Angle Magnetization Rotation Research Articles

Light-Weight and Compact Magnetic Rotation Angle Sensor with Partial Arc Stator Using Three Hall-Effect Sensors

Light-Weight and Compact Magnetic Rotation Angle Sensor with Partial Arc Stator Using Three Hall-Effect Sensors

Current measurement method based on integral reconstruction of magnetic rotation angle

In view of the nonlinear limitation of the sine function on the magnetic rotation angle in the optical current sensor based on the light intensity detection mode, this paper proposes a current measurement method based on the integral reconstruction of the magnetic rotation angle, thus avoiding the large current measurement error caused by the approximate linear measurement of the magnetic rotation angle. In this method, the cosine term in the derivative of the sine signal containing the magnetic rotation angle is eliminated by the constant deformation of the trigonometric function, and then the magnetic rotation angle is reconstructed by integration. The experimental results show that within the current range of 0.20 Arms to 2.40 Arms, the measurement error of the current value of the integral reconstruction method is less than 1.30%, the measurement error is less than the approximate linear measurement method, and there is a good linear relationship between the magnetic rotation angle and the current, with a linearity of 99.987%.

The basic examination of the magnetic rotation angle sensor with the magnetic substance slit

AbstractThe optical rotation angle sensor is characterized in that it is excellent in resolution and angle detection accuracy, and the magnetic sensor is characterized in that it is resistant to foreign matter such as dust and dirt, and that it is possible to achieve low power consumption, small size, and low cost of the sensor, as compared with the optical sensor. However, in the magnetic type, in order to obtain a high resolution as compared with the optical type, it is necessary to make the magnetization period of the magnet fine, so the magnetic rotation angle sensor has the difficulties compared with the optical type. This time, for magnetic rotation angle detection, we carried out a feasibility study by magnetic field simulation and principle verification experiments on a technique of extracting signals of two frequencies from one signal detection track by modulating a magnetic field from a magnet with a slit of a magnetic material, and this paper reports the result.

The Basic Examination of the Magnetic Rotation Angle Sensor with the Magnetic Substance Slit

The Basic Examination of the Magnetic Rotation Angle Sensor with the Magnetic Substance Slit

The basic examination of the magnetic shielding structure to use for a magnetic rotation angle sensor

AbstractThe magnetic rotation angle sensor has more merits such as small‐sized, low‐cost, and the low‐power consumption than the optical sensor. But the magnetic rotation angle sensor has the demerit to be weak to the disturbance magnetic field applied from outside the sensor, so the magnetic rotation angle sensor needs magnetic shielding structure. We proposed the magnetic shielding structure of the parallel plate type that is the simpler technique to the magnetic shielding structure of enclosing the whole sensor with the magnetic substance. We confirmed that the parallel plate type has almost the same shielding performance as the magnetic shielding structure of enclosing the whole sensor with the magnetic substance at the magnetic detecting device. We have made a prototype and evaluated angle detection error with the disturbance magnetic field. As a result, we confirmed that the error is 0.06° when 10 mT disturbance magnetic fields hang over the sensor.

The Basic Examination of the Magnetic Shielding Structure to Use for a Magnetic Rotation Angle Sensor

The Basic Examination of the Magnetic Shielding Structure to Use for a Magnetic Rotation Angle Sensor

A fiber link equipment for the optical rotation measuring based on AC-DC modulation magneto-optical effect

Based on the magnetic-optical effect, an alternating current-direct current (AC-DC) two-stage modulation is applied in the newly developed equipment, which measures the concentration of solution through the optical rotation of optical active substance. A Faraday coil is combined with the AC-DC signal generator controlled by a pulse width modulation controller. To deduct the measuring error caused by the AC modulation or the DC modulation, a two-stage method based on the Superposition of DC component and AC component is demonstrated, which is characterized by removing the interference of the bigger magnetic rotation angle in the AC modulation alone. The tartaric acid, glucose, and sucrose sugar solutions are taken as the standard examples in testifying the equipment. A linear correlation is found between the measured optical rotation angle and the concentration of the solution, with the optical rotation angle being within a 1% margin of error and the maximum relative error smaller than 0.005g/ml. The results show that the equipment has the advantage of high precision, high integration, and strong anti-interference capacity. The fiber link makes the equipment portable and compact. The AC-DC two-stage modulation equipment can potentially be used in the optical rotation measurement.

Dynamic in situ visualization of voltage-driven magnetic domain evolution in multiferroic heterostructures

Voltage control of magnetism in multiferroic heterostructures provides a promising solution to the excessive heating in spintronic devices. Direct observation of voltage-modulated magnetic domain evolution dynamics is desirable for studying the mechanism of the voltage control of magnetism at mesoscale, but has remained challenging. Here we explored a characterization method for the dynamic in situ evolution of pure voltage modulated magnetic domains in the heterostructures by employing the scanning Kerr microscopy function in the magneto optic Kerr effect system. The local magnetization reorientation of a Ni/PMN-PT heterostructure were characterized under sweeping applied voltage on the PMN-PT single crystal, and the results show that the magnetization rotation angle in the local regions is much greater than that obtained from macroscopic magnetization hysteresis loops.

Effect of temperature on magnetic field–induced response of Ni-Mn-Ga single crystals

This study presents an experimental and theoretical investigation into the effect of temperature on the magnetic field–induced responses of Ni-Mn-Ga single crystals, such as reorientation behaviour, critical threshold fields and hysteresis loops. Nano-indentation, differential scanning calorimetry and magnetic field–induced strain tests were conducted. The experimental results reveal that the critical threshold field decreases with an increase in temperature under a constant compressive stress. A revised magnetization rotation angle equation was developed by considering the effect of temperature on material magnetic anisotropy. By comparing with the measured magnetic field–induced strain versus magnetic field curves, the present theoretical model is shown to be capable of predicting the effect of temperature on the macroscopic responses of magnetic shape memory alloy.

Design of Element Configuration on Magnetic Rotation Angle Sensor with Spin-Valve Film

To reduce the error of a magnetic rotation angle sensor, we investigated the effect of sensor element configuration on the output signal of the sensor by using numerical calculations. The sensor elements were made of spin-valve films with a large shape-induced anisotropy. The magnetization of elements was calculated by minimizing the magnetic energy in a framework of the Stoner–Wohlfarth model. The sensor response was calculated as a function of the relative angle between the spin-valve elements. The error of signals was minimized when the relative angle was 99.5°. It is clear that this configuration is robust against the variation of shape-induced anisotropy.

Magnetomechanical characterization and unified energy model for the quasistatic behaviorof ferromagnetic shape memory Ni–Mn–Ga**This work was performed by the authors at The Ohio State University.

This paper presents an overview of the characterization and modeling of single crystalferromagnetic shape memory Ni–Mn–Ga. A continuum thermodynamics model is presentedwhich describes the magnetomechanical characterization of single crystal Ni–Mn–Ga for thefollowing behavior: (i) sensing effect; (ii) actuation effect; (iii) blocked force (stressgeneration). The thermodynamic potentials, namely the magnetic Gibbs energy and theGibbs energy, are obtained from the Helmholtz energy in order to arrive at the set ofrequired independent and dependent variables; the potentials include magnetic energyconsisting of Zeeman, magnetostatic and anisotropy components, and mechanical energyconsisting of elastic and twinning components. Mechanical dissipation and themicrostructure of Ni–Mn–Ga are incorporated in the continuum model through theinternal state variables volume fraction, domain fraction, and magnetization rotationangle. The constitutive response of the material is obtained by restricting theprocess through the second law of thermodynamics. The model requires only sevenparameters identified from two simple experiments. Several interesting characteristics ofNi–Mn–Ga are examined in concert with the magnetomechanical characterization.

Direct Current Effects on High-Frequency Properties of Patterned Permalloy Thin Films

We have investigated experimentally direct current (dc) effects on high-frequency properties of two different permalloy (Py) submicrometer patterns of 0.24 mum and 0.55 mum width, 10 mum length, and 100 nm thickness. The natural ferromagnetic resonance (FMR) frequencies for the two samples are about 8.5 and 11.5 GHz. A 50 mA dc produces a FMR frequency reduction of about 1 GHz in both samples. We extracted susceptibility spectra for the samples from the measurement data. We studied inductance variations of Py embedded transmission lines for different dc levels. With 50 mA dc, the operational frequencies of the inductances decreased by 9% and 12.5%. We also tested effects of magnetic fields generated by external magnets on the submicrometer patterns for comparison. To obtain the same magnetization rotation angle, the external magnetic field needs to be about five times larger than the Ampere field created by the direct current. This behavior is unique and may be associated with the increased thermal energy from the Joule heating effects.

A continuum thermodynamics model for the sensing effect in ferromagnetic shape memory Ni–Mn–Ga

A magnetomechanical model based on continuum thermodynamics is presented which describes the sensing effect in single-crystal ferromagnetic shape memory Ni–Mn–Ga. The model quantifies the stress and magnetization dependence on strain at different values of bias fields under isothermal conditions. A magnetic Gibbs energy is considered as the thermodynamic potential with Zeeman, magnetostatic, and anisotropy energy contributions. Constitutive equations for stress and magnetization are obtained in the isothermal case after restricting the process through the Clausius-Duhem inequality for the second law of thermodynamics. Mechanical dissipation and the microstructure of Ni–Mn–Ga are incorporated in the continuum model through the internal state variables volume fraction, domain fraction, and magnetization rotation angle. Closed-form solutions describing the evolution of the internal state variables are developed. The model requires only seven parameters identified from simple experiments: stress-strain curve at zero field, and easy-axis and hard-axis magnetization curves.

Rotation angle sensors based on spin valve structures: A modeling approach

Spin valve systems are widely considered in magnetic rotation angle sensors. We present a simple magnetostatic model to simulate the electrical and magnetic signal of typical spin valve systems as a function of external magnetic field and rotation angle. To match simulation and experiment only a few parameters are needed, which can be determined by a single measurement. Two types of systems are treated and discussed: a simple spin valve and a spin valve with an “artificial antiferromagnet,” often used to enhance the exchange bias. The model shows a very good correspondence of the predictions to the experimental results of the systems investigated. In order to quantitatively compare experiment and model, we introduce a useful concept to quantify the quality of the angle rotation curves: the total harmonic distortion.