Maximum Magnetostriction Research Articles

Effect of Ga content on the magnetostriction and microstructure of Fe–Ga ribbons

The ribbons with different Ga contents were prepared by the melt-spun method. The maximum magnetostriction of −2100 ppm has been obtained in the ribbons with 17 at% Ga. The microstructures of ribbons were determined by XRD and HRTEM. It was found that DO 3 structure and Ga-rich clusters emerge in those ribbons of Fe 83Ga 17 with wheel speed of 12 m/s. The Ga-rich clusters and modified DO 3 structure result in a giant magnetostriction of Fe–Ga alloy ribbons.

Magneto-elastic modeling of composites containing chain-structured magnetostrictive particles

Magneto-elastic behavior is investigated for two-phase composites containing chain-structured magnetostrictive particles under both magnetic and mechanical loading. To derive the local magnetic and elastic fields, three modified Green's functions are derived and explicitly integrated for the infinite domain containing a spherical inclusion with a prescribed magnetization, body force, and eigenstrain. A representative volume element containing a chain of infinite particles is introduced to solve averaged magnetic and elastic fields in the particles and the matrix. Effective magnetostriction of composites is derived by considering the particle's magnetostriction and the magnetic interaction force. It is shown that there exists an optimal choice of the Young's modulus of the matrix and the volume fraction of the particles to achieve the maximum effective magnetostriction. A transversely isotropic effective elasticity is derived at the infinitesimal deformation. Disregarding the interaction term, this model provides the same effective elasticity as Mori–Tanaka's model. Comparisons of model results with the experimental data and other models show the efficacy of the model and suggest that the particle interactions have a considerable effect on the effective magneto-elastic properties of composites even for a low particle volume fraction.

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.

Improvement of magnetomechanical properties of cobalt ferrite by magnetic annealing

We report dramatic improvements in both magnetostriction level and strain derivative of polycrystalline cobalt ferrite as a result of magnetic annealing. Magnetostrictive cobalt ferrite composites have potential for use in advanced magnetomechanical stress and torque sensors due to their high sensitivity of magnetization to applied stresses and high levels of magnetostriction. Results show that annealing cobalt ferrite at 300/spl deg/C in air for 36 h under a dc field of 318 kA/m (4 kOe) induced a uniaxial anisotropy with the easy axis being along the annealing field direction. Under hard axis applied fields, the maximum magnetostriction measured along the hard axis at room temperature increased in magnitude from -200/spl times/10/sup -6/to -252/spl times/10/sup -6/ after annealing. The maximum strain derivative (d/spl lambda//dH)/sub max/, which is related to stress sensitivity, increased from 1.5/spl times/10/sup -9/ A/sup -1/m to 3.9/spl times/10/sup -9/ A/sup -1/m. The results can be interpreted in terms of the effects of induced uniaxial anisotropy on the domain structure and magnetization processes.

Magnetic, martensitic transformation, magnetostriction and shape memory effect in Co50Ni20Ga30 melt-spun ribbons

The off-stoichiometric Heusler alloy Co50Ni20Ga30 was synthesized by using the melt-spinning technique. The Co50Ni20Ga30 ribbon exhibited a thermo-elastic martensitic transformation from cubic to a tetragonal structure at 270 K during cooling. The martensitic phase at lower temperature exhibited a high-saturated magnetization of 51.00 A m2 kg−1 and a high anisotropy field of more than 1 T. The material showed a recoverable two-way shape memory effect with a strain of 0.15% upon the martensitic transformation. The sample showed the maximum magnetostriction of about 97 ppm shrinkage for an applied magnetic field of 1.5 T at 200 K.

Effect of Boron Addition on Magnetostrictive and Mechanical Properties in Rolled Polycrystalline Fe-187%Ga Alloy

ABSTRACTDuring attempts to roll Fe-18.7%Ga alloy (atomic%), an alloy of interest because single crystal samples exhibit magnetostriction of ∼400 ppm, cracks formed along grain boundaries and subsequently samples fractured during hot rolling such that the alloy was too brittle to make thin sheets. While variations to rolling schedules (temperatures, times, roll diameters, etc.) may improve rollability, in this paper we investigate the effect of boron addition on Fe-18.7% Ga alloy magnetostrictive and mechanical properties. Thin sheets of Fe-18.7%Ga alloy plus 0.5 and 1.0 at.%B were successfully fabricated to thickness of 0.35 mm using rolling processes. It was observed that the fracture surface of the B-free alloy clearly appeared as an intergranular fracture mode and that of the B-added alloys was changed to a transgranular fracture mode with grain refinement. The annealed sheets with boron content of 0.5 and 1.0 at.% exhibit the maximum magnetostriction values of 103 and 184 ppm, respectively. In the case of Fe-18.7%Ga plus 1.0 %B, Fe2B phase presents throughout the α-iron matrix in small amount.

Effect of Magnetic Field on the Crystalline Structure of Magnetostrictive TbFe2 Alloy Solidified Unidirectionally in Microgravity

We performed unidirectional solidification experiments on TbFe(2) alloy in a static magnetic field in microgravity of 10(-4) g for 10 sec obtained by a 490 m free fall of the Japan microgravity center (JAMIC). When the magnetic field strength was increased from zero to 4.5 x 10(-2) T during unidirectional solidification in microgravity, a [1 1 1] crystallographic alignment dominated, and the maximum magnetostriction constant increased from 1,000 ppm to 4,000 ppm. For unidirectional solidification in normal gravity, the maximum magnetostriction constant remained at 2,000 ppm with increasing magnetic field. The columnar structure grows and orients along the magnetic field. TbFe(2) crystals grow in microgravity predominantly in the same direction as the magnetic field.

Influence of rapid cycle annealing temperature on the properties of Tb-Fe magnetostrictive films

In this paper, magnetostrictive Tb-Fe thin films were prepared by DC magnetron sputtering and then heat treated using rapid cycle annealing. The influences of annealing temperature on the phases and magnetic properties are discussed. Results show that increasing annealing temperature can promote the formation of BCC-Fe nanocrystals and cause oxidation of the rare earth element. Annealing does increase the domain size and result in domain boundary irregularities relative to the as-deposited film. Higher temperature has little effect on the domain structure. Magnetization at filed of 1600kA/m is first increased with annealing temperature because of the precipitation of Fe and then decreased because of the oxidation. The latter also caused the coercivity increase when the annealing temperature is above 500°C. Maximum magnetostriction coefficient of ∼145ppm at 40kA/m was obtained for 300°C and 500°C annealed samples.

ＤＣマグネトロンスパッタリング法によるＦｅ‐Ｇａ合金薄膜の作製

The magnetostrictive properties of Fe-Ga (Ga: 8 at%-21 at%) alloy films prepared by DC magnetron sputtering system were investigated. Base pressure was less than 1.0×10-4 Pa and Fe-Ga films were deposited onto Single crystal Si(100) and polyimide substrate at room temperature with DC 200 W in an Ar atmosphere of 2.5×10-1 Pa. The lattice parameter of Fe-Ga films with a bcc structure increased with the increasing Ga concentration. The Fe-Ga films showed columnar grains with a crystalline orientation for ‹110› perpendicular to the film plane. The magnetostriction of Fe-Ga films increased with the increasing Ga concentration. Fe-21 at%Ga film showed a maximum magnetostriction of 180 ppm at an applied magnetic field of 1200 kA/m.

Ion irradiation effects on magnetostriction of Tb–Fe thin film

Giant magnetostrictive TbFe 2 thin films were prepared by the ion plating process. The films were treated by Ar plasma irradiation and heat-treatment. The plasma irradiation was carried out at low plasma energy by a high heat flux sheet plasma system. Both treatments lead to the increase in the maximum magnetostriction and the magnetostrictive susceptibility at low magnetic field. The plasma irradiation effects seem to be due to the heat generation during irradiation. The magnetostrictive characteristics are affected by the increase in in-plane anisotropy magnetization by treatments.

Effects of rare-earth element substitution on magnetostrictive properties of polycrystalline Tb-Dy-Fe alloys

Magnetostrictive properties of (Tb/sub 0.5/Dy/sub 0.5/)/sub 1-x/RE/sub x/Fe/sub 1.9/ (x=0-0.05, RE=Y, Ce, Sm, Gd, Ho, Yb) polycrystalline compounds were studied. Each rare-earth element formed a RE-Fe/sub 2/ Laves compound with a different lattice spacing. Corresponding to this difference, (Tb/sub 0.5/Dy/sub 0.5/)/sub 0.95/RE/sub 0.05/Fe/sub 1.9/ alloys showed a variation in lattice spacing as a result of the substitution of rare-earth elements and the prestress dependence of magnetostriction changed noticeably. In the case of Y, Sm, and Gd substitution, which showed greater lattice spacing than that of the Tb/sub 0.5/Dy/sub 0.5/Fe/sub 1.9/ alloy, the prestress dependence and maximum magnetostriction decreased. On the other hand, in the case of Ce, Ho, and Yb substitution, which showed a decrease in lattice spacing, the conspicuous prestress dependence was the same as that of the Tb/sub 0.5/Dy/sub 0.5/Fe/sub 1.9/ alloy and the maximum magnetostriction was greater than that of the latter alloy.

Unidirectional solidification of magnetostrictive materials using a magnetic field in microgravity.

Unidirectional solidification experiments of magnetostrictive materials of Tb(0.3)Dy(0.7)Fe(2-x), (Terfenol-D) alloy in a static magnetic field and microgravity were performed using the Japan Microgravity Center (JAMIC) free-fall facilities. When the magnetic field strength was increased from 0T to 3.7 x 10(-2) T during unidirectional solidification in microgravity, a <111> crystallographic alignment of the grains dominated, and the maximum magnetostriction constant increased from 500 ppm to 2,000ppm. For unidirectional solidification in normal gravity, the maximum magnetostriction constant remained at 1,000 ppm for increases in the magnetic field.

Magnetoelastic behavior in Co-based glass-covered amorphous wires

The effects of Fe content as well as the dc or ac stress current annealing conditions (current density, annealing time, and tensile stress) on the magnetoelastic behavior of amorphous Co/sub 72.5-x/Fe/sub x/Si/sub 12.5/B/sub 15/ (x=0, 3, 4.35, 5, and 7. at.%) glass-covered wires have been investigated. The saturation magnetostriction at zero applied stress /spl lambda//sub s/ (0) in the as-cast state of the samples is about -2.8/spl times/10/sup -6/; -0.6/spl times/10/sup -6/; -0.11/spl times/10/sup -6/; 0.36/spl times/10/sup -6/, and 0.9/spl times/10/sup -6/ for x=0, 3, 4.35, 5, and 7 at.% Fe, respectively. For nearly zero magnetostrictive amorphous Co/sub 68.15/Fe/sub 4.35/Si/sub 12.5/B/sub 15/ glass-covered wire, after stress current annealing /spl lambda//sub s/ (0) changes from small negative to small positive values. The positive /spl lambda//sub s/ (0) values are obtained after about 3-8 min annealing time for current densities higher than 130/spl times/10/sup 6/ A/m/sup 2/. The ac stress current annealing leads to an increase with maximum 60% of the maximum saturation magnetostriction value /spl lambda//sub s/ (0)/sub max/ (depending on the frequency value) in comparison with dc annealing for the same current density, treatment time, and tensile stress. For alloys with x=0, 3, 5, and 7 at.% Fe, after dc or ac stress current annealing with (60-180)/spl times/10/sup 6/ A/m/sup 2/, under 300-800 MPa, a modification up to 10% in /spl lambda//sub s/ (0) values was observed (the absolute value for negative magnetostrictive samples decreases while for positive magnetostrictive samples increases).

Synthesis of Tb 0.3Dy 0.7Fe 1.9 magnetostrictive alloy by unidirectional solidification in magnetic field and microgravity

We performed unidirectional solidification experiments on magnetostrictive materials of Tb 0.3Dy 0.7Fe 2− x , (Terfenol-D) alloy in a static magnetic field from 0 to 0.1 T and microgravity of 10 −4 g for 10 s. When the magnetic field strength was increased from 0 to 3.7×10 −2 T during unidirectional solidification in microgravity, a [1 1 1] crystallographic alignment of the grains dominated, and the maximum magnetostriction increased from 500 to 2000 ppm. However, when a magnetic field above 3.7×10 −2 T was applied during solidification, magnetostriction decreased to 1000 ppm because cracks were formed. For comparison, unidirectional solidification under field of 3.7×10 −2 T in normal gravity yields a maximum magnetostriction of 1000 ppm.

Temperature and stress dependencies of the magnetic and magnetostrictive properties of Fe0.81Ga0.19

It was recently reported that the addition of nonmagnetic Ga increased the saturation magnetostriction (λ100) of Fe over tenfold while leaving the rhombohedral magnetostriction (λ111) almost unchanged. To determine the relationship between the magnetostriction and the magnetization we measured the temperature and stress dependence of both the magnetostriction and magnetization from −21 °C to +80 °C under compressive stresses ranging from 14.4 MPa to 87.1 MPa. For this study a single crystal rod of Fe0.81Ga0.19 was quenched from 800 °C into water to insure a nearly random distribution of Ga atoms. Constant temperature tests showed that compressive stresses greater than 14.4 MPa were needed to achieve the maximum magnetostriction. For the case of a 45.3 MPa compressive stress and applied field of 800 Oe, the maximum magnetostriction at 80 °C decreases from its value at −21 °C by 12.9%. This small magnetostrictive decrease is consistent with a correspondingly small 3.6% decrease in magnetization over the same temperature range. This well-behaved temperature response makes this alloy particularly valuable for industrial and military smart actuator, transducer, and active damping applications. The measured value of Young’s modulus is low (∼55±1 GPa) and almost temperature independent. The large magnetostriction over a wide temperature range combined with the nonbrittle nature of the alloy is rare.

Unidirectional solidification of TbFe 2 alloy using magnetic field in microgravity

Unidirectional solidification experiments of TbFe 2 alloy using a static magnetic field in microgravity were performed in the Japan Microgravity Center. When the magnetic field strength was increased from 0 to 4.5×10 −2 T during unidirectional solidification in microgravity, a [1 1 1] crystallographic alignment of the grains dominated, and the maximum magnetostriction constant increased from 1000 to 4000 ppm. For unidirectional solidification in normal gravity, the maximum magnetostriction constant remained at 2000 ppm with increasing of magnetic field.

Determination of magnetostriction for spin-valve devices with 5.0 and 10.0 nm Permalloy layers

The objective of this study is to determine the extent of magnetostriction in spin valves. Spin valves were fabricated on a silicon substrate using dc magnetron sputter deposition techniques with the following structure: Ta5.0/NiFe5.0 or 10.0/Co1.0/Cu3.0/Co3.0/Ru0.6/Co2.0/FeMn10.0/Ta5.0, where the subscripts denote the layer thickness in nanometers. The Permalloy composition used in these studies was Ni80Fe20. Spin valves were created in a serpentine shape to maximize the total magnetostriction (ΔL/L) by increasing the device length per die area. Device widths of between 1 and 40 μm with lengths of 1000–40 000 μm were fabricated. Devices were subjected to an external magnetic field while a mechanical force was applied to the backside of the substrate. An increase in the anisotropy field Hk, is observed with increasing stress. This increase is observed for all devices tested but is more distinct for those containing the 5.0 nm Permalloy. Results show that maximum magnetostriction occurs abruptly at lower stress values for the 10.0 nm Permalloy while magnetostriction for the 5.0 nm Permalloy occurs gradually over a wider range of stress values. Magnetoresistance measurements also show an inverse relationship between applied stress and (ΔR/R) performance. Magnetostriction analysis becomes critical as both device complexity and integration levels increase.

Magnetostriction of Invar Alloy under Applied Stresses.

Magnetostriction curves of invar alloy are measured under various levels of uniaxial stress. Because of its low thermal expansion, the invar alloy is used in parts which suffer from large temperature change. To avoid the failure by thermal fatigue, thermal stress should be nondes-tructively evaluated. Since the invar alloy is ferromagnetic, the magnetization is accompanied by the magnetostriction. For ferromagnetic steel, we have already suggested to use the maximum magnetostriction in nondestructive stress measurement. If the magnetostriction of the invar slloy ahows the maximum value during the magnetization, it is expected to be used for the stress measurement. In this study, we measured stress dependence of the magnetostriction of invar alloy. We revealed that the knee point appears in the magnetostriction curve, while the maximum magnetostriction will not arise. It was found that the knee point magnetostriction and the minimum magnetostriction, which appears in the normal direction to the magnetization, can be used as parameters in the nondestructive stress measurement.

希土類元素置換されたＴｂ‐Ｄｙ‐ＲＥ‐Ｆｅ系ラーベス相化合物の構造と磁歪特性

The structures and magnetostrictive properties of (Tb0.5Dy0.5)1-xRExFe2 compounds (x = 0-0.05, RE = Y, Ce, Sm, Gd, Ho, Yb) were investigated. Each rare earth element was present as a solid solution in Laves phase and caused changes in the lattice spacing. In the cases of Y, Sm, and Gd substitution, which resulted in a wider lattice spacing than that of Tb0.5Dy0.5Fe2 compounds, the prestress dependence and maximum magnetostriction decreased. On the other hand, in the cases of Ho and Yb substitution, which decreased the lattice spacing, a conspicuous prestress dependence existed in the same way as for Tb0.5Dy0.5Fe2 compounds, and the maximum magnetostriction was greater than for those compounds.

The Invar Property of Elemental F.C.C. Co and Large Spontaneous Magnetostriction of B.C.C. Fe-Co

The ferromagnetic invar effect in f.c.c. 3d-transition metal alloys spans an (s+d) valence electron concentration range of 8.6 ≤ e/a ≤ 9.5. The maximum spontaneous magnetostriction associated with the invar effect occurs at e/a ≈︂ 8.7. For e/a ≤ 8.6, the anti-invar effect develops, for which the associated volume enhancement increases as the pure f.c.c. Fe composition of e/a = 8 is approached. The progressive change from anti-invar to invar in Fe1—xNix alloys takes place in the range of 0 ≤ x≤ 0.6 (8 ≤ e/a ≤ 9.2). The electron concentration of Fe1—xCox alloys falls within this range with 8 ≤ e/a ≤ 9, implying that Co should be an element having invar properties. To verify this assessment we examine, by thermal expansion measurements in the temperature range of 4 K ≤ T≤ 1500 K, the volumetric properties of FexCo1—x alloys with 0 ≤ x ≤ 1. Indeed, we find invar behavior in the f.c.c. phase of the alloys with concentrations ranging from x = 0.6 to pure Co. Aside from the invar property of pure f.c.c. Co, we observe features associated with the order–disorder transition (B2 ↔ b.c.c.) and a large magnetostriction in the b.c.c. phase related to magnetic ordering.