New 2D fluxgate devices based on the phase modulation of magnetization rotation in AMR films
TL;DR: In this paper, the AMR effect of single-domain film-resistors is used for magnetic field and linear/angular displacement sensing, and a pseudo-super-paramagnetic behavior is observed.
Abstract: The AMR effect of single-domain film-resistors is being widely used for magnetic field and linear/angular displacement sensing. However, several constrains attributed to the repeatability of magnetization orientation limit the accuracy of such devices. There is a trade-off between device sensitivity and measurement repeatability; the anisotropy field HK affects both parameters in an inverse manner. To overcome such problems we propose the employment of AMR film-resistors as fluxgate devices. Using a rotating magnetic field vector as excitation, the anisotropic magnetoresistance material is kept continuously in saturation and a pseudo-super-paramagnetic behaviour is observed. Thus, the signal noise coming from Barkhausen jumps can be narrowed down to zero.
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TL;DR: In this paper, a hybrid 3D Jiles-Atherton/Stoner-Wohlfarth (SW) model is developed, which incorporates both models into one single formulation, capable of modeling simultaneously: temperature effects, pinning and Eddy-current loss, magnetic resonance, and uniaxial anisotropy, the orientation of which can be simulated to vary with time.
Abstract: The Jiles-Atherton (JA) theory of hysteresis is currently used in the majority of commercial CAD tools, mainly due to its implementation simplicity in fast and stable algorithms. The JA model provides precise results in the case of isotropic, polycrystalline, multidomain magnetic devices, where flux-reversal is governed by pinning mechanisms. Dynamic response of such devices, including Eddy-current loss and magnetic resonance, can also be accurately modeled. However, JA theory is not applied for three-dimensional (3-D) magnetization simulations and does not account for anisotropy that affects severely hysteresis curves of single-domain, thin-film devices, which are usually incorporated in miniature inductive sensors and actuators. In that case, the Stoner-Wohlfarth (SW) theory can be applied, which, however, does not account for dynamic response and incremental energy loss. In this work, we employ a virtual 3-D anisotropy-field vector calculated with SW theory that introduces magnetic feedback to the classical equation of Paramagnetism, in order to derive a proper 3-D "input" for the JA algorithm. This way, a hybrid 3-D JA/SW model is developed, which incorporates both models into one single formulation, capable of modeling simultaneously: 1) temperature effects, 2) pinning and Eddy-current loss, 3) magnetic resonance, and 4) uniaxial anisotropy, the orientation of which can be simulated to vary with time. The model that owns a solid physical basis has been implemented in a computation-efficient, stable algorithm capable of functioning with arbitrary excitation-field input. The algorithm has been successfully applied to model the behavior of a series of miniature Fluxgate magnetometers based on the Matteucci effect of thin glass-covered magnetic wires
24 citations
Cites methods from "New 2D fluxgate devices based on th..."
...SINGLE-DOMAIN magnetic devices such as ferromagnetic films are widely used as: 1) magnetic flux concentrators in read-write heads, in micro-actuators, and Hall devices [1], [2], 2) flux modulators in fluxgate sensors [3]–[5], and 3) field sensing heads in magnetoresistive and spin-valve sensors...
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TL;DR: The advances in the field of magnetic sensors: both, sensors of magnetic field and sensors that use magnetic materials or principles for measuring non-magnetic quantities are discussed in this article.
Abstract: In this chapter, we cover the advances in the field of magnetic sensors: both, sensors of magnetic field and sensors that use magnetic materials or principles for measuring nonmagnetic quantities. The overview of materials used for magnetic sensors comprises semiconductor materials and the soft and hard magnetic materials in thin film, bulk, and tape form in detail. We discuss the properties and effects most critical for the decisive parameters of magnetic sensors, for example, remanence, crossfield sensitivity, and temperature stability of the offset. By far, most of the produced magnetic sensors are devices based on the Hall effect. These semiconductor sensors are cheap and can be made small, but their resolution and stability is rather limited. The fast development of ferromagnetic magnetoresistors (AMR, GMR, and SDT) for magnetic reading heads also brought these devices into the sensor scope. In the chapter devoted to fluxgate sensors, we concentrate on miniaturization of these traditional devices and compare them to GMI sensors. We describe the status of resonant sensors, induction coils, and SQUIDs, and briefly mention other more exotic methods of magnetic field measurements. An overview of magnetic sensors for mechanical quantities, such as position and force, is also given with special focus on torque sensors. One section is devoted to the sensing of electric current based on magnetic principles. In conclusion various applications of magnetic sensors are listed and discussed.
23 citations
14 May 2018
TL;DR: In this paper a novel magnetoresistive wheel speed sensor is presented, whereby its transfer function is linearized in the frequency domain, resulting in an improvement of the sensor reliability, since temperature and lifetime drift are significantly reduced.
Abstract: Especially in the automotive domain wheel speed sensors face increasing quality and reliability requirements due to novel vehicle concepts as well as new legal regulations. From this follows, that next generation sensors have to possess a higher robustness against harsh environmental conditions. A large operating temperature range as well as a high stray field immunity are key-requirements. In this paper a novel magnetoresistive wheel speed sensor is presented, whereby its transfer function is linearized in the frequency domain. From this follows directly an improvement of the sensor reliability, since temperature and lifetime drift are significantly reduced. Moreover, the concept enables measurement of disturbing fields perpendicular to sensing direction, which cannot be detected by existing speed sensors. Furthermore, promising measurement results validate the feasibility and performance of the presented sensory system.
12 citations
Cites background from "New 2D fluxgate devices based on th..."
...The same goes for many other AC-biasing techniques – for example presented in [5] or [11]-[16]....
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01 Oct 2016
TL;DR: In this paper, a novel approach for the measurement of weak magnetic fields is presented, using the nonlinear characteristic of AMR sensors, a higher sensitivity is achieved, whereas temperature and life time drift are significantly reduced.
Abstract: Measurement of magnetic fields plays an important role in many application areas such as compassing, current detection or rotational speed sensing. Especially in the field of automotive applications ever increasing requirements demand higher sensitivity, better temperature and life time behavior. In the following a novel approach for the measurement of weak magnetic fields is presented. Using the nonlinear characteristic of AMR sensors, a higher sensitivity is achieved, whereas temperature and life time drift are significantly reduced.
10 citations
TL;DR: The purpose of the experimental process in this paper, was to note if the orthogonal and parallel fluxgate sensors work properly and secondly to observe the reaction of the external magnetic field on their harmonics.
Abstract: Magnetic sensors have been, for many decades, the industrial standard for a variety of applications due to many unique advantages they possess, compared to other sensor types. The purpose of the experimental process in this paper, was initially to note (ascertain) if the orthogonal and parallel fluxgate sensors work properly and secondly to observe the reaction of the external magnetic field on their harmonics.
3 citations
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Journal Article•
TL;DR: In this article, the effects of the size of the MR stripe, of stress in the MR stripes, and of noise posing problems for practical applications are summarized and the characteristics of rotary encoders with sinusoidal output, which can achieve higher resolution without a narrower magnetic recording pitch, are introduced.
Abstract: Magnetoresistive sensors based upon the anisotropic magnetoresistive effect of ferromagnetic thin films are in wide use. A higher resolution is required of these sensors because of the higher performance of equipment for factory automation and office automation. In this report, the effects of the size of the MR stripe, of stress in the MR stripe and of noise posing problems for practical applications are summarized. In addition, the characteristics of rotary encoders with sinusoidal output, which can achieve higher resolution without a narrower magnetic recording pitch, are introduced.
347 citations
TL;DR: Anisotropic and giant magnetoresistive (AMR and GMR, respectively) sensors are attractive for industrial applications, as they are more sensitive and stable than Hall sensors as discussed by the authors.
Abstract: Anisotropic and giant magnetoresistive (AMR and GMR, respectively) sensors are attractive for industrial applications, as they are more sensitive and stable than Hall sensors. Their performance can be improved by AC excitation: flipping for AMR and AC biasing for GMR. AC excitation lowers the hysteresis, reduces the offset and, in some cases, also decreases sensor noise. The sensitivity to perpendicular fields is reduced in case of AMR sensors. AC-driven magnetoresistors are competitive with miniature fluxgate sensors and they are suitable for precise applications such as compasses.
66 citations
TL;DR: In this paper, a novel magnetic field sensor is presented, which combines the classical Fluxgate principle with the anisotropic magneto-resistance (AMR) effect exhibited by barber-pole biased AMR film-resistors.
Abstract: A novel magnetic field sensor is presented in this paper. It combines the classical Fluxgate principle with the anisotropic magneto-resistance (AMR) effect exhibited by barber-pole biased AMR film-resistors. It is shown that such film-resistors can be used as Fluxgate magnetic cores, because they exhibit one high-resistivity state and one low-resistivity state depending on the film magnetization polarity. Periodical alteration of the magnetization polarity, forced by an excitation field, makes the film-resistivity become a rectangular function of time, whose duty-cycle is proportional to the measured ambient field intensity. The proposed design helps with the suppression of repeatability and time-drift errors that are common in AMR sensors; the excitation field enhances the spin-alignment along the easy-axis of the film-resistor. The design also provides excellent temperature stability. Moreover, it is shown how a single AMR film-resistor can be employed for simultaneous sensing of two field components (i.e. on a x – y plane); the first component modulates the duty-cycle of the rectangular function (Fluxgate principle) and the latter its amplitude (conventional AMR effect). A complete mathematical modeling of the proposed sensor is presented in this work. The theoretical results have been verified by the use of a Honeywell HMC1021 single-chip sensor. The calibration data fairly agrees with the theory.
43 citations
TL;DR: The magnetic field transverse to the sensing axis may affect the performance of magnetic sensors as mentioned in this paper, and this effect is not as dramatic as it is for AMR sensors, but it still may cause errors up to 40 nT in the Earth's field.
Abstract: The magnetic field transverse to the sensing axis may affect the performance of magnetic sensors. In the case of fluxgates, this effect is not as dramatic as it is for AMR sensors, but it still may cause errors up to 40 nT in the Earth's field. We performed measurements on voltage output fluxgate sensors of various constructions. Ring-cores are the most susceptible, showing around 10 nT error for 50 μT perpendicular field, while Vacquier-type (bar-core) sensors suppress the crossfield by their shape anisotropy. Racetrack fluxgates are the best candidates for crossfield resistant low-noise sensors.
31 citations
TL;DR: In this article, the noise properties of semiconductor, induction and other types of magnetic field sensors are discussed, and the authors show that the magnetic field sensor can have offset of 10 NT and 15 nT p-p noise at liquid nitrogen temperature.
25 citations