Fig 1 - uploaded by Takahiro Yamazaki
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Fe-Co phase diagram. The red line shows a morphotropic phase boundary (MPB) in Fe-Co alloy system. The (bcc-Fe+fcc-Co)/bcc-Fe interface is a MPB at temperature of around 800 o C of Fe100-xCox (x = 70 mol%) alloys.
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The use of inverse magnetostriction effect is a possible approach for the applications of actuator, sensor and energy harvester. A strong textured Fe100-xCox (x = 70 mol%) magnetostrictive alloys have been studies as a new smart material. The design of microstructure plays important roles in performance enhancement of power generation by heat-treat...
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... (x = 70 mol%) wires having a diameter of 1 mm as specimens were used in this study. For investigating the microstructure dependence of magnetic and magnetostrictive characteristics, several heat treatments were performed with the reference of Fe-Co phase diagram as shown in Fig. 1. Annealing at 420 o C for 24 hours and furnace cooling (hereinafter, 420 o C-FC) were conducted for removing residual stress and internal strain. Also, annealing at 750 o C, 780 o C, 800 o C, 820 o C and 850?C for 5 hours and water quenching (WQ) were conducted for modifying the coarsened microstructures and freezing a coexistence of two phase, which is the (bcc-Fe+fcc-Co)/bcc-Fe interface as a morphotropic phase boundary (MPB). Each heat-treatment was conducted in vacuum-sealed quartz tube with Ar. These wires were cut into a predetermined length as follows, Microstructural observation: 30 mm, X-ray diffraction measurement: 30 mm, VSM measurement: 10 mm, and drop impact test: 10 mm of ...
Context 2
... (x = 70 mol%) wires having a diameter of 1 mm as specimens were used in this study. For investigating the microstructure dependence of magnetic and magnetostrictive characteristics, several heat treatments were performed with the reference of Fe-Co phase diagram as shown in Fig. 1. Annealing at 420 o C for 24 hours and furnace cooling (hereinafter, 420 o C-FC) were conducted for removing residual stress and internal strain. Also, annealing at 750 o C, 780 o C, 800 o C, 820 o C and 850°C for 5 hours and water quenching (WQ) were conducted for modifying the coarsened microstructures and freezing a coexistence of ...
Citations
... Among those, Terfenol-D (Tb 0.3 Dy 0.7 Fe 2 ) exhibits a large magnetostrictive coefficient up to 1400 ppm at a magnetic field of~2 kOe [1][2][3][4]7]. In addition, Galfenol, Fe 0.8 Ga 0.2 , is known as a material, which shows a large magnetostriction up to 400 ppm [5,6] and CoFe shows 260 ppm as well [8][9][10][11][12]. Since these discoveries, those materials have emerged as a smart material for microdevices, including actuators [13,14], wireless sensors, biosensors [15,16], energy harvesting devices [17], and atomic force microscopy [18]. ...
The microfabrication with a magnetostrictive TbxDy(1−x)Fey thin film for magnetic microactuators is developed, and the magnetic and magnetostrictive actuation performances of the deposited thin film are evaluated. The magnetostrictive thin film of TbxDy(1−x)Fey is deposited on a metal seed layer by electrodeposition using a potentiostat in an aqueous solution. Bi-material cantilever structures with the Tb0.36Dy0.64Fe1.9 thin-film are fabricated using microfabrication, and the magnetic actuation performances are evaluated under the application of a magnetic field. The actuators show large magnetostriction coefficients of approximately 1250 ppm at a magnetic field of 11000 Oe.
... Fe-Co alloys are suitable for sensor applications due to rich elements and lower cost compared with Terfenol-D and Galfenol and have many favorable characteristics that allow easy fabrication, high strength, ductility, and excellent workability [4]. Yamazaki et al. have characterized Fe-Co wire and designed a magnetostrictive sensor for SHM [12,13]. These characteristics enable development of magnetostrictive composites [14]. ...
Carbon fiber reinforced plastic (CFRP) is an excellent choice in the areas where weight reduction is important and multi-functionalization of CFRP, especially by adding sensor capabilities, is a promising approach to realize lightweight battery-free devices in structural health monitoring (SHM). In this study, we fabricated hybrid CFRP with Fe-Co fibers and evaluated the inverse magnetostrictive response characteristics. It was shown that the measured magnetic flux density of the CFRP fluctuates in response to cyclic bending load. It was also revealed that our Fe-Co fiber inserted CFRP has damage self-sensing ability. In addition, it seems that the optimization of design and more experimental and numerical investigation improves the capability of the hybrid CFRP with Fe-Co fiber as sensor composite materials.
... Moreover, Fe-Co alloys having high Co content (66 ≦ Co ≦ 75 mol%) with excellent workability, large magnetostriction, high strength, and low production cost have been developed [11][12][13][14][15][16][17][18]. Yamaura et al. prepared cold rolled polycrystalline Fe 1-x Co x (x = 75-85 mol%) alloys (rolling rate ∼97%) and exhibited large magnetostriction (λ s = 128 ppm) along the rolling direction using as-rolled Fe 25 Co 75 alloys [14]. ...
... Yamaura et al. prepared cold rolled polycrystalline Fe 1-x Co x (x = 75-85 mol%) alloys (rolling rate ∼97%) and exhibited large magnetostriction (λ s = 128 ppm) along the rolling direction using as-rolled Fe 25 Co 75 alloys [14]. More recently, we have developed the Fe 30 Co 70 alloy film plate (thickness ∼0.02 mm) [15] and the Fe 30 Co 70 alloy wire (diameter ∼0.02 mm) [16]. These materials having strongly textures of {1 1 0} 〈0 0 1〉 orientation exhibited a relatively high mechanical, magnetic and magnetostrictive properties. ...
... Furthermore, a strong [1 1 0] 〈0 0 1〉 texture was formed by wire drawing processing as a result of electron backscatter diffraction (EBSD) analysis using a field emission scanning electron microscope, FE-SEM (JEOL Ltd., JSM-7001F). Our previous experiments [16] have described that this annealed FeCo alloy wire shows a high strength (UTS ≈ 1100 MPa), low coercivity (H c = 13.1 Oe) and a high saturation magnetization (M s = 200.6 emu/g). Fig. 3 shows the block diagram of the experimental setup for measuring MBN under changing tensile stress. ...
Magnetic Barkhausen noise (MBN) plays significant roles to describe the dynamic of domain walls (DWs), but an in-depth understanding of the correlation between Barkhausen effect and magnetostrictive effect during magnetization process is still limited. In this study, we investigated MBN signals and the frequency spectra in a high-magnetostrictive Fe30Co70 alloy wire (λs = 102 ppm) by evaluating the stress effects on MBN profiles at the stress range of 0–150 MPa using tensile test machine. The results from MBN profiles revealed that MBN in the high magnetic field region was responsible for the localized changes of magnetic flux density, dB/dt induced by magnetic distortion related to non-180° DWs or the magnetization rotation. In MBN spectra, the peak shift towards lower frequencies with the increase of stress indicates that the rough pulse-like MBN outbreaks increase, and it results mainly from the increase of DW jumping length which is caused by the pinning effect at grain boundaries where DW energy is relatively high. In addition, stress dependence of the root mean square (RMS) value of MBN showed a good sensitivity (0.038 mV/MPa). Overall, these findings indicate that new MBN measurement system utilizing magnetostrictive materials can be helpful for a wide range of applications such as mechanical stress sensors and energy harvester systems.
The integration of magneto-electric and spintronic sensors to flexible electronics presents a huge potential for advancing flexible and wearable technologies. Magnetic nanowires are core components for building such devices. Therefore, realizing flexible magnetic nanowires with engineered magneto-elastic properties is key to flexible spintronic circuits, as well as creating unique pathways to explore complex flexible spintronic, magnonic, and magneto-plasmonic devices. Here, we demonstrate highly resilient flexible ferromagnetic nanowires on transparent flexible substrates for the first time. Through extensive magneto-optical Kerr experiments, exploring the Villari effect, we reveal an ultralow magnetostrictive constant in nanowires, a two-order reduced value compared to bulk values. In addition, the flexible magnetic nanowires exhibit remarkable resilience sustaining bending radii ∼5 mm, high endurance, and enhanced elastic limit compared to thin films of similar thickness and composition. The observed performance is corroborated by our micro-magnetic simulations and can be attributed to the reduced size and strong nanostructure-interfacial effects. Such stable magnetic nanowires with ultralow magnetostriction open up new opportunities for stable surface mountable and wearable spintronic sensors, advanced nanospintronic circuits, and for exploring novel strain-induced quantum effects in hybrid devices.
Energy harvesting, particularly through ambient sources, is gaining significant interest in the recent past because of the energy crisis and the pollution associated with fossil fuels. With the emergence of Internet-of-Things (IoT), where billions of IoT devices are expected to communicate with each other, energy harvesting has become even more relevant. In this vision, we have been working on energy harvesting based on magnetic materials, particularly stress-induced domain wall motion. In this paper, we present a detailed overview of our research on stress-induced domain wall motion and the demonstration of energy harvesting. We have carried out micromagnetic simulations, which indicated that an applied stress can change the magnetization direction from transverse direction to the longitudinal direction in a microwire. The experimental results on CoNi/FeCo/CoNi microwires confirmed that such change in domain structure is possible with applied stress. We have shown the details on how a transverse anisotropy is achieved in CoNi/FeCo/CoNi stack. We have also demonstrated that energy can be harvested using the methods described in this paper. The results offer a new magnetic stack, which can be used to achieve energy harvesting through ambient sources.
Energy harvesting is getting significant interest due to the emergence of Internet of Things (IoT). As IoT devices are required to generate power on their own, several researchers are studying ferroelectric materials for voltage generation. However, ferroelectric materials suffer from high resistance at low frequencies, which reduces the output power. Domain wall propagation in ferromagnetic materials, as induced by stress and a pickup voltage using coils, is investigated as an alternate form of energy harvesting. Such studies, which are reported in multiferroic structures, feature a voltage applied to induce the stress, which defeats the purpose of self‐power generation. Here, power generation from mechanical vibrations in purely ferromagnetic structures is shown. These results are achieved by showing that the domain walls can be moved entirely by stress in a trilayer stack of ferromagnetic microwires. The use of flexible substrates with low Young's modulus and a trilayer magnetic stack enables the achievement of significant magnetization rotation or domain wall motion even from ambient vibrations. Here, the rotation of magnetization or domain wall motion is exploited to induce voltages in the pickup coils. The results shown here provide an alternative way to power IoT devices. Energy harvesting is experimentally demonstrated based on domain wall motion in magnetic microwires. FeCo‐based microwires with an anisotropy in the transverse direction change their magnetization to the longitudinal direction with the application of stress. Such a change in magnetization in the presence of a time‐varying stress could be harvested as voltage for pico‐Internet of Things devices.
Co-rich Fe-Co alloy with Co content of 66~75at% is known to have the potential of large saturation magnetostriction, high Curie temperature, high strength and good mechanical workability, however, its properties of thin plate and fine fiber below 1mm thickness remain unknown. Therefore, microstructure, magnetization and magnetostriction of the rolled Fe30Co70 alloy thin plate of 0.05mm in thickness were investigated. Crystalline microstructure becomes very fine and complicated due to the heavily deformation by the rolling process repeated many times at room temperature. Those morphology changes were investigated by the profile figures of XRD and SEM-EBSD/OIM analyses. The increases of magnetostriction value and its sensitivity were confirmed especially in the cold-rolled and subsequently annealed alloy plates. On the other hand, the coercive force decreased by decreasing the internal defects such as residual stress, dislocation density. These results will become useful for small magnetostrictive stress sensor and vibration energy harvesting device in considering of magnetostrictive composite materials for infra-structure health monitoring (SHM).
