Linear Magnetic Field Sensor Research Articles

Design of Linear Magnetic Field Sensor Based on Periodically Magnetized Cold Plasma

We have analyzed the impact of a linear magnetic field on the photonic band gaps exhibited by bulk cold plasma, under external square-wave-like periodic magnetic field of fixed magnitude, conceived as an extrinsic photonic crystal. Here photonic band gaps are determined using transfer matrix method (TMM). Here, the impact of an additional linear magnetic field is determined on the band gaps of plasma photonic crystal with constant magnitude of square like periodic magnetic field, for normal incidence. We determine how the additional and magnetic magnetic field affects the photonic band structure (PBS) and reflectance for such extrinsic photonic crystal. It is noted that, as we increase the additional applied magnetic field, the central frequency of band gaps is shifted toward higher frequency regions in GHz. The band edge increases linearly with the applied magnetic field. The shifting in lower band edge less as compared to upper edge. Sensor is a device which detect the stimuli and give output, and many physical parameters can be measured by sensors. The shifting of band edges can be utilized in design of magnetic field sensor. Here shifting in band gaps by variation in the additional applied magnetic field are determined. The larger value of sensitivity gives a good result for sensing-based application. This analysis is based on the band gaps of extrinsic photonic crystal, and can be employed in design of magnetic field sensor with good sensitivity. Moreover, it can find applications in tunable optical devices.

Exchange coupling and dipolar interactions in FINEMET/Fe50Pd50 composites ribbons

Asymmetrical giant magnetoimpedance (AGMI) effect was investigated in FINEMET/Fe50Pd50 composite ribbons. Composite ribbon samples of 33 μm-thickness FINEMET sputtered with a layer of Fe50Pd50 film were produced, and the microstructure and magnetic properties were investigated. The results showed that the MI response was enhanced by Fe50Pd50 coating layer. The Fe50Pd50 coating layer generates a bias field to FINEMET ribbon, which leads to the asymmetry of GMI curves. The bias field decreases with the increasing of the thickness (t) of Fe50Pd50 coating layer. The asymmetry of GMI curves almost disappears at t = 70 nm. Asymmetry could be tuned by changing the thickness of Fe50Pd50 coating layer, which is analyzed in terms of exchange coupling and dipole–dipole interaction between FINEMET ribbon and Fe50Pd50 layer. The high sensitivity of GMI was used to separate the two interactions for the first time. The results opened the possibilities for application of FINEMET/Fe50Pd50 composite ribbons in linear magnetic field sensors.

MgO based specular spin valve with reversible minor loop and higher exchange bias for futuristic linear magnetic field sensor

Specular spin valves (SVs) containing ultrathin MgO, structured as substrate/seed/AF/PL1/MgO/PL2/Cu/FL/MgO/cap, have been fabricated. Both structural and magnetic characterizations of MgO based specular spin valve (SSV) have been performed and compared them with the measured data on naturally oxidized (NO) and conventional spin valves (CSV), grown under optimised condition. Reversible minor loop characteristics, highest exchange bias of 625 G and 10% magnetoresistive (MR) ratio were important observations in MgO based system. Zero hysteresis behavior was confirmed due to the reduction of grain growth of the stacks above the fine-textured MgO layer, through X-ray diffraction measurements. Interestingly, at 10 K, above 100% enhancement in MR ratio was observed in MgO based system with marginal increase in coercivity of the order 1 G. On the other hand, NO based structure has 10% MR, minor loop hysteresis of ∼2 G and exchange bias of ∼560 G at room temperature; however at 10 K, only 75% enhancement in MR ratio with large anomalies in magnetic measurements attributes due to the AFM nature of oxide materials. The above studies reflects the superior performance of MgO based SSV over a wide range of temperature in comparison to other SV structures and may lead to futuristic linear magnetic field sensor applications.

Highly compliant planar Hall effect sensor with sub 200\u2009nT sensitivity

Being a facet of flexible electronics, mechanically reshapeable magnetic field sensorics enable novel device ideas for soft robotics, interactive devices for virtual- and augmented reality and point of care diagnostics. These applications demand mechanically compliant yet robust sensor devices revealing high sensitivity to small magnetic fields. To push the detection limit of highly compliant and linear magnetic field sensors to be in the sub-µT range, we explore a new fundamental concept for magnetic field sensing, namely the planar Hall effect in magnetic thin films. With their remarkable bendability down to 1 mm, these compliant planar Hall effect sensors allow for an efficient detection of magnetic fields as small as 200 nT with a limit of detection of 20 nT. We demonstrate the application potential of these devices as a direction (angle) as well as proximity (distance) sensors of tiny magnetic fields emanating from magnetically functionalized objects. With their intrinsic linearity and simplicity of fabrication, these compliant planar Hall effect sensors have the potential to become a standard solution for low field applications of shapeable magnetoelectronics in point of care applications and on-skin interactive electronics.

Invariance of the magnetic behavior and AMI in ferromagnetic biphase films with distinct non-magnetic metallic spacers

We investigate the quasi-static magnetic, magnetotransport, and dynamic magnetic properties in ferromagnetic biphase films with distinct non-magnetic metallic spacer layers. We observe that the nature of the non-magnetic metallic spacer material does not have significant influence on the overall biphase magnetic behavior, and, consequently, on the magnetotransport and dynamic magnetic responses. We focus on the magnetoimpedance effect and verify that the films present asymmetric magnetoimpedance effect. Moreover, we explore the possibility of tuning the linear region of the magnetoimpedance curves around zero magnetic field by varying the probe current frequency in order to achieve higher sensitivity values. The invariance of the magnetic behavior and the asymmetric magnetoimpedance effect in ferromagnetic biphase films with distinct non-magnetic metallic spacers place them as promising candidates for probe element and open possibilities to the development of lower-cost high sensitivity linear magnetic field sensor devices.

Improving the sensitivity of asymmetric magnetoimpedance in exchange biased NiFe/IrMn multilayers

We investigate the asymmetric magnetoimpedance effect in exchange biased NiFe/IrMn multilayers and explore the possibility of tailoring the linear region of the curves around zero magnetic field by playing with the thickness of the ferromagnetic layers, probe current frequency, and the orientation between external magnetic field and exchange bias field direction. We quantify the sensitivity by calculating the |dZ/dH|H=0 in a wide range of frequencies. The highest sensitivity is observed for the thicker multilayer, reaching ∼160mΩ/Oe at ∼2.0GHz. The results place exchange biased magnetoimpedance multilayers as attractive candidates for the development of auto-biased linear magnetic field sensors.

DC and AC linear magnetic field sensor based on glass coated amorphous microwires with Giant Magnetoimpedance

Abstract Giant Magnetoimpedance (GMI) effect has been studied in amorphous glass-coated microwires of composition (Fe 6 Co 94 ) 72.5 Si 12.5 B 15 . The impedance of a 1.5 cm length sample has been characterized by using constant AC currents in the range of 400 µA–4 mA at frequencies from 7 to 15 MHz and DC magnetic fields from − 900 to 900 A/m. Double peak responses have been obtained, showing GMI ratios up to 107%. A linear magnetic field sensor for DC and AC field has been designed, using two microwires connected in series with a magnetic bias of 400 A/m with opposite direction in each microwire in order to obtain a linear response from ±70 (A/m) rms for AC magnetic field, and ±100 A/m for DC magnetic field. A closed loop feedback circuit has been implemented to extend the linear range to ±1 kA/m for DC magnetic field.

Tunable asymmetric magnetoimpedance effect in ferromagnetic NiFe/Cu/Co films

We investigate the magnetization dynamics through the magnetoimpedance effect in ferromagnetic NiFe/Cu/Co films. We observe that the magnetoimpedance response is dependent on the thickness of the non-magnetic Cu spacer material. We verify asymmetric magnetoimpedance in films with biphase magnetic behavior and explore the possibility of tuning the linear region of the magnetoimpedance curves around zero magnetic field by varying the thickness of the spacer and probe current frequency. We discuss the experimental results in terms of the different mechanisms governing the magnetization dynamics at distinct frequency ranges, quasi-static magnetic properties, thickness of the spacer, and the kind of the magnetic interaction between the ferromagnetic layers. The results place films with biphase magnetic behavior exhibiting asymmetric magnetoimpedance effect as very attractive candidates for application as probe element in the development of auto-biased linear magnetic field sensors.

Angular dependence of asymmetric magnetoimpedance in exchange biased NiFe/IrMn multilayers

We investigate the angular dependence of asymmetric magnetoimpedance of NiFe/IrMn multilayers and explore the possibility of tuning the linear region of the magnetoimpedance curves by modifying the angle between the applied external magnetic field and exchange bias field, and probe current frequency. We quantify the sensitivity by calculating the ratio |ΔZ|/|ΔH| at low magnetic fields as a function of the frequency for samples cut with different orientations and show that considerable values in the linear region around zero field can be reached. The results extend the possibilities for application of exchange biased magnetoimpedance multilayers as probe element for the development and improvement of auto-biased linear magnetic field sensors.

비정질 리본의 ΔE 특성을 이용한 선형 자기센서에 관한 연구

<TEX>${\delta}$</TEX>E 효과는 재료의 영율(Young's modulus)이 자화 상태에 따라 변화하는 효과를 말한다. 본 연구에서는 두께 <TEX>$25{\mu}m$</TEX>, 길이 30 mm의 비정질 리본 2605SC를 폭 3 mm, 5 mm, 8.5 mm로 각각 에칭하여 외부 자기장 세기와 시편의 폭 변화에 따른 영율의 변화를 임피던스 공명 측정을 이용하여 측정하였다. 인가 자기장이 증가함에 따라 영율이 증가하는 것과, 시편의 폭이 넓을수록 시편에 인가되는 유효 자기장이 감소하여 영율이 감소하는 결과를 볼 수 있었고, 단원자 모델로 계산한 결과와 비교적 잘 일치하는 것을 확인하였으며, 외부 자기장 세기에 따라 변화하는 영율(<TEX>${\delta}$</TEX>E)의 선형적 변화 영역을 이용한 선형 자기센서 제작 가능성을 확인하였다. The width dependence of Delta E has been studied by impedance resonance method in Fe-rich amorphous ribbon of as received state. It can be explained by single domain model include effective magnetic field <TEX>$H_{eff}$</TEX> and demagnetization factor <TEX>$N_d$</TEX>. Wider width ribbon's effective is smaller than narrow it. Young's modulus also smaller than narrow width. These result well agreement in calculation. It has been also studied that linear magnetic field sensor using width dependence of Delta E under the field range 0 Oe~80 Oe. The sensitivity of the sensor was found to be 95 Hz/Oe.

Magnetic Sensor System Using Asymmetric Giant Magnetoimpedance Head

Recently sensitive micro-magnetic sensors are strongly required in various technologies such as BT and IT. This paper gives the comprehensive analysis of the Asymmetric Giant MagnetoImpedance (AGMI) sensor's performance with negative feedback. Asymmetrical behavior of the GMI is required for linear magnetic field sensors as the sensitivity and linearity for magnetic field are the most important parameters in the practical application of GMI to magnetic sensors, and this has been realized by magnetic field annealing in amorphous ribbon. A novel AGMI sensor was developed and the performance of the sensor was carefully studied with and without applying negative feedback. The sensor uses 10 mm times 1 mm times 20 mum Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">66</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> ribbon as a sensing element. On applying the negative feedback the sensor shows excellent linearity free from hysteresis, independent of temperature variations. The sensitivity AGMI sensor was found to be 0.27 V/Oe in dynamic range of -2 ~ 2 Oe.

High frequency magnetoimpedance in Ni81Fe19/Fe50Mn50 exchange biased multilayer

Gigahertz magnetoimpedance (MI) curves obtained in an exchange biased Ni81Fe19/Fe50Mn50 multilayer are reported. Experimental MI curves are shifted by the exchange bias field (HEB), following the features presented by the hysteresis curves. Theoretical MI curves, calculated using the classical expression for the impedance of a planar magnetic conductor, describe well the experimental data. The results open possibilities for application of exchanged biased MI multilayered materials for the development of autobiased linear magnetic field sensors.

Exchange coupling between ferromagnetic and antiferromagnetic layers via Ru and application for a linear magnetic field sensor

Exchange coupling is observed in a trilayer structure of ferromagnet-Ru-antiferromagnet and the coupling strength is found to be a function of the thickness of the Ru spacer layer. This is the first observation for such a trilayer structure and may help to shed light on the illusive mechanism of exchange coupling in these systems. This unique coupling is used to bias the sense layer in a magnetic tunnel junction structure so that the magnetization orientations of the sense layer and the pinned layer can be independently controlled. Sensor devices are fabricated with a bipolar output, a medium sensitivity, and a wide field range. The results show that this biasing scheme is well suited for magnetic tunnel junctions used in magnetic field sensors.

Linear Spin-Valve Bridge Sensing Devices

Spin-valves are applied in a variety of devices including magnetic sensors and isolators. The linear spin-valve sensing element is configured as a Wheatstone bridge consisting of four sensing resistors. The sensing devices are characterized by three parameters: the sensing field range, sensitivity and linearity. The devices using linear spin-valve sensing elements exhibit excellent performance. A Linear magnetic field sensor constructed of a bridge with 4 /spl mu/m wide line serpentine resistors shows a sensitivity of 1.6 mV/V-Oe in the operation range of -5 Oe to 5 Oe. An analog magnetic isolator constructed of a bridge with 4 /spl mu/m wide line serpentine resistors exhibits superior performance with a sensitivity of 1.27 mV/V-mA and a linearity error less than 0.05%.

Low temperature linear magnetic field sensor based on magnetoresistance of the perovskite oxide La–Sr–Co–O

A linear magnetic field sensor for low temperature (T≤60 K) use based on magnetoresistance of the perovskite oxide material La0.7Sr0.3CoO3 is reported. The magnetoresistance is negative and is linear in field up to at least 7 T. It is temperature independent for T≤60 K and has a small anisotropy (20%) with respect to the direction of the measuring field.

Suppressed sidewall injection magnetotransistor with focused emitter injection and carrier double deflection

We present a new linear magnetic field sensor (MFS) made in standard CMOS technology with a sensitivity of 1.26 percent/mT (1 percent/T ≡ 0.01 T <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ). The device is a dual-collector lateral magneto-transistor (LMT) with suppressed injection of the emitter sidewalls, confinement of the injection to the center bottom of the emitter-base junction, and double deflection of carriers. Desirable collector current levels can be set without major loss of sensitivity by choosing from a wide range of operating points.