Giant Magnetostrictive Thin Films Research Articles

The effect of temperature on giant magnetostrictive thin films in high pre-stress environment for sensor application

The high pre-stress environment arises in the manufacturing of amorphous thin films of Terfenol-D through sputtering techniques. The pre-stress thin film of Terfenol-D has been developed due to the mismatch in the thermal coefficient of deposited magnetostrictive film and substrate. In the presence of high pre-stress anisotropic energy has been changed and due to that magnetization and magnetostriction properties of the thin film are affected. A novel three-dimensional hyperbolically generalized constitutive model for giant magnetostrictive materials along with vector generalized Jiles-Atherton hysteresis model was considered for predicting the hysteretic responses precisely under thermo-elasto-magnetic field. The material constants for the generalized constitutive models are taken from calibrated physical and experimental evidence. A non-linear finite element model for the thin films made up of Terfenol-D has been developed for investigating the thermo-elasto-magnetic characteristics, using COMSOL Multiphysics software. The predicted thermo-elasto-magnetic results have been critically analyzed the effect of temperature, the orientation of the applied magnetic field, and in-plane stresses condition. Hence, the present study can be decisive for the development of a more reliable and robust design of magnetostrictive film-based intelligent devices.

Effect of Thickness Ratio on the Magnetic Properties of the Magnetostrictive Thin Film Composite

Magno-elastic coupling characteristics in giant magnetostrictive thin films depend on a myriad of factors, comprising variability in Young’s modulus, thermally induced pre-stresses, the direction of the applied magnetic field and the substrate to film thickness ratio, demagnetization field etc. Due to the aforementioned reasons, the giant magnetostrictive thin films usually display characteristics that may contrast with the bulk giant magnetostrictive materials. This work studies magnetostrictive film on a compliant substrate using a generalized 3-D magneto-thermo-elastic nonlinear constitutive model with the elasticity theory to include such stimuli sensitive coupled magneto-thermo-elastic response. The numerical simulation of the magnetostrictive film on the compliant substrate in the form of a cantilever shows good agreement with the existing experimental data. The substrate and film thickness ratio effect on the thermal strain, Young’s modulus, magnetization and magnetostriction of films was meticulously analyzed. It has been revealed that the magneto-elastic responses rely strongly on the substrate-to-film thickness ratio. Thus, it is possible to obtain the tunable properties by controlling the composite film's thickness ratio in the design state of smart devices.

A Supersonic Aerodynamic Energy Harvester: A Functionally Graded Material Beam with a Giant Magnetostrictive Thin Film

A Supersonic Aerodynamic Energy Harvester: A Functionally Graded Material Beam with a Giant Magnetostrictive Thin Film

Finite element analysis of displacement actuator based on giant magnetostrictive thin film

With the rapid development of science and technology, mechanical and electrical equipment become more and more miniature. In order to achieve precise control in less than 1cm3, the giant magnetostrictive thin film has become a research hotspot. The micro displacement actuator with planar and arc film is designed by the dynamic coupling model based on J-A model and magneto-mechanical effect method which is proposed in this paper. The different structure and thickness of films are analyzed by COMSOL Multiphysics software when the current flows through driving coil. After comparing the simulation results with the test ones, it can be seen that the coupling model is accurate and the structure is reliable. At the same time, MATLAB is used to fit the current density-displacement curve and higher order equation is obtained, and then the feasibility of design can be verified. The actuator with arc structure had advantages of small volume, fast response, high precision, easy integration, etc., which has a broad application prospect in the field of vibration control, micro positioning, robot and so on.

Response of a post-buckled giant-magnetostrictive thin film subject to Gaussian colored noise

Response of a post-buckled giant-magnetostrictive thin film subject to Gaussian colored noise

Response and Reliability of a Giant Magnetostrictive Film Actuator Subject to Axial Random Excitation

A giant magnetostrictive thin film (GMF) actuator designed as a simply supported beam under axial white noise excitation is studied. Firstly, a non-dimensional stochastic difference equation governing the motion is simplified by the modified stochastic averaging method. Subsequently, the stationary probability density function of amplitude and the joint probability density function of displacement and velocity were obtained respectively. Finally, the reliability was studied by the backward Kolmogorov (BK) equation to guarantee the safety of the actuator. Numerical simulations are carried out to verify the theoretical analysis.

Nonlinear vibration of a post-buckled giant-magnetostrictive thin film laminated beam

One buckled simply supported giant magnetostrictive material (GMM) thin film laminated beam model subject to axial magnetic excitations is proposed. Themagnetostrictive force issimplified as a harmonic excitation. Applying the Hamilton principle and Galerkin approach the model is expressed as a one dimensional vibrating model with parametrical excitation. The multi-scales method is used to obtain the approximation of the solution when the vibration is around the buckled position and the amplitude of the oscillation is small. With the help of the undermined fundamental frequency method and normal form theory the Melnikov approach is improved to calculate more precise threshold value of the amplitude of excitation leading to chaos. The numerical simulation shows the performance of the new Melnikov approach is much better than the traditional way.

Study of Giant Magnetostrictive Thin Films With Gas Sensitive Layer for Use as Gas Concentration Sensors

Giant magnetostrictive thin films of double layers with gas sensitive layers as the sensing element being used to develop a gas concentration sensor were proposed in this paper. The double layers giant magnetostrictive thin films with gas sensitive layer were prepared. A magneto-mechanical coupling model was developed based on the assumption that the magnetostriction effect is equivalent to the effect of a body force. These films were tested in a cantilever arrangement and end deflection was measured. The measurement showed that the experimental results were in good agreement with the calculation results, demonstrating that the coupling model developed was effective. Furthermore, the results indicated that the giant magnetostrictive thin films with gas sensitive layer were very useful for gas concentration sensors.

Effects of Vacuum Annealing on Microstructure and Magnetostriction of TbDy-Fe GMFs

In this study, TbDy-Fe giant magnetostrictive thin films were firstly prepared by ion beam sputtering deposition (IBSD) method on water-cooled substrates, and then the films were annealed at different temperatures under vacuum condition. An Inductively Coupled Plasma Spectrometry, Scanning Electron Microscope (SEM), Scanning Probe Microscope (SPM), and Transmission Electron Microscope (TEM) were used to investigate the surface morphology and microstructure for TbDy-Fe GMFs. Besides, DWS type Ultra-precision Displacement Meter was used for measuring magnetostriction coefficient of the films by cantilever method. The results showed that TbDy-Fe GMFs of compact amorphous microstructure, smooth surface morphology, and high interfacial adhesion had been deposited under the fixed fabrication procedure. Moreover, as annealing temperature increased, microstructure of the films had been changed as following order: amorphous → amorphous + microcrystalline → nano-polycrystalline (crystallization temperature was about 400 ). It was noted that magnetostriction of TbDy-Fe GMFs could be drastically improved, particularly for low magnetic field magnetostriction sensitivity when annealed at about 400 (the value of λ was about 500ppm at 200KA•m-1).

An in-pipe wireless swimming microrobot driven by giant magnetostrictive thin film

In this work, the nonlinear vibration characteristics of bimorph giant magnetostrictive thin film (GMF), TbDyFe/PI/SmFe, are measured and analyzed, firstly. Thereafter, by employing the primary resonance and superharmonic resonance performance of GMF cantilever, and simulating the ostraciiform locomotion of boxfish, an in-pipe wireless swimming microrobot is developed, whose caudal fin is fabricated by GMF microactuator. On the basis of the equivalent load model of magnetostrictive effect of GMF, the governing equations for swimming microrobot are established and solved by the method of multiple scales. Experiments on the swimming characteristics of this GMF microrobot in gasoline pipe show that the microrobot can swim at a mean speed of 4.67 mm/s with the external magnetic field driving frequency of 4.7 Hz, which is close to the first primary resonance frequency in gasoline. Besides, the mean swimming speed can reach 2.8 mm/s with the external magnetic field driving frequency of 2.4 Hz, which is close to the superharmonic resonance frequency of order two of GMF cantilever actuator in gasoline.

Design Optimization of a Bidirectional Microswimming Robot Using Giant Magnetostrictive Thin Films

This paper presents a bidirectional optimization method on a wireless microswimming robot. The robot is developed based on fin beating propulsion employing two giant magnetostrictive thin films for left and right fins. An innovative drive approach, using separate second-stage resonance frequencies of the left and right fins to generate right and left thrusts, is proposed and implemented on a bidirectional microswimming robot prototype. Dynamic model of the proposed microrobot has been derived based on theoretical analysis. A discrete variate method for optimizing left fin configuration is proposed under the constraints of fixed surface area and sufficient fin end strength, and a genetic algorithms method for optimizing right fin configuration is employed under constraints of symmetry and linearity of bidirectional swimming. Simulation and experimental results have demonstrated that bidirectional swimming performance of the robot is greatly improved with low driving frequency and a large range of swimming speed in both directions.

An ion momentum as a novel parameter for the preparation of the magnetostrictive thin film

The Sm–Fe system known as Giant magnetostrictive (GM) thin films was prepared by d.c. magnetron sputtering process. The present study has shown the importance of the energetic incidence ions onto the depositing film surface for the magnetostrictive properties. The effect of ion bombardment on the magnetostrictive characteristics of GM films was quantitatively discussed. The new parameter, ion momentum, was proposed for the design of GM films.

Geometrical nonlinear deformation model and its experimental study on bimorph giant magnetostrictive thin film

The geometrical nonlinearity of a giant magnetostrictive thin film (GMF) can be clearly detected under the magnetostriction effect. Thus, using geometrical linear elastic theory to describe the strain, stress, and constitutive relationship of GMF is inaccurate. According to nonlinear elastic theory, a nonlinear deformation model of the bimorph GMF is established based on assumptions that the magnetostriction effect is equivalent to the effect of body force loaded on theGMF.With Taylor seriesmethod, the numerical solution is deduced. Experiments on TbDyFe/Polyimide (PI)/SmFe and TbDyFe/Cu/SmFe are then conducted to verify the proposed model, respectively. Results indicate that the nonlinear deflection curve model is in good conformity with the experimental data.

Magnetostrictive properties of Tb‐Fe and Tb‐Fe‐Co films

AbstractWe studied Tb‐Fe‐Co giant magnetostrictive thin films and researched sputtering conditions to improve their magnetostrictive properties and investigated the possibility of their practical use. The sputtering Ar gas pressure influenced their inner stress and played a very important role for the determination of the magnetic easy axis. The largest magnetostriction was obtained when the Ar gas pressure was set at 0.7 Pa and the inner stress was controlled at a tensile stress of about 50 MPa. In the Tb‐Fe system, the Curie temperature is very low (about 140°C) compared with bulk materials, but the Curie temperature can be improved with increasing Co ratio. For films over 70% Co ratio, the Curie temperature was more than 250°C and the largest magnetostriction (1508 ppm) was obtained at 80.1% Co ratio. For almost all Tb‐Fe‐Co thin films, the values of magnetostriction were very high (over 1000 ppm), and the coercive forces were low (around 8 kA/m). Therefore, the Tb‐Fe‐Co giant magnetostrictive thin films are very appropriate materials for the applications in micro‐actuators and sensors. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(5): 49– 55, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10115

High responsive giant magnetostrictive materials thin film

Magnetostrictive properties of Sm-Fe-N and Sm-Fe-C giant magnetostrictive material (GMM) thin film have been systematically investigated in this study. Film samples were prepared by d.c. magnetron sputtering process in Ar-N2 or Ar-CH4 gases atmosphere. Saturated magnetostriction of formed thin films was decreased with increasing of N2 and CH4 partial pressure because of formation of non-magnetic SmN or SmC2 phases. Maximum value of magnetostrictive susceptibility is 34 ppm/kAm-1 was observed in Sm-Fe-C thin film sample with 1.0 vol% CH4 gas partial pressure. Compressive stress of thin film samples was increased due to the increasing of N2 and CH4 gases pressure. The increasing of compressive stress with small N2 and CH4 addition amount into thin film samples may influence the increasing of magnetostrictive susceptibility.

Nonlinear deformation analysis and experiment of giant magnetostrictive thin film cantilever

Through assuming that the magnetostriction effect of bimorph giant magnetostrictive thin film(GMF) cantilever is equivalent to the effect of a uniformly distributed bending moment, a nonlinear deformation governing equation of GMF is proposed, based on the geometrical nonlinear deformation theory and the Hamilton principle. Moreover, a static geometrical nonlinear deformation model, a nonlinear primary resonance and superharmonic resonance model, are presented. Thereafter, experiments on TbDyFe-PI-SmFe cantilever show that the deformation of cantilever end reaches the 0.67 times size of cantilever thickness, and the GMF exhibits clear superharmonic resonance, where the efficiency of superharmonic resonance of order 2, 3 and 4 is comparable with that of the primary resonance. The comparison between the static deformation model and resonance model with the experimental data indicates that the proposed models can describe well the static and dynamic nonlinear deformation of bimorph GMF cantilever. Thus, the proposed model provides the necessary basis for developing and designing effective microactuators and microsensors with GMF.

Inhomogeneous Spin Reorientation Transition (SRT) in Giant Magnetostrictive TbCo$_2$/FeCo Multilayers

Inhomogeneous magnetization states occurring when inducing the spin reorientation transition (SRT) in uniaxial giant magnetostrictive thin films are studied in detail. Theoretical background of SRT in the layers is given and the limitations of the single domain model are explained. The results of the magneto-optical measurements are then given and discussed. We showed that the behavior of devices using the SRT can be explained by the creation of magnetic domains, if the applied magnetic field is perfectly aligned with the hard axis. Magneto-optic evidence of the hyper sensitivity near the SRT is also given

A nonlinear magnetomechanical coupling model of giant magnetostrictive thin films at low magnetic fields

As magnetomechanical coupling model plays an important role in the application of giant magnetostrictive thin films (GMFs) to the microactuators and the microsensors, in this paper, the properties of GMFs at low magnetic fields, including the large magnetostriction, the soft magnetization and the hysteresis under internal stress (prestress), are analyzed firstly. Thereafter, with neglecting the change of internal stress during magnetic polarization and magnetostriction, a nonlinear magnetomechanical coupling model of GMFs at low magnetic fields is established, which is composed of the modified Rayleigh model for the magnetic polarization and the “butterfly curve” model for the strain. Experiments on TbDyFe-polyimide (PI)-SmFe and TbDyFe-Cu-SmFe are conducted, respectively, to verify the proposed model. Results indicate that the model curve coincides well with the experimental results of the magnetic polarization and the magnetostriction for TbDyFe-PI-SmFe and TbDyFe-Cu-SmFe under a given prestress at a low magnetic field. Besides, the proposed model is also in good conformity with the published experimental data of TbFe, SmFe and TbDyFe thin films.

Tb-Fe及びTb-Fe-Co系薄膜の磁気ひずみ特性

We studied Tb-Fe-Co giant magnetostrictive thin films and researched sputtering conditions to improve their magnetostrictive properties and investigated the possibility of their practical use. The sputtering Ar gas pressure influenced their inner stress and played a very important role for the determination of the magnetic easy axis. The largest magnetostriction was obtained when the Ar gas pressure was set at 0.7 Pa and the inner stress was controlled at an about 50 MPa tensile stress. In the Tb-Fe system, the Curie temperature is very low (about 140°C) compared with bulk materials, but the Curie temperature can be improved with increasing Co ratio. For films over 70% Co ratio, the Curie temperature was more than 250°C and the largest magnetostriction 1508 ppm was obtained at 80.1 % Co ratio. At almost all Tb-Fe-Co thin films, the values of magnetostriction were very high (over 1000 ppm), and the coercive forces were low (around 8 kA/m). Therefore, the Tb-Fe-Co giant magnetostrictive thin films are very appropriate materials for the applications in micro actuators and sensors.

水素吸蔵合金薄膜と超磁歪合金薄膜を用いた複合運動機能素子の開発

A composite mover device constructed with both hydrogen storage and giant magnetostrictive alloy thin films on each side surface of polyimide substrate were prepared by flash vacuum evaporation and DC magnetoron sputtering process, respectively. Although the composite mover device was about 750ppm before hydrogenation, it was about 1150ppm after hydrogenation. The hydrogenation induced strain was approximately corresponded to that of magnetized sample.