Dynamic Magnetostriction Research Articles

Multifactorial impacts of B-doping on Fe81Ga19 alloys prepared by laser-beam powder bed fusion: Microstructure, magnetostriction, and osteogenesis

Magnetostrictive Fe-Ga alloys have captivated substantial focus in biomedical applications because of their exceptional transition efficiency and favorable cytocompatibility. Nevertheless, Fe-Ga alloys always exhibit frustrating magnetostriction coefficients when presented in bulk dimensions. It is well-established that the magnetostrictive performance of Fe-Ga alloys is intimately linked to their phase and crystal structures. In this study, various concentrations of boron (B) were doped into Fe81Ga19 alloys via the laser-beam powder bed fusion (LPBF) technique to tailor the crystal and phase structures, thereby improving the magnetostrictive performance. The results revealed the capacity for quick solidification of the LPBF process in expediting the solid solution of B element, which increased both lattice distortion and dislocations within the Fe-Ga matrix. These factors contributed to an elevation in the density of the modified-D03 phase structure. Moreover, the prepared Fe-Ga-B alloys also exhibited a 〈001〉 preferred grain orientation caused by the high thermal gradients during the LPBF process. As a result, a maximum magnetostriction coefficient of 105 ppm was achieved in the (Fe81Ga19)98.5B1.5 alloy. In alternating magnetic fields, all the LPBF-prepared alloys showed good dynamic magnetostriction response without visible hysteresis, while the (Fe81Ga19)98.5B1.5 alloy presented a notable enhancement of ∼30 % in magnetostriction coefficient when compared with the Fe81Ga19 alloy. Moreover, the (Fe81Ga19)98.5B1.5 alloy exhibited favorable biocompatibility and osteogenesis, as confirmed by increased alkaline phosphatase (ALP) activity and the formation of mineralized nodules. These findings suggest that the B-doped Fe-Ga alloys combined with the LPBF technique hold promise for the development of bulk magnetostrictive alloys that are applicable for bone repair applications.

Magnetoelectric, dielectric, and magnetic investigations of multiferroic NixCo1−xFe2O4−SryBa1−yNb2O6 composites

Magnetoelectric (NixCo1−xFe2O4)0.3−(SryBa1−yNb2O6)0.7 composites with a 0–3 connectivity and different cation stoichiometries were synthesized via a classical mixed-oxide method. XRD patterns of all ceramics show reflections of the target phases SryBa1−yNb2O6 and NixCo1−xFe2O4. The influence of stoichiometry of the ferrimagnetic and ferroelectric phase on the magnetoelectric behavior was studied on composites with composition of (NixCo1−xFe2O4)0.3−(Sr0.5Ba0.5Nb2O6)0.7 and (NiFe2O4)0.3−(SryBa1−yNb2O6)0.7. The magnetic Curie temperature increases with nickel content. However, the saturation magnetizations as well as the Curie temperatures of the composites are always lower than the ones of bulk NixCo1−xFe2O4 samples. The maximum magnetoelectric coefficient (αME) rises with increasing nickel content from 40 (x = 0) to 180 µV Oe−1 cm−1 (x = 1) in accordance with the dynamic magnetostriction coefficient. The evolution of αME of (NiFe2O4)0.3−(SryBa1−yNb2O6)0.7 composites shows an increase with strontium content up to y 0.5. Higher strontium content leads to a significant reducing of αME.

Investigation of Piezomagnetism in Nickel Ferrite

Applications of magnetostrictive materials, such as sensors and energy-harvesting devices, generally involve the use of the dynamic deformation, i.e., the piezomagnetic effect, induced by an exciting magnetic field H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ac</sub> . However, this effect is rarely measured directly but commonly approximated by the strain derivative ∂λ/∂H, which is deduced from the quasi-static magnetostrictive curve. In this article, we propose an investigation of the piezomagnetic effect in nickel ferrite by directly measuring the dynamic magnetostriction under various exciting fields using a dynamic strain-gauge setup. These values are compared with the strain derivative in order to disclose the limitations thereof. In addition, the magnetoelectric effect is measured in a ferrite/PZT bilayer and compared with the calculated magnetoelectric coefficient based on an analytical model. When the dynamic magnetostrictive coefficients are integrated into the calculation, good accuracy is found with experimental values, whereas it is not the case for calculated coefficients based on the strain derivatives. The findings of the present study highlight the importance of accurately characterizing the piezomagnetic effect in magnetostrictive materials in order to optimize their performances in dynamic applications.

Modeling dynamic magnetostriction of amorphous core materials based on Jiles–Atherton theory for finite element simulations

Due to its favorable properties of low core loss and high saturation magnetic flux density, amorphous material is widely used as the core material of low and medium frequency transformers. However, its magnetostriction is much higher than that of grain-oriented sheet steel, a very common material for conventional transformers, resulting in high acoustic noises. This paper proposes a comprehensive model of magnetostriction in amorphous material based on the interdependence between magnetostriction and magnetization by combining the isotropic magnetostriction effect and Jiles-Atherton energy balance theory. Incorporated in coupled magneto-mechanical field calculation, the proposed model can correctly simulate the butterfly loops of magnetostriction, magnetic hysteresis loops and vibration displacements. The theoretical results of magnetostriction characteristic are verified by both single sheet test and the experimental results of amorphous transformer prototype.

Improved Dynamic Magnetostriction measurement method based on M-EMAT for the characterization of residual strain

The Dynamic Magnetostriction (DM) measurement method as a nondestructive testing method of ferromagnetic materials, measures the DM curve using electromagnetic acoustic transducer (EMAT) to characterize material and predict the mechanical properties. Lorentz forces and magnetostriction forces contribute mainly to the ultrasonic generation. Only the range of low field, in which the magnetostriction force mechanism is predominant can be used to measure the DM curve, but the boundaries of this range are uncertain. The improved DM measurement method based on shear wave Magnetostriction EMAT (M-EMAT) is proposed and the theory of generation of shear waves is derived. For the M-EMAT, only magnetostriction force mechanism contributed to the generation of shear waves. A theoretical model for the optimization of the transducer is developed, the model is in good agreement with the experimental results. The microstructure changes caused by residual strain will affect the magnetostriction coefficient and the DM curve. Therefore, the DM curves of low carbon steel specimens with different levels of residual strains are measured by the optimized transducer to characterize the residual strain. The normalized results demonstrate that the slope of the DM curve obviously changes with the residual strain. This leads to the conclusion that the DM measurement method can be used to characterize the residual strain of the low carbon steels.

Effect of Graphene Thin Layer on a Static and Dynamic Magnetostrictive Behavior in TbDyFe Multi-Layered Film for Micro Energy Devices.

Magnetos-mechanical behaviors of TbDyFe/Graphene/TbDyFe film were compared with a tri-layered TbDyFe film to verify the effects of a graphene thin layer on the improvement of magnetic-mechanical performance, as well as decrease of dynamic response time under the low magnetic field. Both of the Heisenberg model and Landau-Lifshitz-Gilbert equation were used to calculate the magnetic domain motion. Time consumptions were simulated to determine a uniformly magnetized state in Graphene and TbDyFe layers. To ensure the magnetostrictive characteristics, the magnetic moment and the magnetostriction were measured using a fabricated magnetostrictive actuator. Compare to the three-layer TbDyFe films, TbDyFe/Graphene/TbDyFe showed a higher magnetostrictive behavior in response to low coercive forces in the range of 0 to 10 kA/m, even with the addition of low magnetic fields. The dynamic magnetostriction response time was faster than the tri-layered TbDyFe film by approximately 24 millisecond.

Dielectric and magnetoelectric properties of (BiBa)(FeTiZn) O3/CoFe2O4 lead-free particulate composites

The magnetic, dielectric, and magnetoelectric (ME) properties of particulate composites containing lead-free piezoelectric 0.97[0.67BiFeO3-0.33BaTiO3]-0.03Bi(Zn0.5Ti0.5) O3 (BF33BT-3BZT) and magnetostrictive CoFe2O4 (CFO); (100-x)[BF33BT-3BZT]-xCFO, x = 13, 25, 37, 47 mol%; have been investigated. The pure ferroelectric BF33BT-3BZT shows a non-dispersive and sharp phase transition, while the composites exhibit relaxor behavior which is described by Vogel - Fulcher law. The ME voltage coefficient is studied as a complex quantity and its dependence on magnetic field is discussed within the framework of dynamic magnetostriction. The composite with x = 37 shows the highest ME voltage coefficient of 5.7 mV/cm.Oe. The results show that, compared to cobalt ferrite, the composite of BF33BT-3BZT with nickel ferrite produces larger ME voltage at a lower magnetic field, confirming that the magnetic field dependence of magnetostriction has a crucial role on the ME properties of the studied multiferroic composites.

Modeling of Anisotropic Magnetostriction Under DC Bias Based on an Optimized BP Neural Network

The existence of direct current (dc) bias magnetic field changes the magnetostrictive properties of electrical steel sheets (ESSs) and intensifies the vibration and noise of transformers. In this article, the dynamic magnetostrictive properties of the ESSs under dc bias are measured and analyzed, and it is shown that the magnetostriction of the ESSs under dc bias has a complex dynamic anisotropy. An optimized backpropagation neural network (BPNN) is proposed to model the dynamic magnetostriction curves under the dc bias. In the construction of the BPNN, the topology is optimized by using the genetic algorithm and the parameters are optimally decided by using particle swarm optimization (PSO), respectively, to get a fast convergence and avoid the local optimal solution. The comparison of the proposed model with experimental measurements shows the accuracy of the proposed model is improved by 6%.

A Dynamic Magnetostriction Model of Grain-Oriented Sheet Steels Based on Becker–Döring Crystal Magnetization Model and Jiles–Atherton Theory of Magnetic Hysteresis

Grain-oriented (GO) sheet steels are widely used as the core material in large power transformers. The strong magnetostriction in GO sheet steels, however, causes undesirable vibrations and acoustic noises, and is difficult to estimate in the design optimization of power transformers. This article proposes a new magnetostriction model of GO sheet steels by combining the Becker-Doring crystal model and the dynamic Jiles-Atherton hysteresis model. Incorporated in the finite-element analysis (FEA), the new model can correctly simulate the butterfly loops of magnetostriction in GO sheet steels. The effectiveness and accuracy of the proposed model are verified by the experimental measurement results on a single sheet sample in a free state with no external stress.

Dynamic Magnetostriction of CoFe2O4 and Its Role in Magnetoelectric Composites

Applications of magnetostrictive materials commonly involve the use of the dynamic deformation, i.e., the piezomagnetic effect. Usually, this effect is described by the strain derivative ∂λ=∂H, which is deduced from the quasistatic magnetostrictive curve. However, the strain derivative might not be accurate to describe dynamic deformation in semihard materials as cobalt ferrite (CFO). To highlight this issue, dynamic magnetostriction measurements of cobalt ferrite are performed and compared with the strain derivative. The experiment shows that measured piezomagnetic coefficients are much lower than the strain derivative. To point out the direct application of this effect, low-frequency magnetoelectric (ME) measurements are also conducted on bilayers CFO/Pb(Zr,Ti)O3. The experimental data are compared with calculated magnetoelectric coefficients which include a measured dynamic coefficient and result in very low relative error (<5%), highlighting the relevance of using a piezomagnetic coefficient derived from dynamic magnetostriction instead of a strain derivative coefficient to model ME composites. The magnetoelectric effect is then measured for several amplitudes of the alternating field H ac , and a nonlinear response is revealed. Based on these results, a trilayer CFO/Pb(Zr,Ti)O3 /CFO is made exhibiting a high magneto-electric coefficient of 578 mV/A (approximately 460 mV/cm.Oe) in an ac field of 38.2 kA=m (about 48 mT) at low frequency, which is 3 times higher than the measured value at 0.8 kA/m (approximately 1 mT). We discuss the viability of using semihard materials like cobalt ferrite for dynamic magnetostrictive applications such as the magnetoelectric effect.

An anisotropic magnetostriction model based on BP neural network combining Levenberg-Marquardt algorithm and particle swarm optimization

In this paper, the dynamic magnetostriction of the electrical steel sheet is measured by a triaxial strain gauge based on a single-sheet tester under the alternating magnetic flux condition. The anisotropic magnetostriction property is analyzed, and an improved back propagation neural network assis ted model is applied to model the anisotropic principal strain of magnetostriction along different excitation directions. To keep the evaluation cost at an acceptable level, the Levenberg-Marquardt algorithm combined with particle swarm optimization is developed. Finally, the proposed model is verified by comparing the measured magnetostriction and computed one.

Nanomechanics of a magnetic shuttle device

We show that self sustained mechanical vibrations in a model magnetic shuttle device can be driven by both the charge and the spin accumulated on the movable central island of the device. Different scenarios for how spin- and charge-induced shuttle instabilities may develop are discussed and shown to depend on whether there is a Coulomb blockade of tunneling or not. The crucial role of electronic spin flips in a magnetically driven shuttle is established and shown to cause giant magnetoresistance and dynamic magnetostriction effects.

Influence of Ni thin layer on a static and dynamic magnetostrictive behavior in TbFe multi-layered film

Static and dynamic magnetostrictive behaviors of the TbFe/Ni/TbFe film are compared with a tri-layered TbFe film to discover the effects of a Ni thin layer on the improvement of magnetic moment and magnetostriction, as well as the reduction of dynamic response time under a low magnetic field. The Heisenberg model and Landau–Lifshitz–Gilbert equation were used to simulate magnetic domain motion. Time consumptions, in particular, were calculated to determine a uniformly magnetized state in Ni and TbFe layers. In addition, the magnetic moment together with the magnetostriction was examined with a fabricated magnetostrictive actuator. Contrary to a tri-layered conventional TbFe film, the TbFe/Ni/TbFe showed a higher magnetostrictive behavior even though a lower magnetic field was applied, corresponding to a low coercive force within the range of 0–10kA/m. The dynamic magnetostriction response time, in particular, was also reduced to about 27ms compared to the tri-layered TbFe film.

Generated Vibration Modes in Ultrasonic Scaler Transducer Components

Magnetostrictive materials have been utilized for the production of resonant ultrasonic-frequency vibrations for a number of years. This effect has been utilised in laminated nickel-based ultrasonic dental scaler cleaning systems. Laser vibrometry measurements were undertaken that showed that a typical dental ultrasonic scaler resonated at 29 kHz due to dynamic magnetostriction of the insert's laminated nickel 'stack.' This, in turn, excited insert probe vibrations that are used to remove dental calculus. 3D Femlab™ mechanical finite element models were created to explore the flexural vibration modes associated with the whole insert at the vibration frequency. These models indicated that it was possible to reproduce similar probe vibration mode-shapes to those seen via scanning laser vibrometry measurements. Also, the models indicate that vibrations, useful for dental scaling, can only be achieved if the coupled flexural and longitudinal resonant modes are stimulated at the same drive frequency.

Magnetostrictive properties of titanate coupling agent treated Terfenol-D composites

As a kind of composites, the bond strength between the polymer matrix and the Terfenol-D particles affects the performance of magnetostrictive composites. By observing the fracture morphologies, the bond strength of the magnetostrictive composites prepared with untreated Terfenol-D was proved weak. Titanate coupling agent was used for particles to improve the bond strength. Contact angle analysis indicates the work of adhesion of the epoxy resin to the treated Terfenol-D is larger than that to the untreated Terfenol-D. Different magnetostrictive composites with 20%, 35% and 50% particle volume fractions were prepared with treated and untreated Terfenol-D particles. Their static and dynamic magnetostriction was tested without pre-stress at room temperature. The results indicate titanate coupling agent treating increases the magnetostrictive properties of magnetostrictive composites, that is probably because the bond strength improves due to the particle treating.

Uniform High Magnetostrictive Properties of Terfenol-D Composites Prepared by a Dry Process

Magnetostrictive composites were usually fabricated using a wet process. The settlement of particles in liquid polymers due to the gravity results in the inhomogeneous and low magnetostrictive properties. To solve the problem, magnetostrictive composites were prepared using a dry process, and their properties were tested in this paper. Measurement of magnetostriction on different positions along the length direction of the material indicates the magnetostrictive composites prepared by the dry process present uniform properties due to the uniform distribution of the active particles in the polymer matrix. The saturation magnetostriction and the maximum dynamic magnetostriction of the [1-3] Terfenol-D composites prepared in the study was 1005ppm and 4.08nm/A, respectively, which was larger than the [0-3] ones.

Dynamic parameters of Tb-Dy-Fe giant magnetostrictive alloy

Tb 0.3Dy 0.7Fe 1.90 <110> oriented rods were prepared by zone melting with unidirectional solidification. The magnetomechanical coupling factor ( k 33) was measured by magnetomechanical resonance under different DC bias fields up to 77.4 mT. An effective method was provided to calculate sonic velocity, elastic modulus and compliance constant through measuring resonate frequency ( f r ), and calculate dynamic magnetostriction( d 33) via measuring magnetic permeability, magnetomechanical coupling factor( k 33) and compliance constant. Without pre-stress, resonate frequency ( f r ), sonic velocity and elastic modulus first decreased and then rose with increasing bias magnetic field. Under 10 MPa pre-stress, resonate frequency ( f r ), sonic velocity and elastic modulus decreased linearly with increasing bias fields. d 33 exhibited the same variation trend before and after heat treatment, but heat treatment weakened the decrease of d 33 in low field range.

Microstructure analysis of magnetostrictive composites

To understand the mechanism and the dependency between magnetostrictive composite performance and the orientation of the magnetic field, composites with 30% particles by volume were fabricated by distributing Terfenol-D particles in an unsaturated polyester resin matrix under various orientation fields. Their static and dynamic magnetostriction was tested without pre-stress at room temperature. The results indicate there is a positive correlation between magnetostrictive property and the orientation field. This study used scanning electron microscopy to observe the material longitudinal microstructures followed by a statistical analysis to evaluate the angle distribution between the major axis of the particles and the orientation field in different composites. In summary, this method can be used to elucidate the microstructure of the composites directly: the higher the orientation field, the closer the microstructure to 1–3 structure. As a result, the static and dynamic magnetostriction is increased as the orientation field increases.

Influence of arrangement field on magnetostrictive and mechanical properties of magnetostrictive composites

Non-aligned and aligned polymer-bonded Tb 0.3Dy 0.7Fe 2 composites with 20% particle volume fraction were prepared under different arrangement fields (i.e. 0, 10 kA/m, 20 kA/m, 30 kA/m, 60 kA/m and 100 kA/m) during their gel process. Static magnetostriction, dynamic magnetostriction, elastic modulus and compressive strength of all specimens were tested and compared. Experimental results indicate that all the parameters are positively dependent on the arrangement field. The dependence is significant at low field levels, the critical value of which is 30 kA/m for the composites fabricated. No obvious improvement of the properties can be observed for a larger field. Such critical values are defined as the optimal arrangement field to manufacture magnetostrictive composites.

Metaelastic transitions in Jahn-Teller crystals withX−Yordering

A microscopic theory of metaelasticity is derived and applied to Jahn-Teller crystals with $x\text{\ensuremath{-}}y$ ordered octahedron distortions. The theory explains the interrelation of the elastic and magnetic properties of those crystals and with modifications, could be applied to other systems. The consequences of the application of pressure along the $z$-axis and a $z$-axis magnetic field are explored. Both, the pressure and the magnetic field applications lead to phase transitions. As a manifestation of the field-induced phase transition giant dynamic magnetostriction in colossal magnetoresistance manganite-type crystals is calculated.