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A dual-output magnetoelectric (ME) energy harvester consisting of strictly concentric toroidal Ni0.8Zn0.2Tb0.02Fe1.98O4/(Pb0.70Ba0.26Sr0.04)(Zr0.52Ti0.48)O3 (PbaS-4)/Ni0.8Zn0.2Tb0.02Fe1.98O4 composite with solenoid wound around it is presented and developed. In this case, spatial electromagnetic energy from power lines can be scavenged by ME element and the solenoid simultaneously, and then, the output power density was improved due to electromagnetic induction involved. Experimental results show that the maximum induced voltage can reach 15 mV (port I) and 1.2 mV (port II) for open-circuit conditions under the amplitude of 70 mA current driving of 50 Hz. Correspondingly, generated output power for ports I and II reaches 0.4285 and 30.1476 nW at optimum load resistances of 250 and $140~\Omega $ , respectively. Through these study results, new research paths to move forward with enhanced flexibility for device design of magnetic energy harvester in application in power line autonomous monitoring systems. Through these study results, new research paths to move forward with enhanced flexibility for device design of magnetic energy harvester were achieved in application of power line autonomous monitoring systems. [ABSTRACT FROM AUTHOR]

A force-driven kinetic energy harvester, designed to be excited with impulse-like mechanical loads, is presented. Energy harvesting is a promising technique to feed wireless sensor networks. The proposed device exploits three rods of Galfenol and has been modeled through FEM COMSOL Multiphysics with nonlinear fully coupled characteristics. They consider the general behaviors of magnetostrictive materials and are compatible with thermodynamics. The preliminary results of the time-domain simulations, with an impulse-like force applied, have been compared with experimental results showing a good agreement. Moreover, the proposed nonlinear modeling has shown better performances with respect to software built-in magnetostrictive models. At the same time, further modeling improvements seem to be needed in the future to better fit the harmonic content of the free evolution of the device. [ABSTRACT FROM AUTHOR]

A partitioned stator-flux reversal (FR) permanent magnet machine (PS-FRPMM) is a new combination of a stator PM machine and a magnetically geared machine and has the specifications of both machines in terms of robust structure and torque density. In this paper, a comprehensive 2-D analytical model is developed for PS-FRPMM based on subdomain technique. The presented model has the capability to accurately and quickly investigate the effects of design parameters on the machine performance. The 2-D analytical model is evaluated on two case studies with 12 stator teeth and 10 rotor poles, and 18 stator teeth and 13 rotor poles, with four different magnetization patterns. The influences of various design parameters such as the rotor slot width, slot opening width, and the segment ratio of the PMs in the two-segment magnetization pattern have been investigated on the quantities, such as the instantaneous torque, torque ripple, unbalanced magnetic force (UMF), and electromotive force (EMF). For evaluating the presented analytical model, the 2-D finite element method (FEM) with and without saturation effects has been used. The comparative study between the analytical and numerical models shows good agreement. Finally, a 3-D FEM has been used, and the results of the 2-D analytical model and 3-D FEM are compared in terms of the accuracy and computational time. The results show that the presented model has lower computational time compared to the 2-D and 3-D FEM, while its accuracy is acceptable under different circumstances, such as saturation. [ABSTRACT FROM AUTHOR]

The magnetostrictive inkjet printhead (MagJet), an example of the 1-D magnetostrictive actuator (MA), consists of one MA, a nozzle, a chamber, and a fluid inlet. The mathematical estimation tells that the droplets are not likely to be made due to the inverse of Ohnesorge number less than one. The experimental results, however, show that the MagJet ejects the high viscosity fluid up to 1000 cP at room temperature. The magnetostrictive motor (MagMotor), an example of the 2-D MA, is composed of one Terfenol-D rod, one toroidal coil, one solenoid coil, a stator, a rotor, and housing. The experimental results show that the MagMotor rotates successfully up to 60 rpm, and about an arbitrary axis. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical and experimental study on high-frequency (>5000 Hz) output characteristics of the giant magnetostrictive transducer (GMT) at varied operating conditions. Based on the Jiles–Atherton model, Maxwell’s equations, Newton’s law, and Fourier’s heat transfer equation, a nonlinear electromagnetic–mechanical–thermal multi-field coupled finite element model for GMT is established. The output displacement amplitude of the magnetostrictive rod and the acceleration of vibrating horn at the GMT device are measured and analyzed at varied exciting amplitude of ac magnetic field and frequencies (from 5600 to 7000 Hz). The frequency dependences of permeability and magnetoelastic coupling coefficient obtained from the experimental results are used in revising the model parameters. These output characteristics analysis results can provide theoretical and experimental guidance in the optimization of structural design and precise controlling for high-frequency GMT system. [ABSTRACT FROM AUTHOR]

The stator vibrations of a bearingless synchronous reluctance motor are investigated with simulations. The influence of the Maxwell stress tensor and magnetostriction on the stator vibrations is studied at different operational conditions. An energy-based magnetomechanical model of iron core is implemented and the influence of the magnetostriction in the iron core on the stator vibrations is further investigated and compared with the case where the magnetostriction is not modeled. The objective of the research is to find out how the stator vibrations can be used to detect the off-center rotor position. The results show that a single frequency component is not able to assess this phenomenon but a combination of two components makes it possible. [ABSTRACT FROM AUTHOR]

This paper deals with practical issues and solutions related to the use of the giant magnetoimpedance (GMI) for electrical current measurement. It presents an overview of a full attempt of design and realization of an almost industrial GMI-based current sensor or clamp. The sensor combines dc and ac measurements with the same flexible sensitive element. This paper addresses several practical problems encountered in a real measurement environment. In this context, main attention was paid to the impact of the influence quantities that largely condition the implementation strategies and solutions of the sensor. For the intended industrial application, these influence quantities first include the operating temperature. Its impact on the intrinsic sensor response was investigated in an almost industrial temperature range. Second, bending stress on the sensitive element is another involved influence parameter in the toroidal and flexible structure of the sensor. The effect of this was also characterized. Finally, the third considered influence parameter is the effect of magnetic disturbances. These include the eccentricity of the conductor of interest and the impact of the surrounding magnetic fields such as the earth’s field or fields produced by other conductors in close proximity to the sensor. Different strategies of implementation and solutions, taking into account the impact of influence parameters, were proposed and compared. A sensor prototype was realized, and its first performances were given. [ABSTRACT FROM AUTHOR]

This paper describes the development of a new magnetometer calibration device using an active magnetic field compensation technique based on the base quantity of time rather than secondary standard field measurements. The proposed arrangement can be used as a laboratory calibration device that monitors and compensates the ambient dc magnetic field in a magnetically quiet environment. Furthermore, it can be developed to serve as a laboratory primary standard since it is based on the measurement of a base quantity, such as time. The proposed technique is based on the fluxgate magnetization principle and the measurement of the time difference between the two successive output pulses. The laboratory arrangement consists of a long solenoid for 1-D applications, which may be extended to 2-D and 3-D using Helmholtz coils, and a microcontroller for fast signal processing operations, which evaluate and compensate the detected ambient magnetic field using a closed-loop control algorithm. The proposed arrangement is used to obtain the calibration curves of a commercial Hall and a custom-made fluxgate sensor. [ABSTRACT FROM AUTHOR]

The optical frequency-domain reflectometry (OFDR) sensing system and signal processing method, which is based on the short-time Fourier transform, enable us to interrogate reflected wavelengths of fiber Bragg gratings (FBGs) and their relative position along the optical fiber with high spatial resolution. An FBG is an optical fiber with an appropriately inscribed periodic refractive index modulation. When a broadband optical signal is launched into the FBG, narrow wavelength bandwidth is reflected. Due to an attached transducer, such as Terfenol-D, the reflected wavelength changes with the applied magnetic field. The proposed magnetic FBG sensor consists of a small rod of magnetostrictive alloy TbDyFe, also known as Terfenol-D, which has large magnetostriction. The FBG is attached to the Terfenol-D rod with UV glue. Consequently, the external magnetic field is applied to the sensor and as a result, the Terfenol-D rod length increases. The reflected wavelength shift is observed and measured by the OFDR sensing system. Therefore, we determine the external magnetic field along the optical fiber from the reflected Bragg wavelength shift. The measurement results show that the proposed magnetic field sensors based on Terfenol-D using OFDR can be successfully used for measurement of the external magnetic field along an optical fiber. [ABSTRACT FROM AUTHOR]

Magnetostrictive actuators show interesting performances related to high-precision actuation with high-energy density, which focused the interest of research in the past years. Nevertheless, the output deformation is related to the current and the applied stress, through a complex multi-input multi-output (MIMO) hysteresis process. As a consequence, a reliable and accurate control task cannot neglect the stress monitoring. Such task, if performed by an ad hoc stress sensor, e.g., a load cell, will face with the sensor’s placement in the device, resulting in an increase in cost, complexity, and bulkiness of the system. This issue can be circumvent if the current and magnetic flux measurements, available in the control chain, are exploited. To this aim, a novel self-sensing approach to deliver real-time estimation of the stress is presented in this paper, involving some recent results of a thermodynamic compatible MIMO model of hysteresis for magnetostrictive materials. [ABSTRACT FROM AUTHOR]

Based on the established equivalent circuit model of a magnetostrictive vibration generator, the low ac voltage and low power produced by the generator under low acceleration are calculated. Comparisons between the calculated and measured results show that the model can provide reasonable data trends of the generator under different loads. To boost the low ac voltage to a high dc voltage required by electronic devices in low power consumption, two energy extraction circuits (EECs) (i.e., a proportion integration-based EEC and an improved EEC) are studied. The corresponding two harvesting systems, which include the generator and the proposed EECs, are designed and simulated in LTspice for system-level evaluation. It is found that the two harvesting systems can effectively boost a few hundred millivolts of ac voltage to the steady dc voltage under low acceleration and varying load conditions. Moreover, the system with the improved EEC can be powered by the harvested energy to maintain self-sustaining operation, and the batteries in the system can be charged for future start-up operations; thus, the system has strong practicability in the dc supply for the electronic devices. [ABSTRACT FROM AUTHOR]

Experimental and calculating analysis of magnetic losses for Terfenol-D is a necessary step for the design of high-power magnetostrictive transducer. In order to further research the magnetic energy losses characteristics, a Terfenol-D rod is sectioned along different directions, and these slices are made into several square annular sheet samples. The influences of material magnetization direction on the losses are compared and analyzed. The values of magnetic energy losses are measured to investigate their variations at different frequencies and magnetic densities of driving magnetic field. Furthermore, the traditional losses formula is improved. The values of the hysteresis losses, eddy-current losses, and anomalous losses are separated out, and the losses coefficients are achieved through polynomial curve fitting. This paper can provide theoretical and experimental guidance for the high-frequency applications of magnetostrictive materials. [ABSTRACT FROM AUTHOR]

Giant magnetostrictive actuator (GMA) becomes more promising in precision positioning, sophisticated manufacturing, and microelectronic system, because of the excellent performance such as high resolution, rapid response, and large mechanical force. However, the intrinsic hysteresis of GMA is the main sticking point preventing its application in the high precision positioning. In this paper, a Prandtl-Ishlinskii (PI) model is established. To obtain the parameters of the model, the internal time-delay recurrent neural network (RNN) with self-tuning ability is proposed. A series of simulations are conducted to testify the availability of proposed method and the results indicates that the PI model identified by the internal time-delay RNN can accurately describe the hysteresis of GMA with the increase of frequency. [ABSTRACT FROM AUTHOR]

In order to reduce the vibration of shunt reactors with gapped iron-core structure, accurate stress computation should be carried out. The magnetization and magnetostrictive anisotropy should be considered in the calculation. In this paper, the magnetization and magnetostrictive properties of non-oriented silicon steel sheets along the rolling direction and the transverse direction are first measured by a magnetization and magnetostriction tester. Based on the measurement results, an electromagneto–mechanical coupled numerical model for shunt reactors, considering magnetization and magnetostrictive anisotropy, has been developed. Then, the stress distribution of the reactor core is calculated and that between isotropy and anisotropy numerical model is compared. From the computation results, it can be seen that magnetization and magnetostrictive anisotropy greatly influences the stress distribution of the reactor core. [ABSTRACT FROM AUTHOR]

Structural Magnetostrictive Alloys: From Flexible Sensors to Energy Harvesters and Magnetically Controlled Auxetics [ABSTRACT FROM PUBLISHER]

The properties of Fe–Ga thin films on PZT substrate were investigated in this paper. In the Fe–Ga/PZT (ME) devices the Fe–Ga magnetostrictive films act as a driver, therefore it should exhibit a good magnetic and mechanical properties. During sputtering, Ar pressure was changed and Fe–Ga thin films were obtained. It is shown that there is a strong relationship between the gas pressure and film adherence, conductivity, magnetic, and mechanical properties of Fe–Ga thin films. We found that the Fe–Ga/PZT devices with high Young’s modulus and high permittivity also performance good in the ME coupling test. The ME coefficient was 0.17 V/cm Oe at resonance frequency, although the thickness of Fe–Ga film only was about 300 nm. [ABSTRACT FROM AUTHOR]

Resonance magnetoelectric (ME) responses are investigated for the ME laminate heterostructure consisting of positive magnetostrictive material FeCuNbSiB, negative magnetostrictive material Ni and piezoelectric material PZT-8. On one hand, both a built-in magnetic field induced by the strong magnetic interactions between positive magnetostrictive and negative magnetostrictive materials and an intrinsic anisotropic field with obvious hysteresis and remnant magnetization in Ni layer result in a large zero-biased ME effect. The corresponding zero-biased ME voltage coefficient reaches 10.12 V/Oe (126.5 V/cm Oe), which is about 3 times larger than that of traditional Ni/PZT-8 (NP) laminate. On the other hand, the additional stress produced by the high magnetic permeability FeCuNbSiB layer enhances the magnetostriction of Ni layer and ME response. The corresponding maximum ME voltage coefficient (dVME/dHac) is 12.09 V/Oe (150.87 V/cm Oe) at bias magnetic field H\mathrm {dc} = 4 Oe. It is further found that even a step change of ac magnetic field less than 10−10 T can be clearly distinguished by the proposed ME composite. The value of ME voltage sensitivity to dc magnetic fields (dVME/dH \mathrm {dc}) reaches ~76.7 mV/Oe at H\mathrm {dc}= 5 Oe and H\mathrm {ac} =0.1 Oe. Correspondingly, the proposed laminate heterostructure is able to possess both strong ac and dc magnetic field sensitivities. [ABSTRACT FROM AUTHOR]

In a previous paper, we discussed wireless strain sensors, based upon the $\Delta E$ effect, employing a number of different field-annealed amorphous ribbons as resonators and transducers. In this paper, we present results for a polycrystalline (Fe0.8Al0.2)98B2 alloy as the transducer and either Metglas 2826MB3 or Beijing Yeke 1K501 as the resonator. Frequency variation curves and tensile stress tests were performed on the sensors. The FeAlB–amorphous alloys ensemble resulted in a linear behavior through a larger deformation amplitude than previously obtained. Gauge factors of up to 190 were obtained over a deformation amplitude of at least 300 ppm. The results are discussed in the light of the magnetization behavior of the materials involved. [ABSTRACT FROM AUTHOR]

This paper concerns the sensing of dynamic force/stress by means of a measuring system based on the use of an Fe–Ga sample (Galfenol) coupled to a magnetic circuit. The study is focused on the measurement of the effective magnetic field, detected at the rod specimen surface, and its variation \Delta \! H\mathrm {eff} under time-dependent applied sinusoidal stress \Delta \sigma , oscillating at frequencies between 5 and 20 Hz at different values of applied bias field H_{\mathrm {bias}} (2.5 kA/m \le H_{\mathrm {bias}} \le 27 kA/m). For the considered frequency and H\mathrm {bias} range, the measured \Delta \! H\mathrm {eff} tends to linearly depend on \Delta \sigma , in contrast with the corresponding induction variation behavior ( $\Delta \! B-\Delta \sigma $ ), where hysteresis effects appear. With $\Delta \sigma $ in the range of ±15 MPa, we obtain 0.06 MPa resolution in the determination of the alternating stress $\Delta \sigma $ , a result pointing to the effectiveness and sensitivity of this Galfenol-based method for detection and measurement of time-dependent stresses. [ABSTRACT FROM AUTHOR]

We present the measurements of the static and dynamic properties of polycrystalline iron–gallium films, ranging from 20 to 80 nm and sputtered from an Fe0.8Ga0.2 target. Using a broadband ferromagnetic resonance setup in a wide frequency range, perpendicular standing spin-wave resonances were observed with the external static magnetic field applied in-plane. The field corresponding to the strongest resonance peak at each frequency is used to determine the effective magnetization, the $g$ -factor, and the Gilbert damping. Furthermore, the dependence of spin-wave mode on field-position is observed for several frequencies. The analysis of broadband dynamic properties allows determination of the exchange stiffness $A = (18 \pm 4)$ pJ/m and Gilbert damping $\alpha = 0.042 \pm 0.005$ for 40 and 80 nm thick films. These values are approximately consistent with values seen in epitaxially grown films, indicating the potential for the industrial fabrication of magnetostrictive FeGa films for microwave applications. [ABSTRACT FROM AUTHOR]

This paper presents an engineering modeling methodology for magnetostrictive materials based on a simplified piezo-electric governing equation. For verifying the modeling performance, a proof-of-concept non-contact strain sensor utilizing a prototype magnetostrictive (Fe–Ga alloy, Galfenol) strip on a steel plate is used to evaluate sensor performance prediction. Typically, the performance of Galfenol is measured in a compressional load region because it has a higher response. However, in this paper, we are aiming to develop a sensor for tensile stress measurement. To achieve a compression effect from a tension load in the sensing element, a Galfenol strip is aligned perpendicular to a tension bar so that tension in the bar creates compression in the strip via the Poisson effect. The experimental setup in this paper consists of a polycrystalline Galfenol strip bonded in the horizontal direction of a steel dog-bone shaped tension specimen. Permanent magnets are attached at each end of the Galfenol strip to provide an even magnetic bias field through the strip. The magnetic flux through the Galfenol strip is measured with non-contact Hall sensors during the tensile load test. The simulation results agree well with the experiments for the value of $H$ studied. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of metallic materials is an emerging technique for the printing of 3-D components using metal powders. The use of thin flakes of magnetostrictive (001)-oriented Fe–Ga powder in a composite matrix for the design of pressure and strain sensors has been demonstrated. This paper extends that work and presents a preliminary evaluation of two methods for the consolidation of magnetostrictive Fe–Ga alloy flakes, using a hot press and arc melting. Flake-shaped powders of Fe80Ga20 and Fe73Ga27 alloys were prepared with varying particle sizes up to 250~\mu \textm in diameter using a high energy wet ball milling process. The surfaces of the flakes produced were predominantly parallel to the (001) crystallographic plane. Hot pressed Fe–Ga disk samples at 850 °C showed increases of packing density and saturation magnetization with an increase of the particle size because higher thickness to diameter aspect ratios in the flakes facilitated ordering of flakes whereby they more easily defaulted to sitting on one another in layers. We also employed arc melting and binder infiltration techniques to demonstrate the potential suitability of the oriented flake form of this magnetostrictive alloy for AM using 3-D printing methods. [ABSTRACT FROM AUTHOR]

Energy harvesting allows the conversion of environmental energy into electrical energy to feed low-power consumption electronics. In particular, this method can be exploited to supply wireless sensors nodes for structural health monitoring (SHM) when the electric network source is not present. Indeed, vibrations induced by vehicle traffic on a bridge could be converted into electrical energy, but suitable devices are needed. This paper presents experimental tests over a device based on three Galfenol rods, where electrical and magnetic parameters are changed and tested with different mechanical sources in order to seek the best performance. [ABSTRACT FROM AUTHOR]

A means to cause continuous vibratory deflection of a flexurally stressed beam of ferromagnetic, non-zero magnetostriction material, by a longitudinally conducted time varying current is described. The deflection of a horizontal cantilever beam, caused by a weight attached at its free end, is due to a difference in strains between those regions under tensile stress and those under compressive stress, in which these strains have both mechanical and magnetoelastic components. The circumferential uniformity of the field from the current acts to reduce the magnetoelastic strain inequality, hence also a small portion of the beam’s deflection. Alternating between current on and current off thus acts to raise and lower the weight. Cycling the applied current at a frequency that matches the prime mode frequency will produce vibratory deflection. Round wire beams, 20–85 mm long, ~1 mm diameter, of three different materials, with attached weights ranging from 60 to 600 mN were made to vibrate at their specific natural frequency (8–80 Hz) with peak strokes up to >10 mm by currents alternating between 0 and up to 9 A. [ABSTRACT FROM AUTHOR]

This paper presents an equivalent strain approach to reduce multiaxial magneto-elastic configurations into 1-D descriptions. It follows similar principles as those used for equivalent stress approaches. The approach can be easily implemented into magneto-elastic constitutive equations using strain as driving mechanical state variable. It is particularly useful to describe 3-D configurations when only 1-D measurements are available to describe the magneto-elastic behavior. [ABSTRACT FROM AUTHOR]

This paper analyzes the output characteristics of a Galfenol magnetostrictive displacement sensor based on the Wiedemann effect, the Jiles-Atherton model, and the piezomagnetic effect. The sensor which is subjected to simultaneously circumferential excitation magnetic field, bias magnetic field, and stress will induce an output voltage. Experiments were performed to describe the induced output voltage versus the applied magnetic fields and stress with an Fe83Ga17 alloy wire as a function of the circumferential excitation magnetic field from 0.5 to 6 kA/m, the bias magnetic field of 3.5 kA/m, and the stress from 5 to 110 MPa. The induced output voltage increases with an increasing magnetic field and decreases with increasing stress. The experimental results agree well with the model calculations. The sensor with a Galfenol alloy wire can be used in displacement control and interface measurement. [ABSTRACT FROM PUBLISHER]

This paper proposes an iterative finite-element scheme that accounts for the inverse-magnetostrictive (Villari) effect. To do so, the permeability of magnetostrictive materials is updated according to the internal mechanical stress of the material at the end of each iteration step until convergence is reached. VSM measurements of prestressed thin-film samples are used to evaluate the stress-dependent permeability. Using the implemented scheme, it is possible to optimize the dimensions of inverse-magnetostrictive microelectromechanical pressure sensors with a view to maximum sensitivity. Such sensors feature a sandwichlike structure with a planar coil embedded between two magnetostrictive layers. To date, only insufficient simulation results regarding the optimization of such devices have been published. We present the results of simulations incorporating the inverse-magnetostrictive effect that show the influence of the dimensions of single layers on the overall sensitivity. [ABSTRACT FROM PUBLISHER]

This paper investigates the resonant bending-mode response of cantilever magnetoelectric (ME) sensors, with focus on the magnetic behavior in an external applied magnetic field, in a theoretical study. A system of coupled linear elastostatic/elastodynamic and electrostatic/magnetostatic equations is solved using 2-D and 3-D finite-element method simulations. The magnetic field is applied at the boundaries of an air-filled volume, surrounding the whole ME sensor, to consider the geometry-dependent deformation of the magnetic field in the presence of materials with high permeability. The deformation of the magnetostrictive (MS) material is calculated and generates an electric potential across a piezoelectric (PE) layer. Structuring the conductive MS layer is necessary to define a pickup region, if the MS layer is produced on top of the PE layer, to enhance the sensor output. For efficient excitation of the resonant bending mode, the tip of the cantilever also needs to be covered with an MS material. Thus, an air gap is necessary to electrically insulate both MS regions and has to be as small as possible to not decrease the magnetic field penetrating into the MS layer. The induced electric potential across the pickup region is optimized for a Metglas-AlN-Si thin-film ME sensor with an length:width:height ratio of 100:20:3. 2-D simulations are performed showing reasonable agreement in induced voltage with approximately 20% deviation compared with 3-D simulations, but with much lower computation times. [ABSTRACT FROM AUTHOR]

The demand for accurate angle measurements in a form that is robust and small is high, due to the advances in virtual reality applications, primarily the virtual reality headsets. The peripheral devices are required to completely immerse the user in a virtual reality setting, and for this purpose, a robust sensor has been developed. The angle measurements can also be used in motion sensing applications for medical purposes, allowing monitoring of a patient’s condition. This paper presents the development of a planar figure-of-eight coil sensor, which has been designed for the purpose of curvature sensing. The copper-plated polyimide material, FR4 FLEX, was used for the fabrication of the planar figure-of-eight coil. A curvature sensor was designed and consists of the figure-of-eight coil along with the magnetostrictive material Metglas 2605SA1. The sensor was incorporated in an oscillator circuit, where curvature-induced stress within the material changes the amplitude and the frequency of the output signal of the circuit. [ABSTRACT FROM AUTHOR]

Magnetostrictive behaviors of Fe100−xBx(001), x=0 , 5, and 13 at. %, single-crystal films are studied in comparison with those of poly-crystal Fe–B films under rotating magnetic fields. The output waveform of poly-crystal Fe–B film is sinusoidal and the saturation magnetostriction, \lambda _{s} , varies from negative to positive with increasing the B composition, x$ , from 0 to 13 at. %. On the other hand, the output waveform of single-crystal Fe–B film is bathtub-like when measured along the easy magnetization axis of bcc[100], while it changes to triangular when measured along the hard magnetization axis of bcc[110]. The output waveform is strongly influenced by the magnetocrystalline anisotropy under a magnetic field of 1 kOe which is larger than the anisotropy field of the material. Variations of $\lambda _{{\mathbf {100}}}$ and $\lambda _{{\mathbf {111}}}$ values are estimated as a function of B content. $\lambda _{{\mathbf {100}}}$ of Fe–B film shows a positive value and increases with increasing the B content from 0 to 13 at. %, while the value of $\lambda _{{\mathbf {111}}} changes from negative to positive with increasing the B concentration. The B content dependence of \lambda s for poly-crystalline Fe–B samples is explained by considering the B content dependence of \lambda {\mathbf {100}} and $\lambda _{{\mathbf {111}}}$ determined with single-crystal film samples. [ABSTRACT FROM AUTHOR]

In this paper, large zero-biased magnetoelectric (ME) effects are experimentally demonstrated in a five-phase laminate composite consisting of high-permeability Fe-based soft magnetic alloy FeCoV, giant magnetostrictive material Terfenol-D, and piezoelectric ceramic Pb(Zr1−x, Tix)O3 (PZT). The coupling effects between FeCoV and Terfenol-D result in a build-in magnetic bias due to their different magnetic permeability and coercivity. As a result, an obvious increase in resonant ME voltage coefficient (MEVC) at zero dc magnetic bias field ( H\text {dc}) for FeCoV/Terfenol-D/PZT/Terfenol-D/FeCoV (FMPMF) composite is obtained. The experimental results demonstrate that the optimum zero-biased resonant MEVC ( \alpha \text {ME,r}) of FMPMF composites with three-layer FeCoV foils can reach 19.6 V/cm Oe, which is 1.75 times as great as that of traditional Terfenol-D/PZT/Terfenol-D (MPM) laminate composites. A low-frequency MEVC ( \alpha \text {ME,l}) of 176 mV/cm Oe is achieved, which is 2.45 times higher than that of the MPM laminate composites. The induced zero-biased ME voltage of FMPMF laminate composite shows an excellent linear relationship to ac magnetic field both at the low frequency (1 kHz) and the resonance frequency (115.14 kHz) over a wide range. This laminate composite shows promising applications for high-sensitivity and small-size magnetic-sensing devices without bias. [ABSTRACT FROM AUTHOR]

This paper shows that a Preisach engine, based on the classical Preisach model of hysteresis and identified using the Everett integrals and the first-order reversal curves, can be used whatever the orientation of the hysteresis loop [counterclockwise or clockwise] and whatever the monotonicity of the branches (increasing/decreasing). This is important for the use of the Preisach model in many innovative applications, such as hysteresis compensators in magnetostrictive devices and lithium-iron-phosphate rechargeable battery, as both the applications are characterized by clockwise hysteresis loops and strictly increasing loop branches. Numerical simulations of both cases, compared with experimental data, prove the validity of the approach. [ABSTRACT FROM AUTHOR]

A typical giant magnetostrictive actuator (GMA) expands a magnetostrictive rod to generate strain by varying the current in the coil that surrounds the magnetostrictive rod. The heat generated by the current deteriorates the GMA performance. In particular, a constant current in the coil is required to produce the desired magnetic field when an output strain should be maintained. The GMA does not produce any mechanical power in this condition, but constant power is being consumed by the excitation coil. This paper presents a new type of motor-driven GMA (MDGMA), which works in a coil-free driven manner. The magnetic field in the iron–gallium alloy (Galfenol), which is a type of magnetostrictive material, is periodically altered by rotating the permanent magnets instead of varying the coil current in the traditional GMA. The proposed MDGMA not only achieves continuous adjustment of the output strain, but can also maintain a constant output strain without consuming any power. In addition, the coil-free design releases the new MDGMA from the heat generated by the excitation coil, which allows the MDGMA to work more stably. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the influence of sheet thickness on abnormal grain growth and texture development in NbC-added Fe80Al20 alloys (Alfenol) that are being used as sensors. Being able to reduce sensor thickness is found to be an important for parameter for avoiding work-hardening as the sensors deflect. The alloy is rolled to form sheets with a thickness of 0.2, 0.35, and 0.5 mm, and then annealed to develop a \(\langle 100\rangle \) preferred orientation along the longitudinal direction. Whisker-like ribbons of alloy are then cut from the textured sheet with widths of 2, 4 and 6 mm and the performance of cantilevered whiskers evaluated for future use as flow sensors. The net voltage changes in the Hall sensor that converts magnetization change to electrical signal output were proportional to the applied tip force when the 0.2 and 0.35 mm thick whiskers were bent, a trend that was not observed beyond a low tip deflection in the 0.5 mm thick whisker. Of particular interest is that the 0.2 mm thick whisker shows good flexibility to withstand severe bending, whereas plastic deformation occurred in the 0.35 mm thick whisker, resulting in fatigue induced fracture/failure due to work hardening of the material after frequent severe bending. [ABSTRACT FROM AUTHOR]

Quantitative results on the magnetostatic and magnetoelastic contributions in amorphous glass-coated Fe77.5Si7.5B15 nanowires with positive magnetostriction are reported. The effects of wire dimensions on both terms have been analyzed. Calculated results have been interpreted in correlation with experimental data obtained from hysteresis loop measurements. The detailed analysis points to a single domain magnetic structure with an axial easy axis of magnetization, in which the origin of the axial magnetic anisotropy is magnetoelastic in the inner, main part of the nanowires, and magnetostatic in the thin, near-surface region. The values of the switching field are predominantly given by the magnetoelastic contribution. [ABSTRACT FROM AUTHOR]

Magnetic hysteresis of rapidly solidified amorphous glass-coated nanowires with nearly zero magnetostriction has been investigated to understand the origin of their bistable behavior. Experimental hysteresis loops and simulated ones have shown that shape anisotropy is responsible for the observed variation of the coercivity values with sample dimensions. The results of this paper provide thorough information about the main contributions to the magnetization reversal mechanism in amorphous nanowires prepared by glass-coated melt spinning. [ABSTRACT FROM AUTHOR]

Iron-Gallium alloy (Galfenol) is a magnetostrictive material ( \(\lambda _{\mathrm {sat}}\sim 400\) ppm) with potential for robust transduction. In addition, Galfenol is auxetic in the <110> direction with Poisson’s ratio values of as low as −0.7. In recent years, this phenomenon has been examined with several experimental protocols. The negative Poisson’s ratio of Fe–Ga (attributed to lattice softening under applied stresses) has been documented using tensile tests (with and without a dc magnetic bias) and resonant ultrasound spectroscopy. In addition, density functional theory has been used to produce simulations that explain atomic mechanisms for the observed highly auxetic behavior in this alloy. This paper examines the auxetic response of Galfenol to varying magnetic fields and zero applied stress. An energy based mathematical model of the coupled magnetoelastic properties of the alloy is derived and used to predict Poisson’s ratio at magnetic saturation. The results from this approach with no mechanical excitation shows an increase in the Poisson’s ratio with increase in the Ga content of the alloy. This is opposite to the trends observed with applied stresses where there is a decrease in the Poisson’s ratio with increase in the Ga content. Experimental results for Galfenol of compositions between 15 and 33 atomic percent Gallium will be presented and compared with values from the magnetoelastic model. [ABSTRACT FROM AUTHOR]

Magnetostrictive materials can play an important role in the realization of energy harvesters, a topic of growing scientific and industrial interest, because of their high-specific energy. Important applications are reported in the literature regarding Fe-Ga and rare-earth based harvester cores, but these materials are not suitable for exploiting low-energy vibrations. In this paper, we discuss the properties and behavior of a harvester based on a magnetostrictive amorphous core. It is made of a bundle of suitably strained (preloaded) Fe-based amorphous strips directly subjected to axial vibration. Using five $20~\mu $ m thick strips of width 10 mm and length 60 mm, the harvester can generate 18~\mu $ W under a vibration-generated sinusoidal stress of 2.3 MPa at 300 Hz. Such a power is equivalent to a \sim 3~\mu $ W/cm power density. We discuss the role of the physical and geometrical parameters on the performance of the harvester and provide a modeling approach successfully validating the device performance. [ABSTRACT FROM AUTHOR]

This contribution presents the concept of a novel miniature pressure sensor that can be queried wirelessly. The sensor consists of a monomorph magnetostrictive microcantilever (MSMC) and a magnetized membrane. The distance between membrane and cantilever and therefore the biasing magnetic field strength varies with the applied pressure. The advantage of the sensor is that the aimed quantity is the bending/resonance frequency, which solely depends on the biasing magnetic field strength. We report on the fabrication of a MSMC with a size of 1500 \(\mu \) m \(\times 72 \mu \) m \(\times 5 \mu \) m and we present two different methods to determine the resonance frequency of the cantilever. One approach is the so-called peak and hold method, where the resonance frequency is determined by measuring the frequency response. In the second method applied, the impulse response of the cantilever is evaluated. We demonstrate that the resonance frequency of the cantilever can be shifted in a range of up to 13% by applying a biasing magnetic dc field of 35 kA/m. In addition, the measured quality factor of the cantilever reveals the low damping. The obtained results show that the fabricated MSMC is applicable for the proposed miniature pressure sensor. [ABSTRACT FROM AUTHOR]

The magnetic energy losses and their frequency dependence are investigated in the TbDyFe/epoxy giant magnetostrictive composites. The value of total loss is extremely low in the composite which is only 3.7% of the monolithic TbDyFe alloy at high frequency of 100 kHz under the peak magnetic induction of 10 mT. With the measured loss values, fitting formulas are suggested to deeply study the contributions of hysteresis loss and eddy current loss to the total loss. The dominant loss is hysteresis loss for the composite and eddy current loss for the monolithic TbDyFe alloy. [ABSTRACT FROM AUTHOR]

This paper presents an energy harvester using a Terfenol-D/PMNT/Terfenol-D magnetoelectric (ME) transducer for scavenging ac magnetic field energy from two-wire power cords connected to household and commercial appliances. The harvester uses a magnetic circuit consisting of six NdFeB magnets mounted on the free end of a cantilever beam. The magnets produce concentrated flux gradient on the ME transducer, and the vertical Ampere forces acting on the two conductors of the power cord are superimposed. An enhanced movement is then induced on the magnetic circuit. The ME transducer undergoes magnetic field variations and generates power output. A prototype is fabricated and tested. Because of the high magnetomechanical coupling effect of the magnetostrictive material and the large flux gradient on the ME transducer, the harvester can generate a maximum power of 671.2 \(\mu \) W with a matching load resistance of 991 k \(\Omega \) at 6 A. The results demonstrate the potential of the proposed device applied to electricity end-use environment in electric power systems. [ABSTRACT FROM AUTHOR]

A new paradigm in energy-assisted magnetic recording, acoustically assisted magnetic recording (AAMR), is investigated. In this approach, a surface acoustic wave (SAW) is applied to a magnetostrictive recording medium to temporarily lower its coercivity below the write field. Akin to other energy-assisted recording technologies, AAMR provides a strategy to enable writing on high-coercivity media required for thermal stability in high-density disk drives. Using a contact recording tester, it is demonstrated that the write current needed to record data on a galfenol film is reduced in the presence of SAWs. Further, it is shown that standing and focused acoustic waves can, respectively, be used to lower the coercivity in selected regions on the medium. [ABSTRACT FROM PUBLISHER]

The magneto-mechanical coupling with deformable bodies is studied using different numerical methods for both physics. The magnetic behavior is considered linear and without magnetostrictive effects; then equations of the magneto-mechanical coupling can be solved separately. A volume integral method using the magnetic scalar potential formulation is used. This method is particularly well suited to compute fields without meshing the air domain. A local application of the virtual work principle, adapted to the integral formulation, is used to compute the nodal magnetic force distribution at the origin of the magneto-mechanical coupling with deformable bodies. An advantage of this approach is that the same mesh can be used by both methods during the resolution steps. [ABSTRACT FROM AUTHOR]

This research introduces a new, numerical and experimental approach to the analysis of the vibration of laminated structures resulting from magnetostriction. The focus is on the in-plane magnetostriction of electrical steel and its transmission into the out-of-plane direction, in which laminated structures (e.g., transformer cores, stators, and rotors) exhibit the greatest vibration. A finite-element magnetostriction model is developed on an experimental basis and enables a general, in-plane and out-of-plane assessment of the magnetostrictive response. The magnetostriction model is compatible with various finite-element structural models and is incorporated into a structural model, updated based on experimental data, representing a clamped laminated structure. An experiment employing the operating-deflection-shapes method is used to assess the presented approach under various operating conditions. [ABSTRACT FROM PUBLISHER]

This paper investigates the suitability of two-dimensional (2D) finite-element method (FEM) simulations to model the quasi-static bending-mode response of cantilever magnetoelectric (ME) sensors. We compute the deformation of the cantilever due to an applied magnetic field across the magnetostrictive (MS) layer as well as the generated voltage across the piezoelectric (PE) layer by solving a system of coupled linear elastostatic/elastodynamic and electrostatic/magnetostatic equations. In the 2D FEM formulation a plane-stress boundary condition is employed. Both 2D and 3D FEM results are compared for varying cantilever length and width. For cantilevers with \length\gg\height\gg\width good agreement is obtained between 2D and 3D results. For cantilevers obeying the condition \length\gg\width\gg\height, a systematic deviation occurs between 2D and 3D results as the plane-stress condition does not model the situation in the center of the cantilever. For a length:width:height ratio of 25:5:1, a difference in generated voltage of \sim12% is obtained for the Terfenol-D–PZT–Si material system. Especially for cantilevers with high aspect ratios, we show that 2D FEM simulations are sufficient to investigate the ME properties. [ABSTRACT FROM AUTHOR]

Electromagnetic launchers (EML) are currently limited due to rail durability. The rail operating environment consists of large electrical currents, high local temperatures, large electromagnetic loads, and high sliding velocities. The desire to maximize magnetic energy for performance and durability for economic viability are the main objectives in selecting a rail material. A systematic process, often referred to as the Ashby method is used. The three steps include translating the design requirements into objectives and constraints, screening out materials that do not meet basic performance criteria, and ranking material candidates to maximize the objectives. Gouges, grooves, and fracture were identified as the three most life limiting forms of rail damage responsible for durability. Material property tradeoff plots show that magnetic energy and durability are conflicting objectives. A hybrid rail material in the form of a monolayer structure with an electrically conductive substrate and a damage resistant surface layer is the ideal configuration for maximizing the objectives. The results suggest that a conductive substrate, such as copper, is best for maintaining performance by means of magnetic energy and a damage resistant surface material consisting of tungsten, chromium, nickel, or tantalum has the best potential for increasing rail durability. [ABSTRACT FROM PUBLISHER]

Magnetostrictive TbFe was chosen as hard layer, and the spin dynamics in the coupled bilayers Py(10 nm)/TbFe(t nm) (Py-permalloy; t=4, 7, 10, 30) were investigated by taking advantage of the engineering magnetostrictive strain under the constraints of the measurement. The dependence of the engineering magnetostrictive strain on TbFe layer thickness reflects a competitive process between the interfacial exchange interaction and the TbFe anisotropy. For the dominant interfacial exchange interaction in the coupled bilayers with 4 and 7 nm TbFe layer, coherent magnetization rotation of Py and TbFe layers is very similar to the behavior described by the Stoner–Wolfarth model. Magnetic hysteresis in the coupled bilayers with 10 nm TbFe layer and the decrease in the maximum engineering magnetostrictive strain in the coupled bilayers with 30 nm TbFe layer were observed. [ABSTRACT FROM PUBLISHER]

The performance prediction of micro-generators based on the Villari effect is a task which involved engineers and physicists in the last years. A number of approaches have been proposed, ranging from the linear one to those including non-linearity and hysteresis, up to phenomenological approaches. The present work particularly focuses on a hysteretic approach derived from a model successfully experimented for the analysis of magneto-mechanical actuators and based on the implementation of stress-dependent hysteretic model within a finite element procedure. The paper presents the validation of the proposed approach, and its effectiveness in the characterization of the generator. [ABSTRACT FROM PUBLISHER]

This paper deals with the modeling and design of magnetostrictive devices in dynamic regime. It starts from an approach which couples a physical model of the magnetostriction with a finite-element electromagnetic field analysis of the entire device. A first study, previously published by the authors and developed under the simplifying hypothesis of steady-state working conditions, is here extended to arbitrary supply conditions, including the mechanical coupling. The proposed time domain model is applied to the analysis of a prototype of magnetostrictive actuator, equipped with sensors for global and local measurements. The model has been validated with experiments and then applied to the analysis of the role of electrical and mechanical parameters. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel rotating actuator based on the interaction of a permanent magnet with a magnetostrictive soft ribbon submitted to mechanical stress. The direction and magnitude of the stress generates a directional magnetic anisotropy (easy axis) in the soft ribbon. A nonzero angle between the polarizing magnet and the induced easy axis results in a torque between the two: hence the magnet being free to rotate aligns itself with the easy axis. A demonstrator of this principle was made using a Nd–Fe–B magnet above a disk cut from an iron-based amorphous ribbon glued between two unidirectional piezoelectric actuators. The analytical model takes into account the magnetic domains and assumes a magnetization mechanism of both coherent rotation and domain-wall displacement, with a uniaxial anisotropy induced by the applied stress. [ABSTRACT FROM AUTHOR]