Magnetostriction Changes Research Articles

Нефарадеевское магнитоэлектричество в контексте мезомеханики

The paper outlines the physical basis of magnetoelectric conversion by means of the piezoelectric effect. The whole class of materials capable of such conversion is termed as multiferroics. An important group of those make composite media in which the ferromagnetic (or ferrimagnetic) and piezoelectric components dwell in close contact. The magnetic field, acting on the ferromagnet arises internal mechanical stresses via it, which are perceived by the other phase of the composite and launches the piezoelectric effect in it, i.e. makes the sample a source of potential difference. Whereas the ferromagnetic phase is always a solid substance, the piezophase can be not only a solid but also a polymer, and this expands considerably the application prospects of such convertors. Fundamental analysis shows that in a polymeric composite, ferromagnet particles under the action of an external field excite the piezoeffect in two ways simultaneously: through magnetostriction (change of the particle shape) and through a mechanical displacement of the particle body. Although these two methods are, in principle, independent, in a ferrite-polymer composite they always coexist, and under a given set of conditions their joint action might either enhance or reduce the conversion ef ficiency. This general conclusion is illustrated by the results of numerical modelling of the magnetoelectric effect in a composite film whose content mimics one of the currently best known polymer multiferroics: the dispersion of cobalt ferrite particles in a matrix of polyvinylidene fluoride (CFO-PVDF).

Study on magnetostriction of ferromagnetic particles–superconducting matrix based on multi-chain model

Based on the magnetic dipole theory and the elastic mechanical plane strain method, this paper establishes a multi-chain model of ferromagnetic particle inclusions–superconducting matrix and investigates the effects of the distribution form of ferromagnetic particle inclusions and elastic parameters on the effective magnetostriction of superconductors. A dimensionless parameter is introduced to describe the spatial distribution form of ferromagnetic particles in the matrix, and the calculation is carried out using the elastic mechanical plane strain method. The change of the effective magnetostriction following the elastic parameter is given for three kinds of distribution forms: single-chain, planar–laminar, and spatial three-dimensional multi-chain, respectively. The results show that the distribution of ferromagnetic particle inclusions and the change of elastic parameters have a notable influence on the displacement and magnetostrictive distribution of superconductors.

Magnetic and Magnetostrictive Behaviors of Laves-Phase Rare-Earth-Transition-Metal Compounds Tb1-xDyxCo1.95.

The magnetic morphotropic phase boundary (MPB) was first discovered in Laves-phase magnetoelastic system Tb–Dy–Co alloys (PRL 104, 197201 (2010)). However, the composition-dependent and temperature-dependent magnetostrictive behavior for this system, which is crucial to both practical application and the understanding of transitions across the MPB, is still lacking. In this work, the composition-dependence and temperature-dependence of magnetostriction for Tb1−xDyxCo1.95 (x = 0.3~0.8) are presented. In a ferrimagnetic state (as selected 100 K in the present work), the near-MPB compositions x = 0.6 and 0.7, exhibit the largest saturation magnetization MS and the lowest coercive field HC; by contrast, the off-MPB composition x = 0.5, exhibits the largest magnetostriction, the lowest MS, and the largest HC. Besides, a sign change of magnetostriction is observed, which occurs with the magnetic transition across the MPB. Our results suggest the combining effect from the lattice strain induced from structure phase transition, and the influence of the MPB on magnetocrystalline anisotropy. This work may stimulate the research interests on the transition behavior around the MPB and its relationship with physical properties, and also provide guidance in designing high-performance magnetostrictive materials for practical applications.

Magnetostriction and damping of forced vibrations in Fe-Cr-Mo-Al alloy

The magnetostriction, damping capacity and mechanical properties of a Fe-Cr-Mo-Al alloy are studied and compared with binary Fe-Cr and Fe-Al alloys. Synchronous change in magnetostriction and damping in Fe-16Cr-0.6Mo-0.6Al alloy: the maximum magnetostriction strain and damping capacity are obtained after annealing at 900 °C followed by air cooling. Frequency dependence of damping in subresonance range is analyzed and interpreted in terms of variations in relaxation time and stiffness of DMA.

Analysis using physics model to understand magnetoelectric nanorobotic structures for targeted cell manipulation

Magnetoelectric (ME) nanorobotic structures has application in targeted biological cell manipulation and optimized drug delivery. An approximate 70 nm diameter of Cobalt Ferrite- Barium Titanate, ferromagnetic core and piezoelectric shell is studied in context to its ability for nanoelectroporation in biological cell. Physics modeling is performed using COMSOL Multiphysics and quantitative analysis is used to understand the impact of applied magnetic field on the generated mechanical waves and electric pulses. The focus of this paper is to compliment relevant in vitro studies with ME nanorobots and to understand real-time changes in magnetostriction, piezoelectric and nanoelectroporation. The design of the magnetic navigation system with the relevant parameters to generate the required flux density for magnetostriction is discussed extensively. Assuming strong coupling between the core-shell, the 20 nm piezoelectric barium titanate contributes to electric pulsation that alters the membrane permeability leading to increased conductivity. This real time theoretical analysis provides scope for relevant clinical studies for engineering swarm of nm range robotic composites for targeted cell manipulation.

Smart Self-Sensing Composite: Piezoelectric and Magnetostrictive FEA Modeling and Experimental Characterization Using Wireless Detection Systems.

This research work focuses on the development of a piezoelectric magnetostrictive smart composite with advanced sensing capability. The composite piezoelectric property is achieved from the dispersion of single-walled carbon nanotubes (SWCNTs) and the magnetostrictive property from Terfenol-D nanoparticles. Finite element analysis (FEA) is used to examine the feasibility of modelling the piezoelectric (change in electric field) and magnetostrictive (change in magnetic field) self-sensing responses in the presence of applied stress. The numerical work was coupled with a series of mechanical tests to characterize the piezoelectric response, magnetostriction response and mechanical strength. Tensile tests of the composite samples manufactured as is (virgin), samples with SWCNTs, samples with Terfenol-D nanoparticles and samples with both SWCNTs and Terfenol-D nanoparticles were conducted. It was observed that an increase in volume fraction of Terfenol-d nanoparticles increases the change in magnetization, therefore increasing voltage response up to the point of saturation. The optimum change in amplitude was observed with 0.35% volume fraction of Terfenol-D nanoparticles. A constant ratio of SWCNTs was maintained, and maximum change in electrical resistance was at 7.4%. Fracture toughness for the samples with all nanoparticles was explored, and the results showed improved resistance to crack propagation.

Magnetic Domain and Magnetic Properties of Tb–Dy–Fe Alloys Directionally Solidified and Heat Treated in High Magnetic Fields

(Tb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.27</sub> Dy <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.73</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.04</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.95</sub> alloys directionally solidified in a 4 T high magnetic field were heat treated in various high magnetic fields. Changes in magnetic domain structure, magnetostriction, and magnetization of the alloys were investigated. The alloys treated at 12 T showed the highest magnetostriction, followed in descending order by the alloys treated at 0, 6, 3, and 9 T. The alloys treated at 12 T showed the highest light and dark contrast in the domain image, followed in descending order by the alloys solidified at 6, 0, 3, and 9 T. The change in magnetostriction can be mainly attributed to the alteration of the light and dark contrast in the domain image induced by the high magnetic fields. It can be proved that the high magnetic field can be effectively applied to the directionally solidification and heat treatment processes of Tb-Dy-Fe alloys to improve their magnetostrictive performance.

Dependence of the noise of an orthogonal fluxgate on the composition of its amorphous wire-core

In this paper we study the effect of magnetostriction of Co-rich amorphous microwire to the noise of the orthogonal fluxgates based on such wires. The magnetostriction was modified by changing the relative amount of iron x with the respect of the total amount of cobalt and iron in the alloy. Specifically we changed x in the composition (Co1−xFex)75Si15B10 casting wires with the following values of x: 0.05, 0.055, 0.06, 0.062, 0.065, 0.07 and 0.08. We found out that the noise indeed depends on the composition of the wire: while it is minimum (2.5 pT/Hz) for x between 0.06 and 0.062 where the magnetostriction is vanishing (λs ≈ 10−7) it significantly increases to tens of pT/Hz for both positive and negative magnetostriction when λs becomes one order of magnitude bigger. We verified that once the composition returns a magnetostriction low enough (around x = 0.06) then the noise does not depend on mechanical stress anymore. In fact the noise of a sensor with x = 0.06 is the identical in its natural curved state and when bended straight; for vanishing magnetostriction the bending does not affect at all the noise, as on the contrary it happens with larger magnetostriction. This suggests that once the wire has composition with x = 0.06 the remaining noise is not caused by mechanical stress. Finally we show how to overcome the problem of offset arising after annealing if continuous annealing current is used. We explain how this could be due by the fact that magnetostriction changes with temperature and even a wire with vanishing magnetostriction at room temperature can became significantly magnetostrictive at annealing temperature. For this reason we propose a method of annealing consisting rising the temperature of the wire while the wire is kept in its natural curved state. In this way no mechanical stress is applied to the wire during the annealing process, when the temperature is high enough to make it magnetostrictive even if it is non-magnetostrictive at room temperature. We show how this method suppresses the offset and significantly reduces the noise.

Investigation of Magnetostriction in Second Generation High Temperature Superconductors

Superconductors help to drastically improve the efficiency in every field by making the transmission losses of electrical energy to minimum. Superconductors show special properties only when their parameters like temperature, magnetic field, current density, mechanical strain are within their critical limits. Effect of magnetic field on second generation high temperature superconducting compounds have been studied in past few years. In this paper, the numerical simulation of the magnetostriction effect of second generation superconductor REBCO is discussed. The results obtained from numerical studies is compared with the experimental results reported in literature. The findings show that there is good agreement and all the three samples are showing rapid change in magnetostriction when the magnetic field is above 106 A/m.

A Vascular Thrombus Therapy Method Based on Magnetic-Induced Vibration.

A vascular thrombus therapy method based on magnetic-induced vibration is presented. It is a mechanicalway of removing vascular thrombus that adopts the combined use of two concepts, namely (i) magnetic-induced vibration of magnetostrictive materials and (ii) changes in physical form of thrombus under high-frequency impact and vibration. This method has many advantages that (i) eliminate the side effects of drug treatment, (ii) reduce the complexity of traditional mechanical method, and (iii) improve the reliability of treatment. Practical results obtained from the simulations and experiments are included. They verify the proposed system and indicate that this method can effectively treat vascular thrombus and reduce patient's suffering and costs. Bioelectromagnetics. 2019;40:391-401. © 2019 Bioelectromagnetics Society.

Spin-charge-lattice coupling in quasi-one-dimensional Ising spin chain CoNb2O6

Magnetization, magnetostriction and dielectric constant measurements are performed on single crystals of quasi-one-dimensional Ising spin chain CoNb2O6 at temperatures below and above the antiferromagnetic phase transition. Field-induced magnetic transitions are clearly reflected in magnetodielectric and magnetostriction data. Sharp anomalies are observed around the critical fields of antiferromagnetic to ferrimagnetic and ferrimagnetic to saturated-paramagnetic transition in both magnetodielectric and magnetostriction experiments. Detailed analysis of temperature and field dependence of dielectric constant and magnetostriction suggests that spins are coupled with lattice as well as charges in CoNb2O6. Below the antiferromagnetic transition temperature, the overall resemblance in anomalies, observed in various physical parameters such as magnetization, dielectric constant, magnetostriction and magnetic entropy change gives a deeper insight about the influence of spin configuration on these parameters in CoNb2O6.

Magnetostrictive Properties of Mn0.70Zn0.24Fe2.06O₄ Ferrite.

This paper presents the results of measurements of magnetostrictive properties of Mn0.70Zn0.24Fe2.06O4 ferrite for power applications. Frame-shaped samples were used for measurements to guarantee a uniform magnetizing field and magnetostrictive strain distribution. Magnetostrictive hysteresis loops were measured by semiconductor strain gauges. The results indicate that the magnetostrictive characteristic of Mn0.70Zn0.24Fe2.06O4 ferrite is non-monotonic and magnetostriction changes have opposite signs for higher values of the magnetizing field.

Large uniaxial magnetostriction with sign inversion at the first order phase transition in the nanolaminated Mn2GaC MAX phase

In 2013, a new class of inherently nanolaminated magnetic materials, the so called magnetic MAX phases, was discovered. Following predictive material stability calculations, the hexagonal Mn2GaC compound was synthesized as hetero-epitaxial films containing Mn as the exclusive M-element. Recent theoretical and experimental studies suggested a high magnetic ordering temperature and non-collinear antiferromagnetic (AFM) spin states as a result of competitive ferromagnetic and antiferromagnetic exchange interactions. In order to assess the potential for practical applications of Mn2GaC, we have studied the temperature-dependent magnetization, and the magnetoresistive, magnetostrictive as well as magnetocaloric properties of the compound. The material exhibits two magnetic phase transitions. The Néel temperature is TN ~ 507 K, at which the system changes from a collinear AFM state to the paramagnetic state. At Tt = 214 K the material undergoes a first order magnetic phase transition from AFM at higher temperature to a non-collinear AFM spin structure. Both states show large uniaxial c-axis magnetostriction of 450 ppm. Remarkably, the magnetostriction changes sign, being compressive (negative) above Tt and tensile (positive) below the Tt. The sign change of the magnetostriction is accompanied by a sign change in the magnetoresistance indicating a coupling among the spin, lattice and electrical transport properties.

Terfenol-D actuator behavior under pre- stress and step input current

Magnetostriction is the change in shape of materials under the influence of an external magnetic field as well as under pre- stress. The cause of magnetostriction change in length is the result of the rotation of small magnetic domains. This rotation and re-orientation causes internal strains in the material structure. The strains in the structure lead to the stretching (in the case of positive magnetostriction) of the material in the direction of the magnetic field. During this stretching process the cross-section is reduced in a way that the volume is kept nearly constant. The size of the volume change is so small that it can be neglected under normal operating conditions. Applying a stronger field and pre-stress leads to stronger and more definite re-orientation of more and more domains in the direction of magnetic field. When all the magnetic domains have become aligned with the magnetic field the saturation point has been achieved.

Evaluation of Tri-Axial Magnetostriction in Cube-Oriented Fe-Ga Single Crystal by Using X-Ray Diffraction Method

We carried out in situ tri-axial magnetostriction analysis for cube-oriented Fe-18%Ga single crystal by X-ray diffraction measurement under magnetic field. Periodic change in tri-axial magnetostriction with applied magnetic field direction was clearly observed. However, those values in [100] and [010] directions were not equivalent. Theoretical calculation of magnetostriction considering domain structure revealed this is caused by the non-equivalent volume fraction of initial magnetic domains.

Tailoring magnetostriction with various directions for directional solidification Fe82Ga15Al3 alloy by magnetic field heat treatment

The magnetostriction of the Fe82Ga15Al3 alloy, along the length and width, can be tailored by applying a magnetic field heat treatment. In this work, the Fe82Ga15Al3 sheet was cut from the directional solidified Fe82Ga15Al3 alloy with the ⟨100⟩ preferred orientation and was annealed at 720 °C for 30 min under a magnetic field of 800 Oe along the length direction with a heating and cooling rate of 100 °C/min. The magnetostrictive properties along the length and width directions were modified to λ// = 7 ppm and λ⊥ = −210 ppm from λ// = 210 ppm and λ⊥ = −10 ppm for the initial sample prior to the magnetic field heat treatment. The cellular-like magnetic domain structure was composed of parallel 180° stripe domains and vertical 90° domains observed using a magnetic-force microscope. The change in magnetostriction along parallel and perpendicular directions was mainly resulted from the rotation of the magnetic domain units.

Successive field-induced transitions in BiFeO3 around room temperature

The effects of high magnetic fields applied perpendicular to the spontaneous ferroelectric polarization on single crystals of BiFeO$_3$ were investigated through magnetization, magnetostriction, and neutron diffraction measurements. The magnetostriction measurements revealed lattice distortion of $2\times 10^{-5}$, during the reorientation process of the cycloidal spin order by applied magnetic fields. Furthermore, anomalous changes in magnetostriction and electric polarization at a larger field demonstrate an intermediate phase between cycloidal and canted antiferromagnetic states, where a large magnetoelectric effect was observed. Neutron diffraction measurements clarified that incommensurate spin modulation along [110] direction in the cycloidal phase becomes commensurate in the intermediate phase. Theoretical calculations based on the standard spin Hamiltonian of this material suggest an antiferromagnetic cone-type spin order in the intermediate phase.

Magnetic Flux Valve: A Magnetoelectric Materials-Based Device for Conversion and Control of Electric Power

This paper introduces a voltage-controlled static magnetic device called magnetic flux valve. It is mainly used in a magnetic circuit to actively control the magnetic flux through the magnetic circuit. The magnetic flux valve has a laminated structure of two different types of layers made of a magnetostrictive material, e.g., amorphous alloy ribbon, and a piezoelectric material, e.g., piezoelectric sheet. The permeability of the magnetostrictive layers changes when an external control voltage applied to the piezoelectric layers changes, which is known as the converse magnetoelectric effect. A permeability change of the magnetic flux valve will lead to a change of the reluctance of the magnetic flux valve and the reluctance of the magnetic circuit containing the magnetic flux valve. As a consequence, the magnetic flux and/or its distribution in the magnetic circuit will change. There is a great potential to use the proposed magnetic flux valve to develop new equipment, such as tunable inductor and adjustable-voltage-ratio transformer for more flexible conversion and control of electric power in many applications. This paper presents the concept, magnetic properties, working principles, and applications of the magnetic flux valve.

Hydrostatic pressure effect on magnetic hysteresis parameters of pseudo‐single‐domain magnetite

AbstractThis paper reports the first in situ magnetic hysteresis measurements of pseudo‐single‐domain (PSD) magnetite under high pressure up to 1 GPa. The magnetic hysteresis measurements of stoichiometric PSD magnetite samples under hydrostatic pressure were carried out using a piston‐cylinder high‐pressure cell, and the pressure dependence of the hysteresis parameters of PSD magnetite was calculated from the hysteresis curves. It was found that coercivity (Bc) increases with increasing pressure as a quadratic function up to 1 GPa by ∼90%, which is different from the pressure dependences of Bc of multidomain and single‐domain magnetites. Coercivity of remanence also increases as a quadratic function, and saturation remanence (Mrs) increases with pressure up to 0.5 GPa by ∼20% until reaching saturation. In contrast, saturation magnetization is constant up to 1 GPa. The approximate demagnetizing factor calculated from the ratio Bc/Mrs increases with increasing pressure, suggesting that the number of lamellar domains increases with increasing pressure. The number of lamellar domains and domain wall width are theoretically estimated to increase under high pressure due to the changes in magnetostriction, elastic, and magnetocrystalline anisotropy constants, and these changes in magnetic domain structure should relate to the changes in the magnetic properties of PSD magnetite.

Stress-Induced Anisotropy and Stress Dependence of Saturation Magnetostriction in the Jiles-Atherton-Sablik Model of the Magnetoelastic Villari Effect

Abstract The paper presents the results of the magnetoelastic Villari effect modelling in high-permeability Mn0.51Zn0.44Fe2.05O4 ferrite. Modelling was performed on the basis of measurements of magnetoelastic characteristics of frame-shaped samples. For the modelling, the corrected Jiles-Atherton-Sablik model was used. On the base of modelling results, the stress dependence of parameter k and stress-induced anisotropy were estimated. As a result the changes of saturation magnetostriction of Mn0.51Zn0.44Fe2.05O4 ferrite subjected to stresses were calculated. Such changes were previously observed experimentally. However, the phenomenon of stress-induced sign change of saturation magnetostriction was never previously explained quantitatively