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EP-4293145-B1 - MAGNETOSTRICTIVE MEMBER AND METHOD FOR MANUFACTURING MAGNETOSTRICTIVE MEMBER

EP4293145B1EP 4293145 B1EP4293145 B1EP 4293145B1EP-4293145-B1

Inventors

  • OKUBO, KAZUHIKO
  • OSAKO, Kazutaka
  • IZUMI, KIYOSHI

Dates

Publication Date
20260506
Application Date
20220204

Claims (5)

  1. A magnetostrictive member (1) formed of a single crystal of an iron-based alloy having magnetostrictive characteristics, being a plate-like body having a long-side direction (D1) and a short-side direction (D2), characterized by having a lattice constant of a <100> orientation in the short-side direction (D2) larger than a lattice constant of an orientation in the long-side direction (D1) orthogonal to the <100> orientation in the short-side direction (D2) by 400 ppm or more.
  2. The magnetostrictive member (1) according to claim 1, wherein the iron-based alloy is an Fe-Ga alloy, the magnetostrictive member (1) has a lattice constant in the long-side direction (D1) of 2.9034 Å or less, wherein the magnetostrictive member (1) has a parallel magnetostriction amount of 250 ppm or more, the parallel magnetostriction amount being a magnetostriction amount when a magnetic field parallel to the long-side direction (D1) is applied and a magnetostriction amount in the long-side direction (D1) is saturated, and the magnetostrictive member (1) has a magnetostriction constant of 250 ppm or more, wherein the magnetostriction constant represents a difference between the parallel magnetostriction amount and a perpendicular magnetostriction amount, wherein the perpendicular magnetostriction amount is a magnetostriction amount when a magnetic field parallel to the short-side direction (D2) is applied and a magnetostriction amount in the short-side direction (D2) is saturated.
  3. The magnetostrictive member (1) according to claim 1 or 2, wherein a thickness of the plate-like body is 0.3 mm or more and 2 mm or less.
  4. The magnetostrictive member (1) according to any one of claims 1 to 3, wherein at least one of a front face (3) and a back face (4) of the plate-like body having a one-direction processed face with the long-side direction (D1) serving as a processing direction.
  5. A method for manufacturing a magnetostrictive member (1), the method comprising acquiring a plate-like body formed of a single crystal of an iron-based alloy having magnetostrictive characteristics and having a long-side direction (D1) and a short-side direction (D2), characterized by having a lattice constant of a <100> orientation in the short-side direction (D2) larger than a lattice constant of an orientation in the long-side direction (D1) orthogonal to the <100> orientation in the short-side direction (D2) by 400 ppm or more.

Description

Technical Field The present invention relates to a magnetostrictive member and a method for manufacturing a magnetostrictive member. Background Art Magnetostrictive materials are attracting attention as functional materials. For example, Fe-Ga alloys, which are iron-based alloys, are materials exhibiting the magnetostrictive effect and the reverse magnetostrictive effect, showing a large magnetostriction of about 100 to 350 ppm. For this reason, in recent years, they have attracted attention as a material for vibration power generation in the energy harvesting field and are expected to be applied to wearable terminals and sensors. As a method for manufacturing a single crystal of an Fe-Ga alloy, a method for growing a single crystal by the pull-up method (the Czochralski method, hereinafter abbreviated as the "Cz method") is known (e.g., Patent Literature 1). In addition, as methods of manufacture other than the Cz method, the vertical Bridgman method (the VB method) and the vertical temperature gradient freeze method (the VGF method) are known (e.g., Patent Literature 2 and Patent Literature 3). The Fe-Ga alloy has an easy axis of magnetization in the <100> orientation of the crystal and can exhibit large magnetic distortion in this orientation. Conventionally, magnetostrictive members of the Fe-Ga alloy have been manufactured by cutting a single crystal part oriented in the <100> orientation from an Fe-Ga polycrystal to a desired size (e.g., Non-Patent Literature 1); crystal orientation significantly affects magnetostrictive characteristics, and thus a single crystal in which the direction in which the magnetostriction of magnetostrictive members is required and the <100> orientation, in which the magnetic strain of the crystal is maximum, are matched with each other is considered to be optimum for the material of magnetostrictive members. The single crystal of the Fe-Ga alloy exhibits positive magnetostriction when a magnetic field is applied in parallel to the <100> orientation of the single crystal (hereinafter referred to as a "parallel magnetostriction amount"). On the other hand, when a magnetic field is applied perpendicularly to the <100> orientation, negative magnetostriction is exhibited (hereinafter referred to as a "perpendicular magnetostriction amount"). As the intensity of the applied magnetic field is gradually increased, the parallel magnetostriction amount or the perpendicular magnetostriction amount is saturated. A magnetostriction constant (3/2λ100) is determined by the difference between the saturated parallel magnetostriction amount and the saturated perpendicular magnetostriction amount and is determined by Expression (1) below (e.g., Patent Literature 4 and Non-Patent Literature 2). 3/2λ100=ε//−ε⊥ 3/2λ100: the magnetostriction constantε(//): the parallel magnetostriction amount when saturated by applying a magnetic field in parallel to the <100> directionε(⊥): the perpendicular magnetostriction amount when saturated by applying a magnetic field perpendicularly to the <100> direction The magnetostrictive characteristics of the Fe-Ga alloy are considered to affect the magnetostrictive and inverse magnetostrictive effects and the characteristics of magnetostrictive vibration power generation devices and are important parameters for device design (e.g., Non-Patent Literature 4). In particular, the magnetostriction constant depends on the Ga composition of the Fe-Ga alloy single crystal, and it is known that the magnetostriction constant reaches its maximum at Ga compositions of 18 to 19 at% and 27 to 28 at% (e.g., Non-Patent Literature 2), and it is desirable to use Fe-Ga alloys with such Ga concentrations for devices. Furthermore, in recent years, it has been reported that, in addition to the magnetostriction constant being large, a larger parallel magnetostriction amount tends to result in higher device characteristics such as output voltage (e.g., Non-Patent Literature 3). A magnetostrictive vibration power generation device, for example, includes an Fe-Ga magnetostrictive member wound by a coil, as well as a yoke and a field permanent magnet (e.g., Patent Literature 5 and Non-Patent Literature 4). In this magnetostrictive vibration power generation device, as a mechanism, when the yoke as a movable part of the device is vibrated, the Fe-Ga magnetostrictive member fixed at the center of the yoke vibrates in tandem, the magnetic flux density of the coil wound on the Fe-Ga magnetostrictive member changes due to the reverse magnetostriction effect, and electromagnetic induction electromotive force is generated to generate power. In the magnetostrictive vibration power generation device, a force is applied in the long-side direction of the yoke to cause vibration, and thus the Fe-Ga magnetostrictive member for use in the device is desirably processed such that <100>, which is the easy axis of magnetization, is in the long-side direction. Other examples of prior art documents are ORR A E