Magnetic field wall moving spatial light modulator

Abstract

To provide a domain wall movement type spatial light modulator with which it is possible to increase the numerical aperture of a domain wall movement type spatial light modulation element by a simple process.SOLUTION: A domain wall movement type spatial light modulator 300 comprises domain wall movement type spatial light modulation elements 30 each having light modulation layers 31 that output polarized light of incident light by changing its direction, and a first magnetization fixed layer 32 and second magnetization fixed layers 33 that are each arranged extending to both ends of the light modulation layer 31. Coercive force of the first magnetization fixed layer 32 of the domain wall movement type spatial light modulation element 30 is smaller than coercive force of the second magnetization fixed layer 33, and the light modulation layer 31 at least partially extends diagonally with respect to a direction in which the first magnetization fixed layer 32 extends.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] This invention relates to a magnetic domain wall moving type spatial light modulator. [Background technology]

[0002] To achieve stereoscopic holography, a viewing angle of 30° or more is practically required. Therefore, the pixel pitch of the spatial light modulator (SLM), which is the display device, needs to be 1 μm or less. Existing SLMs such as liquid crystal displays and digital micromirror devices (DMDs) have a pixel pitch of about 5 μm, and further miniaturization is difficult.

[0003] On the other hand, magneto-optical spatial light modulators (MOSLMs) that use spin-injection magnetization reversal or domain wall movement for pixel rewriting can easily achieve a pixel pitch of about 1 μm, although their performance needs to be improved in terms of light utilization efficiency and operating current (see, for example, Patent Document 1). A MOSLM is a device that modulates light by assigning the rotation of the polarization plane of light according to the direction of magnetization to brightness and darkness.

[0004] A domain wall-moving type spatial light modulator includes a light modulation layer that changes the polarization direction of incident light before emission, and a domain wall-moving type spatial light modulation element having a first magnetization fixed layer and a second magnetization fixed layer with different coercivity, arranged parallel to each other at both ends of the light modulation layer. The expansion and contraction of magnetic domains can be controlled by the direction of the current flowing through the light modulation layer (see, for example, Patent Document 2). Compared to MOSLMs using spin injection magnetization reversal, domain wall-moving type spatial light modulators can be expected to have lower power consumption. However, it is necessary to provide a sufficient difference in coercivity to the three types of ferromagnetic layers—the light modulation layer and the two magnetization fixed layers—and to achieve advanced device design assuming a pixel pitch of 1 μm or less in order to precisely fabricate a complex device structure.

[0005] Patent Document 3 describes a method for designing the coercivity difference between the first and second magnetization fixed layers by forming the first and second magnetization fixed layers in a single process, thereby eliminating the need for multiple high-precision alignments. This allows for the formation of a magnetic domain wall-moving type spatial light modulation element using a simple process. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2012-141402 [Patent Document 2] Japanese Patent Publication No. 2018-206900 [Patent Document 3] Japanese Patent Publication No. 2019-220544 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, because the magnetic domain wall-moving spatial light modulation element is formed on the drain and ground electrodes of the pixel selection transistor, high-precision alignment is required between the drain and ground electrodes and the first and second magnetization fixed layers during the design process. Therefore, it has been difficult to increase the aperture ratio of the magnetic domain wall-moving spatial light modulation element.

[0008] The present invention aims to provide a magnetic domain wall-moving type spatial light modulator that can increase the aperture ratio of a magnetic domain wall-moving type spatial light modulator through a simple process. [Means for solving the problem]

[0009] One aspect of the present invention provides a domain wall-moving type spatial light modulator comprising a light modulation layer that changes the direction of polarization of incident light before emission, and a first magnetization fixed layer and a second magnetization fixed layer extending from both ends of the light modulation layer, wherein the coercivity of the first magnetization fixed layer is smaller than that of the second magnetization fixed layer, and at least a portion of the light modulation layer extends obliquely with respect to the direction in which the first magnetization fixed layer extends.

[0010] In the above-described magnetic domain wall moving type spatial light modulator, the angle between the direction in which at least a portion of the light modulation layer extends diagonally and the direction in which the first magnetization fixing layer extends may be 30° or more and 60° or less.

[0011] At least a portion of the optical modulation layer may be a parallelogram when viewed from above, in the diagonally extending region.

[0012] The first magnetization fixed layer and the second magnetization fixed layer may be arranged parallel to each other at both ends of the optical modulation layer.

[0013] The length of the first magnetization fixed layer in the direction in which it extends may be longer than the length of the second magnetization fixed layer in the direction in which it extends. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a magnetic domain wall-moving type spatial light modulator that can increase the aperture ratio of a magnetic domain wall-moving type spatial light modulator through a simple process. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view showing the structure of a conventional magnetic domain wall moving type spatial light modulation element. [Figure 2] Figure 1 is a side view showing the operation of a magnetic domain wall moving type spatial light modulator. [Figure 3] Figure 1 is a side view showing the structure and operation of a magnetic domain wall moving type spatial light modulator. [Figure 4]It is a top view showing the structure of a conventional magnetic wall movement type spatial light modulator. [Figure 5] It is a top view showing the positional relationship between the magnetic wall movement type spatial light modulation element of FIG. 4 and the drain electrode and the ground electrode of the pixel selection transistor. [Figure 6] It is a top view showing the structure of an example of the magnetic wall movement type spatial light modulator of the present embodiment. [Figure 7] It is a perspective view showing the calculation model of the magnetic wall movement type spatial light modulator of FIGS. 4 and 6. [Figure 8] It is a diagram showing the calculation result of the magnetic wall current drive of the calculation model of the magnetic wall movement type spatial light modulator of FIG. 4. [Figure 9] It is a diagram showing the calculation result of the magnetic wall current drive of the calculation model of the magnetic wall movement type spatial light modulator of FIG. 6. [Figure 10] It is a top view showing the structure of a modified example of the magnetic wall movement type spatial light modulator of FIG. 6. [Figure 11] It is a top view showing the structure of a modified example of the magnetic wall movement type spatial light modulator of FIG. 6. [Figure 12] It is a diagram for explaining the formation of the initial magnetic domain of the magnetic wall movement type spatial light modulation element of FIG. 11. [Figure 13] It is a top view showing the structure of a modified example of the magnetic wall movement type spatial light modulator of FIG. 6. [Figure 14] It is a diagram for explaining the formation of the initial magnetic domain and the magnetic wall movement of the magnetic wall movement type spatial light modulation element of FIG. 13. <​​​​​​​​​​​​​​​Figure 1 shows the structure of a conventional magnetic domain wall-moving type spatial light modulation element. The magnetic domain wall-moving type spatial light modulation element 10 has a light modulation layer 11 that changes the direction of polarization of incident light before emission, and a first magnetization fixed layer 12 and a second magnetization fixed layer 13 arranged at both ends of the light modulation layer 11, which have different coercivity, and is formed on a substrate such as Si.

[0018] The first magnetization fixed layer 12 and the second magnetization fixed layer 13 each have a bottom electrode at their lowest layer, which is made of a common metal electrode material such as metals and alloys of metals such as Cu, Al, Au, Ag, Ru, Ta, and Cr, and a pulse current source is connected to the bottom electrode.

[0019] The magnetic domain wall moving type spatial light modulation element 10 has a top-view rectangular light modulation layer 11 extending in a predetermined direction, with a first magnetization fixed layer 12 and a second magnetization fixed layer 13 positioned at both ends of the rectangular layer, extending parallel to each other. The light modulation layer 11 extends perpendicular to the direction in which the first magnetization fixed layer 12 and the second magnetization fixed layer 13 extend parallel to each other. The lower surface of the light modulation layer 11 and the upper surfaces of the first magnetization fixed layer 12 and the second magnetization fixed layer 13 are in contact on the same plane, and a pulsed current can be applied to the light modulation layer 11 via the first magnetization fixed layer 12 and the second magnetization fixed layer 13.

[0020] Figure 2 shows the operation of the magnetic domain wall moving type spatial light modulation element 10. Specifically, a coercivity difference (Hc2>Hc1) is designed between the coercivity of the first magnetization fixed layer 12 (Hc1) and the coercivity of the second magnetization fixed layer 13 (Hc2), and by applying an external magnetic field, the initial magnetization directions of both ends of the light modulation layer 11, which are essential for light modulation control, are realized. First, when a downward external magnetic field Hx1 (Hx1>Hc2>Hc1), which is greater than Hc2, is applied, the magnetization of the light modulation layer 11, the first magnetization fixed layer 12, and the second magnetization fixed layer 13 becomes downward (see Figure 2(a)). Next, when an upward external magnetic field Hx2 (Hc2>Hx2>Hc1) that is greater than Hc1 and less than Hc2 is applied, the magnetization direction of the optical modulation layer 11 and the first magnetization fixed layer 12 changes to upward (see Figure 2(b)). At this time, the leakage magnetic field Hl from the first magnetization fixed layer 12 forms an initial magnetic domain 11a at the end of the optical modulation layer 11 on the first magnetization fixed layer 12 side, thereby determining the aperture ratio of the domain wall moving type spatial optical modulation element 10 (see Figure 2(c)).

[0021] Figure 3 shows the structure and operation of the magnetic domain wall moving type spatial light modulation element 10. In the magnetic domain wall moving type spatial light modulation element 10A, a non-magnetic metal layer and a buffer layer are formed as an intermediate layer 14 between the optical modulation layer 11 and the first magnetization fixed layer 12 and the second magnetization fixed layer 13, depending on the microfabrication process and magnetic design.

[0022] The first magnetization fixed layer 12 is made of a ferromagnetic material and is a layer in which the magnetization direction is fixed in one direction, and has high coercivity. The first magnetization fixed layer 12 has magnetic anisotropy in the same direction as the optical modulation layer 11, and when a ferromagnetic material having perpendicular magnetic anisotropy is used for the optical modulation layer 11, the first magnetization fixed layer 12 is also made of a ferromagnetic material having perpendicular magnetic anisotropy. It is preferable that the optical modulation layer 11 and the first magnetization fixed layer 12 are made of ferromagnetic materials having perpendicular magnetic anisotropy.

[0023] As the materials constituting the first magnetization fixed layer 12 and the second magnetization fixed layer 13, known ferromagnetic materials can be used that constitute a magnetization fixed layer such as a CPP-GMR (Perpendicular Current Giant Magnetoresistance) element or TMR element, in which a non-magnetic layer is sandwiched between a magnetization fixed layer in which the magnetization is fixed in the vertical direction and a magnetization free layer in which the direction of magnetization can be reversed, and which have perpendicular magnetic anisotropy. Specifically, transition metals such as Fe, Co, and Ni and alloys containing these transition metals can be used, for example, TbFe alloys, TbFeCo alloys, CoCr alloys, CoPt alloys, CoPd alloys, FePt alloys, etc. This makes it possible to increase the coercivity of the first magnetization fixed layer 12 and fix the magnetization direction of the first magnetization fixed layer 12 so that it does not easily change due to an external magnetic field.

[0024] Furthermore, the first magnetization fixed layer 12 may be a multilayer film in which transition metal layers such as Fe layers, Co layers, and Ni layers are alternately stacked with non-magnetic metal layers, for example, a multilayer film of Co / Pt, Fe / Pt, Co / Pd, etc. By using these ferromagnetic materials, a first magnetization fixed layer 12 with high perpendicular magnetic anisotropy and high coercivity can be obtained.

[0025] Here, the multilayer film described above has the property that its coercivity increases when heat-treated. Therefore, when the multilayer film described above is heat-treated to increase the coercivity of the first magnetization fixed layer 12, the coercivity of the ferromagnetic exchange coupling portion after coupling with the optical modulation layer 11 also increases, and the difference in coercivity with the optical modulation region 11b becomes larger.

[0026] The non-magnetic metal layer and buffer layer are placed between the optical modulation layer 11 and the first magnetization fixed layer 12, and can maintain magnetic coupling between the optical modulation layer 11 and the first magnetization fixed layer 12.

[0027] The non-magnetic metal layer is laminated on the first magnetization fixed layer 12. The non-magnetic metal layer is provided to prevent etching damage to the first magnetization fixed layer 12 during the manufacturing process described later. A thin film made of a non-magnetic metal can be used as the non-magnetic metal layer. Examples of non-magnetic metals include Ta, Mo, Ru, etc., with Ta being preferred among these.

[0028] The buffer layer is laminated on a non-magnetic metal layer. Since the buffer layer requires current to flow, whether it is a magnetic domain wall-moving spatial light modulation element 10 or a TMR element, it is composed of a material with appropriate conductivity when thinned. Furthermore, it is desirable that the buffer layer contains elements that have a slow etching rate in the manufacturing process described later, and have high detection sensitivity by SIMS (secondary ion mass spectrometry), and is made of a material visible on a SIMS endpoint monitor. This ensures that etching is reliably stopped at the buffer layer, preventing damage to the first magnetization fixed layer 12.

[0029] The buffer layer can be made of an oxide or nitride, such as MgO, Al2O3, MgAl2O4, TiO2, ZnO, or RuO2. Among these, MgO is preferred. The MgO layer has moderate conductivity, a slow etching rate, and high SIMS sensitivity.

[0030] The optical modulation layer 11 is laminated on the first magnetization fixed layer 12 or on the buffer layer. Known ferromagnetic materials can be used as the material constituting the optical modulation layer 11, and it is preferable to use a material with a large magneto-optical effect (Kerr effect). To increase the magneto-optical effect, the optical modulation layer 11 is preferably a magnetic layer having perpendicular magnetic anisotropy. Specific examples of the optical modulation layer 11 include multilayer films of transition metals such as Co / Pd multilayer films and Pd, Pt, Cu, etc., and alloy films (RE-TM alloys) of rare earth metals and transition metals such as TbFeCo films and GdFe films. Among these, GdFe films are preferred.

[0031] The first magnetization fixed layer 12 and a portion of the optical modulation layer 11 positioned directly above it are ferromagnetically exchanged-coupled via a non-magnetic metal layer and a buffer layer. As a result, the magnetization direction of the first magnetization fixed layer 12 and the magnetization direction of the portion of the optical modulation layer 11 positioned directly above it are simultaneously reversed.

[0032] The second magnetization fixed layer 13 is selected from materials available for use in the first magnetization fixed layer 12, and similarly, the non-magnetic metal layer and buffer layer are selected from materials available for use in the non-magnetic metal layer and buffer layer of the first magnetization fixed layer 12, respectively. The optical modulation layer 11 is designed to behave in the same way as the first magnetization fixed layer 12.

[0033] Here, the first magnetization fixed layer 12 and the second magnetization fixed layer 13 are designed to have different coercive forces in order to form the optical modulation region 11b and the magnetic domain wall 11c. Therefore, by applying an external magnetic field, it is possible to achieve the initial magnetization directions at both ends of the optical modulation layer 11, which are antiparallel to each other, which are essential for optical modulation control.

[0034] Functional layers may be appropriately formed at the interfaces between each layer of the optical modulation layer 11, the first magnetization fixed layer 12, the second magnetization fixed layer 13, each non-magnetic metal layer, and each buffer layer, or at the interface with the lower electrode. For example, to prevent damage to the optical modulation layer 11 during the microfabrication process, a cap layer containing Ta, Ru, or SiN may be provided on the optical modulation layer 11. The cap layer has the function of preventing GdFe or TbFeCo, which are used to form the optical modulation layer 11 and are prone to oxidation, from oxidizing in the atmosphere after the magnetic domain wall moving type spatial optical modulation element 10 is completed.

[0035] As described above, the first magnetization fixed layer 12 and a portion of the optical modulation layer 11 directly above it are ferromagnetically exchanged coupled, and the second magnetization fixed layer 13 and a portion of the optical modulation layer 11 directly above it are also ferromagnetically exchanged coupled, and the magnetization directions of each are simultaneously reversed. Furthermore, as shown in Figures 1 and 3, the magnetization direction of the first magnetization fixed layer 12 is designed to be upward, while the magnetization direction of the second magnetization fixed layer 13 is designed to be downward.

[0036] In the optical modulation layer 11, magnetic domain walls 11c are formed perpendicular to the longitudinal direction of the optical modulation layer 11. That is, the magnetization directions of the magnetic domains formed on both sides of the magnetic domain walls 11c of the optical modulation layer 11 are opposite to each other. For example, as shown in Figures 1 and 3, the magnetization direction of the magnetic domains on the first magnetization fixed layer 12 side of the magnetic domain wall 11c is downward, and the magnetization direction of the magnetic domains on the second magnetization fixed layer 13 side of the magnetic domain wall 11c is upward.

[0037] In this way, by forming magnetic domains with different magnetization directions in the optical modulation layer 11 via the magnetic domain walls 11c, the magnetic domain wall-moving type spatial light modulation element 10 can function as a spatial light modulation element. More specifically, for example, if the magnetic domain wall-moving type spatial light modulation element 10 is configured as a reflective type spatial light modulation element, when light with aligned polarization is incident on the upper surface of the optical modulation layer 11 from above the magnetic domain wall-moving type spatial light modulation element 10, the rotation angle of the polarization plane of the reflected light will differ depending on the direction of magnetization. Therefore, by assigning each reflected light corresponding to these different polarization plane rotation angles to the brightness or darkness of the light via a polarization filter, it becomes possible to modulate the light. On the other hand, by configuring the substrate with a translucent material such as glass or sapphire, it is also possible to make the magnetic domain wall-moving type spatial light modulation element 10 function as a transmissive type spatial light modulation element.

[0038] Figure 4 shows the structure of a conventional magnetic domain wall-moving type spatial light modulator. The magnetic domain wall-moving type spatial light modulator 200 comprises a plurality of magnetic domain wall-moving type spatial light modulation elements 20. The magnetic domain wall-moving type spatial light modulation elements 20, like the magnetic domain wall-moving type spatial light modulation elements 10, have an optical modulation layer 21, a first magnetization fixed layer 22, and a second magnetization fixed layer 23. In this case, the materials constituting the first magnetization fixed layer 22 and the second magnetization fixed layer 23 are the same, but the length in the direction in which the first magnetization fixed layer 22 extends is longer than the length in the direction in which the second magnetization fixed layer 23 extends. Therefore, the coercivity of the first magnetization fixed layer 22 is smaller than the coercivity of the second magnetization fixed layer 23. Here, the magnetic domain wall-moving type spatial light modulation elements 20 arranged on both sides of the first magnetization fixed layer 22 share the first magnetization fixed layer 22. Furthermore, the magnetic domain wall moving type spatial light modulation element 20, which is positioned in the direction in which the first magnetization fixed layer 22 extends, shares the first magnetization fixed layer 22.

[0039] On the other hand, as shown in Figure 5, the first magnetization fixed layer 22 is in contact with the ground electrode 24, and a portion of the second magnetization fixed layer 23 is in contact with the drain electrode 25 of the pixel selection transistor. Therefore, during the design phase, high-precision alignment is required between the ground electrode 24 and the drain electrode 25 and the first magnetization fixed layer 22 and the second magnetization fixed layer 23. For this reason, it was difficult to increase the aperture ratio of the magnetic domain wall moving type spatial light modulation element 20.

[0040] The manufacturing method for the magnetic domain wall moving type spatial light modulator 200 is not particularly limited, but for example, the method described in Patent Document 3 can be used. Specifically, first, a resist corresponding to the shape of the first magnetization fixed layer 22 and the second magnetization fixed layer 23 is patterned on the SiO2 layer of the insulating member formed on the Si backplane, and then etched. Next, the first magnetization fixed layer 22 and the second magnetization fixed layer 23, an intermediate layer, etc. are deposited on the etched region on the Si backplane. Next, after removing the resist layer, the material constituting the light modulation layer 21 is deposited. Next, a resist corresponding to the shape of the light modulation layer 21 is patterned, and then etched. Finally, the resist layer is removed to form the light modulation layer 21.

[0041] [The magnetic domain wall moving type spatial light modulator of this embodiment] Figure 6 shows the structure of an example of a magnetic domain wall-moving type spatial light modulator of this embodiment. The magnetic domain wall-moving type spatial light modulator 300, like the magnetic domain wall-moving type spatial light modulator 200, comprises a plurality of magnetic domain wall-moving type spatial light modulation elements 30. The magnetic domain wall-moving type spatial light modulation elements 30, like the magnetic domain wall-moving type spatial light modulation elements 20, have an optical modulation layer 31, a first magnetization fixed layer 32, and a second magnetization fixed layer 33. In this case, the materials constituting the first magnetization fixed layer 32 and the second magnetization fixed layer 33 are the same, but the length in the direction in which the first magnetization fixed layer 32 extends is longer than the length in the direction in which the second magnetization fixed layer 33 extends. Therefore, the coercivity of the first magnetization fixed layer 32 is smaller than the coercivity of the second magnetization fixed layer 33. Here, the magnetic domain wall-moving type spatial light modulation elements 30 arranged on both sides of the first magnetization fixed layer 32 share the first magnetization fixed layer 32. Furthermore, the magnetic domain wall moving type spatial light modulation element 30, which is positioned in the direction in which the first magnetization fixed layer 32 extends, shares the first magnetization fixed layer 32.

[0042] On the other hand, the first magnetization fixed layer 32 is in contact with the rectangular ground electrode 34, and a part of the second magnetization fixed layer 33 is in contact with the rectangular drain electrode 35 of the pixel selection transistor. However, the region of the optical modulation layer 31 other than the first magnetization fixed layer 32 extends diagonally between the first magnetization fixed layer 32 and the second magnetization fixed layer 33, in the direction in which the first magnetization fixed layer 32 and the second magnetization fixed layer 33 extend parallel to each other. As a result, the aperture ratio of the magnetic domain wall moving type spatial optical modulation element 30 is increased compared to the magnetic domain wall moving type spatial optical modulation element 20.

[0043] The angle between the direction in which the optical modulation layer 31 extends diagonally and the direction in which the first magnetization fixed layer 32 and the second magnetization fixed layer 33 extend parallel to each other is preferably 20° to 70°, and more preferably 30° to 60°. When the angle between the direction in which the optical modulation layer 31 extends diagonally and the direction in which the first magnetization fixed layer 32 and the second magnetization fixed layer 33 extend parallel to each other is 30° or more, the influence of the magnetic field from the adjacent second magnetization fixed layer 33 is reduced, and when it is 60° or less, the aperture ratio of the magnetic domain wall moving type spatial optical modulation element 30 is increased.

[0044] The region where at least a part of the light modulation layer 31 extends obliquely is a parallelogram in plan view. Therefore, the aperture ratio of the magnetic wall movement type spatial light modulation device 30 increases. Here, the light modulation layers 31 disposed on both sides of the first magnetization fixing layer 32 have a line-symmetric structure with respect to the first magnetization fixing layer 32 and have a V shape in plan view.

[0045] Note that the ratio of the region where the light modulation layer 31 extends obliquely is not particularly limited.

[0046] Here, it was verified by computer simulation whether the aperture ratio (light modulation region) of the magnetic wall movement type spatial light modulation device 30 increases as compared with the light modulation region of the magnetic wall movement type spatial light modulation device 20. Specifically, magnetic wall current drive was calculated using the LLG (Landau-Lifsitz-Gilbert) equation representing the dynamic process of magnetization of a magnetic material. At this time, the mesh size was set to 10 nm. Here, the LLG equation is expressed by the formula

[0047]

Equation

[0047] , , eff is the effective magnetic field [A / m], γ is the magnetic gyro constant, α is the damping constant, P is the spin polarization rate, g is the Landé g factor, μ B is the Bohr magneton [J / T], e is the elementary charge of an electron [C], M S is the saturation magnetization [T], J is the current density [A / m2]. Also, H eff is expressed by the formula

[0048]

Equation

[0049] Figure 7 shows the computational models of the magnetic domain wall moving type spatial optical modulators 200 and 300. Here, the sizes of the optical modulation layer, the first magnetization fixed layer, and the second magnetization fixed layer in each direction are as follows. Note that the x' direction refers to the direction in which the optical modulation layer 31 extends, and the angle it makes with the direction in which the first magnetization fixed layer 32 and the second magnetization fixed layer 33 extend parallel to each other is 45°. Optical modulation layer 21; x-direction: 1460 nm, y-direction: 300 nm, z-direction: 10 nm Optical modulation layer 31; x' direction: 2015 nm, y direction: 300 nm, z direction: 10 nm First magnetization fixed layer 22, 32; x direction: 120nm, y direction: 2500nm, z direction: 20nm Second magnetization fixed layer 23, 33; x direction: 120nm, y direction: 500nm, z direction: 20nm

[0050] Furthermore, the parameters and structure of the magnetic properties of the optical modulation layers 21 and 31, the first magnetization fixed layers 22 and 32, and the second magnetization fixed layers 23 and 33 were calculated using the following values, which are close to those obtained through actual measurements. Saturation magnetization M of optical modulation layers 21 and 31: 0.092 [T] Anisotropic magnetic field Hk: 3 [kOe] of optical modulation layers 21 and 31 Exchange coupling constant A of optical modulation layers 21 and 31: 4.0 × 10⁻⁶ -12 [J / m] Saturation magnetization M:2[T] of the first magnetized fixed layers 22, 32 and the second magnetized fixed layers 23, 33 Exchange coupling constant A of the first magnetization fixed layers 22, 32 and the second magnetization fixed layers 23, 33: 1.0 × 10 -11 [J / m]

[0051] Figure 8 shows the calculation results for the domain wall current drive of the domain wall moving type spatial light modulator 200.

[0052] Here, when magnetic domain wall current driving is performed using spin transfer torque, applying a pulsed current in the -y direction causes electrons to move in the +y direction. This phenomenon was used to perform calculations of magnetic domain wall current driving. In these calculations, the purpose was to investigate the effect of the optical modulation layer structure on the magnetic domain walls, and the formation of initial magnetic domains due to leakage magnetic fields was not precisely considered.

[0053] Figure 8 shows that when a pulse current with a pulse width of 5 ns is applied to the magnetic domain wall-moving spatial light modulation element 20, the magnetic domain wall moves to the right in a linear fashion with respect to the time the pulse current is applied.

[0054] Figure 9 shows the calculation results for the domain wall current drive of the domain wall moving type spatial light modulator 300.

[0055] Figure 9 shows that in the magnetic domain wall-moving type spatial light modulator 30, the magnetic domain wall moves in the direction in which the optical modulation layer 31 extends, depending on the time a pulsed current is applied, and it was confirmed that the optical modulation region is increased by about 1.8 times compared to the magnetic domain wall-moving type spatial light modulator 20. Furthermore, in the magnetic domain wall-moving type spatial light modulator 300, a part of the second magnetization fixed layer 33 is closer to the adjacent optical modulation layer 31 compared to the magnetic domain wall-moving type spatial light modulator 200, but it was confirmed that the effect of this is also small.

[0056] Furthermore, the magnetic domain wall-moving type spatial light modulator 300 can be manufactured in the same manner as the magnetic domain wall-moving type spatial light modulator 200, except for patterning a resist corresponding to the shape of the light modulation layer 31.

[0057] Figure 10 shows the structure of a modified example of the magnetic domain wall moving type spatial light modulator 300. The magnetic domain wall moving type spatial light modulator 300A has the same configuration as the magnetic domain wall moving type spatial light modulator 300, except that the optical modulation layers 31A, which are located on both sides of the first magnetization fixed layer 32, are linear in a top view. As a result, the aperture ratio of the magnetic domain wall moving type spatial light modulator element 30A is increased compared to the magnetic domain wall moving type spatial light modulator element 20.

[0058] Figure 11 shows the structure of a modified example of the magnetic domain wall-moving type spatial light modulator 300. The magnetic domain wall-moving type spatial light modulator 300B has the same configuration as the magnetic domain wall-moving type spatial light modulator 300, except that the region of the optical modulation layer 31B other than the vicinity of the first magnetization fixed layer 32 extends diagonally between the first magnetization fixed layer 32 and the second magnetization fixed layer 33, in the direction in which the first magnetization fixed layer 32 and the second magnetization fixed layer 33 extend parallel to each other. This can assist in the formation of the initial magnetic domains of the magnetic domain wall-moving type spatial light modulator element 30B. In the magnetic domain wall-moving type spatial light modulator element 30B, as shown in Figure 12, for example, a downward initial magnetic domain 31a is formed at the end of the optical modulation layer 31B on the first magnetization fixed layer 32 side due to the leakage magnetic field from the upward magnetic field of the first magnetization fixed layer 32. Here, the optical modulation layer 31B is composed of a material having perpendicular magnetization. However, in a nanowire structure, the perpendicular magnetization is in a stable state along the length of the nanowire. Therefore, if a corner is not formed where the optical modulation layer 31B intersects with the ground electrode 34, it is assumed that the initial magnetic domains will expand due to the leakage magnetic field. In this case, the formation of a corner where the optical modulation layer 31B intersects with the ground electrode 34 traps the initial magnetic domains 31a at the corner, suppressing the expansion of the initial magnetic domains 31a. As a result, the optical modulation region of the domain wall-moving type spatial optical modulation element 30B is increased compared to the domain wall-moving type spatial optical modulator 300.

[0059] The distance d required to trap the initial magnetic domain 31a is, for example, approximately 50 nm to 200 nm.

[0060] Figure 13 shows the structure of a modified example of the magnetic domain wall-moving type spatial light modulator 300. The magnetic domain wall-moving type spatial light modulator 300C has the same configuration as the magnetic domain wall-moving type spatial light modulator 300, except that the region of the optical modulation layer 31C, other than the vicinity of the first magnetization fixed layer 32 and the second magnetization fixed layer 33, extends diagonally between the first magnetization fixed layer 32 and the second magnetization fixed layer 33, in the direction in which the first magnetization fixed layer 32 and the second magnetization fixed layer 33 extend parallel to each other. In the magnetic domain wall-moving type spatial light modulator element 30C, after the initial magnetic domain 31a is formed in the same manner as the magnetic domain wall-moving type spatial light modulator element 30B (see Figure 14(a)), the magnetic domain wall 31c moves and stops near the second magnetization fixed layer 33 (see Figure 14(b)), so the magnetic domain can be held more stably compared to the magnetic domain wall-moving type spatial light modulator element 30B.

[0061] Figure 15 shows the structure of a modified example of the magnetic domain wall moving type spatial light modulator 300. The magnetic domain wall moving type spatial light modulator 300D has the same configuration as the magnetic domain wall moving type spatial light modulator 300, except that the first magnetization fixed layer and the second magnetization fixed layer 33D do not extend parallel to each other. As a result, the aperture ratio of the magnetic domain wall moving type spatial light modulator element 30D is increased compared to the magnetic domain wall moving type spatial light modulator element 20.

[0062] The angle between the direction in which the first magnetization fixed layer extends and the direction in which the second magnetization fixed layer 33D extends is not particularly limited, but is, for example, 20° or more and 70° or less.

[0063] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the above embodiments may be modified as appropriate within the scope of the spirit of the present invention. For example, instead of increasing the length in the direction in which the first magnetization fixed layer extends, the width of the first magnetization fixed layer may be increased to reduce the coercivity of the first magnetization fixed layer. [Explanation of symbols]

[0064] 10, 20, 30, 30A, 30B, 30C, 30D Magnetic Domain Wall Moving Type Spatial Light Modulator 11, 21, 31, 31A, 31B, 31C Optical Modulation Layer 11a, 31a Initial magnetic domain 11b Optical modulation region 11c, 31c domain wall 12, 22, 32 First magnetization fixed layer 13, 23, 33, 33D 2nd magnetization fixed layer 14. Middle Class 24, 34 Ground electrodes 25, 35 Drain electrodes 200, 300, 300A, 300B, 300C, 300D Magnetic Field Wall Moving Spatial Light Modulators

Claims

1. The device comprises a magnetic domain wall moving type spatial light modulation element having a light modulation layer that changes the direction of polarization of incident light and emits it, and a first magnetization fixed layer and a second magnetization fixed layer that extend from both ends of the light modulation layer, The domain wall-moving type spatial light modulator is a domain wall-moving type spatial light modulator in which the coercivity of the first magnetization fixed layer is smaller than the coercivity of the second magnetization fixed layer, and at least a portion of the light modulation layer extends diagonally in a straight line with respect to the direction in which the first magnetization fixed layer extends.

2. The magnetic domain wall moving type spatial light modulator according to claim 1, wherein the angle between the direction in which at least a portion of the light modulation layer extends diagonally in a straight line and the direction in which the first magnetization fixing layer extends is 30° or more and 60° or less.

3. The magnetic domain wall moving type spatial light modulator according to claim 1 or 2, wherein at least a portion of the optical modulation layer is a region that extends diagonally in a straight line, and in a top view it is a parallelogram.

4. The magnetic domain wall moving type spatial light modulator according to any one of claims 1 to 3, wherein the first magnetization fixed layer and the second magnetization fixed layer are arranged extending parallel to each other at both ends of the light modulation layer.

5. A magnetic domain wall moving type spatial light modulator according to any one of claims 1 to 4, wherein the length in the direction in which the first magnetization fixed layer extends is longer than the length in the direction in which the second magnetization fixed layer extends.

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