Chihiro Saito

Micromagnetostrictive vibrator using a U-shaped core of iron-gallium alloy (Galfenol)

A micromagnetostrictive vibrator using a U-shaped core made of iron-gallium alloy (Galfenol) was investigated. The vibrator consists of a Galfenol core, with a 1mm2 cross section, a length of 5.8mm, and a 0.3mm separation between the prongs of the “U,” driving coils, and an iron yoke to close the magnetic loop. The Galfenol vibrator is superior to the PZT type in its high mechanical strength, low drive voltage requirements, and wide temperature operating range, and compared to our previous cylindrical type vibrator has a simpler construction and higher bandwidth. A displacement of 1.2μm (220ppm) was verified for the prototype with a 5.8mm long Galfenol core; the high magnetostriction >200ppm is inherited from the stress-annealed Galfenol. The displacement was also maintained under a 21MPa tensile stress (1.5kg hanging weight). Incorporation of a Nd–B–Fe magnet into the magnetic circuit successfully shifted the operating point to the linear portion of the magnetostrictive curves. This biasing effect is use...

Magnetoelectric Coupling in Multi-Ferro Fe-Pd/PZT/Fe-Pd Laminate Composites

Magnetoelectric(ME) coupling in multi-ferroic composite designed by using two material elements of Pb(Zr, Ti)O3 (PZT: 260μm) and magnetostrictive alloys(Galfenol based Fe-Ga-X(X=Al, Co), ferromagnetic shape memory Fe-Pd) was investigated. Output ME Voltage under the driving a.c.magnetic field Hac at f = 1 Hz in Fe81Ga19/PZT/ Fe81Ga19, Fe80Ga15Al5 /PZT/ Fe80Ga15Al5, Fe76Ga17Co7/PZT/ Fe76Ga17Co7 composites, in which the magnetostrictive foils(50μm thickness) were prepared by rapid solidification, increased in proportion to the actuated force than the magnetostriction.Moreover，output ME Voltage in Fe70Pd30 / PZT/ Fe70Pd30 laminates, in which the Fe70Pd30 films (10μm thickness) on PZT were deposited by sputtering method, exhibited 8 V at Hac of 175Oe, which is larger than 7.16 V for Fe76Ga17Co7 (50μm)/PZT/ Fe76Ga17Co7 (50μm) composites

Magnetoelectric Effect of Fe70Pd30 Ferromagnetic Shape Memory Alloy Film: Lead Zirconate Titanate Trilayer Composites at Low and High Magnetic Field Frequencies

Magnetoelectric (ME) coupling in multiferroic composites of Fe70Pd30/lead zirconate titanate (PZT)/Fe70Pd30 trilayers was investigated. An Fe70Pd30 ribbon and Fe70Pd30 films were prepared by rapid solidification and sputtering techniques, respectively. The saturated value of magnetostriction of the ribbon 30 µm in thickness was 95 ppm at a steady magnetic field of 200 Oe. Those of the films were 22 to 67 ppm depending on the film thickness. The output ME voltage VME of the trilayer composites, which was measured at a driving ac magnetic field Hac at 1 Hz, increased with increasing magnetostriction. The VME of the ribbon/PZT/ribbon composite exhibited a very large peak at a resonant frequency of 64 kHz and responded to an Hac of 0.0025 Oe. However, for the film/PZT/film composite, VME linearly increased with increasing Hac in a wide frequency range of 1 to 104 Hz.

Magnetostrictive-ring type torque sensor using two Hall ICs with differential magnetic field detection

A novel magnetostrictive-ring type torque sensor has been developed which used a new detection scheme for detecting the differential magnetic field and signal conditioning circuitry with the temperature drift compensation. Torque of a shaft was measured by detecting the leakage magnetic field emanating from the magnetostrictive-ring made of permendur Fe49Co49V2 which was attached to the stainless shaft. The magnetic sensor was constructed using a pair of commercial Hall ICs and a permalloy magnetic yoke embedded onto the circuit board. The temperature offset adjustment was accomplished by adding only four diodes and resistors to differential amplifiers. The measured sensitivity was 45 mV/Nm for the applied torque range from -4 Nm to +4 Nm.

Magnetostrictive Galfenol Torque Sensor Devices for Smart by-Wire Steering System in Automobile Technology

Polycrystalline Galfenol (Fe-Ga-X, X=Al, C, Zr etc.) alloys were fabricated as a bulk sample from rapid-solidified powders or ark-melted and annealing process method for enhancing various engineering applicabilities of this magnetostrictive alloy. Especially, (Fe-Ga0.15-Al0.05)99.0-Zr0.5-C0.5 [at.%] sample showed a maximum magnetostriction of λmax=90ppm to 150ppm as well as a tensile stress over σ=800MPa. This large magnetostriction is mainly caused by non-precipitating of the ordered A2 phases without the excessive precipitation of ordered phases such as fcc ordered L12, bcc ordered D03 phases and the remained [100] oriented strong textures by a heat treatment. Based on the improvements of these properties in the developed bulk Galfenol alloys, secondarily, we will introduce an application as a smart torque sensor by utilizing Galfenol-ring around the shaft for steering-by-wire system of automobile. A torque sensing system by using the magnetostrictive ring of Galfenol alloy was developed and magnetic flux leakage from the ring attached on the rotating shaft was experimentally measured by using differential Hall probe sensor. The sensitivity of this type of torque-sensor shows a strong dependency of metallurgical microstructure and the residual stress (i.e.hoop-stress) in the ring due to sensor shows a strong dependency of the residual stress (i.e.hoop-stress) in the ring due to the fitting level. A promising result on ring-type and single-structured inverse magnetostrictive torque sensor will be presented.

Miniature spherical motor using iron-gallium alloy (Galfenol)

We propose a miniature spherical motor using iron-gallium alloy (Galfenol). This motor consists of four rods of Galfenol with square cross-section, a wound coil, a permanent magnet, an iron yoke and a spherical rotor placed on the edge of the rods. The magnetomotive force of the magnet provides bias magnetostriction for the rods and an attractive force that maintains the rotor on the rods. When currents of 180 deg phase difference flow in pairs of opposing coils, a torque is exerted on the rotor is by pushing (expansion) and pulling (contraction) of the rods. Rotation about a single axis is realized by a sawtooth current, such that the rotor rotates with slow expansion and slips at the rapid contraction. The motor can be fabricated at small sizes and driven with a low voltage, suitable for application as a microactuator for rotating the camera and mirror in endoscopes.

Translatory and Wobbling Micro Magnetostrictive Actuator

We propose a three-DOF magnetostrictive micro actuator using Iron-Gallium alloy (Galfenol). The actuator consists of two parallel beam structure having a Galfenol core, located at either end of a Galfenol rod of 1 mm square cross-section and length 11 mm, with two orthogonal ditches cut down it of width 0.3 mm. Around the resulting prongs are wound, and the prongs are bonded to an iron end cap to close the magnetic circuit. When current is passed through a coil wound round one of the orthogonal parallel beams, the resulting magnetostriction enables the actuator to bend in two directions. In addition, longitudinal displacement with high frequency bandwidth can be generated by excitation of two or of all four coils. Maximum displacements were observed of 8 to 10 μm in bending and 2.2 μm in the longitudinal direction. This actuator is potentially applicable in machining (drilling), positioning, and in a micro-motor using wobbling or translational motion when powered by a small power supply.

Magnetostriction of polycrystalline strong-textured Fe-17at%Ga alloy fabricated by combining rapid-solidification and sintering processes

Melt-spun, rapid solidified Galfenol (Fe-Ga) ribbon sample showed large magnetostriction and good ductility as compared with conventional bulk sample because the ribbon has fine columnar grain which was formed during melt-spinning process. The large magnetostriction is caused by the release of considerable large internal stresses in as-spun ribbon as well as the remained [100] oriented strong textures after annealing. In order to obtain larger magnetostrictive force than ribbon sample, in this study, magnetostrictive bulky Fe-Ga alloy was fabricated by combining laminate of rapid-solidified ribbons (80 μm in thickness) and spark plasma sintering/joining (SPSJ). SPSJ is characterized by short time and low temperature heating and sintering process. The laminated sample made by SPSJ maintained the unique metallurgical microstructure of polycrystalline texture of columnar grains as well as almost non-equilibrium metastable phase with little existence of ordered precipitations in as-spun ribbons. The excellent sintered sample having large magnetostoriction was obtained under a condition of the compressive stress of 100 MPa at the temperature of 973 K. The magnetostriction depended on compressive pre-stress level for specimen and reached about 100 ppm which was a half of value obtained for the ribbon sample. Furthermore, by following short annealing for this specimen, the magnetostriction increased to 170-190 ppm comparable to the ribbons value.

Thermo- and Magneto-elastic Metalic Actuator/Sensor Materials

materials. These materials , both magnetically hard and magnetically soft, are already seeing technology pull-through for efficiency and weight gains. The data storage industry is actively working in nanostructures in order to satisfy the demand for increases in data storage density. The future for fabricated nanostructures or magnetic nanoparticles has possibilities on many fronts. The key is to enable interdisciplinary activity across a far wider front than perhaps has ever existed previously.

Microstructure and Magnetostriction of Rapidly-solidified Fe-Ga System Alloy

Rapid-solidification method was applied to make Fe-15at%Ga and Fe-17at%Ga ribbons of 100 μm thickness. These ribbons have large magnetostriction of 270 ppm, where the coercive force exhibits a maximum value. The phenomenon is related to special metallic texture, that is, the ribbon has strongly [001]-oriented textured fine columnar microstructure with grain size of 2∼5 μm. The ribbon has little-hysteresis loop of magnetostriction and a good ductility (i.e., full bending is possible). Rapid-solidified Fe-Ga alloy has a promising possibility as a new magnetic-induced sensor/actuator material.