Enhancement Of Magnetostriction Research Articles

Large enhancement of magnetostriction due to compaction hydrostatic pressure and magnetic annealing in CoFe2O4

Polycrystalline CoFe2O4 was produced by a ceramic method. The heat-treated powder was pressed, varying the hydrostatic pressure between 87 and 278 MPa, and was heat-treated again at 1350 °C for 24 h. All magnetic parameters showed a clear dependence on this hydrostatic pressure. The saturation magnetization showed a minimum, and the coercivity, the anisotropy, and the magnetostriction showed a maximum at compaction pressures around 150 MPa. This pressure dependence of the magnetic parameters can be explained by a cation redistribution due to the hydrostatic pressure and heat treatment. Additionally, all samples were field-annealed in an external field of 10 T (at 300 °C for 3 h). The field-annealing process causes an induced uniaxial anisotropy, which results in a reduction of the coercivity (in the easy axis) as well as a dramatic increase in the magnitude of the magnetostriction along the hard axis. Maximum magnetostriction value of -400×10-6 was obtained. Additionally, dλ/dH is increased within a factor of three with magnetic heat treatment.

Mechanism of Large Magnetostriction of Galfenol

Galfenol (Fe100-xGax) and related alloys are very promising new magnetostrictive materials for broad applications. Using the density-functional full-potential linearized augmented plane wave method, we performed systematic theoretical investigations to explore the mechanism that governs the large enhancement of magnetostriction in Galfenol. Here, we review our main theoretical findings on factors that lead to 1) the increase of magnetoelastic coupling; 2) the decrease of the tetragonal shear modulus; and 3) the phase instability. Several ternary FeGaX alloys (X=Zn, Pt, Ir, Ge) were predicted to have large magnetostrictive coefficients, through manipulating electron population and strength of spin-orbit coupling.

Density functional theory study of Fe3Ga

First-principles scalar relativistic calculations in supercells of 16 atoms are used to represent disordered B2 ordering of Fe3Ga in order to observe the effect of Ga–Ga pairs on the electronic structure of this alloy. From a comparison with pure bcc Fe it is observed that the energy position and occupation of eg and t2g states are largely affected by the Ga–Ga pairs and strengthened intraplane interactions takes place. The results show that a larger hybridization of the conduction band is in the source of the magnetostriction enhancement experimentally observed in Galfenol.

Ab initio studies of the effect of nanoclusters on magnetostriction of Fe1−xGax alloys

Using the density functional calculations, we investigated the effect of nanoprecipitation on the magnetostriction of Fe1−xGax alloys. While the B2-like FeGa clusters undergo slight tetragonal distortion, D03-like FeGa clusters remain cubic in the Fe matrix. Moreover, we found that B2-like nanostructures produce negative magnetostriction, whereas D03-like nanostructures give small positive magnetostriction in the hypothetical inhomogeneous structures. Therefore, the formation of nanoscale precipitates cannot be the reason for the extraordinary enhancement of magnetostriction of Fe1−xGax alloys.

Magnetic domains in magnetostrictive Fe–Ga alloys

Lorentz microscopy was applied to the observation of magnetic domains in iron-gallium (Fe–Ga) alloys. Results did not show any link between the magnetic domains and the magnetostriction enhancement by Ga addition, but did reveal that the drastic decrease in magnetostriction for Fe–31.2 at. % Ga was due to the presence of large scale precipitates. Magnetic domain features did not change in the alloys of A2, D03, A2+D03, A2+B2+D03, and A2+fine scale precipitates. Large scale precipitates within the slow-cooled Fe–31.2 at. % Ga affected both the distribution and wall motion of magnetic domains.

Enhancement of Magnetostriction in Internally-Biased Terfenol-D 2-2 Composites

A key issue in the fabrication of Terfenol-D 2-2 composites with internal magnetic field biasing is the selection of appropriate constituent materials to obtain high magnetostriction while keeping optimum magnetomechanical properties. The fabrication process is costly and time consuming and, therefore, numerical methods to predict their properties are useful. In this paper, finite element analysis (FEA) of the magnetostriction of such composites has been carried out using the commercial package ABAQUS. It has been shown that composites fabricated using Nd2Fe14B for the permanent magnetic material layers possess the highest internal fields within the Terfenol-D layers, although the overall strain of these composites is limited to approximately 800 times 10-6 due to the high elastic modulus of Nd2Fe14B. Simulations showed that the strain can be enhanced by choosing a different material with a lower elastic modulus for the permanent magnetic layer even though the internal field is lower. The simulations showed that the strain can increase by 12% if the Nd2Fe14B layer is substituted by SmCo5; by 23 % if it is substituted by Sm2Co17; and by 35 % if it is substituted by Alnico.

Magnetic force microscopy observation of undercooled Fe81Ga19 magnetostrictive alloys

The magnetic domain structure of undercooled Fe81Ga19 alloys has been found to be very sensitive to the variation of undercooling during the solidification process. With increasing degree of undercooling, the evolution of domain patterns, magnetic contrast and the degree of the orientation was investigated which is relative to the magnetostriction. The combination of x-ray diffraction and magnetic force microscopy analyses has been shown to add new insights into the nature of the enhancement of magnetostriction in Fe81Ga19 alloys.

Study on advanced multilayered magnetostrictive thin film coating techniques for MEMS application

This paper is to investigate the multilayer deposition technique with selective DC magnetron sputtering for the fabrication of partially film deposited magnetostrictive actuator. The multilayer of this study was consisted of TbDyFe and Ni layers. The magneto-mechanical characteristics of TbDyFe (called as Terfenol-D) and Ni multilayered thin films with different thickness ratios of TbDyFe/Ni/TbDyFe (0.2/0.1/0.2, 0.2/0.1/0.1, 0.2/0.1/0.0 μm) were considered and the magnetostrictive multilayers were deposited on two kinds of micro-multi-body actuator systems to check the size effect. To fabricate the multilayered film on Si based micro-frame, micromachining process and selective DC magnetron sputtering techniques were combined. The deposited film thicknesses were measured by X-ray diffraction (XRD). To characterize the magneto-mechanical properties of the TbDyFe/Ni/TbDyFe film, the magnetization of the film on the fabricated actuator was observed using vibrating sample magnetometer (VSM) and the magnetostriction of the actuator was determined by measuring the differences of the curvature of the coated silicon substrates using the optical cantilever method. For the application to a micro-actuator, the maximum deflection of the actuator under 0.5 T was 280 ppm. The results indicate that the Ni layer makes 3–5% lower coercive force and 10–15% enhancement of magnetostriction in low magnetic field (<0.5 T).

Enhancement of the magnetostrictive properties of Co0.9Mn0.1Fe2O4 synthesized by using the precursor preparation technique

Co1−xMnxFe2O4 has been prepared by calcining hydrotalcite-like precursors for the first time. The crystallization behaviors and magnetoelastic properties of the samples have been investigated. The experimental results show that precursor preparation technique is superior compared to the traditional ceramic method. By adopting hydrotalcite-like precursor preparation technique, a fine and more uniform microstructure can be developed. An obvious enhancement of magnetostriction from 95 to 122 ppm and saturation magnetization from 66 to 78 emu/g has been obtained in Co0.9Mn0.1Fe2O4 composite under lower magnetic filed. This is propitious to apply to sensors and actuators.

Fabrication Process and Magnetostriction of Infiltrated Terfenol-D/Epoxy Composite

Giant magnetostrictive composites have attracted a great deal of attention by supplementing shortcomings of monolithic Terfenol-D such as brittleness, eddy current loss and formability. Recently, infiltrated Terfenol-D/Epoxy composite has been developed as an alternative composite. This composite was fabricated by an unidirectional solidification of Terfenol-D followed by an infiltration of epoxy. The iron content in composite has been changed in order to control volume fraction of RFe2 phase producing magnetostriction on Terfenol-D/Epoxy composite. The magnetostriction of both as-grown and infiltrated Terfenol-D/Epoxy composite was measured to confirm the effects of eutectic phase and heat treatment on magnetostriction. The enhancement of magnetostriction of Terfenol-D/Epoxy composite was mostly contributed by the eutectic phase through the hindering of movement and rotation of domain walls. The magnetostriction modelling of Terfenol-D/Epoxy composite was suggested, based on the change of texture and elastic modulus. The suggested model was in good agreements with the experimental results on the measurement of magnetostriction of Terfenol-D/Epoxy composite.

2517 マイクロマシン用超磁歪材料の基礎的研究(J10-4 磁歪・圧電材料,J10 知的材料・構造システム)

Influences of electron beam (EB) irradiation on magnetostriction and its susceptibility of Fe_<2.6>Sm alloy thin films have been investigated. The alloy thin film deposited on a (100) plane of silicon wafer is prepared by using direct current magnetron sputtering apparatus. The irradiation enhances compressive magnetostriction and its susceptibility. The enhancement of magnetostriction is caused by decreasing in the volume fraction of low magnetostrictive crystalline phase, resulting in generating the large magnetostriction. The high susceptibility is explained by randomization, induced by EB-irradiation, of Fe_<2.6>Sm amorphous sample, which is easy to rotate the magnetic moment.

Magnetostrictive properties of Kr-ion irradiated multilayers

The influence of irradiation with high energy Kr ions has been experimentally studied on the magnetostrictive properties of TbFe/Co multilayers. Enhancement of magnetostriction at saturation can be obtained at an optimal fluence with a lower saturation field than for the non-irradiated multilayer. For high fluences, these properties are degraded.

Magnetostriction and microstructure of the melt-spun Fe83Ga17 alloy

The ribbons with different thicknesses of Fe83Ga17 alloy were prepared by melt spun. The maximum magnetostriction of −2100ppm has been obtained in the ribbon with the thickness of 75μm. The microstructures of the ribbons were determined by x-ray diffraction. It was found that DO3 structure emerges in those ribbons melt spun at a higher cooling rate. This special DO3 structure is favorable to the enhancement of magnetostriction. It is considered that more short-range ordering of Ga atoms appeared when liquid alloy was solidified with a certain extreme cooling rate. Such short-range ordering of Ga atoms brings a local stress and results in the giant magnetostriction. The large demagnetizing magnetic energy in the normal direction of the ribbons causes the magnetic moments parallel to the ribbon plane. When an applied magnetic field is perpendicular to the ribbon plane, the magnetic moments turn 90° and generate giant magnetostriction.

Origin of large magnetostriction in FeGa alloys

Using the highly precise full potential linearized augmented plane wave method, the phase stability, magnetism, and magnetostriction of Fe3Ga alloys were investigated. The magnetostrictive coefficients strongly depend on the atomic arrangement. The B2-like structure, although it is unstable in the small unit cell chosen here, appears to play a crucial rule for the large positive magnetostriction in the FeGa alloys as observed recently. Electronic origin of enhancement in magnetostriction is discussed in terms of density of states and band structures.

Magnetostriction enhancement in Laves compounds (Sm,Yb)Fe 2

The magnetic and magnetostrictive properties of compounds (Sm 1− x Yb x )Fe 2 (0⩽ x⩽0.3) have been studied. When x<0.15, the compounds crystallize in the cubic structure of a C15 MgCu 2-type Laves phase. For x>0.15 a small amount of (Sm,Yb)Fe 3 compound with a PuNi 3-type structure appears and its amount increases with increasing Yb content. The magnetic ordering of 1 : 2 compounds is slightly strengthened by the substitution of Yb for Sm. Lattice parameters for Laves phase compounds keep almost unchanged for the whole range investigated, indicating the deviation from Vegard's law linear variation with composition. A magnetostriction enhancement of about 15% when x=0.05% both in spontaneous and polycrystalline magnetostrictions in Sm 0.95Yb 0.05Fe 2 has been observed, which can be ascribed to the anisotropy compensation effect.