JP2010271512A - Spin injection-type spatial light modulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spin injection-type light modulator having low electric power consumption and high magneto-optical performance. <P>SOLUTION: The spin injection-type SLM (Spatial Light Modulator) exhibits inversion of magnetization directions by spin injection and includes: a laminate element body including a magnetization direction variable layer (40) in which the magnetization direction is inverted by spin injection; a magnetization direction pinned layer (20) in which the magnetization direction is fixed; and a nonmagnetic intermediate layer (30) interposed between the magnetization direction variable layer (40) and the magnetization pinned layer (20), wherein the nonmagnetic intermediate layer includes a semiconductor material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a spatial light modulation element, and more particularly to a spatial light modulation element used by changing the magnetization direction by spin injection.

  Conventional spatial light modulators (SLMs) generally use liquid crystals. The principle of controlling the transmission and reflection of light by controlling the alignment and orientation by applying a voltage to liquid crystal molecules is used. This is a technique that has already been widely used, and can be said to be a technique that has spread widely in the world, including liquid crystal displays.

  However, the SLM using liquid crystal has a drawback in that the response speed is slow due to the rotation of molecules in principle. In order to increase the response speed, there is an OCB (Optically Compensated Bend) structure in which the initial alignment of liquid crystal molecules is bowed, but the response speed is still only a few milliseconds.

  In addition, since the thickness of the liquid crystal layer is required to be at least several μm, there is a limit to the reduction of the area of the element. It can be said that it is difficult to form.

  On the other hand, an SLM of a type that operates a micromirror manufactured by using a microfabrication technology such as MEMS (Micro Electro Mechanical Systems) has also been proposed. It is difficult to manufacture an element of 10 μm or less. It can also be said that the operation control is complicated.

  In view of this, a new SLM type using magnetization reversal of a magnetic material has been proposed. These use the magneto-optical effect (Faraday effect / Kerr effect) in which transmitted / reflected light is rotated according to the magnetization direction of the magnetic material, and the time required for the magnetization reversal of the magnetic material is generally on the order of nsec. Therefore, it can be said that this is a method that promises high-speed response.

  Among them, the elements disclosed in Japanese Patent Application Laid-Open No. 2008-60906 and Japanese Patent Application Laid-Open No. 2008-83686 are based on spin injection technology (reversing the magnetization direction of a magnetic material by flowing spin-polarized electrons). Technology) is used.

Since an element using magnetization reversal by spin injection has a small area limitation, a fine element of 1 μm ² or less can be produced without any problem. That is, a high-definition element with a high response speed can be manufactured. Note that magnetization reversal by spin injection uses the fact that a torque called spin torque is applied to the magnetization when the angular momentum of the conduction electrons is transferred to the magnetization, and a current in which the electron spin is biased flows to the magnetic material. This is a technique for controlling the magnetization direction according to the circumstances, and is used in, for example, an MRAM.

  Specifically, when electrons move from the magnetization direction fixed layer to the magnetization direction variable layer, the magnetization direction of the variable layer is aligned with the magnetization direction of the fixed layer, and conversely, from the magnetization direction variable layer to the magnetization direction fixed layer. When the electrons move in the direction, the magnetization direction of the magnetization direction variable layer is opposite to the magnetization direction of the magnetization direction fixed layer.

JP 2008-83686 A JP 2008-60906 A JP 2008-64825 A JP 2008-145748 A JP 2008-91842 A

  Note that the above prior art example as the prior art has a drawback that the optical rotation angle is small in principle. In addition, lower power consumption is also required in order to meet the demand for lower energy consumption.

  Under such circumstances, the present invention has been invented, and an object thereof is to provide a spin-injection type light modulation device having low power consumption and high magneto-optical performance.

  In order to solve such problems, the present invention is a spin injection spatial light modulator (SLM) whose magnetization direction is reversed by spin injection, and the element is magnetized by spin injection. A multilayer element body having a magnetization direction variable layer whose direction is reversed, a magnetization direction fixed layer whose magnetization direction is fixed, and a nonmagnetic intermediate layer sandwiched between the magnetization direction variable layer and the magnetization direction fixed layer The nonmagnetic intermediate layer is made of a semiconductor material.

  Further, as a preferred embodiment of the spin injection spatial light modulator of the present invention, a pair of electrode layers for applying a current are disposed on both sides of the laminate element body in the lamination direction, and at least light enters and exits. The electrode layer performed is composed of a transparent electrode material.

In a preferred embodiment of the spin injection spatial light modulator of the present invention, the transparent electrode material is made of indium zinc oxide (IZO), indium tin oxide (ITO), tin oxide ( SnO ₂ ), antimony-doped tin oxide (ATO), zinc oxide (ZnO), fluorine-doped tin oxide (FTO), indium oxide (In ₂ O ₃ ), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (AZO) And niobium-doped zinc oxide (NTO).

As a preferred embodiment of the spin injection spatial light modulator of the present invention, the nonmagnetic intermediate layer is made of ZnO, TiO ₂ , In ₂ O ₃ , SnO ₂ , GaN, GaP, GaAs, GaSb, AlN, AlP, It is composed of at least one selected from the group of semiconductor materials mainly composed of InP, InAs, InSb, ZnS, ZnSe, ZnTe, SiC, and NiO.

  Further, as a preferable aspect of the spin injection type spatial light modulator of the present invention, between the magnetization direction variable layer and the nonmagnetic intermediate layer and / or between the magnetization direction variable layer and the nonmagnetic intermediate layer. A nonmagnetic layer that does not prevent spin conduction is inserted.

  As a preferred embodiment of the spin injection spatial light modulator of the present invention, the nonmagnetic layer is configured to be Cu, Zn, Ag, or Au.

  As a preferred embodiment of the spin injection spatial light modulator of the present invention, the combination of the nonmagnetic intermediate layer and the nonmagnetic layer is a Cu / ZnO / with a nonmagnetic intermediate layer made of a semiconductor material as the center. A three-layer stack of Cu, Zn / ZnO / Zn, Zn / ZnO / Cu, or a two-layer stack in which the upper or lower nonmagnetic layer is omitted from these three-layer stacks.

  The light modulator of the present invention is configured by arranging the spin injection type spatial light modulators described above in a matrix.

  The present invention relates to a spin injection spatial light modulator (SLM) in which the magnetization direction is reversed by spin injection, the element comprising a magnetization direction variable layer whose magnetization direction is reversed by spin injection, A magnetization direction fixed layer having a fixed magnetization direction and a non-magnetic intermediate layer sandwiched between the magnetization direction variable layer and the magnetization direction fixed layer, and the nonmagnetic intermediate layer includes: Since it is made of a semiconductor material, an extremely excellent effect is obtained that high magneto-optical performance can be obtained while keeping power consumption low.

FIG. 1 is a schematic cross-sectional view of a spin injection type spatial light modulator of the present invention. FIG. 2 is a graph showing the current dependency of the normalized magnetoresistance for the sample 7. FIG. 3 is a separate graph so that the dependence of the power consumption on the nonmagnetic intermediate layer can be easily seen. FIG. 4 is a graph showing the results in Table 3 so that the results can be easily seen.

  Hereinafter, the best mode for carrying out a spin injection type spatial light modulator (SLM) in which the magnetization direction is reversed by spin injection according to the present invention will be described in detail.

  FIG. 1 is a schematic cross-sectional view of a spin-injection type spatial light modulator according to the present invention. In the drawing, a simplified image of the spatial light modulator using the Kerr effect is shown.

  As shown in FIG. 1, the spin injection type spatial light modulation device of the present invention includes a lower electrode layer 11, a magnetization direction fixed layer 20, a nonmagnetic intermediate layer 30, a magnetization direction variable layer 40, and an upper electrode from the lower side. It has a columnar (pillar-shaped) structure in which the layers 15 are sequentially stacked.

  That is, the element is sandwiched between the magnetization direction variable layer 40 whose magnetization direction is reversed by spin injection, the magnetization direction fixed layer 20 whose magnetization direction is fixed, and the magnetization direction variable layer 40 and the magnetization direction fixed layer. The lower element layer 11 and the upper electrode layer 15 for applying a current are disposed on both sides of the laminate element body 5 in the stacking direction. It takes a form.

As a method for enhancing the Kerr rotation angle theta _k of total reflected light, for example, to use a multiple reflection of a magnetic material interface.

  In the element shown in FIG. 1, the interface between the upper electrode layer 15 and the magnetization direction variable layer 40, the interface between the magnetization direction variable layer 40 and the nonmagnetic intermediate layer 30, and the nonmagnetic intermediate layer 30 and the magnetization direction fixed layer 20. The reflection at the interface is schematically shown, but the magnetic field due to the reflection at the interface between the magnetization direction variable layer 40 and the nonmagnetic intermediate layer 30 and at the interface between the nonmagnetic intermediate layer 30 and the magnetization direction fixed layer 20 is shown. In order to increase the contribution of the optical effect, multiple reflection in the nonmagnetic intermediate layer 30 is effective.

  In the present invention, since a semiconductor material is used as the material of the nonmagnetic intermediate layer 30 as will be described later, high magneto-optical performance can be obtained while suppressing power consumption when compared with a conventional material system. The effect is manifested. Before describing the constituent features of the present invention in detail, the materials of the nonmagnetic intermediate layer 30 disclosed in the prior art will be briefly described.

In contrast to the present invention, Cu is a material of the nonmagnetic intermediate layer 30 disclosed in the prior art. When Cu is used, the light that has entered the nonmagnetic intermediate layer is attenuated in the layer while repeating multiple reflections because the attenuation coefficient of Cu is large. Therefore, the reflectivity R = I / I ₀ can be obtained from the total reflected light (I) obtained with respect to the incident light (I ₀ ) to the element. As a result, the magneto-optical figure of merit (θ _k · √R), which is one of the indexes representing the magneto-optical effect, also decreases. When an insulating material such as MgO or Al ₂ O ₃ is applied to the nonmagnetic intermediate layer instead of Cu, these materials are transparent in the visible light wavelength region (380 to 780 nm), and the attenuation coefficient is almost zero. Therefore, attenuation of light intensity in the layer when multiple reflection is repeated can be suppressed, and the magneto-optical figure of merit is not lowered. However, spin injection requires a current density on the order of 10 ⁸ A / cm ² or equivalent, and the use of these insulating materials in the structure increases the device resistance, resulting in an increase in required power. End up.

  In order to eliminate such inconveniences, the present inventors have conducted intensive research, and in the present invention, by using a semiconductor material as the material of the nonmagnetic intermediate layer 30, compared with a conventional material system. Thus, it has been found that the effect that high magneto-optical performance can be obtained while suppressing power consumption is low.

  Hereinafter, each component of the present invention will be described in detail.

[Configuration of magnetization direction fixed layer 20]
The magnetization direction fixed layer 20 is a layer whose magnetization direction is fixed, and it is generally preferable to use a material having a high spin polarizability. The magnetization direction may be either the horizontal direction or the vertical direction. In the illustrated example, a perpendicular magnetization film having an easy axis of magnetization in the vertical direction is illustrated as an example, and the magnetization direction is a vertical direction (downward direction in the drawing). Refer to the experimental examples described later for specific vertical film materials.

  In general, suitable specific materials for the magnetization direction fixed layer 20 include Co, Fe, Ni and their alloys, amorphous magnetic materials such as CoFeB and CoZrTa, rare earth amorphous alloys such as TbFeCo and GdFeCo, CoMnSi, CoMnGe, and the like. Examples include Heusler alloys, Co / Pt, Co / Ni artificial lattices, and the like.

  The magnetization direction fixed layer 20 may be formed by laminating a plurality of layers made of each of the above materials to form a laminated structure of layers having different compositions. Further, in order to fix the magnetization of the magnetization direction fixed layer 20, for example, a spin pinned layer made of an antiferromagnetic material may be formed side by side.

  The thickness of the magnetization direction fixed layer 20 is about 2 to 50 nm. As a deposition method, for example, a molecular beam epitaxy method (MBE method), a sputtering method, or the like can be used.

[Configuration of Magnetization Direction Variable Layer 40]
The magnetization direction variable layer 40 is a magnetic layer whose magnetization direction is not reversed and whose magnetization is easily reversed by spin injection.

  The magnetization direction variable layer 40 is preferably made of a ferromagnetic material that produces a magneto-optical Kerr effect and / or a Faraday effect and has a relatively high degree of polarization.

  The magnetization direction may be either the horizontal direction or the vertical direction based on tuning to the magnetization direction fixed layer 20 described above. In the illustrated example, the magnetization direction is the vertical direction. Please refer to the experimental examples to be described later for specific magnetic film materials.

  In general, the material constituting the magnetization direction variable layer 40 includes Co, Fe, Ni and alloys thereof, amorphous magnetic materials such as CoFeB and CoZrTa, rare earth amorphous alloys such as GdFeCo, and Heusler alloys such as CoMnSi and CoMnGe. Examples thereof include artificial lattices such as Co / Pt and Co / Ni.

  The magnetization direction variable layer 40 may be formed by laminating a plurality of layers made of the above materials to have a laminated structure of layers having different compositions.

  The thickness of the magnetization direction variable layer 40 is about 2 to 20 nm. As a deposition method, for example, a molecular beam epitaxy method (MBE method), a sputtering method, or the like can be used.

[Configuration of Nonmagnetic Intermediate Layer 30]
The nonmagnetic intermediate layer 30 is configured to be sandwiched between the magnetization direction fixed layer 20 and the magnetization direction variable layer 40.

  Here, “sandwiched” means (1) a state in which both planes of the nonmagnetic intermediate layer 30 are in direct contact with the magnetization direction fixed layer 20 and the magnetization direction variable layer 40, respectively, and (2) a nonmagnetic intermediate layer. Both planes of the layer 30 include both the state in which the plane is indirectly in contact with the magnetization direction fixed layer 20 and the magnetization direction variable layer 40 with an arbitrary layer interposed. However, in the case of indirect contact, it is limited to the case where the operational effects of the present invention are manifested without interfering with the operational effects of the present invention even if any layer is interposed.

  The nonmagnetic intermediate layer 30 in the present invention is made of a semiconductor material.

Specifically, ZnO, TiO ₂ , In ₂ O ₃ , SnO ₂ , GaN, GaP, GaAs, GaSb, AlN, AlP, InP, InAs, InSb, ZnS, ZnSe, ZnTe, SiC, and NiO are the main components. At least one selected from the group of semiconductor materials.

Such a semiconductor has higher conductivity than an insulator such as MgO or Al ₂ O ₃ . Moreover, it is excellent in the transmittance | permeability of visible light so that it may understand also from being used as a transparent conductive film. It also shows high spin conduction. High spin conduction also leads to efficient spin injection, and magnetization reversal at a lower current density is possible.

  Such a nonmagnetic intermediate layer 30 has a thickness of about 0.5 to 10 nm. As a deposition method, for example, a molecular beam epitaxy method (MBE method), a sputtering method, or the like can be used.

  Moreover, as an aspect in said (2) case, nonmagnetic layers, such as Cu, Zn, Ag, Au, etc. which do not prevent spin conduction may be used as an arbitrary layer interposed. In that case, from a three-layer laminate of Cu / ZnO / Cu, Zn / ZnO / Zn, Zn / ZnO / Cu, etc., centering on the nonmagnetic intermediate layer 30 made of a semiconductor material, or from these three-layer laminates A two-layer laminate in which the upper or lower nonmagnetic layer is omitted can be exemplified.

  The thickness of the intervening nonmagnetic layer such as Cu, Zn, Ag, or Au is about 0.1 to 3 nm.

[Lower electrode layer 11, upper electrode layer 15]
The lower electrode layer 11 and the upper electrode layer 15 are formed on both sides in the stacking direction of the multilayer body 5 for current application. The lower electrode layer 11 and / or the upper electrode layer 15 are made of a transparent electrode material so that light can enter and exit. In the case where light enters and exits only from one electrode layer, only the electrode layer may be made of a transparent electrode material.

Specific examples of transparent electrode materials include indium zinc oxide (IZO), indium tin oxide (ITO), tin oxide (SnO ₂ ), antimony-doped tin oxide (ATO), and zinc oxide. (ZnO), fluorine-doped tin oxide (FTO), indium oxide (In ₂ O ₃ ), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (AZO), niobium-doped zinc oxide (NTO), and the like.

  Between the lower electrode layer 11 and the magnetization direction fixed layer 20, Al, Ti, Cr, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Hf, Ta, W , Re, Ir, Pt, Au, Pb, Bi and alloys thereof can be provided. Between the upper electrode layer 15 and the magnetization direction variable layer 40, Al, Ti, Cr, Cu, Cap layers such as Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Hf, Ta, W, Re, Ir, Pt, Au, Pb, Bi, and alloys thereof can be provided. .

1. Description of Action of Spin-Injection Type Spatial Light Modulation Element In FIG. 1, the magnetization direction of the magnetization direction fixed layer 20 is magnetization fixed downward (arrow 20a). The magnetization direction of the magnetization direction variable layer 40 is aligned in the same direction as the magnetization direction of the magnetization direction fixed layer 20 or in the opposite opposite direction depending on the spin injection specifications.

  That is, when a current is applied from the upper electrode layer 15 to the lower electrode layer 11 and electrons move from the magnetization direction fixed layer 20 toward the magnetization direction variable layer 40, the magnetization direction of the magnetization direction variable layer 40 changes to the magnetization direction fixed layer 20. The magnetization direction is aligned downward with the downward magnetization direction.

  On the contrary, when a current is applied from the lower electrode layer 11 to the upper electrode layer 15 and electrons move from the magnetization direction variable layer 40 toward the magnetization direction fixed layer 20, the magnetization direction of the magnetization direction variable layer 40 changes to the magnetization direction. The direction of magnetization is opposite to the direction of magnetization of the direction fixed layer 20, and the direction of magnetization is upward.

Depending on the case where the magnetization directions of both the magnetization direction variable layer 40 and the magnetization direction fixed layer 20 are aligned and in the same direction, and the case where the magnetization directions of both are opposite and in the opposite direction, reflected light respectively. If the total Kerr rotation angle is set to θ _k , two types of polarized light having a polarization angle of + θ _k and −θ _k can be obtained depending on the magnetization direction of the magnetic material, and light modulation (optical rotation) can be realized. . That is, when the magnetization direction of the magnetization direction variable layer 40 is reversed by spin injection, the polarization axis of light passing through or reflecting the region is observed in the opposite direction to the polarization axis of the magnetization direction variable layer 40 before the reversal. The

  As described above, the spin-injection type spatial light modulation element in the present invention uses rotation of the polarization direction of light by reversal of the magnetization direction, and thus various conventional elements (for example, alignment of liquid crystal molecules and movement / rotation of particles). Or an element that performs control such as angular rotation of the pixel mirror), the operation speed is high, and an operation speed of about 10 to 50 nsec can be obtained.

  In addition, the spin injection type spatial light modulator according to the present invention has a simple structure. That is, no active element (TFT) for maintaining operation like a liquid crystal element is required, and no mechanical operation such as a micromirror is involved. Furthermore, the film thickness of the element for ensuring contrast can be made thinner than that of the liquid crystal element.

  The spin-injection type spatial light modulator according to the present invention has a size of at least submicron or less if it is manufactured using the current microfabrication technology in the form shown in FIG. 1 and forming one pixel of the light modulator. High-definition processing is possible.

As one of the spin of the spatial light modulator in the description the present invention for deployment to an optical modulator to form one pixel, by the elements arranged in a matrix form, to form an optical modulator it can.

  The optical modulator includes a spin-injection spatial light modulator disposed in each of a plurality of pixels arranged in a matrix, and polarization of incident light to the spin-injection spatial light modulator by reversal of the magnetization direction. And a polarizing means (for example, a polarizing plate) for detecting a change in direction. Further, a pixel selection electrode for selecting an arbitrary pixel is connected to each of the spin injection type spatial light modulation elements, and the magnetization direction is inverted through the pixel selection electrode.

  A spin injection type spatial light modulation element is an element such as a columnar (pillar) arranged for each pixel (see FIG. 1), and adjacent spin injection type spatial light modulation elements are electrically connected to each other. And magnetically insulated.

  Further, the spin injection spatial light modulator may be configured such that three-color light corresponding to RGB is incident in a time division manner as incident light.

  Further, a shutter may be further provided between the spin injection spatial light modulator and the polarization means so that the polarization angle of incident light can be varied in a time-sharing manner.

  Hereinafter, specific experimental examples relating to the spin injection type spatial light modulation element of the present invention will be shown, and the present invention will be described in more detail.

[Experimental Example I]
A base layer made of Al having a thickness of 3.0 nm is formed on the lower electrode layer 11 made of NiFe having a thickness of 500 nm, and TbFeCo having a thickness of 15.0 nm and a thickness of 1.0 nm are formed on the base layer. A magnetization direction fixed layer 20 made of a CoFe laminate (TbFeCo 15.0 nm / CoFe 1.0 nm) was formed.

  A nonmagnetic intermediate layer 30 (thickness 1.0 nm) as shown in Table 3 below is formed on the magnetization direction fixed layer 20, and a magnetization direction variable layer 40 is formed on the nonmagnetic intermediate layer 30. did.

  The magnetization direction variable layer 40 is formed by repeatedly forming a laminate of 0.4 nm thick Co and 1.0 nm thick Pt on CoFe having a thickness of 1.0 nm five times. A multilayer film formed of Co (CoFe 1.0 nm / (Co 0.4 nm / Pt 1.0 nm) × 5 / Co 0.4 nm) was used.

  On the magnetization direction variable layer 40, a cap layer made of a two-layered laminate of Ru having a thickness of 1.0 nm and Ta having a thickness of 2.0 nm was formed (Table 1).

  The laminated film thus formed (Table 1) was processed into a 320 × 320 nm square pillar shape, the side surface was covered with an insulating layer made of alumina having a thickness of 20.0 nm, and the cap layer was removed by etching. Samples 1 to 10 were prepared by forming an electrode layer (ITO; thickness 500 nm) on the top.

  Here, before showing a specific experiment, the characteristics of the material of the nonmagnetic intermediate layer 30 used for each sample will be described.

  As the nonmagnetic intermediate layer 30, various conductors, insulators, and semiconductors are used as shown in Table 2 below, and these characteristics are summarized in Table 2.

It is said that the threshold for conductors and semiconductors is about 10 ⁻³ ohm cm, and the threshold for semiconductors and insulators is about 10 ⁶ ohm cm, but there is no firm standard. In fact, generally ITO to be treated as a semiconductor (Sn doped In ₂ O ₃₎ and ZnO also shows the conductivity which is classified into conductor. It is known that the resistivity of these semiconductors varies depending on the manufacturing method, and in reality, it can be said that classification from a unique conductivity value is impossible. Therefore, in the present invention, materials that are likely to be doubted as “semiconductor” are specifically listed as materials and listed as “semiconductor”.

  Magnetization reversal by spin injection was performed on Samples 1 to 10 prepared as described above in the following manner. The magnetization reversal current was determined using the following method. The device is not energized from -100 mA to +100 mA, and further from +100 mA to -100 mA, and the change in resistance is observed. The highest resistance in the range is “1”, and the lower resistance is “0”. The change in magnetoresistance was expressed as a normalized value. Note that energization in the direction from the magnetization direction variable layer 40 to the magnetization direction fixed layer 20 is treated as a positive current value.

  The point where the normalized resistance becomes 0.5 was defined as the reversal current, and the reversal current was obtained for each sample.

  For reference, the current dependency of the normalized magnetoresistance for sample 7 is shown in FIG.

  For sample 7, 53 mA is the reversal current. Note that a resistance at which the normalized resistance becomes 0 was defined as an element resistance.

  Using the above method, as shown in Table 3, (1) inversion current and (2) element resistance were obtained. The reversal current generally showed a low value when the material of the nonmagnetic intermediate layer 30 in which the MR change rate was easily developed was used. This is presumed to be due to the fact that a nonmagnetic intermediate layer with low spin scattering is required in order to exhibit a high MR ratio, and that effective spin injection is performed in a system with low spin scattering.

  Based on the obtained (1) inversion current and (2) element resistance, (3) inversion voltage and (4) power consumption were calculated. Further, the graph of FIG. 3 is separately shown so that the dependency of the power consumption on the nonmagnetic intermediate layer 30 can be easily seen.

  Since power consumption greatly depends on element resistance, Sample 5 and Sample 6 using an insulating layer (AlO, MgO) having high element resistance for the nonmagnetic intermediate layer 30 have a high power consumption of 30 mW or more. Recognize.

  On the other hand, it can be seen that the sample using the conductor layer having a low element resistance and the semiconductor layer as the nonmagnetic intermediate layer 30 has a power consumption of 30 mW or less.

  As a final product form, a shape in which the light modulation elements are spread as a matrix is assumed. In consideration of the construction of such a multi-element device, it is essential to suppress power consumption. It can be seen that it is preferable to use a conductor / semiconductor as the nonmagnetic intermediate layer 30 from the viewpoint of suppressing the power consumption.

  Further, a laser having a wavelength of 633 nm was used to make incidence from a direction inclined by 30 degrees from the normal direction of the upper surface of the sample, the reflectance R and Kerr rotation angle θk in each element were obtained, and the magneto-optical performance index was calculated.

  Table 3 shows various optical properties of these samples.

As shown in Table 3, the sample using the conductor for the nonmagnetic intermediate layer 30 has a high reflectivity R as a whole. However, the Kerr rotation angle θk tended to be small. As a result, the magneto-optical figure of merit (θk · √R = θk · R ^1/2 ) was low for conductors and high for semiconductors / insulators. This result is shown in the graph of FIG. 4 so that it can be easily seen. The result shown in FIG. 4 seems to be due to the enhancement of the Kerr effect due to the multiple reflection effect by using a material that is transparent to visible light.

[Experimental Example II]
A base layer made of Al having a thickness of 3.0 nm is formed on the lower electrode layer 11 made of NiFe having a thickness of 500 nm, and TbFeCo having a thickness of 15.0 nm and a thickness of 1.0 nm are formed on the base layer. A magnetization direction fixed layer 20 made of a CoFe laminate (TbFeCo 15.0 nm / CoFe 1.0 nm) was formed, and a nonmagnetic intermediate layer 30 was formed on the magnetization direction fixed layer 20.

  The nonmagnetic intermediate layer 30 is formed of a three-layer laminate (Cu 0.5 nm / ZnO 1.0 nm / Cu 0.5 nm) of Cu having a thickness of 0.5 nm, ZnO having a thickness of 1.0 nm, and Cu having a thickness of 0.5 nm. ). On the nonmagnetic intermediate layer 30, the magnetization direction variable layer 40 was formed.

  The magnetization direction variable layer 40 is formed by repeatedly forming a laminate of 0.4 nm thick Co and 1.0 nm thick Pt on CoFe having a thickness of 1.0 nm five times. A multilayer film formed of Co (CoFe 1.0 nm / (Co 0.4 nm / Pt 1.0 nm) × 5 / Co 0.4 nm) was used.

  On the magnetization direction variable layer 40, a cap layer made of a two-layered laminate of Ru having a thickness of 1.0 nm and Ta having a thickness of 2.0 nm was formed.

  The laminated film thus formed is processed into a 320 × 320 nm square pillar shape, the side surface is covered with an insulating layer made of alumina having a thickness of 20.0 nm, the cap layer is removed by etching, and then the upper electrode layer (ITO Sample 500 was produced by forming a thickness of 500 nm) on top.

  For this sample 11 as well, the electrical characteristics and optical characteristics were measured in the same manner as in the above sample. The sample 11 and the sample 7 are shown in Table 4 below.

  From the results shown in Table 4, even when a non-magnetic layer is inserted at the interface between the semiconductor layer and the magnetic layer, the material is excellent in spin conduction, and there is almost no decrease in the magneto-optical performance index. I understand that.

  In conclusion, it has been clarified that an optical modulator using a semiconductor as a nonmagnetic intermediate layer has low power consumption and a high magneto-optical performance index, and exhibits excellent performance as a spin injection optical modulator.

  INDUSTRIAL APPLICABILITY The present invention can be used in the technical field of spatial light modulation elements that are used by changing the magnetization direction by spin injection, for example, the stereoscopic image field.

DESCRIPTION OF SYMBOLS 5 ... Laminate body 11 ... Lower electrode layer 15 ... Upper electrode layer 20 ... Magnetization direction fixed layer 30 ... Nonmagnetic intermediate layer 40 ... Magnetization direction variable layer

Claims (8)

A spin injection spatial light modulator (SLM) in which the magnetization direction is reversed by spin injection,
The element is
A magnetization direction variable layer whose magnetization direction is reversed by spin injection, a magnetization direction fixed layer whose magnetization direction is fixed, and a nonmagnetic intermediate layer sandwiched between the magnetization direction variable layer and the magnetization direction fixed layer It consists of a multilayer element body,
The non-magnetic intermediate layer is made of a semiconductor material, and is a spin injection type spatial light modulation element.   The pair of electrode layers for applying a current are disposed on both sides of the stack element body in the stacking direction, and at least the electrode layers where light enters and exits are made of a transparent electrode material. Spin injection spatial light modulator. The transparent electrode material includes indium zinc oxide (IZO), indium tin oxide (ITO), tin oxide (SnO ₂ ), antimony-doped tin oxide (ATO), zinc oxide (ZnO), The spin injection type according to claim 2, which is fluorine-doped tin oxide (FTO), indium oxide (In ₂ O ₃ ), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (AZO), or niobium-doped zinc oxide (NTO). Spatial light modulator. The non-magnetic intermediate layer, the main component _{ZnO, TiO 2, In 2 O} 3, SnO 2, GaN, GaP, GaAs, GaSb, AlN, AlP, InP, InAs, InSb, ZnS, ZnSe, ZnTe, SiC, a NiO 4. The spin injection type spatial light modulator according to claim 1, wherein the spatial light modulation element is at least one selected from the group of semiconductor materials.   The nonmagnetic layer that does not prevent spin conduction is inserted between the magnetization direction variable layer and the nonmagnetic intermediate layer and / or between the magnetization direction variable layer and the nonmagnetic intermediate layer. Item 5. The spin injection type spatial light modulator according to any one of Items 4 to 5.   The spin injection spatial light modulator according to claim 5, wherein the nonmagnetic layer is made of Cu, Zn, Ag, or Au.   The combination of the nonmagnetic intermediate layer and the nonmagnetic layer is a three-layer laminate of Cu / ZnO / Cu, Zn / ZnO / Zn, and Zn / ZnO / Cu with a nonmagnetic intermediate layer made of a semiconductor material as the center. The spin injection spatial light modulator according to claim 6, which is a two-layer laminate obtained by omitting the upper or lower nonmagnetic layer from the three-layer laminate.   An optical modulator comprising the spin-injection spatial light modulators according to claim 1 arranged in a matrix.

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