Methods for using thin-film inductors, thin-film variable inductors, and multilayer thin-film elements.

Abstract

To provide a thin film inductor element capable of presenting a sufficient imaginative inductor function even while reducing an operation current in the case of mounting in an electric circuit.SOLUTION: A thin film inductor element comprises a laminated layer, in which a magnetic substance layer and a non-magnetic substance layer are laminated, and a pair of electrodes. The magnetic substance layer and the non-magnetic substance layer extend in any shape in a direction orthogonal with a lamination direction. The magnetic substance layer has a substantially uniform magnetized structure containing a lamination direction component. The non-magnetic substance layer is a structure which is an insulator and of which the surface can be conducted. The pair of electrodes is provided at positioned in the vicinity of both ends, where the laminated film extends, and in contact with at least a surface of the non-magnetic substance layer. A current which is modulated in frequencies from 1 kHz to 1 GHz is applied.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for using a thin-film inductor element, a thin-film variable inductor element, and a multilayer thin-film element. [Background technology]

[0002] Inductors are known as components that use the induced electromotive force generated in a coil to maintain a constant circuit current. While their primary application is thought to be transformers for voltage transformation, inductors are also used in small electrical devices and high-frequency circuits such as filters in electrical circuits. Circuit components used in various electronic devices such as portable communication terminals require miniaturization and fine-tuning, and naturally, similar specifications are required for inductors. However, in order to achieve the desired functional characteristics, the inductance, which is the strength of the inductor, must be of a certain magnitude. However, since inductance is proportional to the square of the number of turns in the coil and the cross-sectional area of ​​the coil, and there is a trade-off relationship between inductance strength and miniaturization, there have been inherent limitations to the miniaturization of inductors. In this context, with the expectation that it will contribute to the miniaturization of inductor elements necessary for the miniaturization of electrical equipment and circuits, the principle of emergent inductors, which are inductor elements based on emergent magnetic fields generated by spintronics technology, has recently been elucidated and successfully demonstrated. As shown in Figure 8, while conventional induction coils have a trade-off relationship between inductance strength and miniaturization, the emergent inductor disclosed in Non-Patent Literature 1 does not have such a trade-off relationship. Rather, the cross-sectional area of ​​the element is inversely proportional to the inductance, and the inductance increases as the size decreases. For this reason, emergent inductors are expected to make a significant contribution to downsizing. However, in order for emergent inductors to generate inductance due to the emergent magnetic field, the formation of noncollinear magnetic structures such as helical magnetic structures (see Figure 8) or transverse conical magnetic structures is essential. Non-patent document 1 describes Gd3Ru4Al 12It has been confirmed that a noncollinear magnetic structure is formed by using Gd3Ru4Al. 12 Since it is not a common material, emergent inductors require careful material selection for their realization. Even if the problem of appropriately selecting the material is overcome, crystal orientation control is also necessary to form a helical magnetic structure. In addition, previous research has shown that the device performance is highly temperature-dependent. To fundamentally solve the problems inherent in such prior research, attempts have been made to induce emergent inductance function not through non-collinear magnetic structures, but through magnetic materials with spatially uniform magnetic structures. Non-patent document 2 focuses on the exchange interaction, a quantum effect, as well as the spin-orbit interaction, a quantum relativistic effect, and theoretically demonstrates that emergent inductance can be generated even in magnetic materials with uniform magnetic moments, where neither the conductor nor the magnetic moment is torn, through the combined action of these effects. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Tomoyuki Yokouchi, Fumitaka Kagawa, Max Hirschberger, Yoshichika Otani, Naoto Nagaosa & Yoshinori Tokura "Emergent electromagnetic induction in a helical-spin magnet", Nature, Vol.586, 8 October 2020 [Non-Patent Document 2] Yuta Yamane, Shunsuke Fukami, & Jun'ichi Ieda "Theory of Emergent Inductance with Spin-Orbit Coupling Effects", DOI: 10.1103 / PhysRevLett.128.147201 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, in the torsion-free system proposed in Non-Patent Document 2, although the emergence of emergent inductors was confirmed, a certain magnitude of operating current is required to move the spin of the magnetic material, which presents a challenge in that it reduces the effectiveness when implemented in an electrical circuit. To solve this problem, the present invention aims to provide a thin-film inductor element that can exhibit sufficient emergent inductive function while reducing the operating current when implemented in an electrical circuit. [Means for solving the problem]

[0005] The thin-film inductor element of the present invention comprises at least the following configurations. The invention comprises a laminated film in which a magnetic layer and a non-magnetic layer are laminated, and a pair of electrodes, wherein the magnetic layer and the non-magnetic layer are stretched in any shape in a direction perpendicular to the lamination direction, the magnetic layer has a substantially uniform magnetization structure including a component in the lamination direction, the non-magnetic layer is an insulator and its surface is conductive, and the pair of electrodes are provided near both ends where the laminated film is stretched, at least in contact with the surface of the non-magnetic layer, and a current modulated at a frequency of 1 kHz to 1 GHz is applied to them. Furthermore, the thin-film inductor element of the present invention comprises at least the following configurations. The invention comprises a laminated film in which a magnetic layer and a non-magnetic layer are laminated, and a pair of electrodes, wherein the magnetic layer and the non-magnetic layer are stretched in any shape in a direction perpendicular to the lamination direction, the magnetic layer has a substantially uniform magnetization structure including a component in the lamination direction, the pair of electrodes are provided near both ends of the laminated film where it is stretched, at least in contact with the surface of the non-magnetic layer, and a current modulated at a frequency of 1 kHz to 1 GHz is applied to them, and the non-magnetic layer is a topological insulator layer whose composition ratio is adjusted so that the Fermi energy of electrons is within the gap between the conduction band and the valence band, or a topological insulator layer whose gate voltage is adjusted so that the Fermi energy of electrons is within the band gap between the conduction band and the valence band. Furthermore, the thin-film variable inductor element of the present invention comprises at least the following configurations. The invention comprises a laminated film having a magnetic layer and a non-magnetic layer stacked on top of each other, a pair of electrodes for applying a current modulated at a frequency of 1 kHz to 1 GHz, and a thin-film coil surrounding the laminated film, wherein the magnetic layer and the non-magnetic layer are stretched in any shape in a direction perpendicular to the stacking direction, the magnetic layer has a magnetization structure including a component in the stacking direction, the non-magnetic layer is an insulator and has a conductive surface, and inductance modulation operation is realized by controlling an external magnetic field by switching the thin-film coil on and / or the direction of the current. Furthermore, the method of using the multilayer thin-film element of the present invention comprises at least the following configuration. A method for using a laminated thin-film element as an inductor element, comprising a laminated film in which a magnetic layer and a non-magnetic layer are laminated, a pair of electrodes, and a gate electrode, wherein the magnetic layer and the non-magnetic layer are stretched in any shape in a direction perpendicular to the lamination direction, the magnetic layer has a substantially uniform magnetization structure including a lamination direction component, the non-magnetic layer is a topological insulator, and the pair of electrodes are provided near both ends of the laminated film that are stretched and at least in contact with the surface of the non-magnetic layer, the method comprising the steps of: applying a voltage adjusted so that the Fermi energy of electrons is within the band gap between the conduction band and the valence band to the gate electrode; and applying a current modulated at a frequency of 1 kHz to 1 GHz to the pair of electrodes. Common to these inventions is that "laminated film" naturally includes a two-layer film consisting of a magnetic layer and a non-magnetic layer, as well as films with additional layers such as a base layer or gap layer. Furthermore, "arbitrary shape" means that it can be any shape, such as a square, circle, ellipse, or rectangle, but the intention is that inductance will be generated regardless of the shape chosen. Also, "the pair of electrodes are provided near both ends where the laminated film is stretched, and at least in contact with the surface of the non-magnetic layer" means that it includes both the configuration in which the electrodes contact the surface of the non-magnetic layer from the side and the configuration in which they contact the surface of the non-magnetic layer from above. In addition, "a substantially uniform magnetization structure including a component in the lamination direction" means a magnetic structure in which adjacent magnetic moments are collinearly arranged, rather than a non-collinear magnetic structure such as a helical magnetic structure or a transverse conical magnetic structure, which are essential requirements for realizing emergent inductance in Non-Patent Document 1, but it means that it has a component parallel to the lamination direction. [Brief explanation of the drawing]

[0006] [Figure 1] This is a perspective view showing the structural concept of a thin-film inductor element according to the first embodiment of the present invention. [Figure 2]It is an explanatory diagram showing the inductance operation of a thin-film inductor element according to the first embodiment of the present invention. [Figure 3] It is a perspective view showing the structural concept of a thin-film inductor element according to the second embodiment of the present invention. [Figure 4] It is a perspective view showing the structural concept of a thin-film inductor element according to the third embodiment of the present invention. [Figure 5] It is a perspective view showing the structural concept of a thin-film variable inductor element according to the fourth embodiment of the present invention. [Figure 6] It is a diagram for explaining the inductance modulation operation of a thin-film variable inductor element according to the fourth embodiment of the present invention. [Figure 7] It is a graph comparing the characteristics of the energy efficiency (Q value) between the thin-film inductor element according to the embodiment of the present invention and the conventional inductor element. [Figure 8] It is a diagram for explaining by comparing a conventional induction coil and a creative inductor.

Mode for Carrying Out the Invention

[0007] The thin-film inductor element and the thin-film variable inductor element according to the embodiment of the present invention utilize spintronics technology or creative electromagnetic fields. More specifically, the embodiment of the present invention uses a combination of spin-orbit torque (SOT: Spin-orbit torque), which has already been researched and developed in fields such as magnetic resistance memory, and its reverse process, and is used as an inductor.

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following drawings are conceptual diagrams created for the purpose of explanation, and in some cases, members unnecessary for the explanation may not be intentionally shown. Also, for the purpose of explanation, members may be intentionally shown larger or smaller, and they are not drawings showing the exact scale. That is, it should be noted that they do not necessarily show the implemented state as it is.

[0009] (First Embodiment) Figure 1 is a perspective view showing the structural concept of a thin-film inductor element 1 according to the first embodiment of the present invention. The thin-film inductor element 1 is formed by a laminated film in which a magnetic layer 11 and a non-magnetic layer 12 are stacked in that order from top to bottom on the plane of the paper. The magnetic layer 11 has a substantially uniform magnetization structure including a component in the stacking direction. On the other hand, the non-magnetic layer 12 is an insulator and has a structure in which its surface is conductive. The thin-film inductor element 1 is stretched in the left-right direction on the plane of the paper, and drive electrodes D-EL are provided at both ends, to which a current modulated at a frequency of 1 kHz to 1 GHz is applied. The drive current in the first embodiment is a general sine wave current, but it may also be a pulse wave or a triangular wave signal. In the first embodiment, the drive electrodes D-EL are positioned at a location that includes the boundary between the magnetic layer 11 and the non-magnetic layer 12. This is because it is necessary to pass the drive current onto the surface of the non-magnetic layer 12. Here, the vertical relationship between the magnetic layer 11 and the non-magnetic layer 12 is arbitrary, and the inductor will function under the same conditions even if their vertical positions are swapped from those shown in the figure. However, if we consider common modularization with the thin-film variable inductor element described later, the vertical relationship shown in the figure is advantageous. The magnetization direction of the magnetic material will exhibit inductive function if it includes the stacking direction component, but in the first embodiment, it is made to have stable magnetic anisotropy in a direction parallel to the stacking direction in order to obtain a large inductance. Furthermore, the inductive function will be exhibited if the non-magnetic layer is capable of generating spin-orbit torque, but in order to reduce the operating current considering implementation in an electrical circuit, the non-magnetic layer 12 in the first embodiment is an insulator and has a conductive surface structure, for example, a topological insulator layer.

[0010] (Manufacturing method for thin-film inductor elements) First, a topological insulator film is manufactured using molecular beam epitaxy, and then a magnetic film is deposited on it using ultra-high vacuum sputtering. After thin film deposition, heat treatment may be performed in a magnetic field; in the thin film inductor element 1 according to this embodiment, treatment was performed in a 300°C atmosphere for 2 hours. However, the method described here is not limited to the manufacturing method, and it goes without saying that any method that can produce the multilayer film shown in Figure 1 is acceptable, regardless of this film deposition method.

[0011] (Principle of inductor operation) Here, the principle of inductor operation of the thin-film inductor element 1 according to the first embodiment will be explained using Figure 2. Inductor operation is realized by the alternating occurrence of the spin torque process shown in Figure 2(a) and the spin electromotive force process shown in Figure 2(b). It is easier to understand if you consider this as a spintronics version of Lenz's law for electromagnetic induction, which states that when an induced current is generated due to some cause, the direction of current flow coincides with the direction that opposes the cause of the induced current. The following is a more detailed explanation.

[0012] First, in the spin torque process, a current is introduced into the thin-film inductor element 1 according to the first embodiment. At this time, spin accumulates in the plane of the paper at the interface between the magnetic layer and the non-magnetic layer, and a spin-orbit torque acts on the magnetization of the magnetic layer. As a result, the magnetization direction tilts from the energy-stable direction perpendicular to the substrate (up and down direction of the paper). The mechanism of spin accumulation can be explained by the effect of spin-orbit coupling, in which the momentum and spin polarization of conduction electrons are interconverted due to the generation of an effective electric field at the interface between the magnetic layer and the non-magnetic layer. Figure 2 illustrates the relationship between the current and spin torque that appears due to the effect of spin-orbit coupling at the interface. Figure 2 illustrates the case where a torque acts to tilt the magnetization to the right when a current flows to the right (conversely, a torque acts to tilt the magnetization to the left when a current flows to the left). When a current flows through the interface, due to the effect of spin-orbit coupling, electrons exhibit spin polarization corresponding to the direction of the current, and this spin polarization brings about a spin-orbit torque on the magnetization of the magnetic layer. In other words, by reversing the direction of the current at the interface, the direction of the spin-orbit torque acting on the magnetization of the magnetic material layer can be reversed. Therefore, an alternating current is generated when an alternating current is input. Furthermore, if the current introduced into the inductor is alternating current, the magnetization of the magnetic material layer will precess at the alternating frequency of the input current.

[0013] Next, in the spin electromotive force process, the magnetization, tilted from the energy-stable direction perpendicular to the substrate, undergoes precession due to the stored magnetic energy. This creates spin polarization in the electrons at the interface, and through spin-orbit coupling, a countercurrent is generated that counteracts the current introduced into the inductor. As a result, the sum of the introduced current and the countercurrent flows through the inductor, creating an effect that opposes the change in current (inductor).

[0014] (Materials, dimensions, and shapes considered suitable) As understood from the above, for the non-magnetic layer, it is an absolutely necessary condition to exert spin-orbit torque on the magnetic layer. Considering that it is to be implemented in an electric circuit, it only needs to be an insulator with a conductive surface. For example, a topological insulator will be adopted. As a representative example of a specific composition, a substance composed of one or two of Bi and Sb and one or two of Se and Te can be used. Written in a composition formula, it becomes (Bi,Sb)2(Te,Se)3. Even outside this composition formula, the present invention can be implemented if a substance showing the properties of a topological insulator is used for the non-magnetic layer. Specifically, Bi 1-x Sb x , HgTe / CdTe bilayer films, CaAgAs, etc. are exemplified. Generally, by changing the composition ratio of the topological insulator, the number of carriers in the bulk is changed, so that while suppressing the bulk conduction, the conductivity of its surface can be adjusted. For example, Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 In the composition of, the resistivity of the bulk is 140 mΩcm, and the carrier mobility on the surface is 2900 cm 2 V -1 s -1 , and it has been reported that it shows good characteristics as a topological insulator. Different from the second embodiment described later, in the first embodiment without a gate electrode, the composition ratio of the topological insulator is adjusted so that the Fermi energy of electrons falls within about 100 - 500 meV, which is the band gap between the conduction band and the valence band in the topological insulator (Bi,Sb)2(Te,Se)3. As a result, the bulk insulation and surface conduction of the topological insulator are ensured. As the film thickness, 5 nm or more is required. If it is too thin, the surface state will not appear, the front and back surfaces will be mixed, and there will be no difference in properties. Also, even if the film thickness is increased too much, it will become a useless thick part that does not contribute to the manifestation of inductance. Therefore, it is good to select the film thickness in the range of 5 nm to 10 nm. It has been clarified by previous research that at a film thickness of about 10 nm, the states of the front and back surfaces are sufficiently separated.

[0015] On the other hand, the magnetic layer is composed of ferromagnetic, ferrimagnetic, or antiferromagnetic materials (Note: The laminated film can also consist of two layers: an antiferromagnetic layer and an antiferromagnetic layer), and is made of materials containing Fe, Co, Ni, and Mn. Since it is necessary to have a perpendicular easy magnetization axis, specifically, Co / Ni, Co / Pt, Co / Pd, Co / Au, Fe / Au laminated films, Co-Pt, Co-Cr-Pt, Co-Pd, Fe-Pt, Fe-Pd, Fe-Co-Pt, Fe-Co-Pd alloys, CoFeB, FeB alloys, etc. can be used, and a laminated structure such as [Co / Ni] / Ta / CoFeB can also be used. The thinner the magnetic layer film, the higher the inductance that can be obtained, but it is necessary to ensure a film thickness sufficient for magnetism to manifest. Also, as with the non-magnetic layer, increasing the film thickness results in wasted space. For this reason, it is best to select the film thickness of the magnetic layer in the range of a few nm to 30 nm. Furthermore, if the magnetic layer is made of an insulator, the current will concentrate more at the interface of the laminated film, which is advantageous. In this case, rare earth iron garnet R3Fe5O 12 A topological insulator [(Bi,Sb)2(Te,Se)3] can be used, which is doped with approximately 10% of a magnetic element (Fe, Ni, Cr, Mn, etc.) (where R is a rare earth element, i.e., Y, Gd, Tb, etc.). If the shape of each layer in a two-layer film is the same, the planar shape of the multilayer film can be any shape, such as a square, circle, ellipse, or rectangle, and inductance can still be generated. However, considering practical handling, choosing a rectangle would likely be advantageous. Although the diagram shows the inductor element as being composed of two layers, a magnetic layer and a non-magnetic layer, in reality, it may be a laminated film with a base layer to form these layers in a way that yields the desired characteristics during the manufacturing process, and a cap layer to protect the element during the microfabrication process.

[0016] (Advantages over conventional technology: regarding manufacturing costs and operating environment) Using the principles of classical electromagnetism, the inductance of an inductor of the same size manufactured with an air-core solenoid coil can be estimated as follows: Assuming the inductor has a length of 100 μm, a width of 100 nm, and a thickness of 10 nm, and assuming a winding density of one turn per 100 nm, which is achievable with current microfabrication technology, the inductance L of the solenoid coil is given by L = μ0n, where μ0 is the permeability, n is the winding density, l is the length, W is the width, and t is the thickness. 2 Given by lWt, the value is calculated to be 0.013 nH. On the other hand, since the inductor element based on the principle of the present invention can be realized simply by processing a multilayer film into a thin wire shape, the manufacturing cost is significantly lower compared to classical inductors. In other words, the thin-film inductor element according to the embodiment of the present invention can achieve inductance equivalent to or significantly exceeding that of conventional classical inductors at an overwhelmingly lower cost.

[0017] In terms of cost savings, the thin-film inductor element according to the embodiment of the present invention is also advantageous for emergent inductors that utilize a combination of spin-transfer torque (STT) and its reverse process, spin electromotive force. As mentioned above, the formation of non-collinear magnetic structures such as helical magnetic structures is essential for emergent inductors, but materials exhibiting such structures are special and unsuitable for mass production. Furthermore, it is necessary to align the helical axis direction by crystal orientation control, and since the axis in which the magnetization of the helical magnetic structure revolves is determined by the crystal orientation, in order for it to act as an inductor, the current must flow in a specific axial direction of the crystal, and the effect becomes small or disappears entirely in other crystal axis directions. Obtaining the desired inductance by clearing these various conditions requires considerable cost. In contrast, the thin-film inductor elements according to embodiments of the present invention (including the second to fourth embodiments described later, in addition to the first embodiment) only require the use of a standard magnetic material having a collinear magnetic structure. Furthermore, due to the double-layer structure, the easy axis of magnetization is determined to be perpendicular to the film surface, allowing the element to be fabricated with simple film deposition, and enabling the realization of inductance at an overwhelmingly low cost. Furthermore, the thin-film inductor elements according to embodiments of the present invention (Embodiments 1 and 2-4 described below) employ a non-magnetic layer that is an insulator and whose surface is conductive, resulting in a remarkable improvement in the Q value, which represents the energy efficiency of the inductor element, and thus yielding exceptional effects. This will be described in detail later.

[0018] Emergent inductors have advantages in terms of effectiveness from another perspective as well. According to previous research, emergent inductors are Gd3Ru4Al 12 Although inductance was observed at extremely low temperatures below 16K using a somewhat unusual material, the inductance function did not manifest at higher temperatures. Of course, materials that exhibit inductance function at higher temperatures may be discovered in the future, but since this is limited to the temperature range in which noncollinear magnetic structures, including helical magnetism on the magnetic phase diagram, manifest, limitations on the operating temperature remain. In any case, there are still significant hurdles to overcome for use in normal or higher temperature ranges. In contrast, the thin-film inductor element according to the embodiment of the present invention functions sufficiently at normal temperatures. Therefore, the thin-film inductor element according to the embodiment of the present invention faces few obstacles to practical application.

[0019] (Second embodiment) Figure 3 is a perspective view showing the structural concept of a thin-film inductor element 2 according to a second embodiment of the present invention. From top to bottom on the plane of the paper, a magnetic layer 21 and a non-magnetic layer 22 are stacked in this order, and a barrier layer 23 made of an insulator is stacked on the lower surface of the non-magnetic layer 22. Examples of materials include MgO, Al2O3, and AlN, but it is important that perpendicular magnetic anisotropy is exhibited due to the interfacial magnetic anisotropy between the barrier layer 23 and the non-magnetic layer 22, and in this respect, CoFeB / MgO and FeB / MgO are preferred. Furthermore, a gate electrode G-EL made of metal is stacked on the lower surface of the barrier layer 23. Suitable materials for this are metals with good conductivity, such as Ta, Ru, and Cu. The shape of the gate electrode G-EL is set so that it fits inside the barrier layer in the horizontal plane. This is to prevent the gate electrode G-EL from short-circuiting with the inductor. The thin-film inductor element 2 is formed by four laminated films: a magnetic layer 21, a non-magnetic layer 22, a barrier layer 23, and a gate electrode G-EL. The magnetic layer 21 has a substantially uniform magnetization structure including a component in the stacking direction. On the other hand, the non-magnetic layer 22 is an insulator and has a conductive surface. The thin-film inductor element 2 is stretched in the left-right direction of the paper, and drive electrodes D-EL are provided at both ends, to which a current modulated at a frequency of 1 kHz to 1 GHz is applied. The drive current may be a general sine wave current, or a pulse wave or triangular wave signal. In the second embodiment, the drive electrode D-EL is positioned to include the boundary between the magnetic layer 21 and the non-magnetic layer 22. This is because it is necessary to pass the drive current onto the surface of the non-magnetic layer 22. While a magnetic material will function as an inductor if its magnetization direction includes the stacking direction component, in the second embodiment, it is designed to have stable magnetic anisotropy in a direction parallel to the stacking direction in order to obtain a large inductance. Furthermore, while an inductive function will be exhibited if the non-magnetic layer is capable of generating spin-orbit torque, in order to reduce the operating current considering its implementation in an electrical circuit, the non-magnetic layer 22 in the second embodiment is an insulator with a conductive surface structure, such as a topological insulator layer. In the first embodiment, the composition ratio was adjusted so that the Fermi energy of the electrons would fall within the band gap between the conduction band and the valence band. In the second embodiment, however, the adjustment is made by applying a gate voltage to tune the composition ratio within the gap. This is because, in addition to or instead of adjusting the composition ratio, the insulating properties of the bulk nonmagnetic layer and the conductivity of its surface can also be adjusted by applying a gate voltage.

[0020] (Third embodiment) Figure 4 is a perspective view showing the structural concept of a thin-film inductor element 3 according to a third embodiment of the present invention. From top to bottom on the paper, a magnetic layer 31 and a non-magnetic layer 32 are stacked in this order, and a barrier layer 33 made of an insulator is stacked on the lower surface of the non-magnetic layer 32. Examples of materials include MgO, Al2O3, and AlN, but it is important that perpendicular magnetic anisotropy is exhibited due to the interfacial magnetic anisotropy between the barrier layer 33 and the non-magnetic layer 32, and in this respect, CoFeB / MgO and FeB / MgO are preferred. Furthermore, a gate electrode G-EL made of metal is stacked on the lower surface of the barrier layer 33. Suitable materials for this are metals with good conductivity, such as Ta, Ru, and Cu. The shape of the gate electrode G-EL is set so that it fits inside the barrier layer in the horizontal plane. This is to prevent the gate electrode G-EL from short-circuiting with the inductor. A thin-film inductor element 3 is formed by four laminated films: a magnetic layer 31, a non-magnetic layer 32, a barrier layer 33, and a gate electrode G-EL. The magnetic layer 31 has a substantially uniform magnetization structure including a component in the stacking direction. On the other hand, the non-magnetic layer 32 is an insulator, and its surface is conductive. The thin-film inductor element 3 is stretched in the left-right direction of the paper, and a driving electrode D-EL is provided on the surface near both ends, parallel to the interface between the magnetic layer 31 and the non-magnetic layer 32. Since the non-magnetic layer 32 is conductive on both its surface and sides, it is possible to use the electrode structure of the first and second embodiments. However, since the electrode also has a certain size, it is undoubtedly advantageous in terms of ease of placement and processing to place it on a surface with a certain area. Therefore, in the third embodiment, the driving electrode D-EL is placed on the surface of the non-magnetic layer 32, as described above. A current modulated at a frequency of 1 kHz to 1 GHz is applied to the driving electrode D-EL. The driving current may be a typical sine wave current, or it may be a pulse wave or triangular wave signal. While a magnetic material will function as an inductor if its magnetization direction includes a component in the stacking direction, in the third embodiment, it is designed to have stable magnetic anisotropy in a direction parallel to the stacking direction in order to obtain a large inductance. Furthermore, while an inductive function will be exhibited if the non-magnetic layer is capable of generating spin-orbit torque, in order to reduce the operating current considering its implementation in an electrical circuit, the non-magnetic layer 32 in the third embodiment is an insulator with a conductive surface structure, such as a topological insulator layer. Similar to the second embodiment, the application of a gate voltage tunes the electron's Fermi energy so that it falls within the band gap between the conduction band and the valence band. However, one important point should be noted. The third embodiment allows for fine tuning by applying a gate voltage, and the drive electrode D-EL does not contact the magnetic layer 31, thus being completely unaffected by the internal resistance of the metal. From this perspective, the third embodiment can be said to be the best embodiment, which offers the highest reliability as an inductance element.

[0021] (Fourth embodiment) The first to third embodiments were thin-film inductor elements with fixed inductance, but it has also been found that the inductance of the inductor element according to the principle of the present invention can be controlled externally. In principle, the inductance is modulated by controlling the susceptibility (ease of motion) of the magnetic material by applying an external magnetic field. Figure 5 is a perspective view showing the structural concept of a thin-film variable inductor element 4 according to a fourth embodiment of the present invention. Similar to the thin-film inductor element 3 shown in Figure 4, the inductor is formed from a two-layer film in which a non-magnetic layer 42 is laminated onto a magnetic layer 41, and is extended in the left-right direction of the paper. Driving electrodes D-EL are provided on the interfaces near both ends, and an alternating current is applied. Furthermore, although signal lines are omitted in the figure, it is similar to the thin-film inductor element 3 in that it has a gate electrode G-EL for tuning so that the Fermi energy of electrons falls within the band gap between the conduction band and the valence band, and a barrier layer 43. The magnetization direction of the magnetic material exhibits stable magnetic anisotropy in a direction parallel to the lamination direction. The difference from the thin-film inductor element 3 shown in Figure 4 is that it further includes a thin-film coil 44 surrounding the laminated film. A circuit that controls the thin-film coil 44 allows for control of the Oersted magnetic field that penetrates the inductor element in the lamination direction by switching the current on and off and changing the direction of the current.

[0022] (Principle of inductance modulation operation) The principle of inductance modulation operation of a thin-film variable inductor element that functions by applying an external magnetic field will be explained using Figure 6. As shown in Figure 6(a), when a positive magnetic field is applied in the vertical direction of the paper by the control circuit, the effective magnetic anisotropy in the magnetic material of the inductor increases (the susceptibility of the magnetic material to oscillation decreases), and the inductance decreases. Conversely, as shown in Figure 6(b), when a negative magnetic field is applied, the effective magnetic anisotropy in the magnetic material of the inductor decreases (the susceptibility of the magnetic material to oscillation increases), and the inductance increases. Therefore, by performing the inductance operation while applying an external magnetic field generated by a control current, variable inductance can be realized through electrical control without mechanical movement as in conventional technology.

[0023] (Advantages over conventional technology: Regarding energy efficiency) As mentioned above, the objective of the present invention is to provide a thin-film inductor element that can exhibit sufficient emergent inductive function while reducing the operating current when implemented in an electrical circuit. To solve this problem, a non-magnetic layer capable of generating spin-orbit torque was selected that is an insulator and has a conductive surface structure. When the first to fourth embodiments of the present invention were logically verified, a surprising finding was discovered. The Q value, which represents the energy efficiency shown below, was dramatically improved.

number

[0024] (Operating principle and characteristics) We will now explain the operating principle that underlies the phenomena described so far. This operating principle can be explained as a formula obtained through the derivation process described below. Topological insulators do not conduct electricity internally, but they do conduct on their two-dimensional surfaces. In particular, at the interface between a topological insulator and a dissimilar material, conduction electrons undergo strong spin-orbit coupling. At the interface between a topological insulator and a magnetic material, conduction electrons are affected by the following two effects due to spin-orbit coupling: The first effect is the anomalous Hall effect. This is the effect in which a Hall electric field is generated perpendicular to the current flowing through the interface. The Hall electric field generated by this is known to be given by the following equation.

number

number

number

number

number

number

number

number

number

number

number

number

[0025] A notable feature of this invention is that it allows for an extremely high Q-factor, which characterizes energy efficiency. The Q-factor in an inductor can be expressed as follows, using the ratio of internal resistance R to inductance L.

number

[0026] Although the thin-film inductor element and thin-film variable inductor element according to embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and any design changes, etc., that do not depart from the gist of the present invention are also included. For example, it is of course possible to use the first embodiment without a gate electrode as the basis, while using the same type of drive electrode as in the third embodiment. It should be fully understood that the significance of the present invention lies in providing a highly reliable inductance element by eliminating internal resistance as much as possible and obtaining only the necessary inductance. [Explanation of symbols]

[0027] 1…………Thin film inductor element 11……Magnetic layer 12……Nonmagnetic layer 2…………Thin-film inductor element 21……Magnetic layer 22……Nonmagnetic layer 23… Barrier Layer 3…………Thin-film inductor element 31……Magnetic layer 32……Nonmagnetic layer 33… Barrier Layer 4…………Thin-film inductor element 41……Magnetic layer 42……Nonmagnetic layer 43… Barrier Layer 44…Thin film coil D-EL…Drive electrode G-EL… Gate gate

Claims

1. A laminated film comprising a magnetic layer and a non-magnetic layer, and a pair of electrodes, The magnetic layer and the non-magnetic layer are stretched in any shape in a direction perpendicular to the stacking direction. The aforementioned magnetic layer has a substantially uniform magnetization structure including a component in the stacking direction, The non-magnetic layer is an insulator and has a structure on its surface that allows for conductivity. The pair of electrodes are located near both ends of the stretched laminated film, at least in contact with the surface of the non-magnetic layer, and are to which a current modulated at a frequency of 1 kHz to 1 GHz is applied. A thin-film inductor element characterized by the following features.

2. The non-magnetic layer is a topological insulator layer. The thin-film inductor element according to feature 1.

3. The topological insulator layer has a composition suitable for generating spin-orbit torque. The thin-film inductor element according to feature 2.

4. The topological insulator layer has a composition of one or two of Bi and Sb, and one or two of Se and Te. The thin-film inductor element according to feature 2.

5. A laminated film comprising a magnetic layer and a non-magnetic layer, and a pair of electrodes, The magnetic layer and the non-magnetic layer are stretched in any shape in a direction perpendicular to the stacking direction. The aforementioned magnetic layer has a substantially uniform magnetization structure including a component in the stacking direction, The pair of electrodes are located near both ends of the stretched laminated film, at least in contact with the surface of the non-magnetic layer, and are to which a current modulated at a frequency of 1 kHz to 1 GHz is applied. The non-magnetic layer is a topological insulator layer whose composition ratio is adjusted so that the Fermi energy of electrons falls within the band gap between the conduction band and the valence band, or a topological insulator layer whose gate voltage is adjusted so that the Fermi energy of electrons falls within the band gap between the conduction band and the valence band. A thin-film inductor element characterized by the following features.

6. On the side of the non-magnetic layer opposite to the magnetic layer, a gate electrode layer is provided, with a barrier layer interposed between them. By applying a bias to the gate electrode layer, the current is concentrated at the interface between the non-magnetic layer and the magnetic layer. The thin-film inductor element according to feature 1.

7. The magnetic layer and the pair of electrodes are separated so that the current flows more concentratedly at the interface between the non-magnetic layer and the magnetic layer. The thin-film inductor element according to feature 1.

8. The magnetic layer is an insulator, and as a result, the current is concentrated at the interface between the non-magnetic layer and the magnetic layer. The thin-film inductor element according to feature 1.

9. The device comprises a laminated film having a magnetic layer and a non-magnetic layer stacked on top of each other, a pair of electrodes for applying a current modulated at a frequency of 1 kHz to 1 GHz, and a thin-film coil surrounding the laminated film. The magnetic layer and the non-magnetic layer are stretched in any shape in a direction perpendicular to the stacking direction. The aforementioned magnetic layer has a magnetization structure that includes a component in the stacking direction, The non-magnetic layer is an insulator and has a structure on its surface that allows for conductivity. Inductance modulation operation is achieved by controlling the external magnetic field by switching the thin-film coil on and / or the direction of the current. A thin-film variable inductor element characterized by the following features.

10. It comprises a laminated film having a magnetic layer and a non-magnetic layer stacked on top of each other, a pair of electrodes, and a gate electrode. The magnetic layer and the non-magnetic layer are stretched in any shape in a direction perpendicular to the stacking direction. The aforementioned magnetic layer has a substantially uniform magnetization structure including a component in the stacking direction, The non-magnetic layer is a topological insulator layer. A method for using a laminated thin-film element as an inductor element, characterized in that the pair of electrodes are provided near both ends of the stretched laminated film and in contact with at least the surface of the non-magnetic layer, The process involves applying a voltage to the gate electrode that is adjusted so that the Fermi energy of the electrons falls within the band gap between the conduction band and the valence band. A step in which a current modulated at a frequency of 1 kHz to 1 GHz is applied to the pair of electrodes, A method for using a multilayer thin-film element, characterized by including the following.

11. The device comprises a laminated film having a magnetic layer and a topological insulator layer, a pair of electrodes, and a gate electrode. The magnetic layer and the topological insulator layer are stretched in any shape in a direction perpendicular to the stacking direction. The aforementioned magnetic layer has a substantially uniform magnetization structure including a component in the stacking direction, The laminated thin-film element is characterized in that the pair of electrodes are provided near both ends of the stretched laminated film and in a position that is in contact with at least the surface of the topological insulator layer.

12. An electronic device comprising the thin-film element according to claim 11.

Images