Magnetostrictive film and electronic device having the magnetostrictive film

Abstract

To provide a magnetostrictive film with a low threshold magnetic field HTH and a large magnetostriction constant dλ / dH, and an electronic device including the same.SOLUTION: A magnetostrictive film 2a has an amorphous structure that includes a plurality of striated patterns 22 extending along a film thickness direction Z. The plurality of striated patterns includes a plurality of through-striated patterns 22a that is continuous from one film surface to the other film surface. The amorphous structure has a columnar structure formed by the plurality of through-striated patterns. The electronic device uses a magnetostrictive film with a small threshold magnetic field HTH. The magnetostrictive film has a magnetostriction constant dλ / dH larger than that of conventional magnetostrictive films.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a magnetostrictive film containing an amorphous material and an electronic device having the magnetostrictive film. [Background technology]

[0002] Magnetostrictive films such as those shown in Patent Documents 1 and 2 have the property of generating displacements such as expansion and contraction when an external magnetic field is applied (magnetostrictive properties), and are applied to various electronic devices such as actuators, speakers, magnetic sensors, and energy conversion devices. In order to enable output in each electronic device even for a weak input signal, the threshold magnetic field H of the magnetostrictive film must be TH Furthermore, in order to obtain a larger output relative to the input signal, it is necessary to increase the magnetostriction constant dλ / dH of the magnetostrictive film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 016399 [Patent Document 2] Japanese Patent Application Publication No. 6-220602 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in view of the above circumstances, and its object is to TH The present invention provides a magnetostrictive film having a low magnetostriction coefficient and a large magnetostriction constant dλ / dH, and an electronic device including the magnetostrictive film. [Means for solving the problem]

[0005] In order to achieve the above object, the magnetostrictive film according to the present invention comprises: The film has an amorphous structure including a plurality of streaky patterns extending in the film thickness direction.

[0006] The magnetostrictive film of the present invention has a threshold magnetic field H TH It is possible to reduce the film density and increase the magnetostriction constant dλ / dH. In the striped pattern, the film density is thought to be lower than the average for the amorphous phase. It is thought that the low film density striped pattern extending in the film thickness direction improves the magnetostriction characteristics (threshold magnetic field and magnetostriction constant).

[0007] Preferably, the plurality of streak patterns include a plurality of penetrating streak patterns that are continuous from one film surface to the other film surface, The amorphous structure has a columnar structure formed by a plurality of the through-type streaks.

[0008] The amorphous structure has a columnar structure, which reduces the threshold magnetic field H TH and the magnetostriction constant dλ / dH can be further improved.

[0009] The magnetostrictive film according to the present invention can be used in various devices such as actuators, speakers, magnetic sensors, energy conversion devices, vibrators, micropumps, etc. In the electronic device of the present invention, the threshold magnetic field H TH Because it uses a magnetostrictive film with a small resistance, it can respond to a minute external magnetic field of less than 79.58 A / m (1 Oe). In addition, because the magnetostrictive film has a larger magnetostriction constant dλ / dH than conventional magnetostrictive films, it can obtain a larger output for a given input signal. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a main part of a magnetostrictive film according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a main part of a magnetostrictive film according to another embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing a testing mechanism for an actuator. [Figure 4] FIG. 4 is a schematic diagram showing a speaker testing setup. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below based on the embodiments shown in the drawings.

[0012] First embodiment As shown in Fig. 1, a magnetostrictive film 2 according to one embodiment of the present invention is formed directly or indirectly on a substrate 6. "Indirectly formed" means that other functional films, such as a buffer layer, an electrode film, or a piezoelectric thin film, may be interposed between the magnetostrictive film 2 and the substrate 6. In Fig. 1, the magnetostrictive film 2 is located along a plane including the X-axis and the Y-axis, and has a main surface 20a located on the substrate 6 side and a main surface 20b located on the opposite side of the substrate 6. The film thickness direction of the magnetostrictive film 2 coincides with the Z-axis, and the X-axis, Y-axis, and Z-axis are perpendicular to each other.

[0013] The material of the substrate 6 is not particularly limited, but is preferably a single crystal substrate. Examples of single crystal substrates include Si, MgO, strontium titanate (SrTiO3), and lithium niobate (LiNbO3). The shape and dimensions of the substrate 6 are not particularly limited, and may be determined appropriately depending on the type and application of the device to which the magnetostrictive film 2 is applied.

[0014] The magnetostrictive film 2 preferably contains an amorphous material, particularly an amorphous soft magnetic alloy. Examples of amorphous soft magnetic alloys include Fe-Si-B alloys, Fe-Cr-Si-B alloys, Fe-Ni-Mo-B alloys, Fe-Co-B alloys, Fe-Ni-B alloys, Fe-Al-Si-B alloys, Fe-Co-Si-B alloys, Fe-Si-B-Cu-Nb alloys, Co-Fe-Ni-Si-B-Mo alloys, Fe-Ga-B alloys, and Fe-Sm-B alloys. In a cross section of the magnetostrictive film 2, an amorphous phase 21 made of such a soft magnetic alloy exists as the main phase.

[0015] Here, amorphous refers to an atomic arrangement state in which there is no long-range order like in crystals, but short-range order is present. The atomic arrangement of the magnetostrictive film 2 can be analyzed by X-ray diffraction (XRD), electron beam diffraction using a transmission electron microscope (TEM), fast Fourier transform processing (FFT) of TEM images, image analysis based on the phase contrast of TEM images, neutron diffraction (ND), etc. If diffraction peaks or diffraction spots appear in X-ray diffraction (XRD) or electron beam diffraction, it can be determined that long-range order due to crystals is present, and if a halo pattern appears, it can be determined that amorphous short-range order is present. Note that long-range order and short-range order can coexist.

[0016] For example, when structural analysis of the magnetostrictive film 2 is performed by XRD 2θ / θ measurement, it is desirable that the XRD pattern of the magnetostrictive film 2 has a broad halo pattern with a half-width of 0.5° or more in the range of 2θ=30° to 60°, and that no diffraction peaks due to crystals are observed.When structural analysis of the magnetostrictive film 2 is performed by TEM electron diffraction, it is desirable that a concentric halo pattern with unclear contours is observed, and that no diffraction spots due to crystals or Debye rings indicating the presence of polycrystals are observed.

[0017] As described above, the magnetostrictive film 2 of this embodiment has an amorphous phase 21 as its main phase, but may also contain a crystalline phase with long-range order. If the magnetostrictive film 2 contains a crystalline phase, a halo pattern due to the amorphous phase and peaks due to the crystalline phase may be observed in the XRD pattern of the magnetostrictive film 2. However, the degree of amorphization of the magnetostrictive film 2 is preferably 90% or more, more preferably 95% or more, and even more preferably 100%.

[0018] The degree of amorphization can be calculated, for example, from the area ratio of the amorphous phase 21 in the cross section of the magnetostrictive film 2. In a TEM image or HRTEM image using phase contrast, a regularly arranged lattice can be confirmed in the crystalline portion, while a random pattern without regularity can be confirmed in the amorphous portion. Therefore, the crystalline phase and the amorphous phase 21 can be distinguished based on the phase contrast, and the area ratio of the amorphous phase 21 can be roughly calculated.

[0019] Thickness t of magnetostrictive film 2 m is not particularly limited, for example, the thickness t m The average thickness t is preferably in the range of 0.03 μm to 5 μm. m can be obtained by image analysis of a cross-sectional photograph such as that shown in Figure 1. In this case, the thickness t m The thickness t1 is measured at three or more points in the in-plane direction and the average value is calculated. The variation in thickness t1 is preferably ±5% or less.

[0020] 1 shows a cross section of the magnetostrictive film 2 perpendicular to the XY plane. In particular, the cross section does not show the crystalline phase, but shows the amorphous structure (i.e., the metal structure of the amorphous phase 21). As shown in FIG. 1, the amorphous structure in the magnetostrictive film 2 has multiple streaky patterns 22 extending along the film thickness direction.

[0021] "Extending along the film thickness direction" does not necessarily mean that the extension direction of the stripe pattern 22 is parallel to the film thickness direction. The extension direction of the stripe pattern 22 may be tilted within a range of ±60° with respect to the film thickness direction, and the stripe pattern 22 may include a portion parallel to the film thickness direction and a portion tilted with respect to the film thickness direction. Furthermore, the stripe pattern 22 does not need to be a perfect straight line, and may include undulating, wavy, or lightning-like portions, or the stripes may be branched, as long as the extension direction does not deviate from the range of ±60°.

[0022] The streak pattern 22 can be confirmed by observing the cross section of the magnetostrictive film 2 using a TEM. For example, when observing the cross section using a bright-field TEM image, the streak pattern 22 can be recognized as a streak with a contrast brighter than that of the amorphous phase 21. Furthermore, structural analysis of the periphery of the streak pattern 22 using electron diffraction confirms that the streak pattern 22 is dispersed in the amorphous phase 21 and is surrounded by the amorphous phase 21. Therefore, the streak pattern 22 is different from a grain boundary, a boundary between magnetic particles, or a boundary between two layers made of different materials. The streak pattern 22 is considered to be a region where the film density is lower than the average of the amorphous phase 21, and is thought to occur in the amorphous phase 21 due to voids, defects, elongated interatomic distances, traces of desorption of gas remaining during film formation, segregation of light elements within the amorphous phase, etc.

[0023] The width of the streak pattern 22 perpendicular to the film thickness direction is 10 nm or less, preferably 5 nm or less, and more preferably 3 nm or less. There is no particular lower limit to the width of the streak pattern 22, and it is a width that can be seen in a TEM image at a magnification of 100,000 to 1,000,000 times.

[0024] In addition, the length L of the stripe pattern 22 in the film thickness direction S For example, the length L of the stripe pattern 22 is S can be set to 3 nm or more, and the thickness t m The average length of the streak pattern 22, L S The average ratio of (L S / t m ) is preferably 0.01 to 1, and more preferably 0.1 or more. S It is not necessary to take into account minute bends such as undulations when making measurements, and measurements can be made by regarding the stripe pattern 22 as a straight line.

[0025] Predetermined area A of the cross section of the magnetostrictive film 2 M (unit: nm 2 The average number of streak patterns 22 contained in the M It is preferable that the number of wires is 5 to 30 / A.M It is more preferable that N is equal to or greater than the lower limit mentioned above, which makes it easier for distortion to occur. Furthermore, by setting N to be equal to or less than the upper limit mentioned above, it is possible to prevent a decrease in the reliability of the magnetostrictive film, and to ensure sufficient force generation as an actuator. Predetermined area A M is the width d M : 50nm x thickness t m The average number N is determined by changing the observation field of the TEM and measuring the area A at least three times. M The calculation can be performed by counting the number of streak patterns 22 present within the range.

[0026] Next, an example of a method for manufacturing the magnetostrictive film 2 shown in FIG. 1 will be described.

[0027] The magnetostrictive film 2 is formed directly or indirectly on the substrate 6 by a vacuum deposition method. Vacuum deposition methods include sputtering, vacuum evaporation, PLD, and ion beam deposition (IBD), with sputtering being particularly preferred. In order to form an amorphous structure with streaky patterns 22, it is preferable to control the deposition conditions, such as the degree of vacuum, substrate temperature, inert gas flow rate, and deposition pressure, within predetermined ranges.

[0028] When forming a film by sputtering, the degree of vacuum during film formation is preferably 0.1 Pa or less, more preferably 0.05 Pa or less, and even more preferably in the range of 0.02 to 0.05 Pa. The degree of vacuum during film formation means the total pressure due to the process gas and other gases such as residual gas in the film formation chamber during film formation, and the lower the value, the higher the degree of vacuum. On the other hand, the pressure in the film formation chamber before film formation is 1.0 x 10 -5 Pa or less, and 5.0 × 10 -6 Pa or less is more preferable, and 1×10 -6 Pa ~ 5.0 × 10 -6 It is more preferable that the range is 0.1 Pa or less.

[0029] The streaky pattern 22 is more likely to occur by setting the degree of vacuum before film formation high as described above and then lowering the temperature of the substrate 6 during film formation. Specifically, the substrate temperature is preferably less than 60°C, and more preferably within the range of 25°C to 40°C.

[0030] Furthermore, when an inert gas such as Ar is introduced during film formation, increasing the flow rate of the inert gas and increasing the film formation pressure makes it easier for the streaky pattern 22 to occur. Specifically, the flow rate of the inert gas is preferably more than 30 sccm, and more preferably 60 sccm or more. The upper limit of the flow rate of the inert gas is, for example, 100 sccm or less. Furthermore, the film formation pressure is preferably more than 0.016 Pa, and more preferably 0.03 Pa or more. The upper limit of the film formation pressure is, for example, 0.05 Pa or less. The unit: sccm is the flow rate cm when converted to a condition of 1 atm (1013 hPa) and 25°C (standard state conversion). 3 / min.

[0031] The reason why film formation conditions such as substrate temperature, inert gas flow rate, and film formation pressure affect the occurrence of the streak pattern 22 is not entirely clear, but the following reasons are considered, for example.

[0032] When the substrate temperature is low or the inert gas flow rate is high, it is believed that the sputtered particles emitted from the sputtering target are hindered by the inert gas and are deposited on the substrate 6 with the inert gas entrained. In other words, by controlling the substrate temperature and the inert gas flow rate within the above-mentioned ranges, it is believed that the inert gas is more likely to remain in the deposited film. The influence of this residual gas is thought to cause voids, defects, elongated interatomic distances, degassing marks, segregation of light elements, and the like, resulting in an amorphous structure with a streaky pattern 22.

[0033] The above reason is a hypothesis that is difficult to prove, and it is possible that conditions other than the substrate temperature, inert gas flow rate, and film formation pressure are related to the appearance of the streak pattern 22. It is also possible that the film formation conditions described above vary depending on the alloy composition of the magnetostrictive film 2.

[0034] After forming the magnetostrictive film 2 on the substrate 6, the magnetostrictive film 2 may be patterned by etching, lift-off, or other methods. Alternatively, the substrate 6 may be cut, etched, or other processes. By the above methods, a magnetostrictive film 2 having a plurality of stripe patterns 22 is obtained.

[0035] (Summary of the first embodiment) The magnetostrictive film 2 of this embodiment has an amorphous structure including a plurality of streak patterns 22 extending in the film thickness direction. By forming the streak patterns 22 in the amorphous structure, the threshold magnetic field H TH can be reduced and the magnetostriction constant dλ / dH can be increased.

[0036] The reason why this effect is obtained is not entirely clear, but the following reasons are thought to be the cause. It is thought that the film density of the streak pattern 22 is lower than the average of the amorphous phase. It is thought that the low-film-density streak pattern 22 extending in the film thickness direction improves the magnetostriction characteristics (threshold magnetic field and magnetostriction constant).

[0037] The magnetostrictive film 2 can be used in various devices such as actuators, speakers, magnetic sensors, energy conversion devices, vibrators, and micropumps. TH Since the magnetostrictive film 2 has an excellent magnetostriction constant dλ / dH, electronic devices including the magnetostrictive film 2 can respond to even a small external magnetic field of less than 79.58 A / m (1 Oe). Furthermore, since the magnetostrictive film 2 has an excellent magnetostriction constant dλ / dH, electronic devices including the magnetostrictive film 2 have high input / output conversion efficiency and can obtain a larger output for a given input signal. Furthermore, since electronic devices including the magnetostrictive film 2 have high conversion efficiency, they can be easily miniaturized.

[0038] Second embodiment In the second embodiment, a magnetostrictive film 2a shown in Fig. 2 will be described. In the second embodiment, the same reference numerals will be used for the components common to the first embodiment, and the description thereof will be omitted.

[0039] 2 has a plurality of streak patterns 22 extending in the film thickness direction, similar to the magnetostrictive film 2 of the first embodiment. The streak patterns 22 of the magnetostrictive film 2a include penetrating streak patterns 22a and inclusion streak patterns 22b.

[0040] The through-type stripe pattern 22a is continuous from the main surface 20a (one film surface) on the substrate 6 side to the main surface 20b (the other film surface) on the opposite side of the substrate, and extends so as to penetrate the magnetostrictive film 2a along the film thickness direction. That is, the length L of the through-type stripe pattern 22a in the film thickness direction S1 is the thickness t of the magnetostrictive film 2a m (L S1 / t m ≒1.0).

[0041] On the other hand, the inclusion-type streak pattern 22b has a length L S2 is the thickness t of the magnetostrictive film 2a m and one or both ends in the Z-axis direction of the contained stripe pattern 22b do not reach the film surface but are contained within the magnetostrictive film 2a.

[0042] The only difference between the penetrating streak pattern 22a and the contained streak pattern 22b is their lengths in the film thickness direction. The widths of the penetrating streak pattern 22a and the contained streak pattern 22b can be set to be within the same range, and both are 10 nm or less, preferably 5 nm or less, and more preferably 3 nm or less.

[0043] 2, the amorphous phase 21 is divided into a plurality of columnar regions by a plurality of penetrating streak patterns 22a. In other words, the amorphous structure in the magnetostrictive film 2a has a columnar structure formed by a plurality of penetrating streak patterns 22a.

[0044] The average interval d between adjacent through-type stripe patterns 22a in the X-axis direction or the Y-axis direction a is preferably 100 nm or less, more preferably 1 nm or more and 50 nm or less, and even more preferably 5 nm or more and 25 nm or less. a In other words, is the average width of the columnar regions of the amorphous phase 21.

[0045] Predetermined area A of the cross section of the magnetostrictive film 2 M (unit: nm 2 The average number N1 of the penetrating streak patterns 22a contained in the M It is preferable that the number of wires is 2 to 10 / A. M It is more preferable that the predetermined area A M is the width d M : 50nm x thickness t m The range is as follows: Specified area A M The sum of the number of penetrating streak patterns 22a and the number of inclusion streak patterns 22b in the TEM can be calculated as the average number N of streak patterns 22, and N1 / N is preferably 2% to 50%, more preferably 10% to 25%. The average number N1 is calculated by measuring the number of penetrating streak patterns 22a and the number of inclusion streak patterns 22b in the TEM at least three positions in a predetermined area A in the TEM, similar to the average number N. M The calculation can be performed by counting the number of through-type streak patterns 22a present within the range.

[0046] The magnetostrictive film 2a having a columnar amorphous structure can be manufactured under the same conditions as the magnetostrictive film 2 of the first embodiment. To form the penetrating stripe pattern 22a, it is preferable to set the substrate temperature low, at 30°C or less, without heating the substrate during film formation. It is also preferable to set the inert gas flow rate to 70 sccm or more and the film formation pressure high, at 0.04 Pa or more.

[0047] (Summary of the second embodiment) The amorphous structure of the magnetostrictive film 2a in the second embodiment has a columnar structure formed by a plurality of penetrating stripe patterns 22a. The columnar structure of the amorphous structure reduces the threshold magnetic field HTH The magnetostriction constant dλ / dH can be further improved compared to the magnetostrictive film 2 of the first embodiment.

[0048] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified in various ways within the scope of the present invention. [Example]

[0049] The present invention will be described in more detail below using examples and comparative examples. However, the present invention is not limited to the following examples. In the tables shown below, sample numbers marked with * are comparative examples.

[0050] (Experiment 1) In Experiment 1, a magnetostrictive film was formed on a silicon substrate under the film-forming conditions shown in Table 1, and elements relating to Samples 1 to 8 were manufactured. In this case, the magnetostrictive film was formed using an ultra-high vacuum DC sputtering device. The film-forming conditions other than those shown in Table 1 were the same for Samples 1 to 8, and the degree of vacuum before film formation was 1.0 × 10 -5 The pressure was set to 0.016 to 0.05 Pa or less, and the vacuum level during film formation was set to within the range of 0.016 to 0.05 Pa, the output was set to 200 W (DC), and Ar gas was used as the inert gas. In addition, for samples 1 to 5, an Fe-Co-Si-B alloy target was used, and for samples 6 to 8, an Fe-Co-B alloy target was used.

[0051] After the magnetostrictive film was formed, the silicon substrate was cut to a dimension of 10 mm in width in the short direction × 40 mm in width in the long direction. In Samples 1 to 8, the average thickness of the silicon substrate was 640 μm, and the average thickness of the magnetostrictive film was t m was 500 nm in both cases.

[0052] In Experiment 1, the magnetostrictive films according to Samples 1 to 8 manufactured by the above method were evaluated as follows.

[0053] Structural analysis of magnetostrictive films The alloy composition of the magnetostrictive film was analyzed using high-frequency inductively coupled plasma (ICP) analysis. The composition of the magnetostrictive film of samples 1 to 5 was found to be (Fe 70 Co 30 ) 80 Si8B 12 The magnetostrictive film compositions of samples 6 to 8 are (Co 75 Fe 25 ) 80 B 20 Furthermore, when the structure of the magnetostrictive film was analyzed by XRD, only a halo pattern was observed in the range of 2θ = 30° to 60° in the XRD patterns of Samples 1 to 8, and no diffraction peaks from crystals were detected. In other words, the magnetostrictive films of Samples 1 to 8 were all amorphous with a degree of amorphization of 100%.

[0054] Observation of amorphous structure The cross section of the magnetostrictive film as shown in Figures 1 and 2 was observed by TEM (bright field) to measure the average number N of the stripe patterns 22 and the average number N1 of the through-type stripe patterns 22a. m ) is d M :50nm×t m :500nm=2500nm 2 The number of streak patterns contained in the measurement area was measured at five locations, and the average numbers N and N1 were calculated.

[0055] Evaluation of magnetostriction properties The magnetic field-magnetostriction curve of the magnetostrictive film is measured, and the threshold magnetic field H TH and the magnetostriction constant dλ / dH were calculated. Specifically, in an environment where a DC magnetic field of 500 A / m was applied as a bias magnetic field, a rotating magnetic field of 0 to 6400 A / m was applied to the element from the outside, and the amount of strain generated in the element was measured using a laser displacement meter, thereby obtaining a magnetic field-magnetostriction curve. The magnitude of the external magnetic field when a magnetostriction of 0.1 ppm was generated was calculated as the threshold magnetic field H TH The maximum value of the gradient of the magnetic field-magnetostriction curve was calculated as the magnetostriction constant dλ / dH.

[0056] Threshold magnetic field HTH A value of less than 79.58 A / m (1 Oe) was judged to be good, and a value of 30 A / m or less was judged to be particularly good. In the case of the Fe-Co-Si-B alloy films of samples 1 to 5, the magnetostriction constant dλ / dH was 20 ppb m A. -1 Above 70 ppb m A is considered good. -1 The above was judged to be particularly good. In the case of the Fe-Co-B alloy films of samples 6 to 8, the magnetostriction constant dλ / dH was 5 ppb m A. -1 Above 10 ppb m A is considered good. -1 The above was judged to be particularly good.

[0057] The evaluation results of Samples 1 to 8 are shown in Table 1. [Table 1]

[0058] First, the evaluation results of the Fe-Co-Si-B alloy films (samples 1 to 5) will be described. As shown in Table 1, in samples 2 to 4 having the streaky pattern 22, H TH was lower than that of Samples 1 and 5 which did not include the streak pattern 22, and dλ / dH was higher than that of Samples 1 and 5. From these results, it was found that the inclusion of the streak pattern 22 in the amorphous structure improved the magnetostriction characteristics (threshold magnetic field and magnetostriction constant). Also, in Sample 3 which had a columnar structure due to the through-type streak pattern 22a, H TH The magnetostriction was the lowest and the dλ / dH was the highest. This result shows that the magnetostriction property is further improved when the amorphous structure has a columnar structure.

[0059] The Fe-Co-B alloy films of samples 6 to 8 also obtained results similar to those of samples 1 to 5. These results show that even when the amorphous alloy composition is changed, the magnetostriction properties can be improved by providing an amorphous structure with a streaky pattern or a columnar structure.

[0060] (Experiment 2) In Experiment 2, actuators and speakers were manufactured using elements according to Samples 1 to 3 of Experiment 1, and the output performance of each device was evaluated.

[0061] Actuator performance evaluation FIG. 3 is a schematic diagram showing the actuator testing setup. As shown in FIG. 3, in Experiment 2, one end in the longitudinal direction of element 26 having a magnetostrictive film was fixed with clamp 11 to obtain cantilever-type actuator 10a. Then, using AC power supply 30 and coil 40, an AC magnetic field MF of 1 MHz and ±2387 A / m (±30 Oe) was generated and applied to the magnetostrictive film of actuator 10a. At this time, a laser (LA) was irradiated onto the free end of element 26, and the displacement (unit: μm) generated in element 26 was measured with laser displacement meter 50. In the performance evaluation of the actuator, the displacement generated in element 26 was the actuator output, and a displacement of 250 μm or more was considered good.

[0062] Speaker performance evaluation FIG. 4 is a schematic diagram showing a speaker testing setup. As shown in FIG. 4, in Experiment 2, both ends of an element 26 having a magnetostrictive film in the longitudinal direction were fixed with clamps 11, and the element 26 was combined with a diaphragm 8 (cone) to obtain a speaker 10b. Then, an AC magnetic field MF of 2 kHz and ±2387 A / m (±30 Oe) was generated using an AC power supply 30 and a coil 40, and this AC magnetic field MF was applied to the magnetostrictive film of the speaker 10b. At this time, the sound (S) generated from the speaker 10b was collected by a microphone 60, and the sound pressure (unit: dB) was measured by a spectrum analyzer 70. In this test, the distance D from the surface of the element 26 (i.e., the surface of the magnetostrictive film) to the microphone 60 was set to 30 cm. In the speaker performance evaluation, sound pressure was the speaker output, and a sound pressure of 30 dB or higher was considered good.

[0063] The evaluation results of Experiment 2 are shown in Table 2. [Table 2]

[0064] As shown in Table 2, the actuator output and speaker sound pressure of Samples 2 and 3, which had the streak pattern 22, were both improved compared to Sample 1. In particular, the evaluation results for Sample 3, which had a columnar structure, were the best. These results show that the amorphous structure of the magnetostrictive film having the streak pattern 22 can improve the input / output conversion efficiency of electronic devices. In particular, it was found that the conversion efficiency can be further improved by having the amorphous structure of the magnetostrictive film have a columnar structure. [Explanation of symbols]

[0065] 2,2a … Magnetostrictive film 20a, 20b … Main surface (film surface) 21...Amorphous phase 22... streaky pattern 22a ... Penetrating streak pattern 22b: Inclusion-type streak pattern 6... Substrate 10a ... actuator 10b ... Speaker 26...Element 11... Clamp 8... Vibration version 30 … AC power supply 40... Coil 50... Laser displacement meter 60...Mike 70...Spectrum analyzer

Claims

1. A magnetostrictive film having an amorphous structure including a plurality of streak patterns extending along the film thickness direction and an amorphous phase surrounding the streak patterns, the amorphous phase is made of a soft magnetic alloy, A magnetostrictive film, wherein the density of the streak pattern is lower than the average density of the amorphous phase surrounding the streak pattern.

2. the plurality of streak patterns include a plurality of penetrating streak patterns that are continuous from one film surface to the other film surface; 2. The magnetostrictive film according to claim 1, wherein the amorphous structure is divided into a plurality of regions by a plurality of the through-type streak patterns in a cross section parallel to the film thickness direction of the magnetostrictive film.

3. A magnetostrictive film as described in claim 1, wherein the soft magnetic alloy contains Fe, Co and B.

4. The average number of the streak patterns included in a predetermined region of a cross section parallel to the film thickness direction of the magnetostrictive film is 5 to 30, 2. The magnetostrictive film according to claim 1, wherein the length of said predetermined region perpendicular to said film thickness direction is 50 nm, and the length parallel to said film thickness direction is the thickness of said magnetostrictive film.

5. A magnetostrictive film as described in claim 1, which, in XRD 2θ / θ measurement, has a broad halo pattern with a half-width of 0.5° or more in the range of 2θ = 30° to 60°, and no diffraction peaks due to crystals are observed.

6. An electronic device having a magnetostrictive film according to any one of claims 1 to 5.

Images