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An air gap Fabry–Perot fiber interferometric magnetic field sensor based on magnetostrictive effect is proposed. The sensor is composed of single mode fiber (SMF), silica capillary and magnetostrictive material, forming the Fabry–Perot cavity of "single mode fiber-air gap-single mode fiber". With the change of external magnetic field, the magnetic volume of magnetostrictive material changes, the length of gas chamber changes, resulting in the change of optical path difference. Therefore, changes in the magnetic field can be obtained by monitoring the wavelength of the reflection spectrum. Within the magnetic field range of 3.68mT-5.72mT, the magnetic field sensitivity and linearity of the sensor are 0.299 nm/mT and 0.99767, respectively. In addition, temperature changes can also affect the sensor. At 51–56 °C, its temperature sensitivity is 0.163 nm/°C, and its linearity is 0.99831. The temperature cross sensitivity coefficient of the sensor is 0.545mT/℃. This simple, low-cost, and high-performance sensor is a promising candidate for magnetic field monitoring. [ABSTRACT FROM AUTHOR]

The giant magnetostrictive transducer is a transducer device that realizes magneto-mechanical energy conversion. Each mechanical component is connected by the joint surface to realize the transmission of ultrasonic vibration energy. To ensure the efficient transmission of energy, the influence of the contact characteristics of the joint surface on the output stability of the transducer is studied. According to the contact conditions between the mechanical joint surfaces of the giant magnetostrictive ultrasonic transducer (GMUT), the key factors affecting the mechanical vibration performance of the ultrasonic system are obtained by analyzing the vibration transmission characteristics of the joint surfaces. The influence of different joint surface contact characteristics (JSCT) on the amplitude–frequency curve of the transducer is analyzed by the ANSYS software. Simulations and experiments have been conducted to verify the predicted results. As the preload force increases, the natural frequency of the transducer increases, but the growth rate decreases. The natural frequency of the double-rod GMUT with a small joint surface area is slightly higher in the optimal output mode shape, while its amplitude is significantly larger. The optimal prestress for the GMUT with different-sized joint surfaces is 3–5 MPa. This paper acquires the JSCT under a high-frequency vibration condition, reveals the influence of the joint surface on the mechanical output performance of the GMUT, and can provide a theoretical basis for the design and analysis of the rotary ultrasonic vibration processing system. [ABSTRACT FROM AUTHOR]

Accurate measurement of magnetostriction is the basis for calculating the vibration of silicon steel laminated core. In this paper, a laser magnetostriction measurement system (MST500) is used to study the magnetostriction characteristics of silicon steel under sinusoidal, third harmonic, and DC bias magnetization. The magnetostrictive butterfly curves, time domain waveforms, and spectrum diagrams of silicon steel sheets under different excitations are compared and analyzed. The effects of different operating conditions on the magnetostrictive properties of silicon steel sheets were studied and analyzed, mainly including amplitude and spectrum analysis. Finally, the magnetostrictive peak to peak curves under different operating conditions were extracted, providing a data basis for the core vibration of power equipment. [ABSTRACT FROM AUTHOR]

This paper demonstrates an optical technique to measure magnetostrictive strain in a cryogenic environment using a Fabry–Pérot resonator spaced by crystal samples. Optical measurement techniques are calibration-free and highly sensitive. This technique was used to measure the magnetostrictive strain of neodymium gallate at a temperature of 49 mK to be λ = 1.3 × 10−5 at 3 T, with a sensitivity of 3.0 × 10−8. We highlight the interesting properties of the crystal's magnetic ordering. The sensitivity of this technique was limited by the wavemeter used to measure the laser frequency, and significant improvements in the sensitivity should be possible. [ABSTRACT FROM AUTHOR]

Magnetostrictive alloys hold great promise for Energy Harvesting applications due to their inherent durability. However, their implementation often results in usable voltage ranges that fall significantly below common electronic standards like 1.6, 3.3, and 5 volts. Consequently, the utilization of electronic circuits becomes essential to amplify the voltage and enhance energy conversion efficiency. Over the past few decades, numerous conversion techniques have been devised for other intelligent materials, such as piezoelectrics, some of which have even made their way into commercial products. Surprisingly, there is a dearth of specialized techniques, if not a complete absence, tailored to magnetostrictive devices. Among potential solutions, a suitable AC–DC Boost converter stands out as a highly promising candidate for addressing this challenge, but this solution has never been fully characterized. Then, this paper presents thorough experimental validations of such a converter, driven by a real-time Arduino board equipped to measure source time periods and operate under various conditions. We present several cases demonstrating the circuit's substantial potential for enhancing energy harvesting from magnetostrictive materials. [ABSTRACT FROM AUTHOR]

With the advantages of high energy density, high accuracy, and fast response, smart material-driven electro-hydrostatic actuators (SMEHAs) have attracted significant attention in recent years. However, the low flow rate of SMEHAs constrains their application. One potential solution to enhance the flow rate is to increase the number of smart material-actuated pumps. In view of this, this paper proposes a new configuration of an electro-hydrostatic actuator equipped with four magnetostrictive-actuated pumps (FMEHA) to achieve a large flow rate. The mathematical model of the FMEHA is established to investigate the driving phase matching between pumps and the active flow distribution valve. The physical prototype of FMEHA is fabricated. Simulations and experiments are conducted to assess its performance under various driving parameters, including the number of pumps, driving phase, frequency, and amplitude. The optimal driving parameters for the FMEHA are determined based on the results obtained. Experimental findings demonstrate that with a driving phase of 340°, a frequency of 250 Hz, and an amplitude of 20 A, the FMEHA achieves a maximum flow rate of 6.2 l/min. [ABSTRACT FROM AUTHOR]

Chromium (Cr)-doped cobalt ferrite nanoparticles were synthesized using a sol–gel autocombustion method, with the chemical formula CoCrxFe2xO4. The value of x ranged from 0.00 to 0.5 in 0.1 increments. X-ray diffraction analysis confirmed the development of highly crystalline cubic spinel structures for all samples, with an average crystallite size of approximately 40 to 45 nm determined using the Scherrer equation. Pellets were prepared using a traditional ceramic method. The magnetic and magnetostrictive properties of the samples were tested using strain gauge and VSM (vibrating sample magnetometer) techniques. The results of the magnetic and magnetostrictive tests showed that the chromium-substituted cobalt ferrites exhibited higher strain derivative magnitudes than pure cobalt ferrite. These findings indicated that the introduction of chromium into the cobalt ferrite structure led to changes in the material's magnetic properties. These changes were attributed to anisotropic contributions, resulting from an increased presence of Co2+ ions at B-sites due to the chromium substitutions. In summary, this study concluded that introducing chromium into the cobalt ferrite structure caused alterations in the material's magnetic properties, which were explained by changes in the cationic arrangement within the crystal lattice. This study successfully explained these alterations using magnetization and coercivity data and the probable cationic dispersion. [ABSTRACT FROM AUTHOR]

Magnetostrictive transducer, as a kind of high-efficiency transducer, has a broad application in the field of energy harvesting and sensor. However, the voltage generating performance of the transducer limits its application. This paper will endeavor to quantify the load-induced voltage of magnetostrictive transducer by developing a holistic theoretical model and deriving the corresponding analytical solution. On this basis, this paper proposed the concept of voltage sensitivity in transducer optimization, which could quantitatively analyze the normalized voltage generated by a unit excitation. Based on the theoretical simulation and experimental validation, the voltage sensitivities of magnetostrictive transducer under different mechanical loads are investigated. The parametric analysis will be conducted to further optimize the transducer structure to enhance its open-circuit and load voltage. The works of this paper could be instructive to guide magnetostrictive transducer design in sensing and energy harvesting applications. [ABSTRACT FROM AUTHOR]

This paper presents a study of magnetoelectric (ME) properties of the PZT/Terfenol-D composite with a varying number of layers. The composite consists of piezoelectric and magnetostrictive phases that are mechanically coupled. The purpose of this setup is to gain control over the electric polarization of a material via an external magnetic field. Unlike most similar composites, our samples utilize a commercial piezoelectric patch instead of pure PZT. At present, researchers face two main problems regarding magnetoelectric materials: (i) the effect is observed far below room temperature for single-phase materials, and (ii) the ME coupling is too weak to be commercially viable. Our research was carried out via the lock-in technique on two PZT/Terfenol-D samples we synthesized. Relatively strong room-temperature magnetoelectric coupling between piezoelectric and magnetostrictive phases was observed for both samples. Two types of characteristics were investigated: (i) ME voltage versus magnetic AC field frequency, and (ii) ME voltage versus magnetic DC field. We detected multiple, grouped signal peaks ascribed to different resonance modes. Uniquely, the peaks form band-like characteristics which might be an important step in bringing the materials closer to wider commercial use. [ABSTRACT FROM AUTHOR]

For realizing ultrasonic elliptical vibration-assisted cutting, a single excitation elliptical vibration system was proposed in this work, which was composed of a giant magnetostrictive transducer and an asymmetrical stepped ultrasonic horn with arc transition (ASUH). The dynamic simulation of the vibration system was carried out using ANSYS, the output end of the vibration system produced longitudinal and transverse vibrations simultaneously due to the ASUH at the resonant frequency, and the influence of the transition arc of the ASUH on the elliptical vibration performance of the vibration system was studied. The impedance, elliptical vibration trajectory of the output end, and output amplitude of the vibration system were tested experimentally. The results show that the actual resonant frequency of the vibration system was 20.708 kHz, the mechanical quality factor was 106, and the longitudinal amplitude was slightly greater than the transverse amplitude of the output end. The theoretical calculations coincide with the experimentally tested results. [ABSTRACT FROM AUTHOR]

This paper proposes a multilevel three-dimensional constitutive model based on a microscopically phenomenological approach from the domain rotation mechanism, which is a fully coupled self-consistent homogenization scheme considering the interactions between elastic–inelastic strain and hysteresis. Considering the interactions among magnetic domains, grains, polycrystalline complexes, and macroscopic phenomenology, we predict the nonlinear magnetostrictive response of Terfenol-D under different types of external force loads and magnetic excitations in various thermal environments involving multi-fields of coupled magnetic, elastic, thermal, and mechanical phenomena. The average values of the mechanical bulk strains for different magnetization states are obtained at the grain scale utilizing Boltzmann functions and a self-consistent homogenization scheme. A Taylor series expansion of the Gibbs function concerning the field variables and an adapted Jiles–Atherton model are used to construct the hysteresis coupled constitutive relations at the macroscopic scale. The results associated with the experiments show that the established model can reasonably predict the magnetostrictive response under different external mixed stimuli. It can provide theoretical guidance for the precise control of nonlinear vibrations and the optimal design of the rotating giant magnetostrictive transducers at both microscopic and macroscopic multiple scales. [ABSTRACT FROM AUTHOR]

Economic and social development of nations across the globe is demanding enormous need for energy and power resources. Energy production using safe and renewable sources can aid in mitigating the release of greenhouse gases and avoiding the devastating climate changes. In the present case, a linear type magnetostrictive transducer device is designed by employing Terfenol-D magnetostrictive rods for renewable energy harvesting application. A linear device was designed with two Terfenol-D rods, three permanent magnets (neodymium magnets), springs, and primary and secondary coils. Terfenol-D rod crystallizes in cubic Laves phase and exhibits the saturation magnetostriction value of 1242 × 10−6 at the field of 2.5 kOe. An equivalent circuit is constructed for the induced magnetic flux in the designed transducer device. Frequency and wave form dependent output voltage is examined in the designed energy harvesting device. A square wave at the applied frequency of 2200 Hz (100 mA current) produces a maximum output voltage of 4.91 V. Sine and triangle waves produce 3.38 and 2.82 V, respectively, at 1700 and 1600 Hz. The induced voltage is sufficient to ignite the light emitting diode. A linear type magnetostrictive transducer can be employed as a potential renewable energy source for real-time application with moderate output voltage. [ABSTRACT FROM AUTHOR]

Giant magnetostrictive transducer can be widely used in active vibration control, micro-positioning mechanism, energy harvesting system, and ultrasonic machining. Hysteresis and coupling effects are present in transducer behavior. The accurate prediction of output characteristics is critical for a transducer. A dynamic characteristic model of a transducer is proposed, by providing a modeling methodology capable of characterizing the nonlinearities. To attain this objective, the output displacement, acceleration, and force are discussed, the effects of operating conditions on the performance of Terfenol-D are studied, and a magneto-mechanical model for the behavior of transducer is proposed. A prototype of the transducer is fabricated and tested to verify the proposed model. The output displacement, acceleration, and force have been theoretically and experimentally studied at different working conditions. The results show that, the displacement amplitude, acceleration amplitude, and force amplitude are about 49 μm, 1943 m/s2, and 20 N. The error between the model and experimental results are 3 μm, 57 m/s2, and 0.2 N. Calculation results and experimental results show a good agreement. [ABSTRACT FROM AUTHOR]

In recent years, ultrasonic machining has been developing rapidly, and it is used in areas such as abrasive machining, cleaning, and welding. In this research, a magnetostrictive device with pure nickel conical core with cone angle of 30° was constructed. The observed sound pressure level was used as a measure of transducer performance. Also, the ability of the device to reduce the residual pesticide on cucumber surface due to cavitation was evaluated. The results showed that the sound pressure from simulation by JMAG-Designer software is almost the same as the sound pressure produced in the constructed transducer. To assess the performance of the device in removing residual pesticide from cucumber surface and evaluate the changes in peel texture of cucumber, the gas chromatography (GC) and scanning electron microscope (SEM) methods were used, respectively. The GC results showed that with 20 min treatment, the removal of pesticide based on height and chromatogram area was 75% and 83%, respectively. The SEM results showed that by increasing the treatment time, the stomatal pore area reduced from 144.74 μ m 2 (reference) to 30.56 μ m 2 (20 min treatment). These results are promising; hence, further research is suggested towards enhancing the device for commercial use in biomaterials processing operations such as cleaning and removing pesticides from fruits and vegetables. [ABSTRACT FROM AUTHOR]

A numerical study of the delay in the excitation of oscillations of a magnetostrictive transducer in the frequency multiplication mode based on the model of coupled oscillators is presented. The non-stationary nature of the oscillations excited after the amplitude jump is revealed. The phenomenon is interpreted on the basis of the dynamic potential model. A numerical study of the development of oscillations in time has been carried out, and phase portraits of oscillations have been constructed. The fractal-like nature of non-stationary oscillations is established, which manifests itself in the preservation of the degree of their chaoticity with a change in the value of the calculation step in time. [ABSTRACT FROM AUTHOR]

The article addressed the heat exchange efficiency of an antifreeze flow, used as the working substance in a refrigeration system and filled with a magnetostrictive intermetallic alloy. A dynamic two-dimensional gradient magnetic field was employed as a propulsion source for the magnetostrictive coolant. The regulation and control of the volume flow rate of the coolant were achieved by inducing the dynamic magnetic field, which influenced the orientation and size of the scale-shaped particles dispersed within the coolant. Replacing conventional pumps with magnetic field-based propulsion systems for the circulation of antifreeze in heat-exchange systems offers a reduction in energy consumption in technological systems. [ABSTRACT FROM AUTHOR]

In this work, the mask method is applied to design a variety of topological structures in the magnetic layer. Different topological Mo/FeGa/AlN magnetoelectric (ME) devices were fabricated. Controlling the stress conduction mode between the magnetostrictive phase and the piezoelectric phase is one of the goals that enables the coexistence of normal stress and shear stress. In order to improve the ME performance of devices, the second purpose is to induce the ME anisotropy of devices through the magnetostrictive anisotropy caused by the topological structure. The circular topological Mo/FeGa/AlN devices produce the largest ME coupling coefficient along the length direction (7071 mV/cm Oe), which is 1.84 times higher than that of the planar devices (3853 mV/cm Oe). The maximum ME anisotropy coefficient (4.612) is determined from the strip topology ME device, which is 2.45 times higher than that of the planar device. [ABSTRACT FROM AUTHOR]

This paper presents a computationally efficient constitutive model for magnetostrictive materials. High computational efficiency is achieved through the use of local linearization (about easy axes) and discrete energy-averaging techniques. The model is applied to iron-gallium alloys (Galfenol) and tested for different magnetic field orientations relative to the easy axes. It is observed that the model accurately predicts both sensing and actuation characteristics while reducing the computation time by a large factor (> 1000 times) when compared to the nonlinear energy minimization models. Furthermore, the average error observed in λ – H and B – H curves is less than 3.5% with the error increasing at magnetic field orientations farther from easy axes, particularly at large magnetic field values. Finally, the model is integrated with a finite element framework to predict the response of a Galfenol rod transducer system, and parametric studies are performed for different current and prestress conditions to optimize the device performance. [ABSTRACT FROM AUTHOR]

A two-dimensional constitutive model based on micromechanical domain rotation events is presented in this work to demonstrate the nonlinear actuator behavior of magnetostrictive materials, in particular, Galfenol. The model constructed upon thermodynamic principles accounts back fields which resist or aid the domain rotation events inside a grain due to external magnetomechanical loading. The developed model is then incorporated into the polygonal finite element technique that combines Voronoi-based discretization with the hybrid finite element method. In this approach, the stress and magnetic flux density are treated as approximate functions inside the element, but the mechanical displacement and magnetic potential, which act as degrees of freedom, are defined only along the element boundary. This approach allows each randomly generated Voronoi polygon in the plane discretization to act as a single finite element mimicking an individual magnetomechanical grain in a polycrystalline Galfenol, eliminating the need for further subdiscretization of the Voronoi polygon. This coupled framework simulates the nonlinear actuator characteristics of the magnetostrictive material under complex magnetomechanical loading conditions in line with the experimental observations reported in the literature. [ABSTRACT FROM AUTHOR]

The effect of crystal orientation and grain alignment on the properties of magnetostrictive materials was investigated in TbFe2 alloys prepared via solidification under different high magnetic field conditions. The magnetostrictive property and magnetization behavior of the alloys were studied. The results revealed that the alloys that are oriented along the easy magnetization axis exhibit better magnetostrictive property in the low-field intensity region (than in the high-field intensity region). However, in the high-field intensity region, regular alignment of grains in the magnetization direction is essential for continued improvement in the magnetostrictive property of the alloys. If the magnetic phases of the TbFe2 alloy are oriented along the easy magnetization axis and the grains of the magnetic phases are aligned regularly along the direction of magnetization, the alloy will exhibit excellent magnetostriction property. This study may serve as a reference for the preparation of high performance rare-earth iron-based magnetostrictive materials. [ABSTRACT FROM AUTHOR]

A characteristic modulation of the magnetic domain structure on the (001) plane of an Fe–12.8 at. % Ga alloy single crystal under tensile stress was observed by magneto-optic Kerr effect microscopy. The magnetic domain structure under zero applied stress was composed of magnetic domains with magnetizations in four types of <100> magnetic easy directions on the (001) plane, which were separated by straight 90° domain walls and stair-like 180° domain walls. When a tensile stress of 11.4 MPa was applied parallel to the [010] direction, these 90° domain walls disappeared to release the tensile stress. A stripe domain structure that was composed of straight 180° domain walls parallel to the tensile stress direction was thus formed by the inverse magnetostrictive effect. Young's modulus of the alloy below the applied 11.4 MPa tensile stress was estimated to be 32 GPa, which is 57% smaller than the corresponding value above that tensile stress value. Consequently, a significant reduction in Young's modulus is caused by the characteristic modulation of the magnetic domain structure that occurs as a result of the inverse magnetostrictive effect. [ABSTRACT FROM AUTHOR]

Preparing Fe–Ga sheets with excellent magnetostrictive coefficients by rolling and annealing methods can greatly promote the development of high-efficiency magnetostrictive devices. 0.3 mm thick Fe–Ga thin sheet was produced by the one-stage large-reduction cold rolling method without intermediate annealing. Trace V and Nb elements addition improves the rolling formability of the Fe–Ga sheet by precipitating a large number of (Nb,V)C particles. The evolution of precipitation, microstructure, texture, and magnetostrictive coefficients in the Fe–Ga sheet was investigated. The microstructure of primary recrystallization is composed of homogenous distribution of fine grains with an average grain size of about 22 μm. The composite inhibitors composed of MnS and (Nb,V)C precipitates with a particle size of 40∼80 nm suppress the matrix grains effectively. The primary recrystallization texture consists of a strong γ texture with a peak at {111}<112> and a relatively strong {114}<481> texture. The secondary recrystallization of Goss grain occurs at the annealing temperature of 900 °C and is completed at 1100 °C by the combined effects of the existing inhibitor and texture. The Fe–Ga thin sheets composed of several millimeter-sized grains of Goss texture accompanied by small grains oriented by {114}<481> were obtained after annealing at 1100 °C, and its measured magnetostriction value is about 238 ppm. The present work proposes a promising routine to produce high-performance Fe–Ga thin sheets. [ABSTRACT FROM AUTHOR]

Magnetostrictive alloys are very promising for Vibration Energy Harvesting applications to supply power to Wireless Sensor Network (WSN) and Internet of Things (IoT) devices, especially because of their intrinsic robustness. Typically, vibration energy sources are random in nature, usually providing exploitable voltages much lower than the electronic standards 1.6, 3.3 and 5 V. Therefore, a Power Electronic Interface (PEI) is needed to improve the conversion to DC output voltage from AC input over a wide range of frequencies and amplitudes. Very few or no conversion techniques are available for magnetostrictive devices, although several have been presented over the years for other smart materials, such as piezoelectrics. For example, hybrid buck–boost converters for piezoelectrics use one or more external inductors with a high-frequency switching technique. However, because of the intrinsic nature of harvesters based on magnetostrictive materials, such energy conversion techniques are proved to be neither efficient nor applicable. An improved AC–DC boost converter seems very promising for our purpose instead. The key feature is represented by the direct exploitation of the active harvester coil as a storage element of the boost circuit, without using other passive inductors as in other switching methods. Experimental tests of such a converter, driven with a real-time operating Arduino controller to detect the polarity of the input voltage, are presented with the aim to assess the potentiality of the scheme with both sinusoidal and impulse-like inputs. Simulations have been performed with LTspice, and the performance and efficiency have been compared with other energy conversion techniques. [ABSTRACT FROM AUTHOR]

The applications of sensors in the aerospace industry are mostly concentrated in the middle and high frequencies, and low-frequency sensors often face the problems of low power and short working bandwidth. A lightweight, thin, high-power, low-frequency broadband transducer based on giant magnetostrictive material is designed. The design and optimization processes of the core components are introduced and analyzed emphatically. The finite element simulation results are validated by the PSV-100 laser vibration meter. Three basic configurations of the work panel are proposed, and the optimal configuration is determined by modal, acoustic, and vibration coupling analyses. Compared with the original configuration, it is found that the lowest resonant frequency of the optimal configuration is reduced by 24.6% and the highest resonant frequency within 2000 Hz is 1744.9 Hz, which is 54.2% higher than that of the original configuration. This greatly improves the vibration power and operating frequency range of the transducer. Then, the honeycomb structure is innovatively applied to the work panel, and it is verified that the honeycomb structure has a great effect on the vibration performance of the work panel. By optimizing the size of the honeycomb structure, it is determined that the honeycomb structure can improve the vibration power of the work panel to its maximum value when the distance between the half-opposite sides of the hexagon is H = 3.5 mm. It can reduce the resonant frequency of the work panel; the lowest resonant frequency is reduced by 12.8%. At the same time, the application of a honeycomb panel structure can reduce the weight of the transducer. [ABSTRACT FROM AUTHOR]

The giant magnetostrictive transducer (GMT) can be widely used in ultra-precision machining in precision-fluid-control fields. The temperature stability of GMT is critical for the reliable generation of output characteristics. This study presents a magnetic-energy-losses method for the GMT working at high frequency, and designs a temperature-stable control system to improve energy transmission and heat dissipation. Based on the loss-separation theory and experimental data, the temperature-rise characteristics of the transducer are analyzed. The temperature rise considers the effects of hysteresis loss, the eddy-current loss, the anomalous loss and the Joule heat. A constitutive relation among losses, frequency and magnetic-flux density is given. The temperature distribution of the transducer can be quickly and accurately calculated, using the constitutive equation. According to the convective heat-transfer and the thermal-compensation method, a temperature-control system is designed. A prototype of the system is then fabricated and tested to verify the feasibility and efficacy of the proposed design methods. The results demonstrate that the output- displacement deviation can be controlled at less than 0.65 μm, and the temperature difference is less than 3 °C. [ABSTRACT FROM AUTHOR]

The vibration characteristics of a giant magnetostrictive transducer play a significant role in the stability and processing effect of spinning ultrasonic machining. The output characterization of the giant magnetostrictive transducer is unstable subject to an powerful external load, which severely restricts the application of giant magnetostrictive transducer in industry. In this study, the effect of change of load force and electrical parameter in the different directions on the high-frequency (about 20 kHz) vibration output characteristics of the giant magnetostrictive transducer is investigated, through finite element analysis and static loading experimental. The result shows that the electrical parameter of a giant magnetostrictive transducer has a similar changing trend with the increasing of the axis and radial force load; The resonant frequency also increases with the increase of electrical parameter and load force; The amplitude attenuation of ultrasonic vibration will become extraordinary intense even almost to stop beat when the axis force load increase to 750 N and radial force load increase to 550 N; The gradient of resonant frequency in a radial direction is more significant than that in an axial direction. Based on the results of theoretical analysis and static loading experimental, the measures to reduce amplitude attenuation and improve output stability of amplitude under resonant frequency are proposed. The results can provide theoretical guidance for a magnetostrictive transducer used in the actual spinning ultrasonic vibration processings. [ABSTRACT FROM AUTHOR]

We studied the depth dependent magnetization profile of the magnetostrictive Co thin film layer in a (PbMg0.33Nb0.67)1-x:(PbTiO3)x (PMN-PT) (011)/Ta/Co/Ta structure under both zero and nonzero applied electric field using polarized neutron reflectometry. Application of an electric field across the PMN-PT substrate generates a strain, which rotates the magnetization of the Co layer consistent with the Villari effect. At low magnetic fields (near remanence and coercive field conditions), we find that the depth dependent magnetization profile is non-uniform, under both zero and nonzero applied electric fields. These variations are attributable to the depth dependent strain profile in the Co film, as determined by finite element analysis simulations. [ABSTRACT FROM AUTHOR]

Due to high piezomagnetic coefficient of the synthetic giant magnetostrictive materials, they are able to provide good enough force and displacements for industrial applications. Some natural materials such as nickel also exhibit magnetostrictive properties, but with poor performance, which might be improved by some electromagnetic manipulations. In this study, the effect of different coil parameters such as current, frequency, the number of coil turn, and the core lamination factor in different directions ([X or Y] and Z axes), on the performance of a nickel‐core magnetostrictive transducer is investigated. Since the fluctuation of magnetostrictive force in the longitudinal direction of core (along the Z‐axis) is an important parameter for generating the ultrasonic waves, the results showed that this force fluctuation decreases with increasing frequency. By increasing the lamination factor in the X direction, the fluctuation of magnetostrictive force along the Z‐axis remains constant. However, the ultrasonic performance of the magnetostrictive transducer may be optimized by proper selection of lamination factor along the X‐axis. The relationships between the results were investigated in more detail and presented as linear equations. Based on these equations, it was concluded that current and turn number of coil has the greatest positive impact on the magnetostrictive performance of the transducer, while increasing the frequency and lamination factor have a weakening effect. [ABSTRACT FROM AUTHOR]

Vibration energy harvesting is a new alternative to lithium battery power for low-power devices, attempting to recover wasted or lost vibration energy to generate electricity. Magnetostrictive-based energy harvesting exploits the coupling properties of the Villari and Faraday electromagnetic induction effects to achieve mechanical–magnetic–electric energy conversion. In order to better apply to the actual vibration environment, such as buses, and improve the ability to capture low-frequency vibration energy, a double-stage rhombus vibration energy harvesting device, based on Terfenol-D rods, was developed. By establishing an analytical model of the force amplification ratio of the harvesting device, the design is optimized using the Single-Objective Genetic Algorithm, and the safety and pre-magnetization layout methods are analyzed by Finite Element Analysis. The output characteristics of the prototype, including the output voltage frequency response under low-frequency regular excitation and random excitation, the effect of external resistance, and the vibration energy capture performance under random excitation, are investigated in detail through experiments. The results of the experiments showed that the peak output power of the fabricated prototype was 1.056 mW at 30 Hz operating frequency, the energy harvesting capability reached 41.4 μW/N, and the peak open circuit voltage and output power were 2.92 V and 266 mW, respectively, under random excitation. Practical application test results showed that the peak voltage generated was 1.06–1.51 V when the excitation level was 2.2–4.9 m/s2. The comparative study indicates that the output performance of the proposed double-stage rhombus magnetostrictive vibration energy harvesting system is a great improvement over the proposals of existing literature. [ABSTRACT FROM AUTHOR]

At present, the research of electronically controlled injectors is mostly limited to the non-direct drive structure. Although the research on the direct drive structure is involved, it mostly stays in the conceptual machine or simulation stage. In this paper, based on the direct-drive structure, the giant magnetostrictive material is used as the energy conversion material, the prototype of the direct-drive giant magnetostrictive fuel injector is designed and manufactured, and the experimental test system and AMESim simulation model are built. By means of experiment and simulation, the injection characteristics of Giant magnetostrictive injector (GMI) are tested. It is found that the minimum single injection quantity of GMI is 5.9 mm3 under the condition of 30 MPa rail pressure, which shows high injection accuracy. The experimental results are in good agreement with the simulation results under different driving pulse widths and voltages. When the driving pulse width is not less than 650 µs, the relative errors are all less than 5%, which verifies the effectiveness of the simulation model. The injection performance of GMI is analyzed. The results show that this injector has a stable injection performance, fast response speed (the shortest injection pulse width is about 200 µs), and the injection process can be completed five times in 5 ms. [ABSTRACT FROM AUTHOR]

A novel alternating current (AC) magnetic field sensor that has a stable operating point and is insensitive to ambient temperature fluctuations is presented. The sensor is based on a high attenuation fiber Bragg grating (HAFBG) attached to a magnetostrictive rod. A stable operating point is achieved by regulating a heating laser based on a feedback algorithm that compensates the temperature fluctuations of the surrounding environment. Experimental results show that the sensor responds well to dynamic magnetic fields and is able to ensure a stable operating point in the range of at least 15 °C in an ambient temperature disturbance test. The ease of fabrication and excellent performance suggest that the proposed fiber sensor is suitable for practical AC magnetic field sensing applications, such as health monitoring of transformers and fault diagnosis of induction motors. [ABSTRACT FROM AUTHOR]

We report on the enhanced magnetostrictive properties of nanocrystalline Dysprosium (Dy3+) substituted iron-rich cobalt ferrites (Co0.8Fe(2.2-x)DyxO4, referred to as CFDO). The CFDO samples with a variable Dy concentration (x = 0.000–0.075) were synthesized by the sol-gel auto-combustion method. The phase purity and crystal structure were confirmed from X-ray diffraction analyses coupled with Rietveld refinement. Surface morphology analysis using scanning electron microscopy imaging indicates the agglomerated magnetic particles with a non-uniform particle size distribution, which is desirable to transfer the strain. The magnetostriction coefficient (λ11) measurements indicate that the CFDO with Dy concentration x = 0.025 exhibits the highest strain sensitivity, (dλ/dH) ∼1.432 nm/A (for H ≤ 1000 Oe). On the other hand, the magnetostriction coefficient (λ12) measurements indicate that the Dy concentration x = 0.075 exhibits the larger (dλ/dH) ∼ 0.615 nm/A (for H ≤ 1000 Oe). The maximum λ11value of 166 ppm (at H = 3300 Oe) was observed for a compound with Dy concentration x = 0.050. Magnetization measurements indicate that the saturation magnetization and coercivity of CFDO samples are dependent on the Dy3+content; the highest value of squareness ratio of 0.424 was observed for x = 0.050. The interplay between strain sensitivity (dλ/dH) and instantaneous susceptibility (dM/dH), as derived from magnetostriction and magnetization results, demonstrates that these CFDO materials may be useful for developing torque/stress sensors, as a constituent magnetostrictive phase for making the magnetoelectric composite materials and thus suitable for magnetoelectric sensor applications. [ABSTRACT FROM AUTHOR]

This paper reports the effect of the film thickness on the magnetostrictive behavior of (Fe,Co) rich Tb-(Fe,Co) films grown on Si <100> by electron beam evaporation. Magnetostriction was found to decrease with an increase in film thicknesses. To understand the variation of magnetostriction with the film thickness, detailed structural, microstructural, magnetization, and magnetic microscopy studies were carried out. X-ray diffraction studies indicated the presence of two phases, viz., Tb2 (Fe, Co)17 and Fe-Co phases, for all the films. With the increase in the film thickness, the peak intensity of the Tb2 (Fe, Co)17 phase decreased and that of the Fe-Co phase increased. Magnetization studies showed the presence of strong in-plane anisotropy for all the films. In addition to this, the presence of the out-of-plane component of magnetization was also observed for the films grown with higher thicknesses. This anisotropic behavior was also validated through magnetic microscopy studies carried out along the in-plane and out-of-plane directions employing magneto-optic Kerr microscopy and magnetic force microscopy, respectively. The decrease in magnetostriction was explained on the basis of dual phase formation and complex interplay between the in-plane and out-of-plane magnetic anisotropies present in the film. [ABSTRACT FROM AUTHOR]

Lead-free multiferroic ceramics consisting of (1-x) 80Bi0.5Na0.5TiO3-20Bi0.5K0.5TiO3 (BNTBKT)-xNi0.8Zn0.2Fe2O4 (NZFO) (x=0, 0.15, 0.25, 0.35, and 0.45) were synthesized by the in situ sol-gel method. The structural, ferroelectric, piezoelectric, ferromagnetic, and magnetoelectric (ME) properties were measured as a function of the NZFO content x. The results showed that the coexistence of BNT-BKT and NZFO phases and the presence of the morphotropic phase boundary in the BNT-BKT phase with a high piezoelectric coefficient d33 (~131 pC/N) were confirmed. The composites exhibited a homogeneous microstructure and well-combined interfaces between the magnetostrictive and piezoelectric phases, as well as an improved ME response. The largest ME voltage coefficient (αME) of 42.41 mV/cm Oe was achieved for the 0.65(BNT-BKT)-0.35NZFO composite, which is in fact the highest one reported so far for lead-free particulate ME composites fabricated via in situ processing. [ABSTRACT FROM AUTHOR]

In this work, a sensitive tool to detect magnetic nanoparticles (Fe3O4) based on a non-linear Giant Magnetoimpedance (GMI) effect is presented. The GMI sensor is designed with four nearly zero magnetostrictive ribbons connected in series and was analysed as a function of a constant external magnetic field and exciting frequency. The influence of the magnetic nanoparticles deposited on the ribbon surface was characterized using the first (fundamental) and second (non-linear) harmonics of the magnetoinductive voltage. The results show a clear enhancement of the sensor response in the high magnetic field region (H=1.5 kA/m) as a consequence of the stray field generated by the magnetic nanoparticles on the GMI ribbons' surface. The highest sensitivity ratios are obtained for the non-linear component in comparison with the fundamental response. The results open a new research strategy in magnetic nanoparticle detection. [ABSTRACT FROM AUTHOR]

A multiferroic magnetic field sensor capable of producing an output for threshold magnetic fields has been fabricated and characterized. The sensor consists of a trilayer composite of piezoelectric X-cut lanthanum gallium tantalate and magnetostrictive Metglas placed inside a solenoid and a wide-band amplifier. The composite plays two distinct roles in the device; it forms the feedback loop of an oscillator and sets the frequency of sustained oscillations. The sensor generated an output of 2.5V at the longitudinal acoustic resonance frequency of 87.5 kHz for the trilayer for DC magnetic fields H=0.3 to 50 Oe parallel to the composite plane. The device functions as a threshold magnetic field sensor for this H-interval, and the threshold ON and OFF H-values for an ac voltage output could be controlled electronically or with a proper choice of the ferromagnetic phase in the composite. [ABSTRACT FROM AUTHOR]

Comparative studies have been made to understand the role of different crystallographic site preferences of the substituted non-magnetic divalent metal ions in the magnetostrictive properties of cobalt ferrite, by substitution of Zn2+ and/or Mg2+ for Fe3+ in CoMgxFe2-xO4, CoZnxFe2-xO4, and CoMgx/2Znx/2Fe2-xO4 (0.0≤x≤0.2). Detailed Raman spectral and magnetic characterizations are made to extract the information on the tetrahedral/octahedral site preferences of Zn and Mg in the spinel lattice of cobalt ferrite. The structural, microstructural, magnetic, Raman spectral, and magnetostrictive parameters of the studied compositions show distinguishable variations for x<0.1 and x ≥0.1. Co-substitution of a small amount of Mg and Zn for Fe in CoMgx/2Znx/2Fe2-xO4 (x < 0.1) showed relatively larger strain sensitivity, [dk/dH]max (-2.6 ×10-9mA-1 for x=0.05), higher than that for the Mg-substituted samples (-2.05 × 10-9mA-1 for x=0.05) and comparable to that for the Zn-substituted samples (-2.47 × 10-9mA-1 for x=0.05), without much drop in the maximum value of magnetostriction, kmax (-189 ppm for x=0.05) compared to that for the unsubstituted counterpart (-221 ppm). The results show that it is possible to obtain high strain sensitivity (at fields <50 kA/m), along with high magnetostriction strain at low magnetic fields (∼250 kA/m), by tuning the distribution of the substituted cations in the tetrahedral and octahedral sites of the cobalt ferrite lattice. [ABSTRACT FROM AUTHOR]

This article presents a design method of Longitudinal-Bending Coupled Horn (L-BCH) of a giant magnetostrictive transducer utilized in spinning ultrasonic machining. The structural parameters are initially determined by the design theory of the horn and thick disc. Then, the effect of the structural parameters of the rotating wheel on the vibration characteristics of the L-BCH are explored by the model and harmonic response analysis through the finite element method. Through continuous modification of the geometrical parameters of the rotary wheel, the L-BCH meeting the requirements of a giant magnetostrictive transducer is designed. Finally, the frequency and amplitude measurements are performed on the prototype by the impedance analyzer and the laser vibrometer. The finite element analysis and experimental results show that: the large diameter, small diameter, thickness, and fillet radius of the rotating wheel have different impacts on the dynamic characteristics of the L-BCH. Among them, the thickness of the rotary wheel has the most significant influence on the natural frequency and amplitude. In addition, the rotating wheel has a pitch circle when the longitudinal-bending coupled vibration occurs, and the structure itself also has the characteristic of amplifying amplitude. [ABSTRACT FROM AUTHOR]

We study steady-state three bipartite entanglements in a cavity magnomechanical system which is composed of magnon, two cavities, and mechanical resonator. The two cavities are connected by an optical fiber, one of cavities couples to the magnon via the magnetic dipole interaction, at the same time, the magnon couples to the mechanical resonator via magnetostrictive interaction. Making use of logarithmic negativity, magnon, cavity, and mechanical resonator are entangled with each other by selecting appropriately the parameter. We find that the steady-state entanglements in the magnon–mechanical resonator subsystem and in the magnon–cavity subsystem are very sensitive to the effective magnomechanical coupling strength. Moreover, the entanglement is robust with respect to the certain environment temperature. [ABSTRACT FROM AUTHOR]

Studies have substantiated that the vibration and noise produced by the iron core of an electromagnetic device are closely related to the magnetostriction of the iron core silicon steel sheet. Moreover, when the induction motor works under the condition of frequency conversion, the symmetry of the core silicon steel sheet will change, and the distribution of the vibration and noise field of the motor will be asymmetric, which will aggravate the vibration and noise. This paper completes the experimental measurement and analysis of the electromagnetic characteristics and magnetostrictive characteristics of silicon steel sheets. The magnetic field of a 1140 V/75 kW variable-frequency motor is calculated analytically based on the analytical method, and the stator/rotor magnetic induction intensity and permeance are calculated separately to obtain the air gap magnetic density and the radial electromagnetic force. The vibration and noise of the 1140 V/75 kW variable-frequency motor are analyzed by the finite element method, while the magnetization curve and magnetostrictive characteristic curve of a silicon steel sheet under different conditions are considered. An experimental platform is built to measure and analyze the vibration displacement and acceleration of the variable frequency motor, which verifies the correctness of the proposed scheme. Considering the influence of the magnetostrictive effect will make the result of calculating the vibration and noise of variable-frequency motors more accurate. [ABSTRACT FROM AUTHOR]

Electric field control of magnetism (EFCM) at low voltage (≤5 V) and high temperature (≥353 K) is crucial to micro-integrated magnetoelectric devices. In this work, the BaFe10.2Sc1.8O19 (BFSO)/BaTiO3(BTO) bilayer epitaxial thin films are fabricated. Results show that compared to the single BFSO film, there are significant increases in magnetic susceptibility, multiferroic transition temperature (Tcone), and EFCM in BFSO/BTO bilayer films. The room temperature magnetoelectric coupling coefficient in BFSO (80 nm)/BTO (300 nm) bilayer films (189.6 ns/m) is 14.7 times higher than that in the single layer BFSO film and 345 times larger than single crystalline BiFeO3. A change in magnetization Δ M % about 38% at 20 K and 7.1% at 390 K is obtained in the BFSO (80 nm)/BTO (300 nm) bilayer film. Moreover, repeatable low voltage (≤4 V) EFCM with a high signal-to-noise ratio in the BFSO/BTO bilayer film device is verified at temperatures ranging from 20 K to above 390 K. This high temperature EFCM is mainly contributed by the high Tcone of BFSO and strong piezoelectric/magnetostrictive coupling at the BFSO/BTO interface. The above findings enable the potential usage and integration of BFSO/BTO bilayer films into micro-integrated microwave devices. [ABSTRACT FROM AUTHOR]

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 comprehensive model is a basis for adequately understanding the energy conversion mechanism of magnetostrictive materials and guides the design of magnetostrictive devices. This paper established a fully coupled model that fully considered the piezomagnetic effect and the electromagnetic effect in its procedure of energy conversion. The proposed model can accurately predict the output voltage with different excitation levels and illustrate the interaction between physical fields. Based on the established model, we quantify the voltage contributed by the piezomagnetic effect and the electromagnetic effect. After a thorough analysis, we discovered that even though the voltage generation is always dominated by the piezomagnetic effect of the magnetostrictive material, the proportion from the electromagnetic effect will increase moderately with larger excitation levels. In addition, the magnetostrictive effect toward the output performance is also discussed, which proved to lead to a marginal impact on the voltage waveform. [ABSTRACT FROM AUTHOR]

The performance of vibration power generation using the inverse magnetostrictive effect increases with increasing its device size. In this study, grain-oriented electrical steel that can be largely produced was investigated as a core material, using a U-shaped unimorph device at a laboratory scale. The device using a grain-oriented electrical steel core (16mm long with a 1.4mm² cross-section) with the rolling direction (RD) along the stress direction exhibited the effective open-circuit voltage of 0.89V under an optimum bias magnetic field, when the free-end of the device was vibrated with a maximum amplitude of 2.0mm at a mechanical resonance frequency of 108 Hz. In addition, an average output power of 300µW was obtained by adjusting the load resistance. The above-mentioned properties of the RD unimorph core device were superior to those of the transverse direction (TD) unimorph core device, because the magnetic flux density change in the RD core was approximately 0.65 T, which was larger than that in the TD core. Therefore, grain-oriented electrical steel with the RD direction is a useful core material for developing large-sized devices with high performance. [ABSTRACT FROM AUTHOR]

Objective: The aim of this paper was to identify the appropriate power setting and operation time required to achieve optimal efficiency in calculus debridement while preventing excessive cementum loss. Method and Materials: The study included 30 extracted molars with heavy deposits of calculus, visible to the the naked eye. Experimental areas (3x4 mm) were delineated below the cementoenamel junction. The teeth were cut cross-sectionally and randomly allocated into three groups: low, medium, and high power settings. A magnetostrictive ultrasonic scaler with Dentsply slimline plain insert was used with light force at 0-degree tip angulation for a 10 second interval. Before and after treatment, the samples were visualized using digital stereo microscopy at 100X magnification. Results: Mean time required for dental calculus removal was 70,50, and 30 seconds for low, medium, and high power settings, respectively. Root calculus removal rates for low, medium, and high power settings were 4.5, 6.7, and 8.2 µm/s, respectively (P = .0045, P < .01). Mean time required for dental cementum removal was 30, 30, and 20 seconds for low, medium, and high power settings, respectively. Cementum removal rates for low, medium, and high power settings were 1.7, 2.2, and 3.3 µm/s, respectively (P = .0127, P<.05). Conclusion: The most efficient dental calculus removal occurred within the first 30 seconds using a high power setting with light force at 0-degree tip angulation, which was recommended for roots with heavy calculus. Later on, to minimize cementum loss, the low power setting should be used for less than 30 seconds to balance between rapid calculus removal and a potential risk of cementum loss resulting in dental sensitivity. Ultrasonic scaling using the high power setting in the first 30 seconds, followed by continuous scaling for less than 30 seconds, using the low power setting, is recommended for roots with heavy calculus. [ABSTRACT FROM AUTHOR]

This article introduces a new method to realize the 180° magnetic moment reversal of a ferromagnetic and ferroelectric heterostructure through electrostriction-induced magnetic anisotropy. A rectangular magnetic FeAl alloy island with a large magnetostrictive coefficient on a PZN (011) substrate was adopted in our investigation through micromagnetic simulation. Using electrostriction along the [11-1] and [1-11] directions, the magnetic moment was rotated from the long axis of the rectangular island to the direction of the strain and finally reversed to the opposite direction despite the strain sequence. The magnetic moment can be oriented to a certain direction through a certain sequence of strain if a several hundred Oe magnetic field is applied along the short axis of the island. The suitable stress-induced magnetic anisotropy energy and external magnetic field were also investigated. In consideration that a high magnetic field along the short axis leads to small thermal stability of the magnetic moment, the suitable value of stress-induced anisotropy energy is around the critical value where the stress can reverse the magnetic moment without a magnetic field. We compared the stress-induced magnetic reversal processes for same-sized semicircular, elliptical, and rectangular islands and found that the semicircular island can be more easily reversed. [ABSTRACT FROM AUTHOR]

The direct nonlinear magnetoelectric (ME) effect and the magnetostriction of piezoelectric CsCuCl3 single crystals were comprehensively studied over a wide temperature range in stationary magnetic fields of up to 14 T. The direct nonlinear ME effect measurements were also performed in pulsed magnetic fields up to 31 T, at liquid helium temperature in the antiferromagnetic (AF) state for the crystallographic direction in which effect has the maximum value. The nonlinear ME effect was quadratic in the paramagnetic state for the whole range of magnetic fields. In the AF state the phase transition between different configurations of spins manifested itself as plateau-like peculiarity on the nonlinear ME effect. The nonlinear ME effect was saturated by the phase transition to the spin-saturated paramagnetic state. Two contributions to the nonlinear ME effects in CsCuCl3 were extracted from the experimental data: the intrinsic ME effect originated from the magnetoelectric interactions, and the extrinsic one, which resulted from a magnetostriction-induced piezoelectric effect. [ABSTRACT FROM AUTHOR]

Magnetostrictive behavior is characterized by a complex coupling between magnetic and mechanical quantities. While this behavior can be quite easily exploited for both actuation and sensing or energy conversion purposes, the complex hysteresis interaction between magnetization and magnetic field and mechanical stress and strain is hard to model. Nevertheless, magnetic and magnetostrictive experimental curves are quite self-similar, assuming stress as self-similarity parameter. The quantification of this concept would help modeling. Here, this concept is quantified and experimentally confirmed over different types of magnetostrictive samples. [ABSTRACT FROM AUTHOR]

A theoretical model quantifying the effect of temperature variations on the magnetic properties and static and dynamic behavior of the straintronics magnetic tunneling junction is presented. Four common magnetostrictive materials (Nickel, Cobalt, Terfenol-D, and Galfenol) are analyzed to determine their temperature sensitivity and to provide a comprehensive database for different applications. The variations of magnetic anisotropies are studied in detail for temperature levels up to the Curie temperature. The energy barrier of the free layer and the critical voltage required for flipping the magnetization vector are inspected as important metrics that dominate the energy requirements and noise immunity when the device is incorporated into large systems. To study the dynamic thermal noise, the effect of the Langevin thermal field on the free layer's magnetization vector is incorporated into the Landau-Lifshitz-Gilbert equation. The switching energy, flipping delay, write, and hold error probabilities are studied, which are important metrics for nonvolatile memories, an important application of the straintronics magnetic tunneling junctions. [ABSTRACT FROM AUTHOR]

A positive magnetostrictive single layer (CoFe) and top-pinned spin-valve structure with positive magnetostrictive free (NiFe) and pinned (CoFe) layers were deposited on flexible polyethylene terephthalate film to investigate the changes in the magnetic properties in flexible environments, especially with a repetitive bending process. It was found that the stress, applied by repetitive bending, changes significantly the magnetic anisotropy of both layers in a single and spin-valve structure depending on the direction of applied stress. The changes in magnetic anisotropy were understood in terms of the inverse magnetostriction effect (the Villari effect) and the elastic recovery force from the flexibility of the polymer substrate. Repetitive bending with tensile stress transverse (or parallel) to the magnetic easy axis was found to enhance (or reduce) the magnetic anisotropy and, consequently, the magnetoresistance ratio of a spin-valve. The observed effects of bending stress in this study should be considered for the practical applications of electro-magnetic devices, especially magneto-striction sensor. [ABSTRACT FROM AUTHOR]