Magnetic Microsensors Research Articles

Evidence of Magnetoresistance in the Prussian Blue Lattice during a Voltammetric Scan

This manuscript reports evidence of magnetoresistance effects in the Prussian Blue lattice during a voltammetric scan at room temperature. Accordingly, the PB is a well-known semiconductor that becomes surprisingly an almost metallic conductor in the presence of an internal magnetic field induced during the voltammetric scan. This offers appealing perspectives for the control of this interesting phenomenon from electrochemical techniques that could be used for the fabrication of the recent phase-change computational memories, which are electronically configurable. Herein, the PB magnetic properties have been monitored in situ by means of resonating magnetic microsensors based on the shift in the resonant frequency of microelectromechanical systems.

The influence of laser annealing in the presence of longitudinal weak magnetic field on asymmetrical magnetoimpedance response of CoFeSiB amorphous ribbons

Abstract Asymmetrical magnetoimpedance (AMI) is very important to further improve micromagnetic sensor performance in terms of linearity and sensitivity. This behavior was investigated for Co68.15Fe4.35Si12.5B15 amorphous ribbons irradiated by a 1064 nm Nd:YAG pulsed laser in air and in the presence of 3 Oe longitudinal magnetic field with changing pulse repetition rate. Results indicate that for different pulse repetition rates, various types of AMI profiles appear. For the samples annealed in the presence of longitudinal field, because of induced anisotropy, rising in asymmetry factor takes place and another peak in the magnetoimpedance (MI) profile transpires.

A Concept for a Toolbox of Components for Modular Magnetic Microsensors

Magnetic micro sensors are capable of covering a range of functions, for instance measurement of distance, force, or material properties like magnetic behavior or surface defects. By coming up with a toolbox of sensor components for the basic functions and considering their technology compatibility, a modular micro sensor family has been created. Combining the appropriate building blocks allows to achieving the sensor function desired. To demonstrate the approach, components to facilitate a micro strain gauge sensor for force measurement and a sensor allowing to analyzing magnetic material properties were created and used to build up the respective micro sensors.

Analysis of Electrodeposited NiFe Thin Films for the Development of Planar Fluxgate Magnetic Sensors

ABSTRACTNife alloys are potential candidates for the development of planar fluxgate magnetic microsensors. In this work, electrodeposition was used to produce NiFe thin films on top of copper substrates. When using this technique the variation of the electric potential, and thus the current density, alters the final stoichiometry of the deposited films, while the final thickness is determined by the total deposition time. We used current densities varying from 4.0 mA/cm2 to 28 mA/cm2, with steps of 4.0 mA/cm2. For each current density, total deposition times of 10, 20, 30 and 40 minutes were used. The morphology was characterized using scanning electron microscopy, structure was characterized using X-ray diffraction experiments, and the composition of the films were determined using energy dispersive spectroscopy. The magnetic properties were investigated evaluating the materials hysteresis cycle. The materials were optimized aiming for lowest coercivity values, and the final result was about 0.215 kA/m.

A micro-LC-resonator fabricated by MEMS technique for high-frequency sensor applications

A novel magnetic LC-resonator for micromagnetic sensor devices was fabricated by means of microelectromechanical system (MEMS) technique. The micro-LC-resonator consists of a solenoidal microinductor with a bundle of annealed soft magnetic Co83.2B3.3Si5.9Mn7.6 microwires as microcore and a capacitor connected in parallel to the microinductor. The dimensions of solenoidal microinductors fabricated by MEMS technique were 500–1000μm in length with 10–20 turns. Because the permeability of the microcore is changing rapidly as a function of external magnetic field, the inductance of the microinductors can change drastically according to the external magnetic field. Therefore, the resonance frequency as well as the impedance of a micro-LC-resonator can be sensitively altered as the external magnetic field changes. The maximum magnetoimpedance ratio value for a micro-LC-resonator was reached as much as 500%. The impedance change of the LC-resonator can be greatly enhanced by selecting operating frequencies at near the resonance frequency.

An orthogonal fluxgate-type magnetic microsensor with electroplated Permalloy core

In this paper, we present a new microfabricated orthogonal fluxgate sensor structure. The sensor consists of an electroplated copper excitation rod surrounded by an electroplated Permalloy layer and has planar pick-up coils for signal detection. The use of electroplating leads to a low-cost fabrication process and the use of planar pick-up coils provides easy integration with CMOS processes. The fabricated sensor has an excitation independent linear range of ±200 μT, a sensitivity of 510 μV/mT, and an average power dissipation of 8.1 mW for 100 mA-peak sinusoidal excitation current at 100 kHz frequency. The equivalent magnetic noise is 95 nT/√Hz at 1 Hz, and the RMS noise is 215 nT for 10 Hz bandwidth.

A Concept For a Toolbox for Modular Magnetic Microsensors

not Available.

A class of micromachined magnetic resonator for high-frequency magnetic sensor applications

A class of LC resonators for micromagnetic sensor devices is reported, which is fabricated by means of the microelectromechanical system (MEMS) technique. The micro-LC resonator consists of a solenoidal microinductor with a bundle of soft magnetic microwire cores and a capacitor connected in parallel to the microinductor. The core magnetic material is a tiny glass-coated Co83.2B3.3Si5.9Mn7.6 microwire fabricated by a glass-coated melt-spinning technique. The solenoidal microinductors fabricated by the MEMS technique were 500–1000μm in length with 10–20 turns. The changes of inductance as a function of external magnetic field in microinductors with appropriately annealed microwire cores were varied as much as 370%. Because the permeability of ultrasoft magnetic microwire is changing rapidly as a function of external magnetic field, the inductance ratio as well as magnetoimpedance ratio (MIR) in a LC resonator is varied accordingly as a function of external magnetic field. The MIR curves can be tuned very precisely to obtain maximum sensitivity.

A new class of LC-resonator for micro-magnetic sensor application

A new class of LC-resonators for micro-magnetic sensor device was invented and fabricated by means of micro-electromechanical system (MEMS) technique. The micro- LC-resonator consists of a solenoidal micro-inductor with a bundle of soft magnetic micro-wire cores and a capacitor connected in parallel to the micro-inductor. The core magnetic material is a tiny glass-coated Co 83.2B 3.3Si 5.9Mn 7.6 micro-wire fabricated by a glass-coated melt spinning technique. The core materials were annealed at various temperatures 150, 200, 250, and 300 °C for 1 h in a vacuum to improve soft magnetic properties. The solenoidal micro-inductors fabricated by MEMS technique were 500–1000 μm in length with 10–20 turns. The changes of inductance as a function of external magnetic field in micro-inductors with properly annealed micro-wire cores were varied as much as 370%, since the permeability of ultrasoft magnetic micro-wire changes rapidly as a function of external magnetic field. The inductance ratio as well as magnetoimpedance ratio (MIR) in an LC-resonator was varied drastically as a function of external magnetic field. The MIR curves can be tuned very precisely to obtain maximum sensitivity.

극미세 교류 플라즈마 내에서의 홀 효과를 이용한 마이크로 자기센서

This paper presents a new class of magnetic microsensors based on the Hall effect in AC microplasma. In the theoretical study, we develop a simple model of the plasma Hall sensor and express the plasma Hall voltage as a function of magnetic field,plasma discharge field, pressure, and electrode geometry. On this basis, we have designed and fabricated magnetic microsensors using Ac neon plasma. In the experiment, we have measured the Hall valtage output of the plasma microsensors for varying five different conditions, including the frequency and the magnitude of magnetic field, the frequency and the magnitude of plasma discharge valtage, and the neon pressure.The fabricated magnetic microsensors show a magnetic field sensitivity of 8.87±0.18mV/G with 4.48% nonlinearity.

Dependence of signal-to-noise ratio on excitation current and signal frequency in spin valve sensors

Spin valves are widely used as magnetic microsensors. Their performance is limited by the presence of noise. In this article, signal and noise responses of microfabricated spin valve sensors are investigated in the linear region and in the nonlinear region close to saturation where peaks in noise output have been reported. The anisotropy of the free layer and the pinned layer are in a cross configuration. The noise of the sensor is of 1/f type at low frequency. The signal-to-noise ratio (SNR) as a function of signal frequency was measured near saturation. It is found that below 300 Hz the SNR increases almost linearly as the signal frequency increases. The variation of SNR with excitation current, measured at different frequencies, is shown. The SNR shows a nonlinear characteristic. At low frequency the increase in signal power is matched by that in noise. The SNR curve at 35 Hz shows a maximum as the current increases. The slope of other curves increases with increasing frequency. We explain these curves in a model with thermal excitation.

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.

Experimental determination of optimum coil pitch for a planar mesh-type micromagnetic sensor

To overcome the directional properties of planar meander-type sensors, a new planar micromagnetic sensor having a mesh-type configuration is reported in this paper. Analytical models are usually used for the characterization of planar-type sensors. Sensors having a mesh-type configuration have been fabricated for the derivation of the optimum coil pitch.

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.

Asymmetrical giant magneto-impedance (AGMI) in amorphous wires

The discovery of giant magneto-impedance (GMI) in soft magnetic amorphous wires and films has opened new horizons in the development of micromagnetic sensors operating at nano-Tesla range. Asymmetrical GMI (AGMI) is very important to further improve sensor performance in terms of linearity and sensitivity. This paper presents a review on AGMI in Co-based amorphous wires with two types of anisotropy: circumferential and helical. Physical concepts of AGMI supported by theoretical and experimental results and problems of significant practical importance are discussed.

Quality inspection of electroplated materials using planar type micro-magnetic sensors with post-processing from neural network model

The possibility of employing planar type micro-magnetic sensors for the evaluation of the quality of electroplated materials as well as to inspect the presence of defects in its near-surface is investigated. The impedance of a planar type micro-magnetic sensor in the proximity of any metal surface is a complex function of many parameters including near-surface material properties. A two-dimensional model of two types of planar micro-magnetic sensors having meander and mesh type configurations has been developed for the analytical calculation of magnetic vector potential, flux-linkage and impedance. The impedance of the sensor is used for the evaluation of the quality of the electroplated materials. Usually an off-line generated grid system is used for the on-line evaluation of near-surface material properties. Use of a simple neural network model is proposed for the post-processing of output parameters from the measured impedance data as an alternative to the grid system.

New plasma Hall effect magnetic sensors: macrosensors versus microsensors

This paper is the first attempt to use the plasma Hall effect for magnetic field detection. The plasma Hall sensor measures the Hall voltage induced by ac electrons plasma in the magnetic field. In a theoretical analysis, we develop an analytical model of the plasma Hall sensor in order to express the plasma Hall voltage as a function of electrode geometry, magnetic field, plasma discharge field, and fluid pressure. On these bases, we have designed, fabricated, and characterized the neon plasma Hall sensors in the macroscale as well as those in the microscale. The plasma Hall macrosensor, using steel wire electrodes in a low-pressure chamber, shows a magnetic field sensitivity of 136.7±10.1 mV/G with 8.43% nonlinearity at a neon pressure of 80±5 Torr for a circuit gain of 15.56. The macrosensor, however, shows long-term instability due to the neon pressure instability in the vacuum chamber, which motivates the research on the plasma Hall microsensor. The plasma Hall microsensors using the electroplated copper electrodes in on-chip vacuum package show a magnetic field sensitivity of 8.87±0.18 mV/G with 4.48% nonlinearity at a neon pressure of 7±1 Torr for a circuit gain of 5.5. The microsensor shows good stability for 12 h. Fundamental characteristics of the macrosensors and microsensors are compared and discussed, thus verifying the feasibility of the plasma Hall sensor for a new class of magnetic microsensor.

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.

Wirelessly interrogable magnetic field sensor utilizing giant magneto-impedance effect and surface acoustic wave devices

A micro-magnetic field sensor is developed using the giant magneto-impedance (GMI) effect in a 30 /spl mu/m diameter amorphous FeCoSiBNd wire of zero magnetostriction. Surface Acoustic Wave (SAW) devices are described 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 GMI sensors and SAW transponders is discussed by several measurements. The device shows a relative signal sensitivity of 80 dB/T at low magnetic flux density B<30 mT, quick response (/spl ges/40 MHz bandwidth), and a high-temperature stability.

Magneto-impedance in multilayer films

This paper reviews results on magneto-impedance (MI) in multilayers consisting essentially of two soft ferromagnetic films (F) and a conductive inner lead (M): F/M/F. Multilayer film MI has a potential to be utilized for developing highly sensitive and quick-responding micro-magnetic sensors for advanced intelligent measurement and control systems and high-density magnetic recording. In materials with a uniform conductivity, a large change in impedance is accountable to a strong skin-effect, requiring the operation frequencies to be of the order of several gigahertz, for a submicron MI element. In the multilayer films F/M/F with sufficiently large difference between the conductivity values of layers M and F, the impedance can vary considerably at relatively low frequencies when the skin effect is not essential. The theory predicts that the MI ratio in multilayers 1-μm thick with a Cu inner lead and soft magnetic amorphous films (CoSiB) or permalloy (NiFe) films is as much as 400–500% at frequencies of 10–100 MHz; in the case of a sandwich 0.1-μm thick, the MI ratio, although drops considerably, is still large being 15–20% at frequencies of 300–400 MHz, which is in good agreement with the experimental results. On the other hand, in narrow films, the flux leakage across the inner conductor may result in a considerable drop in MI ratio if the film width is smaller than some critical value depending on the transverse permeability and the thickness of the M and F layers.