA, 1 second. A sensitive, quick response, and low power consumption wireless FM type MI sensor is constituted using the high FOM amorphous wire head combined with all CMOS IC sensor circuit. The wireless MI sensor is successfully applied to a torque sensor fixed on an automobile power steering steel.

アモルファスワイヤのパルス励磁ＭＩ効果とＦＭ無線方式ＣＭＯＳ ＩＣ形磁界センサ

The figure of merit (FOM) of the magneto-impedance (MI) effect in amorphous wires is defined as (| ∂ Z / ∂ Hex| / Z0) · f cutoff. The magnitude of the FOM was found to be almost the same at two operating points on the MI characteristic curve in pulse-magnetized amorphous wires in the domain-wall-displacement-dominant range and the magnetization-rotation-dominant range. The magnitude of the FOM was increased in a twisted amorphous wire by increasing the efficiency of the magnetization rotation for the wire pulse current.A frequency-modulation-(FM)-type wireless magnetic sensor with low power consumption was devised, utilizing the magnetization-rotation-dominant MI effect in a zero-magnetostrictive amorphous wire combined with two kinds of CMOS IC multivibrators. The wireless MI sensor has been successfully used as an automobile torque sensor.

Passive wirelessly requestable sensors for magnetic field measurements

A direction-sensitive micro-magnetic field sensor is developed using the giant magneto-impedance (GMI) effect in a 30-μm diameter amorphous FeCoSiBNd wire. Consisting of a micro-sized zero-magnetostrictive amorphous wire of about 70-μm length, the GMI sensor was connected to a self-oscillating Colpitts oscillator circuit by laser welding. It shows a high sensitivity with a resolution of 100 nT for DC fields, quick response, and a high temperature stability. Reproducible measurements of a surface-flux distribution of mechanically 100 μm structured magnetic bar codes were carried out. Surface Acoustic Wave (SAW) devices are shown as passive, radio-requestable sensor devices. A new type employs the electrical load of the SAW device by the impedance of conventional sensors. In order to develop a wirelessly interrogable magnetic field sensor, the combination of the GMI sensors and SAW transponders is discussed and the results are shown.

Highly stable MI micro sensor using CMOS IC multivibrator with synchronous rectification [for automobile control application

A new highly stable magneto-impedance (MI) micro magnetic sensor with a pair of zero-magnetostrictive amorphous wires is presented. The sensor picks up a first pulse in an induced oscillatory pulse voltage at a wire coil using an analog switch. High temperature stability in the MI sensor is established in which zero drift for temperature variation from 20/spl deg/C to 80/spl deg/C is 0.6%/FS (0.01.%/FS/spl deg/C). The highly stable MI sensor will be useful for application to automobile controls.

Magneto-impedance effect in etched thin amorphous wires

The magneto-impedance (MI) effect is investigated in etched thin zero-magnetostrictive amorphous wires having 4.5-30 /spl mu/m diameters. The MI effect gradually decreased with decreasing diameter and then the large Barkhausen effect appeared in thinner wires having 5-10 /spl mu/m diameters. Longitudinal BH loops are measured and estimated the average anisotropy direction in each etched wire considering the anisotropy energy change. A sensitive MI field sensor is constituted using the etched wire head having 16 /spl mu/m diameter and 0.7 mm length magnetized with a pulse current using CMOS multivibrator.

Recent advances of micro magnetic sensors and sensing application

Principle and basic performance of micro magnetic sensors such as the Hall element, the magneto-resistance (MR) element, the giant magneto-resistance (GMR) element, the thin-film fluxgate sensor (FGS), and the magneto-impedance (MI) element are summarized. Their basic properties are compared with each other considering a new sensing target in various modern industrial fields. A new micro-sized magnetic field sensor with a high sensitivity and a quick response is developed using the MI effect in amorphous wires and thin films. The MI sensor having a micro-sized zero-magnetostrictive amorphous wire head of about 1 mm installed in self oscillation circuits such as the Colpitts oscillator and a multivibrator circuit shows a high sensitivity with a resolution of 10−6 Oe for ac fields and 10−5 Oe for dc fields, quick response with a cutt-off frequency of about 1 MHz, and a high temperature stability of less than 0.05%FS °C −1 up to 70°C. A very low power consumption and highly stable MI sensor is constructed using a CMOS multivibrator. A stable measurement for a surface-flux distribution around a 2000-pole ring magnet with a diameter of 19 mm for a high density rotary encoder was carried out using the MI sensor. A small pin hole of 100 mm diameter in an iron sheet was detected at non destructive testing (NDT) using a gradient-field detection type MI sensor cancelling back ground disturbance fields. A sample of clustered magnetic particles was magnetically detected using the MI sensor probe in a simulation of detection of a brain tumor at which an injected sol was induced with the magnetic particles.

Quenching of magnetostriction by torsional strain in zero-magnetostrictive amorphous wire

Simple model band calculations show that torsional stress reduces the absolute value of the Joule magnetostriction . This is the consequence of the quenching of orbital magnetism by torsion. The calculations provide an explanation of recent experimental data on almost zero-magnetostrictive amorphous Co-based wire.

アモルファス磁性ワイヤＭＩ素子によるコルピッツ自己発振形高感度・高速応答電流センサ

A new high-performance micro-current sensor with circular amorphous wire magneto-impedance (MI) element installed in a Colpitts oscillator is presented. A zeromagnetostrictive amorphous wire ((Fe0.06Co0.94)72.5 Si12.5B15, λs = -10-7) was used to make a circular head with a 10 mm diameter set around a conductor. The current sensor is of the amplitude modulation-demodulation type with a strong negative feedback loop. It has a sensing performance of a high linearity (a non-linearity of less than 0.5%FS (± 1.5 A)), quick response with a cur-off frequency of about 1 MHz due to a high oscillation frequency of 30 MHz, and a high sensitivity of about ±10μA(ƒ=1kHz). This sensor works stably in uniform-distrubance magnetic field such as the terrestrial magnetic field (≅0.3 Oe), because of the cancelling in the circular MI head.

Stress dependence of bistability in a zero-magnetostrictive amorphous wire

New data on the bistability of (Co95Fe5)72.5Si12.5B15 amorphous wire are discussed in the framework of a simple model of magnetic interaction between inner core and outer shell of a wire. Experimental results are reported on the tensile stress and annealing-time dependence of switching field and remanence magnetization, for longitudinal and circular hysteresis loops. Theoretical considerations allow various scenarios of the bistability effect to be distinguished, which are helpful in our understanding of the experimental data.

Magnetic bistability in as-cast non-magnetostrictive amorphous wire

Nearly zero-magnetostrictive amorphous wires do not present in the as-cast state the striking bistable magnetization process typical of high-magnetostrictive wires. Such a difference can be interpreted as a consequence of the low strength in the intrinsic magnetoelastic anisotropy. However, if such an anisotropy is reinforced the magnetic behavior can be significantly changed. Here, the authors report the achievement of magnetic bistability in the as-cast state in a nearly zero magnetostrictive amorphous wire. The results show that a decrease of the measuring temperature below 250 K or the introduction of an additional magnetoelastic anisotropy, by means of the simultaneous application of tensile and torsional stresses, causes the appearance of a well-defined single Barkhausen jump in the magnetization process. >

Magneto-inductive effect in tension-annealed amorphous wires and MI sensors

Small sized and sensitive MI elements are presented using cold drawn and then tension-annealed zero-magnetostrictive amorphous wires having a 50 mu m diameter and a 2 mm length. An amplitude of an inductive voltage induced between both ends of the wire which is circumferentially magnetized with a wire AC current decreases about 80% against an external DC field of about 200 A/m, while the voltage amplitude increases from almost zero value for an external DC field when a rectifield or DC-biased AC field is applied to the wire. A new MI effect is also presented. An amplitude of a double frequency voltage induced between both ends of a folded amorphous wire due to magnetizing with a circumferential flux in an adjacent amorphous wire increases about ten times for a perpendicularly applied external DC field. >

Magneto-inductive element

A novel sensitive magnetic head using a magnetoinductive (MI) effect in zero- or negative-magnetostrictive amorphous wires is described. The MI effect refers to the change of an inductance L for an external magnetic field in a ferromagnetic wire element magnetized with a wire AC current I/sub AC/. A 5-mm-length MI element using a folded almost zero-magnetostrictive amorphous wire having a 120- mu m diameter showed a sensitive rate of change of its inductance of more than 50% for an external low frequency field of about 10 Oe (800 A/m) applied in parallel with the element. The a-wire MI element works for a wire current having frequencies up to 1 MHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

磁気インダクタンス素子による眼けん運動検出用磁石変位センサ

We previously constructed an accurate magnetdisplacement sensor for detection of eyelid movement, using an amorphous magnetic core multivibrator. However, some improvements in the eyelid movement sensor are necessary in order to achieve independence of the magnetization direction of the cores and a wider sight space. We therefore constructed another accurate magnet-displacement sensor for detection of eyelid movement, this time, using amorphous wire magnetoinductive (or MI) elements. The elements were formed by using tension annealed zeromagnetostrictive amorphous wires. The MI effect and the symmetrical MI characteristics of the elements are used to form thinner sensor heads having no coils and to change their inductances independent of the magnetization directions.

300 A current sensor using amorphous wire core (invertor control of AC motors)

A noncontact small-size 300-A current sensor for inverter control of AC motors was constructed using zero-magnetostrictive amorphous wire cores combined with a hybrid-integrated circuit including a multivibrator bridge. The sensor head cores could be set close to a conductor bar by using a negative feedback circuit, which simultaneously improved linearity, stability against temperature changes, signal-to-noise ratio, and dynamic range. Experimental results for detection of DC and AC currents up to 300 A showed good linearity with less than 0.5% FS nonlinearity, temperature stability with less than 0.3%/ degrees C FS variation up to 80 degrees C, and cut-off frequency of 5 kHz. The noise due to external disturbance by adjacent bar current could be reduced to less than 0.3% FS by the sensor's dual-core arrangement and the use of a simple silicon steel shield shell. Both size and weight could be reduced as compared with conventional current sensors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mechanocardiograph Sensors Using Amorphous Star-Shaped Core Multivibrators

Highly stable and accurate mechanocardiograph sensors are presented using linear magnet-displacement sensors with a star-shaped amorphous core multivibrator. 2N zero-magnetostrictive amorphous wire cores are combined in a new star-shape configuration, in which the influence of external disturbance fields such as terrestrial fields is almost completely eliminated and the signal field generated by a small magnet is stably detected. These linear displacement sensors can detect the displacement of a magnet through about 3 mm with a drift of less than 0.2 ?m. Mechanocardiographs of a heartbeat, a phonocardiograph, and blood-vessel pulsation are stably and easily detected by fixing a small magnet on the chest wall or the blood-vessel position, combined with a non-contact type displacement sensor.

アモルファス放射状磁心マルチ形心機図センサ

Highly stable and accurate mechanocardiograph sensors are presented using linear magnet-displacement sensors with a star-shaped amorphous core multivibrator. 2N zero-magnetostrictive amorphous wire cores are combined in a new star-shape configuration, in which the influence of external disturbance fields such as terrestrial fields is almost completely eliminated and the signal field generated by a small magnet is stably detected. These linear displacement sensors can detect the displacement of a magnet through about 3 mm with a drift of less than 0.2 ?m. Mechanocardiographs of a heartbeat, a phonocardiograph, and blood-vessel pulsation are stably and easily detected by fixing a small magnet on the chest wall or the blood-vessel position, combined with a non-contact type displacement sensor.

アモルファスワイヤ磁心マルチ形非接触変位センサと心機図測定

New con-contact type linear displacement (oscillation) sensors are presented which combine a two amorphous-wire core multivibrator bridge with a small magnet. The nonlinearity of the relationship between magnetic field from the magnet and the distance between the detection point and the magnet is cancelled by utilizing the saturation characteristics of the amorphous-core magnetometer. Linear ranges as large as 8mm have been obtained using a zero-magnetostrictive amorphous wire (made by UNITIKA Co.) of 44mm in diameter on which two 20mm long coils are placed separately. The cut-off frequency is about 4 kHz in the displacement sensor, and the minimum detectable displacement is about 1 μm.A new sensing technique is developed using these non-contact linear displacement sensors for mechanocardiography for cardio-function diagnosis combined with the electrocardiograph.