Magnetic device

Abstract

To provide a magnetic material device capable of suppressing oxidation of the magnetic material, reducing capacitance of a laminated body of the magnetic material, an insulating layer, or conductive layer, and driving at high frequencies.SOLUTION: In a magnetic wire device 60 as a magnetic material device, a magnetic wire 61 and a conducting wire 62 as magnetic materials are arranged via an insulating layer 63. The insulating layer 63 is a laminated body of an insulating non-oxidized film and an insulating oxide film. The insulating non-oxidized film is connected to the magnetic wire 61.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a magnetic device. [Background technology]

[0002] Although magnetic memory, such as hard disk drives (HDDs), records magnetic data semi-permanently, it is difficult to dramatically improve the speed of magnetic data recording and playback due to the constraints of having mechanical moving parts such as a magnetic disk rotation mechanism and a magnetic recording head alignment mechanism. Furthermore, mechanical moving parts have also been a cause of malfunctions. If magnetic data could be electrically controlled without using such mechanical moving parts, it would be possible to realize a highly reliable memory with high magnetic data recording and playback speeds.

[0003] For this reason, in recent years, attention has been focused on magnetic nanowire devices, which generate magnetic domains in magnetic materials processed to widths of several hundred nanometers to several micrometers, i.e., magnetic nanowires, record magnetic data, and then drive domain walls by passing a pulse current through the magnetic nanowire.

[0004] Among these, a magnetic fine wire device that has multiple magnetic fine wires arranged in parallel and records and reproduces magnetic data using a magnetic recording head and a magnetic reproducing head is expected to be a magnetic recording device with high recording and reproducing speeds (see, for example, Patent Document 1).Furthermore, this magnetic fine wire device is also expected to be used as a spatial light modulator for displaying three-dimensional images by repeatedly controlling the formation of magnetic domains and the driving of magnetic domain walls with high precision (see, for example, Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6417259 [Patent Document 2] Patent No. 4939489 [Patent Document 3] Patent No. 5782334 Summary of the Invention [Problem to be solved by the invention]

[0006] One possible method is to place a conventional HDD magnetic recording head in contact with the magnetic nanowire and record magnetic data on the magnetic nanowire.

[0007] However, because the magnetic recording head is covered with a protective film several hundred nanometers thick, it is not possible to position the magnetic recording head closest to the magnetic nanowire, and because the magnetic recording head has mechanical components, there are problems with misalignment during alignment.

[0008] Therefore, as shown in Fig. 1, it is conceivable to arrange a conductor 12 as a magnetic recording element so that it is twisted relative to the magnetic nanowire 11, thereby forming a magnetic nanowire device 10. Here, the magnetic nanowire 11 and the conductor 12 are electrically isolated by an insulating layer 13. In this case, as shown in Fig. 2, when a pulse current 21 is passed through the conductor 12, a magnetic field 22 is generated around the conductor 12. At this time, if the strength of the magnetic field 22 is greater than the anisotropy magnetic field of the magnetic nanowire 11 having perpendicular magnetic anisotropy, an upward (or downward) magnetic domain 23 is generated in the magnetic nanowire 11.

[0009] Here, FIGS. 2(a) and 2(b) are a perspective view and a cross-sectional view, respectively.

[0010] On the other hand, metals such as terbium (Tb) and gadolinium (Gd), which are commonly used as magnetic materials for the magnetic nanowire 11, have low oxidation resistance. Therefore, when an insulating oxide such as silicon dioxide (SiO2) or silicon dioxide with carbon (SiOC) is used as the material for the insulating layer 13, oxygen diffuses from the insulating layer 13 into the magnetic nanowire 11 during film formation or heating in processes such as lithography and etching, which causes the magnetic nanowire 11 to oxidize.

[0011] Therefore, it is conceivable to use insulating non-oxides such as silicon nitride (Si3N4) and aluminum nitride (AlN) as materials for forming the insulating layer 13. However, since the dielectric constant of insulating non-oxides is approximately twice that of insulating oxides (see Table 1), the capacitance of the laminate of magnetic wire 11 / insulating layer 13 / conductor 12 increases.

[0012] [Table 1]

[0013] Therefore, for example, when a laminate of magnetic nanowire 11 / insulating layer 13 / conductive layer 32 is formed on substrate 31 (see FIG. 3) and a high-frequency pulse current having the waveform shown in FIG. 4(a) is passed through conductive layer 32, an induced current having the waveform shown in FIG. 4(b) flows from conductive layer 32 to magnetic nanowire 11 via insulating layer 13. At this time, positive and negative peaks A and B of the induced current corresponding to the differential waveform of the high-frequency pulse current are generated. Furthermore, the induced current increases in proportion to the electrostatic capacitance of the laminate of magnetic nanowire 11 / insulating layer 13 / conductive layer 32. Furthermore, the induced current increases in proportion to the frequency of the applied high-frequency pulse current.

[0014] 5 shows the measured values ​​of the high-frequency pulse current applied to the conductive layer 32 and the induced current flowing from the conductive layer 32 to the magnetic nanowire 11 via the insulating layer 13 when a silicon nitride film is used as the insulating layer. Here, the dashed line represents the high-frequency pulse current applied to the conductive layer 32, and the solid line represents the measured value of the induced current flowing from the conductive layer 32 to the magnetic nanowire 11 via the insulating layer 13.

[0015] As can be seen from Figure 5, when a high-frequency pulse current, for example, a rectangular pulse current, is applied to the conductive layer 32 to form a magnetic domain, an induced current (see the area surrounded by the dashed line) due to the high-frequency component flows from the conductive layer 32 to the magnetic nanowire 11 via the insulating layer 13. If the induced current exceeds a certain threshold, it can inadvertently drive a domain wall already formed on the magnetic nanowire 11 or formed by the conductive layer 32, causing variations in the length of the magnetic domain, resulting in problems with the shape stability of the magnetic domain and leading to bit errors and other problems. Increasing the frequency of the applied high-frequency pulse current is also considered to increase the driving speed of the magnetic nanowire device, but this generates a large induced current proportional to the frequency, which also leads to bit errors and other problems. Therefore, it is necessary to reduce the electrostatic capacitance of the magnetic nanowire 11 / insulating layer 13 / conductive layer 32 stack and drive it at high frequencies.

[0016] An object of the present invention is to provide a magnetic device that can suppress oxidation of the magnetic material, reduce the electrostatic capacitance of a magnetic material / insulating layer / conductive layer laminate, and can be driven at high frequencies. [Means for solving the problem]

[0017] One aspect of the present invention is a magnetic device in which a magnetic material and a conductive layer are arranged via an insulating layer, the insulating layer being a laminate of an insulating non-oxide film and an insulating oxide film, and the insulating non-oxide film being in contact with the magnetic material.

[0018] The insulating non-oxide film may be an insulating nitride film.

[0019] The insulating non-oxide film may have a thickness of 1 nm or more and 10 nm or less.

[0020] The insulating oxide film may have a thickness of 5 nm or more and 30 nm or less.

[0021] The magnetic body may be a magnetic nanowire, the conductive layer may be a conductor, and the magnetic nanowire device may be arranged so as to be twisted relative to the conductor. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a magnetic device that can suppress oxidation of the magnetic material, reduce the electrostatic capacitance of the magnetic material / insulating layer / conductive layer laminate, and can be driven at high frequencies. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 2 is a perspective view showing the configuration of the main part of a magnetic fine wire device. [Figure 2] 2A to 2C are diagrams illustrating a method for forming magnetic domains in the magnetic nanowire of the magnetic nanowire device of FIG. [Figure 3] FIG. 2 is a cross-sectional view showing the structure of a magnetic nanowire / insulating layer / conductive layer stack. [Figure 4] 4 is a diagram showing the waveform of a pulse current applied to the conductive layer in FIG. 3 and the waveform of an induced current flowing from the conductive layer to the magnetic nanowire. [Figure 5] FIG. 4 is a diagram showing actual measurement values ​​of a pulse current passed through the conductive layer of FIG. 3 and an induced current flowing from the conductive layer to the magnetic nanowire when a silicon nitride film is used as the insulating layer. [Figure 6] 1 is a diagram illustrating an example of a magnetic device according to an embodiment of the present invention. [Figure 7] 1 is a cross-sectional view showing an example of the structure of a magnetic fine wire / insulating layer / conductive wire laminate of the present embodiment. [Figure 8] FIG. 10 is a cross-sectional view showing another example of the structure of the magnetic fine wire / insulating layer / conductive wire laminate of the present embodiment. [Figure 9] FIG. 10 is a cross-sectional view illustrating the capacitance of a stack of magnetic fine wires / insulating layer / conductive layer. [Figure 10] 1 is a top view showing the structure of a magnetic fine wire device according to a first embodiment. [Figure 11] 1 is a diagram showing the results of evaluating the capacitance of the magnetic material / insulating layer / conductive layer laminates of Examples 1 and 2 and Comparative Example 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0025] A magnetic fine wire device is shown as an example of the magnetic device of this embodiment in Figure 6. Figures 6(a) and 6(b) are a schematic perspective view and a schematic cross-sectional view, respectively.

[0026] In the magnetic fine wire device 60, a conductor 62 serving as a magnetic recording element is arranged so as to be in a twisted position relative to a magnetic fine wire 61 serving as a magnetic body, and the magnetic fine wire 61 and the conductor 62 are arranged via an insulating layer 63. The magnetic fine wire device 60 also has a pulsed power supply 64 that applies a pulsed current to the conductor 62, and a pulsed power supply 65 that applies a pulsed current to the magnetic fine wire 61.

[0027] When a pulse current is applied to the conductor 62 using a pulse power supply 64 so that the strength of the current-induced magnetic field generated around the conductor 62 is greater than the anisotropy magnetic field of the magnetic nanowire 61, which has perpendicular magnetic anisotropy, upward (or downward) magnetic domains are generated in the magnetic nanowire 61, and binary magnetic data is recorded. In this state, when a pulse current is applied to the magnetic nanowire 61 using a pulse power supply 65, the magnetic domain walls are driven, and as a result, the magnetic domains sandwiched between the magnetic domain walls move. Furthermore, by repeatedly generating and driving the magnetic domains, magnetic data can be recorded and stored as multiple magnetic domain trains in the magnetic nanowire 61. In this case, if a magnetic reproducing element (not shown) is provided near the right end of the magnetic nanowire 61, the magnetic data can be sequentially reproduced by the magnetic reproducing element by moving the magnetic domains rightward in the magnetic nanowire 61 with a pulse current. Alternatively, when multiple magnetic domain rows have accumulated in the magnetic nanowire 61, by irradiating coherent light, the polarization plane of the reflected light rotates in two directions, left and right, corresponding to the magnetization direction of each magnetic domain that makes up the magnetic domain row, due to the magneto-optical Kerr effect that occurs on the surface of the magnetic nanowire 61.By passing this reflected light through a polarizing filter, a binary spatial light modulation output of light and dark can be obtained.

[0028] Here, the insulating layer 63 is a laminate of an insulating non-oxide film and an insulating oxide film, and the insulating non-oxide film is in contact with the magnetic nanowire 61. This suppresses oxidation of the magnetic nanowire 61 and reduces the electrostatic capacitance of the laminate of the magnetic nanowire 61 / insulating layer 63 / conductive wire 62, allowing for high-frequency driving. As a result, the induced current 66 flowing between the magnetic nanowire 11 and the conductive layer 32 can be reduced.

[0029] FIG. 7 shows an example of the structure of a magnetic nanowire / insulating layer / conductive layer stack of this embodiment.

[0030] A laminate of a magnetic nanowire 61, an insulating layer 63, and a conductive layer 72 is formed on a substrate 71. Here, the insulating layer 63 is a laminate of an insulating non-oxide film 63a and an insulating oxide film 63b, and the insulating non-oxide film 63a is in contact with the magnetic nanowire 61.

[0031] Examples of materials that can be used to form the substrate 71 include surface thermally oxidized silicon, sapphire, magnesium oxide, glass, and quartz.

[0032] The material for forming the magnetic nanowire 61 is not particularly limited, but examples thereof include terbium-cobalt (Tb-Co) alloy, terbium-iron-cobalt (Tb-Fe-Co) alloy, gadolinium-cobalt (Gd-Co) alloy, gadolinium-iron-cobalt (Gd-Fe-Co) alloy, etc. Among these, materials having perpendicular magnetic anisotropy are preferred.

[0033] The magnetic thin wire 61 may be a multilayer laminate of terbium (Tb) / cobalt (Co), a multilayer laminate of gadolinium (Gd) / cobalt (Co), or the like.

[0034] Examples of insulating non-oxides that form the insulating non-oxide film include insulating nitrides such as silicon nitride (Si3N4) and aluminum nitride (AlN). Among these, insulating nitrides are preferred.

[0035] Examples of insulating oxides that form the insulating oxide film include silicon dioxide (SiO2) and carbon-added silicon oxide (SiOC).

[0036] Table 2 shows examples of combinations of insulating non-oxides and insulating oxides.

[0037] [Table 2]

[0038] The conductive layer 72 may be made of a commonly used known conductive material such as gold (Au), silver (Ag), copper (Cu), or aluminum (Al).

[0039] The magnetic nanowire 61 / insulating layer 63 / conductive layer 72 laminate is obtained, for example, by sequentially forming the magnetic nanowire 61, the insulating layer 63 (a laminate of an insulating non-oxide film 63a / insulating oxide film 63b), and the conductive layer 72 on a substrate 71 using a sputtering method.

[0040] The thickness of the insulating non-oxide film 63a is not particularly limited as long as it can uniformly cover the surface of the magnetic nanowire 61, but is preferably 1 nm or more and 10 nm or less.

[0041] The thickness of the insulating oxide film 63b is not particularly limited as long as it can electrically insulate the magnetic nanowire 61 from the conductive layer 72 and ensure the dielectric constant of the insulating layer 63, but is preferably 5 nm to 30 nm. Increasing the ratio of the thickness of the insulating oxide film 63b to the thickness of the insulating non-oxide film 63a can relatively lower the dielectric constant. On the other hand, if the total thickness of the insulating non-oxide film 63a and the insulating oxide film 63b becomes too thick, the magnetic nanowire 61 and the conductive layer 72 will separate, increasing the recording current required to form magnetic domains. Therefore, the thickness of the insulating oxide film 63b should be selected to be as thin as possible while still ensuring insulation and dielectric constant.

[0042] The thickness of the conductive layer 72 is preferably 5 nm or more and 5 μm or less.

[0043] FIG. 8 shows another example of the structure of the magnetic nanowire / insulating layer / conductive layer stack of this embodiment.

[0044] Here, the laminate of FIG. 8 has the same configuration as the laminate of FIG. 7 except that the insulating layer 63 is a laminate of an insulating non-oxide film 63a, an insulating oxide film 63b, and an insulating oxide film 63c, i.e., the insulating oxide film has a laminated structure.

[0045] In this case, the insulating oxides constituting the insulating oxide film 63b and the insulating oxide film 63c may be the same or different. For example, if a silicon dioxide film and a carbon-added silicon oxide film are used as the insulating oxide film 63b and the insulating oxide film 63c, respectively, the surface flatness of the insulating layer 63 can be improved.

[0046] The total thickness of the insulating oxide films 63b and 63c is not particularly limited as long as it can ensure the dielectric constant of the insulating layer 63, but is preferably 5 nm to 30 nm. Increasing the ratio of the total thickness of the insulating oxide films 63b and 63c to the thickness of the insulating non-oxide film 63a can relatively lower the dielectric constant. On the other hand, if the total thickness of the insulating non-oxide film 63a and the insulating oxide films 63b and 63c becomes too thick, the magnetic nanowire 61 and the conductive layer 72 become separated, increasing the write current required to form magnetic domains. Therefore, the total thickness of the insulating oxide films 63b and 63c should be selected to be as thin as possible while still ensuring the required insulation and dielectric constant.

[0047] The capacitance of a magnetic nanowire / insulating layer / conductive layer stack will be explained using Figure 9. Figures 9(a) and 9(b) show the cases where the insulating layer has a single-layer structure of an insulating non-oxide film and a stacked structure of an insulating non-oxide film / insulating oxide film, respectively.

[0048] In FIG. 9(a), the thickness of the insulating non-oxide film 63a is a+b, and the dielectric constant is ε a Let's say.

[0049] In FIG. 9(b), the thickness of the insulating non-oxide film 63a is a, and the dielectric constant is ε a , the thickness of the insulating oxide film 63b is b, and the dielectric constant is ε b Since the dielectric constant of the insulating non-oxide film 63a is higher than the dielectric constant of the insulating oxide film 63b, the formula ε a >ε b In this case, the formula a The insulating non-oxide film 63a and the insulating oxide film 63b are configured to satisfy the following equation:

[0050]

number

[0051] where the formula a≪b When the insulating non-oxide film 63a and the insulating oxide film 63b are configured so as to satisfy the formula

[0052]

number

[0053] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0054] Example 1 A magnetic nanowire device having the structure shown in Figure 10 was fabricated by photolithography, ion beam sputtering, and lift-off. Figure 10(b) is an enlarged view of the area surrounded by the dashed line in Figure 10(a). Here, the cross-sectional structure of the central part (3 μm×3 μm) of the region surrounded by the dotted line in FIG. 10(b) is the structure in FIG. As the substrate 71, a silicon substrate with a thermally oxidized surface was used.​ After forming a 3 nm thick Pt film on the substrate 71, a five-layer laminate of a 0.3 nm thick Co film / 0.6 nm thick Tb film was formed to form a magnetic nanowire 61 having a width of 3 μm and a length of 40 μm. On the magnetic nanowire 61, a 5 nm thick Si3N4 film was formed as an insulating non-oxide film 63a, and then a 13 nm thick SiO2 film was formed as an insulating oxide film 63b, forming an insulating layer 63 of 40 μm×40 μm. On the insulating layer 63, an Ag film having a film thickness of 90 nm, a width of 3 μm and a length of 40 μm was formed as the conductive layer 72. Magnetic domain driving electrodes A and B are formed at both ends of the magnetic nanowire 61 , and magnetic recording electrodes C and D are formed at both ends of the conductive layer 72 . Example 2 A magnetic nanowire device was fabricated in the same manner as in Example 1, except that a 3 nm thick Si3N4 film was formed on the magnetic nanowire 61 as an insulating non-oxide film 63a, and then a 15 nm thick SiO2 film was formed as an insulating oxide film 63b to form an insulating layer 63 of 40 μm × 40 μm. (Comparative Example 1) A magnetic fine wire device was fabricated in the same manner as in Example 1, except that an SiO 2 film with a thickness of 18 nm was formed as the insulating layer 63. (Capacitance of laminated body of magnetic material / insulating layer / conductive layer) The capacitance of the magnetic / insulating / conductive layer laminate was evaluated using an LCR meter ZM2371 (NF Corporation). The voltage measurement terminals (L) and (H) were connected to magnetic domain drive electrodes A and B, and the current application terminals (L) and (H) were connected to magnetic recording electrodes C and D. The frequency was swept and the data was imported into a PC. FIG. 11 shows the results of evaluating the capacitance of the magnetic material / insulating layer / conductive layer laminate. 11, it can be seen that the magnetic fine wire devices of Examples 1 and 2 have a lower electrostatic capacitance of the magnetic body / insulating layer / conductive layer stack than the magnetic fine wire device of Comparative Example 1. As shown in FIG. [Explanation of symbols]

[0055] 10, 60 magnetic wire device 11, 61 Magnetic thin wire 12, 62 conductor 13, 63 Insulating layer 21 Pulse Current 22 Magnetic Field 23 magnetic domain 31, 71 board 32, 72 Conductive layer 63a Insulating non-oxide film 63b, 63c Insulating oxide film 64, 65 Pulse power supply 66 Induced current

Claims

1. a magnetic material and a conductive layer are disposed with an insulating layer interposed therebetween; the insulating layer is a laminate of an insulating non-oxide film and an insulating oxide film, the insulating non-oxide film is in contact with the magnetic body, the magnetic body is a magnetic nanowire, the conductive layer is a conductor, The magnetic device is a magnetic fine wire device in which the magnetic fine wire is arranged in a twisted position relative to the conductive wire.

2. 2. The magnetic device according to claim 1, wherein the insulating non-oxide film is an insulating nitride film.

3. 3. The magnetic device according to claim 1, wherein the insulating non-oxide film has a thickness of 1 nm or more and 10 nm or less.

4. 4. The magnetic device according to claim 1, wherein the insulating oxide film has a thickness of 5 nm to 30 nm.

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