Magnetostrictive material and element containing same

Abstract

Provided is a novel magnetostrictive material that has a high magnetostrictive property despite being rare-earth-free. This magnetostrictive material contains copper cobalt ferrite wherein cubic crystals are the primary crystal phase.

Description

Magnetostrictive material and element containing same

[0001] The present invention relates to a magnetostrictive material and an element including the same.

[0002] Magnetostrictive materials are materials that utilize the magnetic property of "magnetostriction." "Magnetostriction" refers to the distortion of a crystal lattice that depends on the direction of the magnetic moment. Magnetostrictive materials exhibit the magnetostrictive effect (Joule effect), which allows the length of a material to be changed without contact by applying a magnetic field. In addition, when a magnetostrictive material is compressed, a change in magnetization occurs, and an inverse magnetostrictive effect (Villari effect) is also observed, in which a change in magnetic permeability occurs. For example, magnetostrictive materials are currently used in ultrasonic generators, fish finder transducers, actuators, etc., utilizing the magnetostrictive effect. Magnetostrictive materials are also used in sensors and vibration power generation elements, etc., utilizing the inverse magnetostrictive effect.

[0003] A wide variety of magnetic materials are known, ranging from metal and alloy-based materials to metal oxide-based materials. Among these, materials containing rare earth elements are generally known to have higher magnetostriction constants than other materials. However, due to supply risks associated with rare earth elements, they are considered unsuitable for mass, low-cost production. Furthermore, it has been pointed out that materials containing rare earth elements have poor mechanical properties, and that industrial use requires high-quality single crystals, presenting many limitations.

[0004] AE Clark, “Extraordinary magnetoelasticity and lattice softening in bcc Fe-Ga alloys” 2003, Journal of Applied Physics 93, 8621

[0005] For this reason, there is a need for the development of new materials that are rare earth-free and have high magnetostriction properties.

[0006] The present inventors have conducted extensive research to solve the above problems and have found that copper-cobalt ferrites with a cubic crystal as the main crystal phase have high magnetostriction properties despite being rare earth-free. The present invention has been completed through further research based on this finding and includes the following aspects.

[0007] Item 1. A magnetostrictive material comprising copper-cobalt ferrite having a cubic crystal as a primary crystal phase. Item 2. The magnetostrictive material according to Item 1, wherein the copper-cobalt ferrite is substantially composed of a cubic crystal phase. Item 3. The copper-cobalt ferrite is Cu x Co y-x Fe 3-y Item 4. The magnetostrictive material according to any one of Items 1 to 3, which is polycrystalline or single crystalline. Item 5. The magnetostrictive material according to Item 4, wherein the polycrystalline is a non-oriented polycrystalline. Item 6. The magnetostrictive material according to Item 4, wherein the polycrystalline is a crystal-oriented polycrystalline. Item 7. An element that operates by utilizing the magnetostrictive effect or inverse magnetostrictive effect of the magnetostrictive material according to any one of Items 1 to 6. Item 8. The element according to Item 7, which is a vibrator, actuator, sensor, or vibration power generation element. Item 9. A method for operating an element, comprising a step of operating an element containing the magnetostrictive material according to any one of Items 1 to 6 by utilizing the magnetostrictive effect or inverse magnetostrictive effect of the magnetostrictive material. Item 10. Item 11. A method for producing copper-cobalt ferrite having a cubic crystal as the main crystal phase, comprising the step of obtaining copper-cobalt ferrite using iron oxide, copper oxide, and cobalt oxide as raw materials. x Co y-x Fe 3-y Item 11. A method for producing copper-cobalt ferrite according to Item 10, comprising: obtaining copper-cobalt ferrite represented by the formula O4 (0<x / y≦0.75 and 0.8≦y≦1.2) (wherein at least one of Co, Fe, and Cu may be partially substituted with one or more other elements); and adjusting the molar ratio of the raw materials to a stoichiometric composition based on the chemical formula.

[0008] According to the present invention, it is possible to provide a novel magnetostrictive material that is rare earth-free yet has high magnetostriction properties.

[0009] 1 is a diagram showing a method of an embodiment; 2 is a diagram showing a method of an embodiment; 3 is a diagram showing a method of an embodiment; 4 is a diagram showing a result of an embodiment; 5 is a diagram showing a result of an embodiment; 6 is a diagram showing a result of an embodiment; 7 is a diagram showing a result of an embodiment; 8 is a diagram showing a result of an embodiment; 9 is a diagram showing a result of an embodiment; 10 is a diagram showing a result of an embodiment; 11 is a diagram showing a result of an embodiment; 1 is a diagram showing the results of an example.

[0010] 1. Magnetostrictive Material The magnetostrictive material of the present invention is a magnetostrictive material containing copper-cobalt ferrite having a cubic crystal as the main crystal phase.

[0011] Copper cobalt ferrite has a spinel structure, which contains 32 oxygen atoms in a face-centered cubic unit cell, with 8 metal atoms occupying the A lattice sites (tetrahedral 4-coordinate sites) and 16 metal atoms occupying the B lattice sites (octahedral 6-coordinate sites).

[0012] Without being bound by theory, it is believed that the magnetostrictive material of the present invention exhibits high magnetostrictive properties due to the copper-cobalt ferrite having a cubic crystal as the primary crystal phase. The inventors have discovered that copper-cobalt ferrite having a cubic crystal as the primary crystal phase has higher magnetostrictive properties than copper-cobalt ferrite having a single tetragonal crystal phase. Therefore, the magnetostrictive material of the present invention may be copper-cobalt ferrite having a cubic crystal as the primary crystal phase, and may be a mixture of a cubic phase and a different phase.

[0013] The cubic phase of the copper-cobalt ferrite may be a single phase, or may be two or more kinds of cubic phases.

[0014] In terms of exhibiting higher magnetostriction characteristics, the copper-cobalt ferrite preferably consists essentially of a cubic phase, and more preferably consists of a cubic phase.

[0015] In the present invention, the copper-cobalt ferrite has a magnetostriction constant λ s (10000 O e ) is preferably −200 ppm or less, more preferably −250 ppm or less, and even more preferably −300 ppm or less.

[0016] In the present invention, the magnetostriction constant λ s (10000 O e ) is determined by measuring magnetostriction in an applied magnetic field of -10000≦H (Oe)≦10000. Specifically, the magnetostriction constant λ s (10,000 Oe) is calculated as follows (Reference: Hiroshi Shimada and three others, "Magnetic Materials - Physical Properties, Engineering Characteristics and Measurement Methods," 1999, Kodansha Scientific, pp. 136-143, p. 296).

[0017] In the case of polycrystals, if the angle between the applied magnetic field direction and the strain measurement direction is θ, the strain is expressed by the following formula:

[0018]

[0019] At this time, the strain λ parallel to the applied magnetic field direction || Since θ=0,

[0020] The strain in the direction perpendicular to the applied magnetic field can be expressed as

[0021] Since θ=π / 2,

[0022] Therefore, the magnetostriction constant λ s teeth,

[0023] Using this, it can be expressed as follows:

[0024]

[0025] Thus, at the applied magnetic field of 10,000 Oe

[0026] By using the data, the magnetostriction constant λ s (10000 O e ) can be obtained.

[0027] In the present invention, the crystalline phase of copper-cobalt ferrite is identified by indexing the diffraction pattern obtained by X-ray diffraction measurement in the range of, for example, 25≦2θ (degrees)≦45.

[0028] The copper-cobalt ferrite used in the present invention is a CoFe2O4 in which at least Co is partially substituted with Cu. The copper-cobalt ferrite used in the present invention also includes those in which one or more of Co, Fe, and Cu are partially substituted with one or more other elements. The other elements are not particularly limited, but include, for example, Li, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Ni, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Rh, Ag, Cd, In, Sn, Sb, Ba, Hf, Ta, W, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Ti, Mn, and Zn are particularly preferred as other elements.

[0029] In the present invention, the copper-cobalt ferrite is Cu x Coy-x Fe 3-y O4 (0<x / y≦0.75 and 0.8≦y≦1.2) is preferred. When the ratio of x to y (x / y) is within this specific range, the crystalline phase of the copper-cobalt ferrite becomes as described above, resulting in high magnetostriction properties. In this respect, x / y is preferably 0.7 or less, and more preferably 0.65 or less. When 0<x / y≦0.6, the crystalline phase tends to consist solely of a cubic phase. In terms of high magnetostriction properties, x / y is more preferably 0.2 or more and 0.6 or less, and even more preferably 0.3 or more and 0.6 or less. However, Cu x Co y-x Fe 3-y For the same reason, those represented by O4 (0<x / y≦0.75 and 0.8≦y≦1.2) in which one or more of Co, Fe, and Cu are partially substituted with one or more of the other elements described above can also be preferably used.

[0030] In the above, y is preferably in the range of 0.85≦y≦1.15, more preferably in the range of 0.9≦y≦1.1, and most preferably in the range of y=1.

[0031] Copper cobalt ferrite can be produced by, for example, a solid-state reaction method, a sol-gel method, or a flux method.

[0032] In the solid-state reaction method, the value of x can be appropriately adjusted by adjusting the stoichiometric composition of the raw materials. For example, the copper-cobalt ferrite used in the present invention can be obtained by using α-type iron (III) oxide (α-FeO), copper (I) oxide (CuO), and cobalt (II) oxide (CoO) as raw materials and adjusting the molar ratio of these to a stoichiometric composition such that the value of x is the desired value. For example, in the case of the solid-state reaction method, the copper-cobalt ferrite used in the present invention can be obtained by mixing and pulverizing the raw materials prepared as described above in an aqueous solution, followed by firing.

[0033] In the above-mentioned manufacturing method, the raw materials can be mixed and pulverized in, for example, ultrapure water.

[0034] In the above manufacturing method, the raw materials may be pulverized using, for example, a ball mill.

[0035] After mixing and pulverizing the raw materials, filtration may be carried out as necessary before firing. Alternatively, the filtration may be followed by further drying and pulverization. This pulverization may be carried out using, for example, a mortar.

[0036] In the sol-gel method, the value of x can be adjusted appropriately by adjusting the concentration of the metal salt dissolved in the aqueous solution. For example, iron nitrate, cobalt nitrate, and copper nitrate are dissolved in a citric acid solution, and then ethylene glycol is added and heated to form a gel. The gel can then be further heated to obtain a precursor powder of copper-cobalt ferrite.

[0037] Before firing, the pulverized material and precursor powder obtained as described above are preferably pelletized. The means for pelletizing is not particularly limited, but a press or the like can be used.

[0038] The firing conditions are not particularly limited, but examples include a holding temperature of 700°C or higher, preferably 750°C to 1200°C, and more preferably 800°C to 1000°C, a holding time of 2 hours or longer, and air atmosphere. More specific conditions include a holding temperature of 950°C, a holding time of 20 hours, and air atmosphere.

[0039] In the above-mentioned manufacturing method, the fired product may be further pulverized as needed. This pulverization can be carried out using, for example, a mortar.

[0040] The copper cobalt ferrite may be polycrystalline or single crystalline.

[0041] Polycrystalline copper-cobalt ferrite is non-oriented or crystal-oriented. Non-oriented polycrystalline copper-cobalt ferrite can be obtained, for example, by simply pulverizing the fired product and compacting the resulting powder sample. Crystal-oriented polycrystalline copper-cobalt ferrite can be obtained, for example, by pulverizing the fired product in a magnetic field and compacting the resulting powder sample. The magnetic field is preferably a unidirectional magnetic field or a rotating magnetic field. The specific method for compacting in a unidirectional magnetic field or a rotating magnetic field is not particularly limited, but the method used in the examples can be used, for example.

[0042] Crystal-oriented polycrystalline copper-cobalt ferrite is preferred due to its improved magnetostriction properties.

[0043] 2. Elements The elements of the present invention are elements that operate by utilizing the magnetostrictive effect or inverse magnetostrictive effect of the magnetostrictive material of the present invention. Specific examples include vibrators, actuators, sensors, and vibration power generation elements.

[0044] Examples of the transducer include an ultrasonic generator and a transducer of a fish finder.

[0045] The actuator utilizes the magnetostrictive effect (Joule effect) and obtains displacement and driving force through a magnetic field.

[0046] The sensor utilizes the inverse magnetostrictive effect (Villari effect) and senses force or displacement (the amount of movement of an object) by converting the change in magnetic permeability caused by the application of stress to a magnetostrictive material into a change in inductance of an excitation coil (a change in coil impedance).

[0047] The vibration power generation element utilizes the inverse magnetostriction effect (Villari effect), and generates induced electromotive force according to Faraday's law of electromagnetic induction from the change in magnetic permeability caused by the application of stress to a magnetostrictive material wrapped around a coil.

[0048] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0049] Example 1 Manufacturing of the Copper-Cobalt Ferrite of the Present Invention The general flow of sample preparation procedures and evaluation is shown in Figure 1. As shown in Figure 1, the starting materials were weighed and mixed, and then the sample was sintered into a disk-shaped pellet. Magnetostriction measurements were performed on the pellet as is. X-ray diffraction measurements and magnetization measurements were performed on the sample after crushing the pellet in a mortar. Details of each will be described in later sections.

[0050] The target Cu x Co 1-x To obtain Fe2O4, α-Fe2O3, Cu2O, and CoO were used as starting materials. The CoO used had a purity of 90.0% or higher. The raw materials actually used are shown in Table 1.

[0051]

[0052] The sample preparation flow is shown in Figure 2, and the stoichiometric compositions of the prepared samples are summarized in Table 2. α-Fe2O3, Cu2O, and CoO were weighed to obtain the stoichiometric molar ratios shown in Table 2. The weighed sample was placed in a Teflon ball mill container along with zirconia balls and 200 ml of ultrapure water. The mixture was mixed and ground for 2 hours using a pot mill turntable (Nitto Kagaku Co., Ltd., ANZ-51S). The mixture was then filtered, and the sample on the filter paper was removed, dried, and ground in an agate mortar. The pellets were then pressed into pellets (10 mm diameter, approximately 2.4 mm thick) using a manual 100 kN Mighty Press (NPa Systems Co., Ltd., MT-100H) and fired in an electric furnace (AS ONE Corporation, high-performance muffle furnace, model HPM-0N). The firing was carried out in an air atmosphere under the conditions of a temperature rise time of 5 hours, a holding time of 20 hours, a temperature fall time of 5 hours, and a firing temperature of 950°C.

[0053]

[0054] The crystalline structure of the resulting calcined powder was identified by X-ray diffraction (XRD). Atoms and ions in a crystal are regularly arranged three-dimensionally. X-ray diffraction measurement is a method in which, when a crystalline powder sample is irradiated with X-rays of a certain wavelength, the scattered waves are intensified at an incident angle that satisfies the Bragg reflection condition expressed by equation (1), and the crystalline structure is identified from the resulting X-ray diffraction pattern.

[0055]

[0056] Figure 3 shows a schematic diagram of the X-ray diffraction measurement. The constituent phases of the obtained powder sample were identified using a laboratory X-ray diffractometer (Rigaku SmartLab SE diffractometer) with Cu-Kα radiation (λ = 0.1541862 nm). Measurements were performed at an accelerating voltage of 40 kV, a target current of 30 mA, and a 2θ range of 20° to 120° with a step width of 0.02° and a sweep speed of 2° / min. The X-ray diffraction pattern was obtained with the diffraction angle 2θ (degrees) on the horizontal axis and the diffraction line intensity (counts per second) on the vertical axis.

[0057] The lattice constant of the sample was calculated from the diffraction pattern obtained by the measurement using the Cohen method (BD Cullity, "Elements of X-Ray Diffraction, second edition," Addison-Wesley Publishing Company, (BD Cullity, Gentaro Matsumura (translation), "New Edition Cullity's Essentials of X-Ray Diffraction," Agne (1980) pp. 320-337).

[0058] Magnetization measurements were performed using a vibrating sample magnetometer (VSM) (Toei Kogyo Co., Ltd., model number: VSM-C7-10). The VSM measures magnetization by detecting the induced electromotive force generated by changes in magnetic flux density generated by a magnetized magnetic material when the measurement sample is vibrated at a constant frequency in a uniform magnetic field. In this example, the fired pellets were ground in an agate mortar to obtain powder, which was then packed into vegetable capsules (Matsuya Co., Ltd., No. 5) and attached to a rod for measurements (room temperature, maximum applied magnetic field: 10,000 Oe). The obtained magnetization was converted to magnetization per unit mass to obtain a magnetic field-magnetization curve, and the saturation magnetization Ms and coercivity Hc were calculated.

[0059] Magnetostriction measurements were performed using strain gauges (Kyowa Electric Co., Ltd., Models: KFRB-05-120-C1-11 L1M2R, KFRB-05-120-C1-11 L3M2R) and the same VSM (Toei Kogyo Co., Ltd., Model: VSM-C7-10) used for magnetization measurements. A magnetic field of -10,000 ≤ H (Oe) ≤ 10,000 was applied using a strain gauge. Similarly, magnetostriction measurements were performed at room temperature using a Physical Property Measurement System (PPMS) (Quantum Design, PPMS-KITR) under a magnetic field of -70,000 ≤ H (Oe) ≤ 70,000. Measurements were performed under both atmospheric pressure and vacuum conditions using the PPMS. Since the strain gauge must be integrated with the object to be measured and expand and contract, it was attached using instant adhesive for strain gauges (Kyowa Electronics Co., Ltd., model CC-33A).

[0060] In general, the magnitude of a metal's electrical resistance is inversely proportional to its cross-sectional area and proportional to its length. When a metal wire is pulled, its cross-sectional area decreases and its length increases, resulting in an increase in electrical resistance. Conversely, when it is compressed, its electrical resistance decreases. The expansion and contraction of a metal and the change in its electrical resistance are proportional, with a certain constant. If this metal wire is attached to the material whose strain you want to measure, the wire will expand and contract in accordance with the expansion and contraction of the material, and by measuring the change in its electrical resistance, you can determine the expansion and contraction of the material, i.e., the strain. We measured strain when the strain gauge and the applied magnetic field were parallel and when the strain gauge and the applied magnetic field were perpendicular.

[0061] In order to accurately measure the change in the electrical resistance of the strain gauge, a bridge circuit is constructed and the change in electrical resistance is converted into a change in voltage for measurement. Because the magnitude of this voltage is small, in the μV range, it is generally amplified 5,000 to 10,000 times using a strain amplifier. In this example, the strain gauge was attached to a disc-shaped pellet (10 mm diameter, approximately 2.4 mm thick) sample, and the pellet was attached to the rod with double-sided tape. By replacing the double-sided tape for each measurement, it was possible to measure the change in the electrical resistance by converting the voltage from λ to λ when the magnetic field application direction and the strain measurement direction are parallel. || " and "When the direction of applying the magnetic field and the direction of measuring the strain are perpendicular:

[0062] The magnetostriction constant λ was calculated based on the measured values. s was calculated and a comparison was carried out.

[0063] Crystal structure of the prepared sample Crystal phase identification Figure 5 shows the diffraction patterns obtained by X-ray diffraction measurement, indexed in the range of 25 ≦ 2θ (degrees) ≦ 45. Crystal phase identification revealed that x = 0.0 to 0.5 is a single cubic phase, and x = 0.9 is a nearly single tetragonal phase. Since x = 0.7 and 1.0 showed diffraction peaks of different phases, albeit at very low intensity, between 38 and 39° (Figure 6), it was thought that x = 0.7 is a two-phase mixture of cubic and different phases, and x = 1.0 is a two-phase mixture of tetragonal and different phases.

[0064] The enlarged X-ray diffraction pattern for x = 0.6 in the range of 35 ≤ 2θ (degree) ≤ 37 and 42 ≤ 2θ (degree) ≤ 45 is shown in Figure 7. The intensity ratio of the two peaks near 35.5° and 43.2° is not 2:1, which indicates that the K α1 line, K α2 This is unlikely to be a line. Furthermore, both peaks near 35.5° and 43.2° show shoulders that do not fully form peaks. Therefore, x = 0.6 is considered to exist in two cubic phases. Figure 8 also shows an enlarged view of the 32 ≦ 2θ (degrees) ≦ 40 portion of the X-ray diffraction peak for x = 0.8. Since the 311 diffraction peak of the cubic phase and the 103 diffraction peak of the tetragonal phase are observed near 35.5°, we believe that x = 0.8 exists in two phases: cubic and tetragonal.

[0065] The tetragonal crystal structure at x = 0.9 and 1.0 is due to the Jahn-Teller effect caused by the partial substitution of Cu. The Jahn-Teller effect is a phenomenon in which the loss of elastic energy competes with the gain of energy in the electronic system due to distortion, making the distortion more energetically stable. The Jahn-Teller effect is caused by the hexacoordinated Cu 2+ Therefore, at x = 0.9 and 1.0, Cu is included in the B lattice of the inverse spinel structure. 2+ It is thought that the increase in γ caused the Jahn-Teller effect, resulting in a tetragonal crystal.

[0066] Calculation of lattice constants The lattice constants of the main crystalline phases were calculated from the patterns obtained by X-ray diffraction measurement. x Co 1-xThis shows the dependence of the lattice constant of Fe2O4 on the Cu substitution amount x. When x ≦ 0.8, where the primary crystalline phase was cubic, the lattice constant had almost no compositional dependence. When x = 0.9 or 1.0, where the primary crystalline phase was tetragonal, the lattice's base edges a and b shrank, while the height c expanded. The Jahn-Teller effect is expected to be stronger at x = 1.0, where the Cu substitution amount is higher, resulting in greater tetragonal distortion. However, the lattice was found to be more distorted at x = 0.9. As mentioned above, the presence of a heterophase was observed at x = 1.0. Since this heterophase was related to Cu, it is inferred that the lattice constant was more distorted at x = 0.9 than at x = 1.0 due to the Cu not fully reacting.

[0067] The crystal phase and lattice constant results for the samples of each composition are summarized in Table 3.

[0068]

[0069] Magnetization Measurement The magnetic field magnetization curve of the prepared sample at room temperature is shown in Figure 10. The values ​​of saturation magnetization Ms and coercive force Hc calculated from the magnetic field magnetization curve are plotted in Figures 11 and 12.

[0070] The saturation magnetization M of each sample s was calculated by approximating the Frohlich equation to the area where the magnetization M of the magnetic field magnetization curve saturates. The Frohlich equation represents a hyperbola, and is said to well represent the area where the magnetization M rapidly increases and saturates. The Frohlich equation is expressed as equation (2).

[0071] Dividing the numerator and denominator on the right-hand side by H transforms it into equation (3).

[0072] Saturation magnetization M s is equal to y when the applied magnetic field H is infinite, so taking the limit of H in equation (3) gives equation (4).

[0073] Therefore, by using the Frohlich equation, we can approximate the part of the magnetization curve where the magnetization M increases rapidly and then becomes saturated. s asked for.

[0074] From Figure 11, the saturation magnetization M s The saturation magnetization M s CoFe2O4 has an inverse spinel structure, and most of the A lattice is occupied by Fe. 3+ is occupied by Fe, and half of the B lattice is occupied by Fe 3+ But the remaining half is Co 2+ The magnetic moments of the B lattice and the A lattice are opposite due to the superexchange interaction between the A and B lattices, so Fe 3+ The magnetic moment due to Cu is cancelled. x Co 1-x Saturation magnetization M of Fe2O4 s The decrease in Co 2+ A part of Cu 2+ However, at x = 0.7 and 1.0, the saturation magnetization M s When comparing the results of the X-ray diffraction measurements in Figure 5, the saturation magnetization M s Therefore, the presence of a different phase that has not completely reacted is the saturation magnetization M s is thought to be affecting

[0075] From Figure 12, the coercive force H at x = 0.0 c The coercive force H at x = 1.0 was 942 Oe, and the minimum value was at x = 0.7 and the maximum value was at x = 0.9. c The minimum value was 80 Oe.

[0076] Magnetostriction Measurement The results of magnetostriction measurement when the applied magnetic field was −10000≦H (Oe)≦10000 are shown in FIGS. 13 and 14.

[0077] From the results of magnetostriction measurement, the magnetostriction constant λ s In the case of polycrystals, the strain is expressed by equation (5), where θ is the angle between the applied magnetic field direction and the strain measurement direction.

[0078] At this time, the strain λ parallel to the applied magnetic field direction || Since θ = 0,

[0079] The strain in the direction perpendicular to the applied magnetic field is expressed as

[0080] Since θ=π / 2,

[0081] Therefore, the magnetostriction constant λ s is λ || ,

[0082] Using this, it can be expressed as equation (8).

[0083]

[0084] Therefore, the magnetostriction constant λ s Equation (8) was used to calculate λ at an applied magnetic field of 10,000 Oe for all compositions. || ,

[0085] Data from the following sources was used.

[0086] The horizontal axis represents the Cu substitution amount x, and the vertical axis represents the calculated magnetostriction constant λ s The results of the magnetostriction constant λ (10,000 Oe) are shown in Figure 15. The magnetostriction constant λ increases with increasing Cu substitution amount x when x ≦ 0.6. s The increase in the absolute value of the magnetostriction constant (10,000 Oe) may be due to the Jahn-Teller effect causing a phenomenon called lattice softening. Lattice softening is a phenomenon in which the cubic lattice tends to distort into a tetragonal one, resulting in a decrease in the modulus of elasticity. Similarly, titanium ferrite (TiFe2O4), which may experience lattice softening due to the Jahn-Teller effect, has a large magnetostriction constant λ at low temperatures compared to other metal oxide materials. s Therefore, when Co is partially substituted with Cu, the magnetostriction constant λ is s As the absolute value of increases, the lattice distortion due to the Jahn-Teller effect begins to occur in the crystalline phase of the sample, and the magnetostriction constant λ s It is estimated that the absolute value of

[0087] Next, we present the results of magnetostriction measurements at an applied magnetic field of -70,000 ≦ H (Oe) ≦ 70,000. PPMS allows measurements to be performed both at atmospheric pressure and in a vacuum. First, we confirmed whether there were any significant differences in the measurements between atmospheric pressure and vacuum. Figure 16 shows the results of measurements of strain perpendicular to the applied magnetic field using a sample with x = 0.0 under both conditions. As shown in Figure 16, the measurement noise is smaller in vacuum. This is thought to be due to the fact that temperature changes around the sample are almost eliminated in vacuum, reducing the effect of temperature changes on strain. Based on these results, we decided to perform magnetostriction measurements at an applied magnetic field of -70,000 ≦ H (Oe) ≦ 70,000 in a vacuum.

[0088] Figure 17 shows the results of magnetostriction measurements for x = 0.0, 0.4, and 0.6 when the applied magnetic field was -70,000 ≦ H (Oe) ≦ 70,000. It was found that for all compositions, the strain did not saturate at a constant value when the applied magnetic field was 10,000 Oe, and the strain decreased as the applied magnetic field increased. At an applied magnetic field of 70,000 Oe, the strain reached a state close to saturation. The magnetostriction constant λ can be accurately calculated using equation (8). s When calculating λ || and

[0089] Therefore, when investigating the intrinsic magnetostrictive properties of a sample, it is necessary to measure the strain of the sample under a strong applied magnetic field. || and

[0090] Using the data of the magnetostriction constant λ s The magnetostriction constant λ (70,000 Oe) was calculated. The values ​​obtained were -138 ppm for x = 0.0, -233 ppm for x = 0.4, and -266 ppm for x = 0.6. The absolute value for x = 0.0 was s However, the absolute value of the magnetostriction constant λ (10,000 Oe) was smaller than 206 ppm. s (10000 Oe) compared to the magnetostriction constant λ at x = 0.0 sThe magnetostriction constant λ (70,000 Oe) was closer to the literature value of -164 ppm. Also, considering that the sample is porous, the magnetostriction constant λ is affected by the density of the sample. s It is quite reasonable that the absolute value of λ (70,000 Oe) is smaller than the literature value. Therefore, since the strain was close to saturation, the data of 70,000 Oe is more likely to be used to estimate the magnetostriction constant λ. s It can be said that the magnetostriction constant λ is obtained. And, the magnetostriction constant λ is smaller for x = 0.4 and x = 0.6 than for x = 0.0. s (70,000 Oe). Therefore, the partial substitution of Cu reduces the magnetostriction constant λ of CoFe2O4. s The absolute value of x is clearly larger. In addition, the magnetic field susceptibility of the strain is improved at x=0.4 and 0.6 compared to x=0.0.

[0091] Table 4 shows the results of measuring the magnetic properties and magnetostriction properties of the samples of each composition obtained in this example.

[0092]

[0093] Example 2: Production of copper-cobalt ferrite of the present invention (example of different starting material (CuO) and mixing of other elements) The starting materials were weighed and mixed, and then the sample was sintered into a disk-shaped pellet. Magnetostriction measurement was performed on the pellet as is. X-ray diffraction measurement was performed on the sample after crushing the pellet in a mortar. The details of each are the same as in Example 1.

[0094] As an example of contamination with other elements, Zn, a typical element that forms spinel ferrite, was added to investigate the effect of its contamination. z Cu 0.5-z Co 0.5 The crystal structure and magnetostriction properties of Fe2O4 were investigated. z Cu 0.5-z Co 0.5 To obtain Fe2O4, α-Fe2O3, CuO, CoO, and ZnO were used as starting materials. The raw materials actually used are shown in Table 5.

[0095]

[0096] The sample preparation flow is the same as in Figure 2. The stoichiometric compositions of the prepared samples are summarized in Table 6. α-Fe2O3, CuO, CoO, and ZnO were weighed to obtain the stoichiometric molar ratios shown in Table 6. The weighed samples were placed in a Teflon ball mill container along with zirconia balls and 200 ml of ultrapure water. They were mixed and ground for 2 hours using a pot mill turntable (Nitto Kagaku Co., Ltd., ANZ-51S). The mixture was then filtered, and the sample on the filter paper was removed, dried, and ground in an agate mortar. The pellets were then pressed into pellets (10 mm diameter, approximately 2.4 mm thick) using a manual 100 kN Mighty Press (NPa Systems Co., Ltd., MT-100H) and fired in an electric furnace (AS ONE Corporation, high-performance muffle furnace, model HPM-0N). The firing was carried out in an air atmosphere under the conditions of a temperature rise time of 5 hours, a holding time of 20 hours, a temperature fall time of 5 hours, and a firing temperature of 950°C.

[0097]

[0098] The constituent phases of the obtained powder samples were identified using a laboratory X-ray diffractometer (Rigaku SmartLab SE diffractometer) with Cu-Kα radiation (λ = 0.1541862 nm). Measurements were performed at an accelerating voltage of 40 kV, a target current of 30 mA, and a 2θ range of 20° to 120° with a step width of 0.02° and a sweep speed of 2° / min. The X-ray diffraction pattern was obtained with the diffraction angle 2θ (degrees) on the horizontal axis and the diffraction line intensity (counts per second) on the vertical axis.

[0099] The lattice constant of the sample was calculated from the diffraction pattern obtained by the measurement using the Cohen method (BD Cullity, "Elements of X-Ray Diffraction, second edition," Addison-Wesley Publishing Company, (BD Cullity, Gentaro Matsumura (translation), "New Edition Cullity's Essentials of X-Ray Diffraction," Agne (1980) pp. 320-337).

[0100] Magnetostriction measurement Magnetostriction was measured at room temperature and atmospheric pressure using a strain gauge (Kyowa Electric Co., Ltd., model: KFRB-05-120-C1-11 L1M2R) and the same VSM (Toei Kogyo Co., Ltd., model: VSM-C7-10) as used in the magnetization measurement, applying a magnetic field of -10000 ≦ H (Oe) ≦ 10000. Since the strain gauge must be integrated with the object to be measured so that it can expand and contract, it was bonded using instant adhesive for strain gauges (Kyowa Electric Co., Ltd., model: CC-33A).

[0101] Crystal structure of the prepared sample Crystal phase identification Figure 18 shows the diffraction pattern obtained by X-ray diffraction measurement, indexed in the range of 25 ≦ 2θ (degree) ≦ 45. As a result of the crystal phase identification, it was found that z = 0.0 to 0.5 was a single cubic phase.

[0102] Calculation of lattice constants The lattice constants of the main crystalline phases were calculated from the patterns obtained by X-ray diffraction measurement. z Cu 0.5-z Co 0.5 The graph shows the dependence of the lattice constant of Fe2O4 on the amount of Zn substitution z. The lattice constant for Zn substitution z = 0.0 is 8.383 Å, and the lattice constant for the same composition shown in Example 1 (x = 0.5 (Cu x Co 1-x The lattice constant (8.381 Å) is very close to the value of Fe2O4. In this example, CuO was used as the starting material, while Cu2O was used in Example 1, but this difference has almost no effect on the lattice constant. The lattice constant increases monotonically as the amount of Zn substitution increases.

[0103] The crystal phase and lattice constant results for the samples of each composition are summarized in Table 7.

[0104]

[0105] Magnetostriction Measurement The results of magnetostriction measurement when the applied magnetic field was −10000≦H (Oe)≦10000 are shown in FIG.

[0106] From the results of magnetostriction measurement, the magnetostriction constant λ s The magnetostriction constant λ was calculated. s Equation (8) was used to calculate λ at an applied magnetic field of 10,000 Oe for all compositions.|| ,

[0107] Data from the following sources was used.

[0108] The horizontal axis represents the Zn substitution amount z, and the vertical axis represents the calculated magnetostriction constant λ s The results of the magnetostriction constant λ (10000 Oe) are shown in Figure 21. s The absolute value is -282 ppm, and the absolute value is x Co 1-x The absolute value (λ) of the same composition shown in s = -336), but the absolute value of x = 0.0 (λ s = -206). In this example, CuO is used as the starting material, while in Example 1, CuO is used. In other words, copper-cobalt ferrite exhibits excellent magnetostriction properties regardless of which starting material is used. As shown in Figure 21, the magnetostriction constant λ s The absolute value of decreases monotonically with increasing Zn substitution. However, when we look at the magnetostriction curve for Zn substitution z = 0.1 in Figure 20, we see that the magnetic susceptibility to strain is higher than that for z = 0.0. Therefore, excellent magnetostriction properties are obtained even after partial Zn substitution.

[0109] Table 8 shows the results of measuring the magnetostriction properties of the samples of each composition obtained in this example.

[0110]

[0111] <Example 3> Preparation of starting powder for magnetic field compaction Starting materials were prepared in the stoichiometric composition ratio of Cu 0.5 Co 0.5 After weighing and mixing with Fe2O4, the mixture was compacted into disk-shaped pellets and sintered. The details of the starting materials were the same as in Example 1. Sintering was carried out under the following conditions: air, heating time 5 hours, holding time 10 hours, cooling time 5 hours, and a sintering temperature of 950°C. The resulting sintered pellets were pulverized in a mortar to form the starting powder for the magnetic field compaction sample. X-ray diffraction measurements confirmed that the starting powder was a single-phase cubic spinel structure.

[0112]

[0113] Jig for powder compaction in a magnetic field A jig for applying a magnetic field was created by adhering neodymium magnets to one pair of opposing sides of a square cylindrical acrylic piece with open top and bottom. An image of the jig is shown in Figure 22. A non-magnetic die was inserted into the hollow part of this jig, and a magnetic field was applied to the sample position on the die.

[0114] Preparation of Compacted Powder Samples in a Unidirectional Magnetic Field: 675 mg of starting powder was placed in a 10 ml small beaker, and 1.5 ml of ultrapure water was added. The mixture was then stirred for approximately 20 seconds with an ultrasonic generator to produce a slurry. The jig shown in Figure 22 was attached to a nonmagnetic die, and the slurry was poured into the die while a unidirectional magnetic field was applied to the sample position on the die. The magnetic field applied to the sample position on the die was approximately 38 mT. With the unidirectional magnetic field applied, the mixture was compressed using a hydraulic press (RIKEN Co., Ltd., P-1B) to obtain a plate-shaped pellet (10 × 10 mm, approximately 2 mm thick). An image is shown in Figure 23. The plate-shaped pellet was sintered in air under the following conditions: a 5-hour heating time, a 10-hour hold time, a 5-hour cooling time, and a sintering temperature of 950°C to obtain a compacted powder sample in a unidirectional magnetic field.

[0115] Preparation of Compacted Powder Samples in a Rotating Magnetic Field: 600 mg of calcined powder was placed in a 10 ml small beaker, and 1.5 ml of ultrapure water was added. The mixture was stirred for approximately 20 seconds with an ultrasonic generator to create a slurry. The jig shown in Figure 22 was attached to a non-magnetic die, and the slurry was poured into the die while a unidirectional magnetic field was applied to the sample position. The magnetic field applied to the sample was 46 mT. With the non-magnetic die fixed, the jig was rotated clockwise (once per second for approximately one minute). With the sample subjected to the rotating magnetic field, the jig was pressed using a hydraulic press (RIKEN Co., Ltd., P-1B) to obtain a disk-shaped pellet (10 mm diameter, approximately 2 mm thick). An image is shown in Figure 24. This disk-shaped pellet was sintered in an air atmosphere at 950°C for 5 hours, with a heating time of 5 hours, a holding time of 10 hours, and a cooling time of 5 hours. A rotating magnetic field compacted powder sample was obtained.

[0116] Magnetostriction Measurement The results of the magnetostriction measurement are shown in Figure 25. The magnetostriction measurements of the samples prepared by applying a unidirectional magnetic field and a rotating magnetic field were carried out in an applied magnetic field of -25,000 ≦ H (Oe) ≦ 25,000. For comparison, the results of a sample prepared by compacting in no applied magnetic field are also shown.

[0117] Parallel to the strain measurement direction (H / / In the magnetostriction curves obtained by applying a magnetic field in the unidirectional and rotating magnetic fields, the absolute values ​​of ΔL / L for the samples prepared with no applied magnetic field are comparable to those for the samples prepared with no applied magnetic field. ⊥ In the magnetostriction curves obtained by applying a magnetic field to the sample, the absolute value of ΔL / L for the sample prepared by applying a unidirectional magnetic field and a rotating magnetic field is larger than that for the sample prepared without applying a magnetic field. As a result, in the sample prepared by applying a unidirectional magnetic field and a rotating magnetic field, H / / and H ⊥ The difference between ΔL / L (ΔL / L / / - ΔL / L ⊥ ) has a larger absolute value than that of the sample prepared without an applied magnetic field. In other words, the magnetostriction properties are improved by compacting the polycrystalline powder sample in a unidirectional magnetic field and a rotating magnetic field.

[0118] Example 4: Production of copper-cobalt ferrite of the present invention (example of Mn incorporation) After weighing and mixing the starting materials, the samples were sintered into disk-shaped pellets. Magnetostriction measurements were performed on the pellets as they were. X-ray diffraction measurements were performed on samples after crushing the pellets in a mortar. The details of each are the same as in Example 1.

[0119] To investigate the effect of Mn contamination, Cu 0.5 Co 0.5 Mn w Fe 2-w The crystal structure and magnetostriction properties of O4 were investigated. 0.5 Co 0.5 Mn w Fe 2-w To obtain O4, α-Fe2O3, Cu2O, CoO, and Mn2O3 were used as starting materials. The raw materials actually used are shown in Table 10.

[0120]

[0121] The sample preparation flow is the same as in Figure 2. The stoichiometric compositions of the prepared samples are summarized in Table 11. α-Fe2O3, Cu2O, CoO, and Mn2O3 were weighed to achieve the stoichiometric molar ratios shown in Table 11. The weighed sample was placed in a Teflon ball mill container along with zirconia balls and 200 ml of ultrapure water and mixed and ground for 2 hours using a pot mill turntable (Nitto Kagaku Co., Ltd., ANZ-51S). The mixture was then filtered, and the sample on the filter paper was removed, dried, and ground in an agate mortar. It was then compressed into pellets using a hydraulic press (Riken Co., Ltd., P-1B) and fired in an electric furnace (AS ONE Corporation, high-performance muffle furnace, model HPM-0N). The firing was performed in an air atmosphere with a heating time of 5 hours, a holding time of 20 hours, and a cooling time of 5 hours at a firing temperature of 950 °C.

[0122]

[0123] The constituent phases of the obtained powder samples were identified using a laboratory X-ray diffractometer (Rigaku SmartLab SE diffractometer) with Cu-Kα radiation (λ = 0.1541862 nm). Measurements were performed at an accelerating voltage of 40 kV, a target current of 30 mA, and a 2θ range of 20° to 120° with a step width of 0.02° and a sweep speed of 2° / min. The horizontal axis represents the diffraction angle 2θ (degrees), and the vertical axis represents the intensity of the diffraction line, obtaining an X-ray diffraction pattern.

[0124] The lattice constant of the sample was calculated from the diffraction pattern obtained by the measurement using the Cohen method (BD Cullity, "Elements of X-Ray Diffraction, second edition," Addison-Wesley Publishing Company, (BD Cullity, Gentaro Matsumura (translation), "New Edition Cullity's Essentials of X-Ray Diffraction," Agne (1980) pp. 320-337).

[0125] Magnetostriction measurements were performed using a strain gauge (Kyowa Electric Industry Co., Ltd., model number: KFRB-05-120-C1-11 L1M3R) and instant adhesive for strain gauges (Kyowa Electric Industry Co., Ltd., model number: CC-33A). Magnetostriction measurements were performed at room temperature and atmospheric pressure using a VSM (Toei Kogyo Co., Ltd., model number: VSM-C7-10) in an applied magnetic field of -10000 ≦ H (Oe) ≦ 10000.

[0126] Crystal structure of the prepared sample Crystal phase identification Figure 26 shows the diffraction pattern obtained by X-ray diffraction measurement, indexed in the range of 25 ≦ 2θ (degree) ≦ 45. As a result of crystal phase identification, it was found that 0.00 ≦ w ≦ 1.00 is a single cubic phase.

[0127] Calculation of lattice constants From the pattern obtained by X-ray diffraction measurement, Cu 0.5 Co 0.5 Mn w Fe 2-w The lattice constant of the cubic phase of O4 was calculated. Figure 27 shows the dependence of the lattice constant on the Mn substitution amount w. The lattice constant increases as the Mn substitution amount w increases.

[0128] The crystal phase and lattice constant results for the samples of each composition are summarized in Table 12.

[0129]

[0130] Magnetostriction measurement Cu 0.5 Co 0.5 Mn w Fe 2-w Figure 28 shows the magnetostriction curves of O4 at room temperature. Magnetic fields were applied parallel and perpendicular to the measurement direction of the strain ΔL / L. In the magnetostriction curves for both parallel and perpendicular magnetic fields, the absolute value of ΔL / L at 10,000 Oe decreases with increasing Mn substitution. However, when compared at 2,000 Oe, for example, the absolute values ​​of the strain ΔL / L for the partially Mn-substituted samples (w = 0.05, 0.10, 0.15, 0.20) are greater than that for w = 0.00. In other words, partial Mn substitution improves the magnetic susceptibility of the magnetostriction curve and improves the magnetostriction properties in the low magnetic field range.

[0131] Example 5: Preparation of copper-cobalt ferrite single crystals by the flux method

[0132] To obtain copper-cobalt ferrite single crystals, α-Fe2O3, Cu2O, and CoO were used as starting materials, and NaB4O7·10H2O was used as a flux. The CoO used had a purity of 90.0% or higher. The raw materials and fluxes actually used are shown in Table 13.

[0133]

[0134] Ten grams of NaB4O7·10H2O, α-Fe2O3, Cu2O, and CoO were weighed out to the stoichiometric molar ratios shown in Table 14 and placed in a platinum crucible (product name: PT crucible with lid, model number: 56-PT-1030C, Tanaka Kikinzoku Kogyo Co., Ltd.). The raw materials and flux were mixed uniformly with a spoon, then the lid was placed on the crucible and fired in an electric furnace (Yamada Electric Co., Ltd., tabletop rapid heating electric furnace, model number: MSFT-1020). The firing conditions were as shown in Table 15, and the six-step process was carried out. All firing processes were carried out in air.

[0135] After firing, the resulting sample was placed in a small beaker along with the crucible, and 20% nitric acid aqueous solution was poured into the beaker until the crucible was submerged. This small beaker was then placed in a container filled with water, and the container was placed on a hot magnetic stirrer (IKA, model C-MAG HS4 S27) for heating. This heated the inside of the small beaker using a hot water bath. The temperature of the hot magnetic stirrer was set to maintain the water temperature at around 70°C. This condition was maintained for approximately 5–10 days, and once the flux in the small beaker had dissolved and the crystals adhering to the inside of the crucible had been removed, the mixture was filtered. Since the flux dissolves in nitric acid, only the crystals remained on the filter paper. Ultrapure water was then repeatedly poured over the filter paper to confirm that the pH of the filtered ultrapure water was neutral, and the crystals were then recovered. The recovered crystals were washed with acetone to remove any fine crystal grains around the crystals and any remaining flux.

[0136] The crystals obtained by this method were up to about 4 mm in size.

[0137]

[0138]

[0139] Electron microscope observation and elemental analysis: A scanning electron microscope (SEM, JSM-7000F type) was used for electron microscope observation and elemental analysis of the prepared samples. Elemental mapping and quantitative analysis of the sample composition were performed using EDX (Energy Dispersive X-ray Spectroscopy).

[0140] Figure 29 shows the results of electron microscope observation of the prepared sample. A typical field of view of a sample obtained by the flux method was selected as an example. Facets were observed in part of the sample, suggesting that the sample is a single crystal. Figure 30 shows the elemental mapping results of Cu, Co, Fe, and O of the prepared sample. It can be seen that Cu, Co, and Fe are distributed throughout the sample. Furthermore, quantitative elemental analysis revealed that the composition of the obtained sample was roughly Cu. 0.21 Co 0.64 Fe 2.1 Although the composition differed from the stoichiometric composition, the formation of ferrite containing Cu, Co, and Fe was confirmed.

[0141] X-ray diffraction measurement of the prepared sample Figure 31 shows the diffraction pattern obtained by X-ray diffraction measurement, indexed in the range of 10 ≦ 2θ (degree) ≦ 120. The principle of X-ray structural analysis is the same as that shown in <Example 1>. Diffraction peaks of 111, 222, 333, 444, and 555 of the cubic spinel structure were observed, and no other diffraction peaks were observed. In other words, the obtained sample is a single-phase single crystal of the cubic spinel structure. In comparison with the above elemental analysis results, it can be seen that Cu was detected by the flux method. x Co 1-x It has become clear that it is possible to produce single crystals of Fe2O4.

[0142] Example 6: Production of copper-cobalt ferrite of the present invention (example of Ti mixing) After weighing and mixing the starting materials, the samples were formed into disk-shaped pellets and sintered. Magnetostriction measurements were performed on the pellets as they were. X-ray diffraction measurements were performed on samples after crushing the pellets in a mortar. The details of each are the same as in Example 1.

[0143] To investigate the effect of Ti contamination, v Cu 0.5 Co 0.5+v Fe 2-2v The crystal structure and magnetostriction properties of the target TiO4 were investigated. v Cu 0.5 Co 0.5+v Fe 2-2v To obtain O4, α-Fe2O3, CuO, CoO, and TiO2 were used as starting materials. The raw materials actually used are shown in Table 16.

[0144]

[0145] The sample preparation flow is the same as in Figure 2. The stoichiometric compositions of the prepared samples are summarized in Table 17. α-Fe2O3, CuO, CoO, and TiO2 were weighed to achieve the stoichiometric molar ratios shown in Table 17. The weighed sample was placed in a Teflon ball mill container along with zirconia balls and 200 ml of ultrapure water and mixed and ground for 2 hours using a pot mill turntable (Nitto Kagaku Co., Ltd., ANZ-51S). The mixture was then filtered, and the sample on the filter paper was removed, dried, and ground in an agate mortar. It was then compressed into pellets using a hydraulic press (Riken Co., Ltd., P-1B) and fired in an electric furnace (AS ONE Corporation, high-performance muffle furnace, model HPM-0N). The firing was performed in an air atmosphere with a heating time of 5 hours, a holding time of 20 hours, and a cooling time of 5 hours at a firing temperature of 950 °C.

[0146]

[0147] The constituent phases of the obtained powder samples were identified using a laboratory X-ray diffractometer (Rigaku SmartLab SE diffractometer) with Cu-Kα radiation (λ = 0.1541862 nm). Measurements were performed at an accelerating voltage of 40 kV, a target current of 30 mA, and a 2θ range of 20° to 120° with a step width of 0.02° and a sweep speed of 2° / min. The horizontal axis represents the diffraction angle 2θ (degrees), and the vertical axis represents the intensity of the diffraction line, obtaining an X-ray diffraction pattern.

[0148] The lattice constant of the sample was calculated from the diffraction pattern obtained by the measurement using the Cohen method (BD Cullity, "Elements of X-Ray Diffraction, second edition," Addison-Wesley Publishing Company, (BD Cullity, Gentaro Matsumura (translation), "New Edition Cullity's Essentials of X-Ray Diffraction," Agne (1980) pp. 320-337).

[0149] Magnetostriction measurement: Magnetostriction measurements were performed using a strain gauge (Kyowa Electronics Co., Ltd., model number: KFRB-05-120-C1-11 L1M3R) and instant adhesive for strain gauges (Kyowa Electronics Co., Ltd., model number: CC-33A). Magnetostriction measurements were performed using a VSM at room temperature and atmospheric pressure in an applied magnetic field of -25,000 ≦ H(Oe) ≦ 25,000.

[0150] Figure 32 shows the diffraction patterns obtained by X-ray diffraction measurement of each composition, enlarged in the range of 25° ≦ 2θ (degrees) ≦ 45°. All diffraction peaks could be indexed to the cubic spinel structure, and no diffraction peaks other than those of the cubic spinel structure were observed. This indicates that all compositions are single-phase cubic spinel structures.

[0151] Calculation of lattice constants Ti v Cu 0.5 Co 0.5+v Fe 2-2v The lattice constant of the cubic phase of O4 was calculated. Figure 33 shows the dependence of the lattice constant on the Ti content v. The lattice constant increases as the Ti substitution content v increases.

[0152] Magnetostriction measurement Ti v Cu 0.5 Co 0.5+v Fe 2-2v The magnetostriction curve of O4 at room temperature is shown in Figure 34. Magnetic fields were applied parallel and perpendicular to the measurement direction of the strain ΔL / L. In the magnetostriction curves for parallel and perpendicular magnetic fields, the absolute value of ΔL / L at the maximum applied magnetic field decreases with increasing Ti substitution.

[0153] Figure 35 shows the magnetic field dependence of the magnetic susceptibility to strain (dΔL / L / dH), obtained by differentiating the magnetostriction curve in the applied magnetic field process when a parallel magnetic field is applied in Figure 35. With partial Ti substitution, the maximum of the magnetic susceptibility to strain occurs at low magnetic fields. Furthermore, the maximum value of the magnetic susceptibility to strain also increases with partial Ti substitution. In other words, partial Ti substitution improves the magnetostriction properties in the low magnetic field region.

Claims

1. A magnetostrictive material containing copper-cobalt ferrite with a cubic crystal as the main crystal phase, and having a magnetostriction constant λ s (10,000 O e ) of -200 ppm or less.

2. The copper cobalt ferrite is Cu x Co y-x Fe 3-y O 4 The magnetostrictive material according to claim 1, wherein the x / y is expressed as 0<x / y≦0.75 and 0.8≦y≦1.2 (wherein at least one of Co, Fe and Cu may be partially substituted with one or more other elements).

3. A magnetostrictive material as described in claim 1, wherein the copper cobalt ferrite is polycrystalline or single crystalline.

4. The magnetostrictive material according to claim 3 , wherein the polycrystal is a non-oriented polycrystal.

5. The magnetostrictive material according to claim 3 , wherein the polycrystal is a crystal-oriented polycrystal.

6. An element that operates by utilizing the magnetostrictive effect or the inverse magnetostrictive effect of the magnetostrictive material according to any one of claims 1 to 5.

7. The element according to claim 6 , which is a vibrator, an actuator, a sensor, or a vibration power generation element.

8. A method for operating an element, comprising the step of operating an element containing the magnetostrictive material according to any one of claims 1 to 5, by utilizing the magnetostrictive effect or inverse magnetostrictive effect of the magnetostrictive material.

9. A method for producing copper-cobalt ferrite having a cubic crystal as the main crystal phase, comprising the steps of: using iron oxide, copper oxide, and cobalt oxide as raw materials to obtain copper-cobalt ferrite having a magnetostriction constant λ s (10,000 O e ) of −200 ppm or less.

10. The copper cobalt ferrite is Cu x Co y-x Fe 3-y O 4 (0<x / y≦0.75 and 0.8≦y≦1.2) (however, one or more of Co, Fe, and Cu may be partially substituted with one or more other elements), and The method according to claim 9, further comprising the step of obtaining copper-cobalt ferrite after adjusting the molar ratio of the raw materials to a stoichiometric composition based on the chemical formula.

11. A step of mixing and firing raw materials adjusted to the stoichiometric composition; The method according to claim 10, further comprising the step of compacting the sintered powder in a unidirectional magnetic field or a rotating magnetic field.