JP5873363B2 - Light modulator and spatial light modulator - Google Patents

Description

  The present invention relates to a light modulation element of a spatial light modulator that spatially modulates incident light by using a magneto-optic effect, and to a spatial light modulator using the light modulation element.

  A spatial light modulator uses an optical element (light modulation element) as a pixel and arranges it in a two-dimensional matrix to spatially modulate the phase, amplitude, etc. of light. Widely used in fields such as equipment, display technology, and recording technology. In addition, since optical information can be processed in two dimensions in parallel, its application to optical information processing technology is also being studied. As a spatial light modulator, liquid crystal has been conventionally used and widely used as a display device, but for holography and optical information processing, since response speed and high definition of pixels are insufficient, in recent years, Development of a magneto-optic spatial light modulator using a magneto-optic material that is expected to be capable of high-speed processing and pixel miniaturization is in progress.

  In a magneto-optical spatial light modulator (hereinafter referred to as a spatial light modulator), when light incident on a magneto-optical material, that is, a magnetic material is transmitted or reflected, the direction of polarization is changed (rotation) and emitted. The effect (Kerr effect in the case of reflection) is used. That is, the spatial light modulator emits light from the selected pixel with the magnetization direction of the light modulation element in the selected pixel (selected pixel) different from the magnetization direction of the light modulation element in the other pixels (non-selected pixels). The light and the light emitted from the non-selected pixels cause a difference in the rotation angle (rotation angle) of the polarization. As a method of changing the magnetization direction of such a light modulation element, in addition to a magnetic field application method in which a magnetic field is applied to the light modulation element, in recent years, a spin injection method in which spin is injected by supplying a current to the light modulation element ( For example, there is Patent Document 1).

  Specifically, the spin injection type light modulation element is a TMR (Tunnel MagnetoResistance) element or a CPP-GMR (Current Perpendicular to the Plane Giant MagnetoResistance) element. A spin-injection magnetization reversal element that is also applied to a magnetoresistive random access memory (MRAM) can be applied. As an example, FIG. 15 shows a cross-sectional view of such a conventional light modulation element. As shown in FIG. 15, the light modulation element 101 is connected to a pair of electrodes 151 and 152 on the upper and lower sides and supplied with a current perpendicular to the film surface. With this current, the light modulation element 101 is injected with spin, and the magnetization direction of the magnetization free layer 103 can be reversed in the same manner as in the MRAM write. The light modulation element 101 functions as a pixel that modulates and emits incident light by forming at least one electrode (the upper electrode 152 in FIG. 15) from a transparent electrode material. An optical modulation element to which such a spin-injection magnetization reversal element is applied enables further miniaturization than a magnetic field application method in which electrodes (wirings) are provided along the outer periphery of each optical modulation element in order to generate a magnetic field. .

  Further, as another aspect of the light modulation element, Patent Document 2 discloses a spatial light modulator that uses a thin line-processed magnetic body (magnetic fine wire) as a light modulation element. This is because in magnetic thin wires, two or more magnetic domains are easily formed in the thin line direction, and the domain walls that delimit these magnetic domains move by supplying current to the magnetic thin line in the thin line direction. doing. More specifically, this spatial light modulator is provided with one magnetic thin line for each pixel along the surface direction (two-dimensional array surface of the pixels), and a current is applied in the thin line direction by a pair of electrodes connected to both ends thereof. When supplied, the domain wall moves in the direction opposite to the direction of the current, and the magnetization direction in the area sandwiched between the positions before and after the domain wall movement is reversed, so this area is reflected light as the light incident area (effective area). Can be taken out.

Japanese Patent No. 4829850 JP 2010-20114 A

  The light modulation elements described in Patent Documents 1 and 2 have room for improvement in the following points. In the spin-injection magnetization switching element applied to the light modulation element of Patent Document 1, since electrodes for supplying a current are connected vertically, in order to enter and output light as a light modulation element, light input / output On the side, a transparent electrode material that transmits light must be applied. Since the transparent electrode material is greatly inferior in conductivity as compared with the metal electrode material, there is a possibility that the operation is delayed in the central portion as the high-definition spatial light modulator has a larger number of light modulation elements arranged in a matrix. In order to operate such a spatial light modulator, it is necessary to supply a large current, and there is room for improvement in terms of power saving. Furthermore, since it is difficult for the spin injection magnetization reversal element to operate properly (spin injection magnetization reversal) unless the side is about 300 nm or less, the size of the light modulation element with respect to the wiring pitch is reduced. Ratio (pixel aperture ratio) becomes low.

  On the other hand, in the magnetic thin wire applied to the light modulation element of Patent Document 2, both of the pair of electrodes to be connected can be formed of a metal electrode material, but the magnetization direction is different from the magnetization direction in the opening region across the domain wall. Magnetic domains are formed. Therefore, the light that can be extracted as pixel information in the magnetic thin line is limited to the reflected light from the region sandwiched between the positions of the central domain wall before and after the movement, and the aperture ratio of the pixel is limited.

Furthermore, the spatial light modulator may be capable of error detection that electrically detects whether each light modulation element of the pixel performs light modulation according to the setting, that is, indicates the magnetization direction as written. desirable. For example, in the light modulation element 101 to which the spin injection magnetization reversal element shown in FIG. 15 is applied, the magnetization directions of the magnetization fixed layer 111 and the magnetization free layer 103 are the same (parallel: P, see FIG. 15A). than the resistance R101 _P of the opposite: greater resistance R101 towards _AP when a (antiparallel AP, Fig 15 (b) refer). Therefore, the spatial light modulator described in Patent Document 1 supplies a current that does not cause spin injection magnetization reversal to the light modulation element 101 and reads the voltage between the electrodes 151 and 152 in the same manner as the read in the MRAM. By measuring the magnetization direction of the magnetization free layer 103. On the other hand, since the resistance of the magnetic thin wire hardly changes even when the domain wall moves, it is difficult for the spatial light modulator described in Patent Document 2 to detect the write error.

  The present invention was devised in view of the above problems, and when a pixel of a spatial light modulator is used, a transparent electrode material is not used for wiring, and the pixel aperture ratio is sufficiently maintained and further miniaturized and further written. It is an object to provide an optical modulation element that facilitates error detection and a spatial light modulator using the same.

  The inventors of the present application have used the dual pin structure spin-inversion magnetization switching element 101A (see, for example, Japanese Patent Application Laid-Open No. 2010-60748) shown in a sectional view in FIG. The two fixed layers 111 and 112 are stacked on the same side surface of the magnetization free layer 103 so as to be spaced apart from each other in the plane direction, thereby forming a U-shaped current path in cross section with the magnetization free layer as a bottom. We have developed a light modulation device consisting of a spin-injection magnetization reversal device with a dual pin structure. A spin-injection magnetization reversal element having a dual pin structure has a structure in which two spin-injection magnetization reversal elements are connected so as to share a magnetization free layer, and a pair of electrodes are connected to two magnetization fixed layers at both ends of the U-shape. Then, the spin injection magnetization reversal operation can be performed. Therefore, a light modulation element using a spin injection magnetization reversal element having a parallel dual pin structure can enter light into the magnetization free layer at the bottom of the U-shape without transmitting through the electrodes. Both can be formed of a metal electrode material. Further, the area of the light modulation element can be expanded to twice that of the conventional spin injection magnetization reversal element, and the effective area of the pixel can be widened.

  On the other hand, in the spin-injection magnetization reversal element having a dual pin structure, the magnetization direction of the magnetization free layer is always parallel to one of the two magnetization fixed layers and antiparallel to the other, The overall resistance, which is the combined resistance, becomes constant, making it difficult to detect write errors. Therefore, the inventors of the present application connect the two spin-injection magnetization reversal elements having the above-mentioned parallel dual pin structure so as to share the one spin-injection magnetization reversal element. It was conceived that the write error can be detected by changing the resistance.

  That is, the light modulation element according to the present invention includes a spin-injection magnetization reversal element structure in which a magnetization free layer, an intermediate layer, and a magnetization fixed layer are sequentially laminated on a substrate, and is incident from the side on which the magnetization free layer is laminated. The reflected light is reflected and emitted by changing the direction of the polarized light. The magnetization fixed layer includes a first magnetization fixed layer, a third magnetization fixed layer, and a second magnetization fixed layer disposed between the first magnetization fixed layer and the third magnetization fixed layer. The first magnetization pinned layer and the second magnetization pinned layer are fixed to magnetizations in antiparallel directions, spaced apart in the plane direction and sandwiching the intermediate layer on the magnetization free layer, respectively. The third magnetization fixed layer is fixed to magnetization in the same direction as the first magnetization fixed layer, one of a pair of electrodes is connected to the first magnetization fixed layer and the third magnetization fixed layer, and the second magnetization fixed layer By connecting the other of the pair of electrodes to the layer and supplying a current, the magnetization direction of the magnetization free layer is changed.

  With this configuration, the light modulation element can be enlarged as the area of two spin-injection magnetization reversal elements, and furthermore, no two magnetization fixed layers connecting the electrodes are arranged on the light incident side, so that the magnetization reversal The transparent electrode material need not be applied to the electrode that supplies the current for operation. Further, the light modulation element is composed of three spin-injection magnetization reversal element structures, so that the magnetization directions of two magnetization fixed layers are fixed in parallel, and the combined resistance of these two spin-injection magnetization reversal element structures. Changes due to the magnetization reversal of the magnetization free layer. Such a light modulation element can detect the magnetization direction of the magnetization free layer by measuring the resistance between the electrodes connected to the two magnetization fixed layers fixed in the parallel magnetization directions.

Further, in the light modulation element, it is preferable that the second magnetization fixed layer has a different coercive force from the first magnetization fixed layer and the third magnetization fixed layer. Alternatively, the light modulation element preferably has a multilayer structure in which at least one of the first magnetization fixed layer, the third magnetization fixed layer, and the second magnetization fixed layer includes a magnetic film exchange-coupled.
With this configuration, it becomes easy to fix one of the three magnetization fixed layers in the light modulation element in the magnetization direction antiparallel to the other two.

The light modulation element can be a pixel of a spatial light modulator by connecting an electrode to each of the three magnetization fixed layers. That is, the spatial light modulator according to the present invention includes a substrate that transmits light and a plurality of pixels that are two-dimensionally arranged on the substrate, and transmits light incident on the plurality of pixels through the substrate. Reflected and emitted, and the pixel includes the light modulation element, a first electrode connected to the first magnetization fixed layer of the light modulation element, a second electrode connected to the second magnetization fixed layer, And a third electrode connected to the third magnetization fixed layer. Then, the spatial light modulator selects one or more pixels from the plurality of pixels, and further selects one of two different directions of magnetization of the magnetization free layer of the light modulation element of the selected pixel. A current is supplied to the pixel selection unit and the light modulation element of the pixel selected by the pixel selection unit using the first electrode and the third electrode as one of the pair of electrodes and the second electrode as the other of the pair of electrodes. Current supply means for setting the magnetization direction of the magnetization free layer of the light modulation element to the direction selected by the pixel selection means, and the magnetization direction of the magnetization free layer of the light modulation element to which the current supply means supplies current. And a pixel determination unit that performs pixel determination to determine the direction selected by the pixel selection unit by detecting a change in resistance of the light modulation element. In the spatial light modulator, the pixel may include two or more light modulation elements connected in parallel to the first electrode, the second electrode, and the third electrode.

  Furthermore, the spatial light modulator may include a sub-current supply unit that supplies a predetermined current to the light modulation element of the pixel selected by the pixel selection unit. In this spatial light modulator, the pixel determination means has a voltage value between the first electrode and the third electrode connected to the light modulation element to which a current is supplied to the sub-current supply means. Is compared with a threshold value set in advance based on the resistance of the light modulation element when the magnetization direction of the magnetization free layer is the direction selected by the pixel selection means.

  With this configuration, the spatial light modulator is configured with three spin-injection magnetization reversal element structures, and the pixel includes a light modulation element that does not connect the electrode to the light incident side. Therefore, the light is applied to the pixel with a high aperture ratio. It can enter without being blocked by. The spatial light modulator has a total of three spin-injection magnetization reversal element structures, one at the center and two at both sides thereof, when the pixel selection means selects a pixel and supplies current from the current supply means to the light modulation element. In order to be spin-injected via the electrodes connected to the respective magnetization fixed layers, the shared magnetization free layer is reversed by spin-injection magnetization so as to obtain a desired magnetization direction corresponding to the direction of current for each pixel. be able to. Furthermore, the spatial light modulator can diagnose whether the pixel determination unit has normally reversed the magnetization of the magnetization free layer of the light modulation element in the desired magnetization direction by the current supply unit. Specifically, in the spatial light modulator, the pixel selection unit selects a pixel and performs light modulation from the sub-current supply unit via the respective electrodes connected to two magnetization fixed layers fixed in parallel magnetization directions. If a current of a predetermined magnitude that does not perform the spin injection magnetization reversal operation is supplied to the element, the voltage changes within a specific range due to the resistance of the light modulation element. Therefore, the pixel determination means sets the voltage value to a preset threshold value. By comparing, it is possible to determine which magnetization direction the magnetization free layer has.

  Further, the spatial light modulator may be configured such that electrical connection between the first magnetization fixed layer and the first electrode, or between the third magnetization fixed layer and the third electrode can be disconnected. It is preferable to provide an element. With this configuration, the spatial light modulator can suppress current leakage to the light modulation element of the non-selected pixel, and thus diagnosis by the pixel determination unit is facilitated.

  Alternatively, the spatial light modulator may be configured such that the pixel includes the first magnetization fixed layer and the first electrode, the second magnetization fixed layer and the second electrode, and the third magnetization fixed layer. It is preferable that a selection element that can freely disconnect the electrical connection is provided at two locations selected from between the third electrode and the third electrode. With this configuration, the spatial light modulator does not connect the light modulation element to two or more electrodes in non-selected pixels, so that current does not leak through the light modulation element, and diagnosis by the pixel determination unit is possible. Further, the current for the magnetization reversal operation of the light modulation element is increased in efficiency.

  According to the light modulation element of the present invention, the magnetization reversal operation can be suitably performed even when the area is expanded, and the transparent electrode material need not be used for the electrode to be connected when used for the pixel of the spatial light modulator. Therefore, it is easy to miniaturize while increasing the aperture ratio of the pixels of the spatial light modulator. Also, according to the light modulation element of the present invention, the resistance changes due to the magnetization reversal operation. Therefore, the pixel determination (write error) using the electrode for the magnetization reversal operation is used for the pixel of the spatial light modulator. Detection).

  According to the spatial light modulator according to the present invention, since all the wiring can be formed using only the metal electrode material by using the light modulation element in a pixel, high definition and power saving can be achieved. Furthermore, the aperture ratio of the pixel can be increased to achieve high contrast. Further, according to the spatial light modulator according to the present invention, it is possible to perform a read operation similar to that of the MRAM by using a driving wiring, and it is possible to detect a write error for each of all pixels.

It is a bottom view of the spatial light modulator using the light modulation element which concerns on this invention, and is a schematic diagram explaining the structure of the spatial light modulator which concerns on 1st Embodiment of this invention. It is a schematic diagram explaining the cross-sectional structure of the light modulation element which concerns on this invention, and is equivalent to the AA fragmentary sectional view of FIG. It is a schematic diagram explaining the planar view shape of the light modulation element which concerns on this invention, (a) is equivalent to the enlarged view of FIG. 1, (b), (c) is a top view of the light modulation element which concerns on a modification. It is. It is sectional drawing of the light modulation element which concerns on this invention, and is a schematic diagram explaining magnetization reversal operation | movement. It is sectional drawing of the light modulation element which concerns on this invention, and is a schematic diagram explaining the operation | movement of light modulation, and the change of resistance. It is a schematic diagram of the display apparatus using the spatial light modulator which concerns on this invention, and is equivalent to AA sectional drawing of FIG. 1 is an equivalent circuit diagram of a spatial light modulator according to a first embodiment of the present invention. It is a schematic diagram explaining the manufacturing method of the spatial light modulator which concerns on this invention, (a)-(e) is corresponded in the AA fragmentary sectional view of FIG. It is a schematic diagram explaining the manufacturing method of the spatial light modulator which concerns on this invention, (a)-(d) is equivalent to the AA fragmentary sectional view of FIG. It is a schematic diagram explaining the manufacturing method of the spatial light modulator which concerns on this invention, (a)-(c) is corresponded to the AA fragmentary sectional view of FIG. 1, (d) is a top view in (c). It is. It is a top view explaining the structure of the pixel of the spatial light modulator which concerns on 2nd Embodiment of this invention. FIG. 5 is an equivalent circuit diagram of a spatial light modulator according to a third embodiment of the present invention. FIG. 6 is an equivalent circuit diagram of a spatial light modulator according to a fourth embodiment of the present invention. It is the equivalent circuit schematic of the spatial light modulator which concerns on the modification of 4th Embodiment of this invention. It is sectional drawing of the conventional light modulation element using a spin injection magnetization reversal element, and is a schematic diagram explaining the operation | movement of magnetization reversal and light modulation. It is a cross-sectional view of a conventional light modulation element using a spin-injection magnetization reversal element having a dual pin structure and is a schematic diagram for explaining the magnetization reversal operation.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for realizing a light modulation element and a spatial light modulator according to the present invention will be described with reference to the drawings.

[Light modulation element]
The light modulation element according to the present invention is used as the pixel 8 of the spatial light modulator 10 shown in FIG. 1 (refers to means for displaying information (light / dark) in the minimum unit of display by the spatial light modulator). Thus, the light incident from below is reflected, modulated into different binary light (polarized component), and emitted downward.

  As shown in FIG. 2, the light modulation element 1 includes one magnetization free layer 3, three intermediate layers 21, 22, and 23, and three magnetization fixed layers 11, 12, and 13 (first magnetization fixed layer, first magnetization layer, 2 magnetization fixed layers and 3rd magnetization fixed layers). In this light modulation element 1, a magnetization free layer 3 is formed on a substrate 7 that transmits light, and three intermediate layers 21, 22, and 23 are spaced apart from each other on the magnetization free layer 3 in a plane direction. The first magnetization fixed layer 11 is laminated on the intermediate layer 21, the second magnetization fixed layer 12 is laminated on the intermediate layer 22, and the third magnetization fixed layer 13 is laminated on the intermediate layer 23. Specifically, the intermediate layer 22 and the second magnetization fixed layer 12 are disposed between the intermediate layer 21 and the first magnetization fixed layer 11 and the intermediate layer 23 and the third magnetization fixed layer 13 in the plane direction. The light modulation element 1 further includes a protective film 4 stacked on each of the magnetization fixed layers 11, 12, and 13. In FIG. 3A, shaded areas are the magnetization fixed layers 11, 12, and 13 (the protective film 4 is not shown). Here, the light modulation element 1 has an E shape in which the cross-sectional view is rotated 90 ° to the left. The light modulation element 1 shown in FIG. 2 is formed on a substrate 7, and the first electrode (electrode) 51, the second electrode (electrode) 52, and the third electrode (electrode) 53 are composed of the magnetization fixed layers 11 and 12. , 13 are connected to each other through a protective film 4.

  In plan view, as shown in FIGS. 1 and 3A, the light modulation element 1 is a square (rectangular). Therefore, the magnetization free layer 3 is the same square as the light modulation element 1. On the other hand, the intermediate layers 21, 22, 23 and the magnetization fixed layers 11, 12, 13 have the same long side as the light modulation element 1 (magnetization free layer 3), as the light modulation element 1 is divided into three vertically. These three rectangles are arranged in such a manner that three portions are spaced apart from each other in the short side direction (lateral direction in FIGS. 1 and 2). Hereinafter, in the present specification, unless otherwise described, the intermediate layers 21, 22, and 23 are not described because the shapes and arrangements in plan view coincide with the magnetization fixed layers 11, 12, and 13. Regarding the size in plan view, the total of the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 each have an area equivalent to 300 nm × 400 nm or less in order to suitably perform the magnetization reversal operation described later by the light modulation element 1. It is preferable that the area is equivalent to about 300 nm × 100 nm, which is one size of a general spin-injection magnetization switching element. On the other hand, the entire area of the light modulation element 1, that is, the area of the magnetization free layer 3 is not particularly defined, and will be described later even if it is expanded in the film surface direction with respect to the total area of the magnetization fixed layers 11, 12, and 13. Can be reversed. Specifically, when the light modulation element 1 is two-dimensionally arranged as a pixel array of a spatial light modulator (see FIG. 1), the adjacent light modulation elements 1 and 1 are insulated with a gap therebetween. That's fine. In the light modulation element 1 according to this embodiment, the magnetization fixed layers 11 and 13 have the same shape, and therefore the magnetization fixed layer 12 has a length in the short side direction twice that of the magnetization fixed layers 11 and 13.

  The light modulation element 1 has a structure in which three spin-injection magnetization reversal elements are connected by sharing a magnetization free layer. That is, the light modulation element 1 includes a spin-injection magnetization reversal element structure (hereinafter, appropriately referred to as a first element structure MR1) including a first magnetization fixed layer 11, an intermediate layer 21, and a magnetization free layer 3, and a second magnetization fixed. A spin-injection magnetization reversal element structure (hereinafter, appropriately referred to as a second element structure MR2) comprising a layer 12, an intermediate layer 22, and a magnetization free layer 3, and a third magnetization fixed layer 13, an intermediate layer 23, and a magnetization free layer 3. It can be said that a spin-injection magnetization reversal element structure (hereinafter, referred to as a third element structure MR3 as appropriate) is provided (see FIG. 4A). The “first”, “second”, and “third” attached to the magnetization fixed layers 11, 12, 13, the element structures MR 1, MR 2, MR 3 and the electrodes 51, 52, 53 distinguish each other. It is intended to make it easier, and does not prescribe the positional relationship or any ranking.

  The element structures MR1, MR2, and MR3 include magnetization fixed layers 11, 12, and 13 in which magnetization is fixed in one direction and a magnetization free layer 3 in which the magnetization direction is rotatable, an intermediate layer 21 that is nonmagnetic or insulating, Spin injection magnetization reversal elements such as CPP-GMR (Current Perpendicular to Plane Giant Magneto-Resistance) elements and TMR (Tunnel MagnetoResistance) elements provided with 22 and 23 sandwiched therebetween Structure. In particular, the element structures MR1 and MR3 in which the magnetization directions of the magnetization fixed layers 11 and 13 are parallel are preferably TMR elements having a high resistance change rate. Further, the light modulation element 1 is provided with a protective film 4 on the uppermost layer in order to protect these layers from damage during manufacture of the light modulation element 1. Hereafter, each element which comprises a light modulation element is demonstrated in detail.

(Magnetic pinned layer)
The magnetization fixed layers 11, 12, and 13 are magnetic bodies, and the magnetization directions are fixed as will be described later. Such magnetization fixed layers 11, 12, and 13 can be made of a known magnetic material used for a CPP-GMR element or a TMR element. In particular, the rotation angle θk is set by the polar Kerr effect of the magnetization free layer 3. It is preferable to apply a perpendicular magnetic anisotropy material that increases. Specifically, a multilayer film such as a Co / Pd multilayer film in which transition metals such as Fe, Co, and Ni and noble metals such as Pd and Pt are repeatedly stacked, and a rare earth such as Tb—Fe—Co and Gd—Fe. an alloy of the metal and the transition metal (RE-TM alloy), FePt was L1 ₀ type ordered alloys, FePd, and the like.

Further, the magnetization fixed layers 11, 12, 13 have their coercive forces Hcp ₁ , Hcp ₂ so that the magnetization of the magnetization fixed layers 11, 12, 13 is fixed even when the magnetization direction of the magnetization free layer 3 rotates. , Hcp ₃ is selected so that the coercive force Hcf of the magnetization free layer 3 is sufficiently larger than that of the magnetization free layer 3, and is formed thicker than the magnetization free layer 3. Specifically, the thickness of the magnetization fixed layers 11, 12, and 13 is preferably designed in the range of 3 to 50 nm.

In the light modulation element 1, the magnetization fixed layers 11 and 13 are fixed to the magnetization in the same (parallel) direction, and the magnetization fixed layer 12 is fixed to the magnetization in the opposite (antiparallel) direction to the magnetization fixed layers 11 and 13. In order to facilitate the initial setting of such a magnetization direction, the magnetization fixed layers 11, 12, and 13 have coercive forces Hcp ₁ , Hcp ₂ , and Hcp ₃ larger than the coercive force Hcf of the magnetization free layer 3. In addition, it is preferable that the coercive force Hcp ₁ and the coercive force Hcp ₃ are designed so as to be substantially the same as each other and different from the coercive force Hcp ₂ . Here, the coercive force Hcp _{2 of} the second magnetization fixed layer 12 is larger, that is, Hcf << Hcp ₁ = Hcp ₃ <Hcp ₂ . In the light modulation element 1 according to the present embodiment, the coercive force Hcp _{2 of} the second magnetization fixed layer 12 is relatively large because the magnetization fixed layer 12 has an area twice that of the magnetization fixed layers 11 and 13 in plan view. Although there is a tendency, the magnetization fixed layers 11, 12, and 13 (the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12) may be made of different materials and thicknesses.

(Magnetization free layer)
The magnetization free layer 3 is a magnetic material, and the magnetization fixed layers 11, 12, and 13 have fixed magnetization directions, whereas the magnetization free layer 3 easily reverses magnetization (rotates 180 °) by spin injection. And shows the same magnetization direction as any one of the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12. The magnetization free layer 3 can be made of the above-mentioned known magnetic material, and it is preferable to apply a perpendicular magnetic anisotropic material, like the magnetization fixed layers 11, 12, and 13. In particular, it is more preferable to select a material having a large magneto-optic effect at the wavelength of light incident on the light modulation element 1 (pixel of the spatial light modulator) for the magnetization free layer 3. For example, a Co / Pt multilayer film is suitable for the short wavelength region (near 400 nm), and a Gd—Fe alloy is suitable for the long wavelength region (near 700 nm).

Further, as described above, the magnetization free layer 3 is made of a material selected or fixed in magnetization so that the coercive force Hcf is smaller than the coercive forces Hcp ₁ , Hcp ₂ , and Hcp _{3 of the} magnetization fixed layers 11, 12, and 13. It is formed thinner than the layers 11, 12, and 13. Specifically, the thickness of the magnetization free layer 3 is preferably designed in the range of 1 to 20 nm.

(Middle layer)
The intermediate layers 21, 22, and 23 are provided on the magnetization free layer 3 and between the magnetization fixed layers 11, 12, and 13, respectively. If the element structures MR1, MR2, MR3 are TMR elements, the intermediate layers 21, 22, 23 are made of an insulator such as MgO, Al ₂ O ₃ , HfO ₂ or an insulator such as Mg / MgO / Mg. The thickness is preferably about 0.6 to 2 nm, more preferably 1 nm or less. Further, if the element structures MR1, MR2, and MR3 are CPP-GMR elements, the intermediate layers 21, 22, and 23 are made of a nonmagnetic metal such as Cu, Ag, Al, or Au, or a semiconductor such as ZnO, and its thickness. The thickness is preferably 1 to 10 nm. In particular, the intermediate layers 21, 22, and 23 (hereinafter referred to as the intermediate layer 2 as appropriate when not distinguished from each other) are highly reflective for light incident on the light modulation element 1 when Ag is applied to a thickness of 6 nm or more. Since the light is reflected at a high rate, the amount of emitted light is increased and the contrast is improved, which is preferable.

(Protective film)
The protective film 4 is provided in the uppermost layer in order to protect each layer such as the magnetization fixed layers 11, 12, and 13 from damage during manufacture of the light modulation element 1. The protective film 4 is composed of a single layer of Ta, Ru, Cu, or a double layer of Cu / Ta, Cu / Ru. In addition, when setting it as the said 2 layer structure, all make Cu inside (lower layer). If the thickness of the protective film 4 is less than 1 nm, it is difficult to form a continuous film. On the other hand, even if the thickness exceeds 10 nm, the effect of protecting the magnetization fixed layers 11, 12, 13, etc. in the manufacturing process is reduced. It does not improve above. Therefore, the thickness of the protective film 4 is preferably 1 to 10 nm. The protective films 4, 4, and 4 provided on the magnetization fixed layers 11, 12, and 13 do not have to be made of the same material and thickness.

(Magnetic reversal operation of the light modulator)
Next, the magnetization reversal operation of the light modulation element in this embodiment will be described with reference to FIG. In FIG. 4, the protective film 4 is not shown. In the light modulation element 1, the first magnetization fixed layer 11 and the third magnetization fixed layer 13 are fixed upward, and the second magnetization fixed layer 12 is fixed downward. In the light modulation element 1, the first electrode 51 and the third electrode 53 are connected to the same polarity of the power source 95, and the second electrode 52 is connected to a different polarity (counter electrode).

First, the operation of the light modulation element 1 for reversing the magnetization free layer 3 from the downward magnetization shown in FIG. 4A to the upward magnetization shown in FIG. 4C will be described. As shown in FIG. 4B, the current −I _W is supplied from the power source 95 to connect the first electrode 51 connected to the first magnetization fixed layer 11 and the third electrode 53 connected to the third magnetization fixed layer 13. In “−”, the second electrode 52 connected to the second magnetization fixed layer 12 is set to “+”, and electrons are injected from each side of the first magnetization fixed layer 11 and the third magnetization fixed layer 13. Then, the first magnetization pinned layer 11 discriminates the electron d ₂ having a downward spin opposite to the magnetization of the first magnetization pinned layer 11, and only the electron d ₁ having an upward spin from the first electrode 51. It is injected into the first magnetization fixed layer 11 and further injected into the magnetization free layer 3 below it through the intermediate layer 21. Similarly, the third magnetization fixed layer 13 discriminates the electron d ₂ having a downward spin opposite to the magnetization of the third magnetization fixed layer 13, and only the electron d ₁ having an upward spin has the third electrode 53. To the third magnetization fixed layer 13 and further injected into the magnetization free layer 3 thereunder via the intermediate layer 23. In the magnetization free layer 3, the spin of internal electrons of the magnetization free layer 3 is reversed by the action of spin torque due to the upward spin of the electron d ₁ , and the magnetization is upward from the region immediately below each of the magnetization fixed layers 11 and 13. Invert to. Further, the electrons d ₁ injected into the magnetization free layer 3 remain in the magnetization free layer 3 because the magnetization is discriminated by the second magnetization fixed layer 12 in the reverse direction, and as a result, as shown in FIG. In addition, the magnetization free layer 3 includes not only a region where the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 are stacked, but also two layers of the magnetization fixed layer 11 and the magnetization fixed layer 12, and the magnetization fixed layer 13 and the magnetization fixed layer 12. Including the respective regions sandwiched between the regions, that is, the entire region changes to a state showing the upward magnetization that is the same as the magnetization direction of the first magnetization fixed layers 11 and 13 (magnetization reversal).

Next, the operation of the light modulation element 1 for reversing the magnetization free layer 3 from the upward magnetization shown in FIG. 4C to the downward magnetization shown in FIG. 4A will be described. Contrary to the operation shown in FIG. 4B, as shown in FIG. 4D, the current + I _W is supplied from the power source 95, and the first electrode 51 and the third electrode 53 are set to “+”. Then, the second electrode 52 is set to “−”, and electrons are injected from the second magnetization fixed layer 12 side. Then, only the electron d ₂ having a downward spin from the second magnetization fixed layer 12 is injected into the magnetization free layer 3 through the intermediate layer 22, and the magnetization due to the spin torque due to the downward spin of the electron d ₂ acts. The spin of the internal electrons of the free layer 3 is reversed, and the magnetization is reversed downward from the region immediately below the second magnetization fixed layer 12. Furthermore, the electrons d ₂ injected into the magnetization free layer 3 spread left and right in FIG. 4D so as to go to the first magnetization fixed layer 11 and the third magnetization fixed layer 13, but these magnetizations are in opposite directions. As a result, as shown in FIG. 4A, the magnetization free layer 3 is in a state where the whole exhibits the same downward magnetization as the magnetization direction of the second magnetization fixed layer 12. Change (magnetization reversal).

As described above, the light modulation element 1 according to the present embodiment includes the three magnetization fixed layers 11, 12, and 13 stacked on the same side (upper side) of the magnetization free layer 3 with the intermediate layers 21, 22, and 23 interposed therebetween. Are connected to the electrodes 51, 52, 53, respectively, and the current -I _W (or + I _W ) is supplied to the electrodes 52 between the electrodes 51, 53 at both ends, whereby two cross-sections symmetrical in FIG. A U-shaped current path is formed, and the magnetization direction of the magnetization free layer 3 can be changed (magnetization reversed). In other words, in the light modulation element 1, the spin injection magnetization reversal element of the parallel dual-pin structure spin splitting magnetization reversal element is divided into two element structures MR1 and MR3, and the other spin injection magnetization reversal element is used as it is. This is an element structure MR2. Therefore, the light modulation element 1 in the present embodiment is a film in which a current flows in the shared magnetization free layer 3 with the total of the element structures MR1 and MR3 and the element structure MR2 each having a small area suitable for spin injection magnetization reversal. Since the domain wall moves in the plane direction and magnetization is reversed, the magnetization free layer 3 can be formed in a large area. Further, the light modulation element 1 has a stable magnetization reversal operation because of the spin injection drive by the magnetization fixed layers corresponding to the magnetization fixed layers 11 and 12 and the magnetization fixed layers 13 and 12, respectively. The magnitudes | I _W | of the currents −I _W and + I _W may be equal to or greater than the current (magnetization reversal current) I _{STS that} reverses the magnetization of the magnetization free layer 3 of the light modulation element 1. This magnetization reversal current I _STS is the magnetization reversal current density of the three spin-injection magnetization reversal element structures MR1, MR2, MR3 of the light modulation element 1, and the material and thickness of each layer of the element structures MR1, MR2, MR3. It is determined by etc.

4A and 4C, the light modulation element 1 is supplied with a current + I _W when the magnetization free layer 3 exhibits downward magnetization, or on the contrary, the magnetization free layer 3 Even if the current −I _W is supplied when showing upward magnetization, the magnetization direction of the magnetization free layer 3 does not change. Further, in the light modulation element 1, even when the current supply is stopped when the magnetization direction of the magnetization free layer 3 is uniform upward or downward, the magnetization direction changes due to the coercive force Hcf of the magnetization free layer 3 itself. There is no. Therefore, a current that temporarily reaches a current value (≧ I _STS ) that reverses the magnetization direction, such as a pulse current, can be used as the drive current of the light modulation element 1.

(Light modulation operation of light modulation element)
Next, the light modulation operation of the light modulation element 1 will be described with reference to FIG. When the light incident on the light modulation element 1 is reflected by the magnetization free layer 3 that is a magnetic material, the direction of polarization of the light changes (rotates) due to the magneto-optic effect, and the light is emitted. Further, if the magnetization direction of the magnetic material is different by 180 °, the direction of optical rotation due to the magneto-optical effect of the magnetic material is reversed. Therefore, the optical rotation angles in the optical modulation elements 1 shown in FIGS. 5A and 5B, in which the magnetization directions of the magnetization free layer 3 are 180 ° different from each other, are −θk and + θk, and the planes of polarization rotate in opposite directions. . As described above, the light modulation element 1 functions as a pixel of a spatial light modulator or the like described later by changing the direction of polarization of the emitted light in accordance with the direction (positive / negative) of the supplied current I _W. The optical rotation angles −θk and + θk are not limited to optical rotation (Kerr rotation) by one reflection at the light modulation element 1, and include, for example, angles accumulated by multiple reflection.

As described above, the light modulation elements according to the present invention are provided in a two-dimensional array as pixels of the spatial light modulator. Here, a spatial light modulator having a structure in which a large number of pixels are regularly arranged in a two-dimensional manner, when light traveling straight and having a parallel wavefront is incident on each pixel, the spatial light modulator at the end of the pixel. The direction in which the light travels is bent (diffraction phenomenon), and the direction in which the light is strengthened is separated into multiple lines by the interference effect (wave strengthening and weakening) due to the emitted light. Due to this diffraction phenomenon, diffracted light of ± 1st order, ± 2nd order,..., ± nth order that is bent to an angle of diffraction angle φ _{n with} respect to the straight direction of incident light is generated (n is 0 or a natural number ). The diffraction angle φ _n depends on the wavelength λ of incident light and the pixel pitch p. Note that first-order diffracted light is generally used when applying a spatial light modulator to a holographic device. The 0th-order diffracted light at n = 0 is equivalent to reflected light that is reflected at the same angle as the incident angle in the reflective spatial light modulator (in the case of a transmissive spatial light modulator, the rectilinear direction of the incident light). Is equivalent to transmitted light in the same direction). Therefore, in the present specification, the description will be made assuming that the reflected light (emitted light) emitted from the light modulation element (pixel of the spatial light modulator) includes the n-th order diffracted light. Also in this diffracted light, a change in polarization direction (optical rotation) due to the Faraday effect or the Kerr effect occurs depending on the magnetization direction of the magnetic material (magnetization free layer).

  The light modulation element 1 according to the present invention receives light from the side of the magnetization free layer 3, that is, from below, reflects the light, and emits it downward. Therefore, as shown in FIG. 2, the light modulation element 1 is formed on a transparent substrate 7, and light transmitted through the substrate 7 is incident thereon. Since the electrodes 51, 52, and 53 provided on the magnetization fixed layers 11, 12, and 13 do not need to transmit light, a low-resistance metal material can be applied (the spatial light modulator described later). Will be described in the embodiment).

(Resistance change of light modulation element)
Next, a change in resistance due to the magnetization reversal of the light modulation element in the present embodiment will be described with reference to FIG. The light modulation element 1 shown in each of FIGS. 5A and 5B is in the same magnetization state as the light modulation element 1 shown in FIGS. 4A and 4C. Although details will be described later, in FIG. 5, the current I _TST supplied to the optical modulation element 1 from the sub power supply 96 is smaller than the magnetization reversal current I _STS and changes the magnetization state of the optical modulation element 1. is not. As described above, the light modulation element 1 includes the three spin-injection magnetization reversal element structures MR1, MR2, and MR3 (see FIG. 4A).

In the light modulation element 1 shown in FIG. 5A, the magnetization direction of the magnetization free layer 3 is downward and the magnetization direction of the first magnetization fixed layer 11 is antiparallel, that is, the magnetization of the first element structure MR1 is antiparallel (AP). (See FIG. 15B). The resistance of the first element structure MR1 at this time is expressed as R1 _AP. At this time, the magnetization direction of the magnetization free layer 3 and the third magnetization fixed layer 13 is antiparallel, that is, the magnetization of the third element structure MR3 is antiparallel (AP), and the resistance of the third element structure MR3 at this time Is represented as R3 _AP . At the same time, in the light modulation element 1 shown in FIG. 5A, the magnetization free layer 3 has a magnetization direction parallel to the second magnetization fixed layer 12, that is, the magnetization of the second element structure MR2 is parallel (P) (FIG. 15A ))). The resistance of the second element structure MR2 in this case represented as R2 _P.

On the other hand, in the light modulation element 1 shown in FIG. 5B, the magnetization direction of the magnetization free layer 3 is upward, the magnetization directions of the first magnetization fixed layer 11 and the third magnetization fixed layer 13 are parallel, and this magnetization is parallel. The resistance of the first element structure MR1 which is (P) is represented as R1 _P , and the resistance of the third element structure MR3 is represented as R3 _P. At the same time, the light modulation element 1 shown in FIG. 5B has a second element structure MR2 in which the magnetization free layer 3 is antiparallel to the second magnetization fixed layer 12 and the magnetization direction is antiparallel (AP). _Is represented by R2AP.

The resistance of the spin-injection magnetization reversal element when the magnetization is parallel or antiparallel is determined by the area, the material and thickness of each layer, etc. Therefore, the material of the element structure MR1, MR2, MR3, and further the element structure MR1, MR3 When the shape or the like is the same, or the influence of the difference on the resistance is small and the area of the element structure MR2 in plan view is twice that of the element structures MR1 and MR3, the following expressions (1) to (4) ). Here, R _P and R _AP represent standardized resistances of the element structures MR1 and MR3.
R _P = R 1 _P = R 3 _P (1)
R _AP = R 1 _AP = R 3 _AP (2)
R _P / 2 = R2 _P (3)
R _AP / 2 = R2 _AP (4)

For the light modulation element 1, the resistance measured between the electrode 52 and the electrodes 51 and 53 that are electrically connected to each other is connected in parallel as in the connection with the power supply 95 in the magnetization reversal operation (see FIG. 4). This is the sum of the combined resistance of the element structures MR1 and MR3 and the resistance of the element structure MR2. Since the element structures MR1 and MR3 have the same magnetization parallel and antiparallel states, their combined resistances are R _P / 2 and R _AP / 2. Therefore, the sum of the element structure MR2 which becomes antiparallel when the magnetizations of the element structures MR1 and MR3 are parallel and becomes parallel when the magnetizations are antiparallel and the combined resistance of the element structures MR1 and MR3 is the sum of the magnetization free layer 3 Does not change due to magnetization reversal.

  On the other hand, in the light modulation element 1, the combined resistance of the element structures MR1 and MR3 in which the magnetization parallel and antiparallel states are the same changes due to the magnetization reversal of the magnetization free layer 3. Specifically, the resistance measured between the electrode 51 and the electrode 53 connected to the magnetization fixed layers 11 and 13 of the element structures MR1 and MR3 with the second electrode 52 in an open state is the element structure It is the sum of the resistances of MR1 and MR3 and changes as follows.

For the light modulation element 1 shown in FIG. 5A, the resistance R13 _D measured between the electrodes 51 and 53 is expressed by the following equation (5). Similarly, for the light modulation element 1 shown in FIG. 5B, the resistance R13 _U measured between the electrodes 51 and 53 is expressed by the following equation (6).
R13 _D = R1 _AP + R3 _AP = 2R _AP (5)
R13 _U = R1 _P + R3 _P = 2R _P (6)

The spin-injection magnetization reversal element has higher resistance when the magnetization is antiparallel than when parallel. The amount of change in resistance (R _AP −R _P ) due to magnetization reversal per one of the spin-injection magnetization reversal element structures MR1 and MR3 of the light modulation element 1 is represented by ΔR (> 0). Then, from the equations (5) and (6), the variation ΔR13 of the resistances R13 _D and R13 _U of the light modulation element 1 measured between the electrodes 51 and 53 is expressed by the following equation (7). .
ΔR13 = R13 _D −R13 _U = 2R _AP −2R _P = 2ΔR (7)

  As described above, the light modulation element 1 includes three spin-injection magnetization reversal element structures sharing a magnetization free layer, and two of them, that is, the element structures MR1 and MR3, have the same magnetization parallel and antiparallel. By fixing the magnetizations of the magnetization fixed layers 11 and 13 in the same (parallel) direction, the resistance between the electrodes 51 and 53 connected to the same polarity of the power supply 95 in the magnetization reversal operation is as shown in FIG. In the same manner as a general spin-injection magnetization reversal element, the magnetization reversal operation changes. The amount of change is twice the amount of change ΔR of one resistance of the element structures MR1 and MR3. The amount of change in resistance does not require a difference in the resistance per area of the three spin injection magnetization reversal element structures MR1, MR2, and MR3 of the light modulation element 1 and the amount of change thereof. Design and manufacturing are not complicated without particularly selecting different ones.

  If the light modulation element 1 is a resistance measured between the electrodes 51 and 53, it is changed by the magnetization reversal operation, and the resistance is measured by connecting the second electrode 52 to one of the electrodes 51 and 53 without setting the open state. You can also. For example, the resistance measured between the electrodes 52 and 53 connected to the same polarity and the first electrode 51 is the combined resistance of the element structures MR2 and MR3 connected in parallel and the resistance of the first element structure MR1. It is sum. The element structure MR2 differs from the element structures MR1 and MR3 in the parallel and antiparallel states of magnetization (see FIG. 5), and when the above equations (1) to (4) are satisfied, the resistance of the element structure MR1 is It is 1/2 of MR3, that is, the amount of change due to magnetization reversal is 1/2. Accordingly, the combined resistance of the element structures MR2 and MR3 connected in parallel increases and decreases in the same manner as the resistance of the first element structure MR1, although the amount of change is smaller than that of the third element structure MR3 alone. From this, the resistance change ΔR123 measured between the electrodes 52, 53 and the first electrode 51 is larger than one resistance change of the element structure MR1, that is, ΔR123> ΔR.

The light modulation element 1 can also measure the resistance between the electrodes 53 and 52 or between the electrodes 51 and 52 with one of the electrodes 51 and 53 in an open state. Since the resistance measured in this case is the sum of the resistance of the second element structure MR2 and the resistance of the first element structure MR1 or the third element structure MR3, the above equations (1) to (4) are established. In this case, the amount of change due to magnetization reversal is ΔR / 2.
Details of the method of measuring the resistance value of the light modulation element 1 will be described later in the description of the write error detection (pixel determination) method of the spatial light modulator.

As another embodiment of the light modulation element 1, the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 are exchanged at least one of them instead of providing a difference in coercive force Hcp ₁ (Hcp ₃ ) and Hcp _2. A multilayer structure including a combined magnetic film may be used. Specifically, the magnetization fixed layers 11, 12, and 13 are formed by further stacking a Co—Fe film or a laminated film such as Co—Fe / Tb—Fe—Co with a magnetic exchange coupling film such as Ru interposed therebetween 3. It is good also as a multilayer structure of about four layers. For example, from the intermediate layer 2 side, a Co—Fe / Ru / Co—Fe three-layer structure of Co—Fe / Ru / Co—Fe is laminated with a perpendicular magnetization film having a large coercive force such as Tb—Fe—Co. / Tb—Fe—Co four-layer structure. In such a multilayer structure, the magnetic films sandwiching the magnetic exchange coupling film exhibit anti-parallel or parallel magnetization directions depending on the thickness of the magnetic exchange coupling film.

  For example, the magnetization fixed layers 11 and 13 are single layers of Co—Fe (5 nm), and the magnetization fixed layer 12 is Co—Fe (2 nm) / Ru (0.7 nm) / Co—Fe (from the intermediate layer 22 side). 5 nm). In addition, () shows thickness. When a magnetic field is applied to such a light modulation element 1, the magnetization direction of the 5 nm thick Co—Fe film in each of the magnetization fixed layers 11, 12, 13 is aligned with the direction of the applied magnetic field, and the intermediate layer of the magnetization fixed layer 12 The magnetization direction of the Co-Fe film having a thickness of 2 nm on the 22 side is an antiparallel magnetization direction. Alternatively, when a magnetic exchange coupling film is provided on all of the magnetization fixed layers 11, 12, and 13, the magnetization fixed layer 12 has the same three-layer structure as described above, and the magnetization fixed layers 11 and 13 are from the intermediate layers 21 and 23 side. A three-layer structure in which the thickness of each layer of Co—Fe (5 nm) / Ru (0.7 nm) / Co—Fe (2 nm) is changed is adopted. Even when a magnetic field is applied to such a light modulation element 1, the magnetization direction of the Co-Fe film having a thickness of 5 nm is aligned in the direction of the magnetic field, and the magnetization direction of the Co-Fe film having a thickness of 2 nm across the Ru film is Since the magnetization directions are antiparallel, the magnetization directions of the Co—Fe film on the intermediate layer 2 side of each of the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 are antiparallel to each other. Since at least one of the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 has such a multilayer structure, the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 (magnetic film on the side of the intermediate layer 2 in the multilayer structure) are formed. Initialization can be easily set to magnetizations in opposite directions. Such a light modulation element 1 is also provided in the pixel 8 of the spatial light modulator 10 because the magnetization free layer 3 undergoes magnetization reversal to perform a light modulation operation and the resistance changes as described above. Can do.

  Further, as another embodiment of the light modulation element 1, the magnetization fixed layers 11, 12, 13 and the magnetization free layer 3 may be formed of an in-plane magnetic anisotropic material. Specifically, transition metals such as Ni, Fe, Co, Ni-Fe, Ni-Fe-Mo, Co-Cr, Co-Fe, Co-Fe-B, Co-Fe-Si, Co-Fe Examples thereof include transition metal alloys such as —Ge or alloys of transition metals such as Co—Pt and noble metals. Alternatively, a Mn-containing magnetic alloy having a large magneto-optical effect such as a Mn—Bi alloy, a Mn / Bi multilayer film, a Pt—Mn—Sb alloy, or a Pt / Mn—Sb multilayer film can be used. Further, when the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 have a multilayer structure including a magnetic film in which at least one of them is exchange-coupled, for example, Co—Fe / Ru / Co—Fe / A four-layer structure of Ir—Mn can be formed. Instead of the uppermost Ir—Mn, an antiferromagnetic material such as Fe—Mn or Pt—Mn can be used.

  The magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 having such in-plane magnetic anisotropy have magnetization fixed in one direction in the in-plane direction and the opposite direction. For example, as shown in FIG. 1 and FIG. In the light modulation element 1 having a planar shape shown in the figure, it is preferably fixed in the long side direction (vertical direction in FIG. 1) of the rectangular magnetization fixed layers 11, 12 and 13. As in the case of perpendicular magnetic anisotropy, such a light modulation element 1 has a magnetization direction in which the magnetization free layer 3 is parallel to one of the magnetization fixed layers 11 and 12 and antiparallel to the other by magnetization reversal. In addition, the resistance between the electrodes 51 and 53 changes with the magnetization reversal operation (not shown).

  As described with reference to FIG. 4, the element structures MR1, MR2 and MR3 of the light modulation element 1 undergo spin injection magnetization reversal by bipolar (bipolar) drive, but unipolar drive type spin injection magnetization reversal elements. A structure may be applied. As an example, the magnetization described in Yuta Otsuka et al., “Spin-injection magnetization reversal by unipolar current”, Proceedings of the 59th Joint Lecture on Applied Physics in Spring 2012, 17p-B4-8, February 2012. Examples thereof include a spin-injection magnetization reversal element in which a specific ferrimagnetic material is applied to the free layer. By applying such a spin-injection magnetization reversal element to the element structures MR1, MR2, MR3, the light modulation element 1 (1D) supplies a binary current in one direction, so that the magnetization of the magnetization free layer is magnetized. A magnetization reversal operation in both directions from downward to upward and upward to downward is possible (not shown).

  The light modulation element 1 has a square shape in plan view in FIGS. 1 and 3A, but is not limited thereto. Furthermore, the arrangement and shape of the magnetization fixed layers 11, 12 and 13 (element structures MR 1, MR 2 and MR 3) are not limited to the same rectangular shape divided into three vertical parts. Hereinafter, the light modulation element according to the modification will be described with reference to FIGS. 3B and 3C, the shaded regions are the magnetization fixed layers 11, 12, and 13 (the protective film 4 is not shown). For example, in the light modulation element 1B according to the modification shown in FIG. 3B, the magnetization fixed layers 11 and 13 are formed in a right triangle including two corners of a square in a plan view. . Between the magnetization fixed layers 11 and 13, the magnetization fixed layer 12 is formed in an elongated hexagonal shape including the remaining two corners. In other words, the light modulation element 1B is obtained by dividing the square into three along an oblique 45 ° line and providing the magnetization fixed layers 11, 12, and 13.

  Further, the light modulation element 1 does not have to be arranged with the magnetization fixed layers 11, 12, and 13 (element structures MR1, MR2, and MR3) arranged in one direction. For example, in the light modulation element 1C according to the modification shown in FIG. 3C, the rectangular magnetization fixed layers 11 and 13 are arranged side by side without providing the magnetization fixed layer 12 therebetween in plan view. The magnetization fixed layer 12 is arranged to face the side orthogonal to the direction in which the magnetization fixed layers 11 and 13 are arranged (the left-right direction in FIG. 3C), and has a full width including the magnetization fixed layers 11 and 13. In addition, it is formed in a rectangular shape having an area corresponding to the total of the magnetization fixed layers 11 and 13. Even if the light modulation elements 1B and 1C have such a planar view shape, the current is supplied from the electrodes 51 and 53 and the electrode 52 to perform the magnetization reversal operation, and accordingly the electrodes 51, The resistance between 53 changes. As described above, the light modulation element according to the present invention has the magnetization free layer 3 in the region (here, the whole) in which the light modulation element modulates the incident light by the spin injection magnetization reversal of the element structures MR1, MR2, and MR3. It is only necessary to reverse the magnetization direction. In the light modulation element 1C, a region where electrons are not injected and magnetization is not reversed is generated in a part of the magnetization free layer 3 between the element structures MR1 and MR3, but the width (length) is less than the diffraction limit of incident light. If so, it can be said that there is no influence on the light modulation.

  In the light modulation element 1, the intermediate layers 21, 22, and 23 are provided in the same shape as the magnetization fixed layers 11, 12, and 13 so as to be separated from each other, but the present invention is not limited thereto, and may be provided without being separated. Specifically, when two adjacent intermediate layers 2 and 2, that is, both of the intermediate layers 21 and 22, or both of the intermediate layers 23 and 22 are made of only an insulator, such two adjacent intermediate layers 2 and 2 are arranged. The two may be in contact with each other, and may be provided integrally (not shown) in the same manner as the magnetization free layer 3 as long as they are made of the same insulator material.

  As described above, the light modulation element according to the present invention has a magnetization reversal operation stabilized by two magnetization fixed layers and can increase the entire area. The aperture ratio can be increased. Furthermore, since the light modulation element according to the present invention is a magnetoresistive effect element in which the resistance between specific electrodes changes due to magnetization reversal, it is easy to detect the magnetization direction of the magnetization free layer, such as a spatial light modulator. The present invention can be applied not only to the above-mentioned pixels but also to a memory element for MRAM in the same manner as a conventional spin transfer magnetization switching element.

[Spatial light modulator]
(First embodiment)
Next, an embodiment of the spatial light modulator including the light modulation element according to the present invention in a pixel will be described with reference to the drawings.
As shown in FIG. 1, the spatial light modulator 10 according to the first embodiment of the present invention includes a substrate 7, a pixel array 80 including pixels 8 arranged in a two-dimensional array on the substrate 7, and a pixel array. A current control unit 90 that selects and drives one or more pixels 8 from 80 is provided. FIG. 1 is a bottom view from the substrate 7 side. In the pixel 8, the light modulation element 1 is disposed on the substrate 7 below the electrodes 51, 52, and 53 (see FIGS. 2 and 6). The light incident surface of the spatial light modulator 10 is a bottom surface (lower surface), and the spatial light modulator 10 modulates the light transmitted through the substrate 7 and incident on the pixel 8 (pixel array 80) from below to move downward. A reflective spatial light modulator that emits light (see FIG. 6).

  As described above, the light modulation element 1 provided in the pixel 8 of the spatial light modulator 10 has the second electrode with the power supply 95 and the electrodes 51 and 53 having the same polarity and different polarity in the magnetization reversal operation (writing). 52 is connected, and on the other hand, in the reading of the change in resistance caused by the magnetization reversal operation (write error detection), the first electrode 51 and the third electrode 53 are connected to different polarities of the sub power source 96, and the second electrode 52 is set to the open state. In the pixel array 80 of the spatial light modulator 10 according to the present embodiment, the electrodes 51, 52, and 53 are independent of each other in order to enable the connection for each pixel 8 (light modulation element 1). 1 is provided as follows.

  In the present embodiment, the pixel array 80 is exemplified by a configuration including 16 pixels 8 of 4 rows × 4 columns for the sake of brevity. The pixel array 80 includes four first electrodes 51 extending in the Y direction (vertical direction in FIG. 1) in plan (bottom) view, and an X direction (in FIG. 1) orthogonal to the first electrode 51 in plan view. 4 second electrodes 52 extending in the lateral direction) and 7 third electrodes 53 extending in the diagonal direction (hereinafter referred to as Z direction). In this manner, in the pixel array 80, the electrodes 51, 52, and 53 are provided to be shared by the pixels 8 in column units, row units, and diagonal units so as to be non-parallel wirings. Therefore, as appropriate, the first electrode 51 is referred to as an X electrode 51, the second electrode 52 is referred to as a Y electrode 52, and the third electrode 53 is referred to as a Z electrode 53. In order to select all the pixels 8, the X electrode 51 and the Y electrode 52 may have the same number as the number of columns and rows in the pixel array 80, respectively. The number of number-1) is provided.

  Here, as described above, the light modulation element 1 provided in the pixel 8 of the spatial light modulator 10 has the electrodes 51, 52, 53 is connected. Further, in the pixel array 80, the light modulation element 1 is arranged with the arrangement direction of the magnetization fixed layers 11, 12, and 13 being the X direction. Therefore, the first electrode 51 extending in the Y direction orthogonal to the arrangement direction and connected to the first magnetization fixed layer 11 is adjacent to the second magnetization fixed layer (on the right or left adjacent light modulation element 1). 12 or the third magnetization fixed layer 13 is formed in a strip-like wiring having a width that does not come into contact with the third magnetization fixed layer 13 and is provided at a height position directly connected on the light modulation element 1 as shown in FIG.

  On the other hand, the third electrode 53 extending in the Z direction and connected to the third magnetization fixed layer 13 does not disturb the connection between the first magnetization fixed layer 11 and the first electrode 51 and As shown in FIG. 2, the band-shaped wiring portion (wiring portion 53a) is disposed on the first electrode 51 (on the side away from the light modulation element 1) via an interlayer insulating layer (insulating member 6) so as not to short-circuit. Provided. Similarly, the second electrode 52 extending in the X direction and connected to the second magnetization fixed layer 12 does not hinder the connection between the first magnetization fixed layer 11 and the first electrode 51, and the first electrode 51. 1 and the third electrode 53 are provided with a belt-like wiring portion (wiring portion 52a) shown in FIG. 1 on the wiring portion 53a of the third electrode 53 via an interlayer insulating layer (insulating member 6). Further, as indicated by a two-dot chain line in FIG. 3A, the connection portions 52c and 53c of the electrodes 52 and 53 are formed on the magnetization fixed layers 12 and 13 so as not to short-circuit each other and the first electrode 51. Is formed. As shown in FIG. 2, the third electrode 53 connects the connection portion 53c and the wiring portion 53a with an interlayer connection portion 53b (contact). On the other hand, the second electrode 52 connects the connection part 52c to the wiring part 52a via the interlayer connection part 52b1, the relay connection part 52d, and the interlayer connection part 52b2. In particular, the connection portion 52c disposed between the first electrode 51 and the connection portion 53c of the third electrode 53 protrudes in the Y direction in the plan view (above the light modulation element 1 in FIG. 3A) and It is provided in a size in plan view that can be connected to the connection portion 52b1. 2 and 6, the wiring part 53 a of the third electrode 53 is a position hidden behind the wiring part 52 a of the second electrode 52. Moreover, in FIG. 1, the 2nd electrode 52 and the 3rd electrode 53 show only wiring parts 52a and 53a, respectively.

The X electrode 51, the Y electrode 52 (wiring part 52a), and the Z electrode 53 (wiring part 53a) are respectively appropriate for flowing currents −I _W and + I _W for the magnetization reversal operation of the light modulation element 1. Formed in width and thickness (height). In the present embodiment, the wiring portion 52a of the Y electrode 52 connected to the second magnetization fixed layer 12 having a larger area than the magnetization fixed layers 11 and 13 is larger than the X electrode 51 and the Z electrode 53 (wiring portion 53a). It is formed thick. Further, the pixel array 80 includes adjacent light modulation elements 1, 1, X electrodes 51, 51, Z electrodes 53, 53, Y electrodes 52, 52, and X electrode 51, Z electrode 53, Z electrode 53. Insulating members 6 are formed between the respective layers of the Y electrode 52 and the Y electrode 52, that is, in a region represented by a blank in FIG.

(Light modulation element)
The light modulation element 1 has the configuration already described, and a description thereof is omitted. Here, all the light modulation elements 1 provided in the pixel array 80 are fixed with the first magnetization fixed layer 11 and the third magnetization fixed layer 13 facing upward and the second magnetization fixed layer 12 facing downward. (See FIG. 6). The magnetization free layer 3 rotates the polarization direction of incident light by an angle of + θk when the magnetization direction is upward and −θk when the magnetization direction is downward (see FIG. 5). The light modulation element 1 may include a base film made of a metal thin film between the substrate 7 (under the magnetization free layer 3) in order to obtain adhesion to the substrate 7 (not shown). Such a base film is preferably made of a nonmagnetic metal material such as Ta, Ru, or Cu and has a thickness of 1 to 10 nm. If the base film has a thickness of less than 1 nm, it is difficult to form a continuous film. On the other hand, if the thickness exceeds 10 nm, light entering and exiting is absorbed and efficiency is lowered.

(electrode)
Since the electrodes 51, 52, and 53 are all disposed on the opposite side of the light incident / exit side with respect to the light modulation element 1 (magnetization free layer 3), they do not block light and are made of a low-resistance metal material. Can be formed. Therefore, the electrodes 51, 52, and 53 are formed of a general metal electrode material such as a metal such as Cu, Al, Au, Ag, Ta, or Cr, or an alloy thereof. Then, it is processed into a desired shape such as a stripe shape by a known method such as a sputtering method, by film formation, photolithography, etching, lift-off method, or the like.

(substrate)
The substrate 7 is a base for two-dimensionally arranging the pixels 8, and is a broad substrate for manufacturing the light modulation element 1. Further, since the spatial light modulator 10 according to the present embodiment emits light from the substrate 7 side, the substrate 7 is made of a material that transmits light. As such a substrate 7, a known transparent substrate material can be applied, and specifically, SiO ₂ (silicon oxide, glass), MgO (magnesium oxide), sapphire, GGG (gadolinium gallium garnet), SiC (silicon carbide). A Ge (germanium) single crystal substrate or the like can be applied. Further, on the substrate 7, a dielectric (such as Si—N (silicon nitride), ZnO (zinc oxide), HfO ₂ (hafnium oxide), ZrO ₂ (zirconium oxide)) having a high refractive index with respect to the substrate 7 ( An insulator) layer may be provided, and the light modulation element 1 may be formed thereon. Alternatively, a transparent oxide semiconductor (transparent conductor) layer having a high refractive index such as ITO (indium tin oxide) or IZO (indium zinc oxide) is formed on the substrate 7, and SiO ₂ (glass) is formed thereon. A dielectric (insulator) layer such as Si—N (silicon nitride) may be stacked, and the light modulation element 1 may be further formed thereon. Further, a multilayer film in which the transparent oxide semiconductor (conductor) layer and the dielectric (insulator) layer are alternately stacked may be formed, and the light modulation element 1 may be formed thereon (not shown). ). The light reflected by the light modulation element 1 (magnetization free layer 3) is reflected at the interface between the dielectric layer and the substrate 7 and is incident on the light modulation element 1 again. Until the light is emitted, the optical modulation element 1 repeats the optical rotation many times and the optical rotation angle is accumulated to increase, thereby improving the contrast between light and dark.

(Insulating material)
The insulating member 6 is formed between the magnetization fixed layers 11 and 12 and the intermediate layers 21 and 22 (between the element structures MR1 and MR2), between the magnetization fixed layers 12 and 13 and between the intermediate layers 22 and 23 (element structure). MR2 and MR3), between adjacent light modulation elements 1 and 1, between X electrodes 51 and 51, between Y electrodes 52 and 52, between Z electrodes 53 and 53, and between X electrode 51 and Z electrode 53 and Z electrode 53. And the Y electrode 52 are provided to insulate the respective layers. For the insulating member 6, for example, an oxide film such as SiO ₂ or Al ₂ O ₃ or a known insulating material such as Si ₃ N ₄ can be applied.

(Current controller)
As shown in FIG. 1, the current control unit 90 includes an X electrode selection unit 91 that selects the X electrode 51, a Y electrode selection unit 92 that selects the Y electrode 52, and a Z electrode selection unit 93 that selects the Z electrode 53. A power source (current supply means) 95 for supplying current to the electrodes 51, 53 and the electrode 52; a pixel selection section (pixel selection means) 94 for controlling the power supply 95 and the electrode selection sections 91, 92, 93; . A known device capable of the operations described below can be applied to each of these. Furthermore, the current control unit 90 includes a sub power source (sub current supply unit) 96 that supplies current to the electrodes 51 and 53, and a determination unit (pixel determination unit) 97 that detects pixel writing errors. As will be described later, a device similar to the power source 95 can be applied to the sub power source 96 except that the magnitude of the supplied current is different. The determination unit 97 includes a voltage comparator 97a and an inspection unit 97b. As will be described later, the voltage comparator 97a applies a known read circuit in the MRAM, and the inspection unit 97b applies a so-called CPU that performs arithmetic processing. be able to.

The pixel selection unit 94 selects one or more specific pixels 8 of the pixel array 80 based on, for example, an external signal (not shown), and electrodes based on the X and Y coordinates in the pixel array 80 of the selected pixel 8. The selection units 91, 92, 93 are made to select the electrodes 51, 52, 53, and the direction of the current supplied by the power source 95 is selected. Then, as shown in FIG. 7, the X electrode selection unit 91 selects one or more of the X electrodes 51 according to a command from the pixel selection unit 94 (represented by the circled number 94 in the figure), and the Z electrode selection unit 93. Selects one or more of the Z electrodes 53, and the Y electrode selection unit 92 selects one or more of the Y electrodes 52, makes the selected electrodes 51, 53 have the same polarity and the electrodes 52 have different polarities, and supplies a power source 95. Are connected (see FIG. 4). The power source 95 is a known power source that supplies an appropriate voltage / current for reversing the magnetization of the light modulation element 1 provided in the selected pixel 8, and can supply a DC pulse current so that it can be inverted. Then, the power supply 95 supplies the positive or negative current (+ I _W / −I _W ) selected by the pixel selection unit 94 to the light modulation element 1 through the connected electrodes 51 and 53 and the electrode 52. With such a configuration, the spatial light modulator 10 selects a desired pixel 8 from the pixel array 80 and supplies a pulse current of a predetermined magnitude to the light modulation element 1 of the pixel 8 in the selected direction. Thus, the magnetization free layer 3 is set to a desired magnetization direction. The magnetization reversal operation of the light modulation element 1 is as described with reference to FIG. The magnetization reversal operation of the light modulation element 1 of the selected pixel 8 changes the magnetization direction of the magnetization free layer 3 of the light modulation element 1, so that the light incident on the selected pixel 8 can be selectively selected. The light can be emitted after being modulated in the direction of polarization (described in detail in the light modulation operation of the spatial light modulator described later (see FIG. 6)).

Further, the pixel selection unit 94 connects a sub power source 96 in place of the power source 95 to the X electrode 51 and the Z electrode 53 in a pair of different polarities (a pair), so that the magnetization reversal current I _STS of the light modulation element 1 is greater. A small predetermined current I _TST can be supplied. In the determination unit 97, the voltage comparator 97 a is connected in parallel with the sub power supply 96, and the voltage between the electrodes 51 and 53 when the current I _TST is supplied to the light modulation element 1 is referred to as a reference potential (threshold) Vref. In comparison, the result is output to the inspection unit 97b (not shown in FIG. 7). This comparison result indicates the actual magnetization direction of the magnetization free layer 3 of the light modulation element 1, and the inspection unit 97b determines whether the magnetization direction indicated by the comparison result is the magnetization direction selected by the pixel selection unit 94. Write error detection to be verified. The voltage comparator 97a receives a voltage between the electrodes 51 and 53, and outputs a differential sense amplifier SA (see FIG. 7) that outputs 1 or 0 higher or lower than the reference potential Vref, or a reference potential. A Vref output circuit (not shown) is provided, and a known read circuit in the MRAM can be applied. In order to improve accuracy, the voltage comparator 97a is connected via an amplifier that amplifies the voltage from the electrodes 51 and 53, or a circuit that amplifies the difference from the threshold Vref in the differential sense amplifier SA. It may be provided (not shown). The write error detection method of the spatial light modulator 10 will be described in detail later.

[Method of manufacturing spatial light modulator]
An example of a method for manufacturing a pixel array of a spatial light modulator according to the present invention will be described with reference to FIGS. The pixel array 80 is manufactured by first forming the light modulation element 1 on the substrate 7 and then forming the electrodes 51, 52, 53 connected to the light modulation element 1.

(Formation of light modulation element)
First, on the substrate 7, materials for forming the magnetization free layer 3, the intermediate layer 2, the magnetization fixed layers 11, 12, 13, and the protective film 4 (indicated by the same reference numerals as those of the respective layers in the figure, the same shall apply hereinafter). To form a film. A resist pattern having a planar view shape of the light modulation element 1 is formed thereon as shown in FIG. Then, by etching using an ion beam milling method, as shown in FIG. 8B, the substrate 7 is exposed by removing from the protective film 4 to the magnetization fixed layers 11, 12, 13, the intermediate layer 2, and the magnetization free layer 3. Let Next, as shown in FIG. 8C, an insulating film (insulating member 6) is formed, and the resist is removed together with the insulating film (lift-off).

  Next, the spin injection magnetization reversal element structures in the light modulation element 1 are separated from each other. As shown in FIG. 8D, a resist pattern is formed on the protective film 4 with a space between the element structures MR1 and MR2 and between the element structures MR2 and MR3 of the light modulation element 1. By etching, as shown in FIG. 8E, the magnetization fixed layers 11, 12, 13 and the intermediate layer 2 are removed from the protective film 4 to expose the magnetization free layer 3. Next, as shown in FIG. 9A, an insulating film (insulating member 6) is formed, and the resist is removed together with the insulating film (lift-off). As a result, as shown in FIG. 9B, three separate spin-injection magnetization reversal element structures are formed, and the space between them is filled with the insulating member 6, so that the light having the three element structures MR1, MR2, MR3 is formed. The modulation element 1 is formed, and the upper surface (the surface of the protective film 4) is filled with the insulating member 6 in a flush manner. The resist pattern may be formed in a stripe shape continuous in the Y direction (vertical direction in FIG. 1), and even if the insulating member 6 between the light modulation elements 1 and 1 in the Y direction is etched, it is filled with the insulating member 6 again. So no problem.

(Formation of electrodes)
First, a connection portion of the X electrode 51 connected to the upper surface (protective film 4) of the element structure MR1 of the light modulation element 1, and the Y electrode 52 connected to the upper surfaces (protective film 4) of the element structures MR2 and MR3. 52c and the connection part 53c of the Z electrode 53 are formed. An insulating film (insulating member 6) is formed on the light modulation element 1 and the insulating member 6 with the thickness of the X electrode 51. Then, as shown in FIG. 9C, a resist pattern is formed on the insulating member 6 so as to leave a region where the X electrode 51 is provided and a region where the connection portions 52c and 53c of the electrodes 52 and 53 are provided. . Then, the insulating member 6 is removed by etching until the protective film 4 is exposed as shown in FIG. Next, as shown in FIG. 10A, a metal electrode material is formed, and the resist is removed together with the metal electrode material (lift-off). As a result, as shown in FIG. 10B, the connection portions 52c and 53c of the X electrode 51 and the electrodes 52 and 53 are connected to the spin injection magnetization reversal element structures MR1, MR2 and MR3 of the light modulation element 1. The

  Next, the Z electrode 53 is completed, and the relay connection portion 52d (see FIG. 2) of the Y electrode 52 is formed. An insulating film (insulating member 6) is formed on the X electrode 51, the connecting portions 52c and 53c, and the insulating member 6 with a thickness between the electrodes 51 and 53. Next, a resist pattern is formed on the insulating member 6 so that the contact regions on the connection portions 52c and 53c are opened. Then, the insulating member 6 is removed by etching until the connecting portions 52c and 53c are exposed. Next, a metal electrode material is formed, and the resist is removed together with the metal electrode material (lift-off). Accordingly, as shown in FIGS. 10C and 10D, the interlayer connection portion 52b1 for connecting the relay connection portion 52d and the wiring portion 53a to the connection portions 52c and 53c of the Y electrode 52 and the Z electrode 53, respectively. , 53b are formed. In addition, illustration of the insulating member 6 is abbreviate | omitted in FIG.10 (d). Further, an insulating film (insulating member 6) is formed on the interlayer connection portions 52b1 and 53b and the insulating member 6 with the thickness of the wiring portion 53a of the Z electrode 53, and relayed by lift-off as with the X electrode 51 and the like. The connection part 52d and the wiring part 53a are formed.

  Finally, the Y electrode 52 is completed. An insulating film (insulating member 6) is formed between the electrodes 53 and 52 on the X electrode 51, the Z electrode 53 (wiring portion 53a), the relay connection portion 52d, and the insulating member 6. Next, a resist pattern is formed on the insulating member 6 with a contact region on the relay connection portion 52d. Then, the insulating member 6 is removed by etching until the relay connection portion 52d is exposed. Next, a metal electrode material is formed, and the resist is removed together with the metal electrode material (lift-off). Thereby, an interlayer connection part 52b2 (see FIG. 2) for connecting the wiring part 52a to the relay connection part 52d of the Y electrode 52 is formed. Further, an insulating film (insulating member 6) is formed on the interlayer connection portion 52b2 and the insulating member 6 with the thickness of the wiring portion 52a of the Y electrode 52, and the wiring portion 52a is lifted off similarly to the X electrode 51 and the like. Form.

  According to such a manufacturing method, the pixel 8 having the light modulation element 1 having the three spin-injection magnetization reversal element structures and the electrodes 51, 52, and 53 connected to the light modulation element 1 as non-parallel wirings. Can be formed on the substrate 7. In forming the light modulation element 1, after forming the material of each layer, the entire shape was formed first, and then the element structures MR1, MR2, MR2 were divided and formed. , MR3 and the element structures MR3, MR3 may be processed and then processed into the entire shape of the light modulation element 1.

(Initial setting of light modulator)
As described above, in the light modulation elements 1 of all the pixels 8 of the pixel array 80, the first magnetization fixed layer 11 and the third magnetization fixed layer 13 are upward, the second magnetization fixed layer 12 is downward, and the magnetization is fixed. Need to be. Since the magnetization fixed layers 11, 12, and 13 do not undergo magnetization reversal when a current is supplied from the power supply 95, the optical modulation element 1 is initialized by the following method.

Light modulation element 1 according to this embodiment, the coercive force Hcp ₁ of the first magnetization fixed layer 11 and the third magnetization fixed layer 13, the coercivity Hcp ₂ of the second magnetization fixing layer 12 is larger than Hcp ₃ (Hcp ₁ ≒ Hcp ₃ <Hcp ₂ ). Therefore, first, a downward external magnetic field larger than Hcp ₂ is applied to the pixel array 80 so that the magnetizations of all the magnetization fixed layers 11, 12 and 13 are directed downward. Next, an upward external magnetic field smaller than Hcp ₂ and larger than Hcp ₁ and Hcp ₃ is applied to make the magnetizations of the first magnetization fixed layer 11 and the third magnetization fixed layer 13 upward. The two-step magnetic field application is not limited to the completed (after manufacturing) pixel array 80, but after the magnetic film material for the magnetization fixed layers 11, 12, and 13 is formed during the manufacturing process of the pixel array 80. Thereafter, it can be carried out at any stage.

In the case of the light modulation element 1 having a multilayer structure in which at least one of the magnetization fixed layers 11 and 13 and the magnetization fixed layer 12 includes a magnetic film exchange-coupled, all the magnetization fixed layers 11, 12, and 13 are maintained. While applying an external magnetic field exceeding the magnetic force (Hcp ₁ , Hcp ₂ , Hcp ₃ ), heat treatment is performed at about 200 ° C. in a vacuum, so that the initial stage of the light modulation element 1 can be achieved by one application of the magnetic field (one step). Settings can be made.

[Light modulation operation of spatial light modulator]
The light modulation operation of the spatial light modulator according to the present invention will be described with reference to FIG. 6 using a display device using this spatial light modulator. The display device may have the same configuration as that of the conventional spin-injection magnetization reversal element as a light modulation element (see Patent Document 1). The spatial light modulator 10 according to the present embodiment is of a reflective type, and the magnetization free layer 3 of the light modulation element 1 serving as the light modulation unit is provided on a transparent substrate 7 and has perpendicular magnetic anisotropy. Since it is made of a material and the magnetization direction indicates upward or downward, the display device preferably has the following configuration. Below the pixel array 80 of the spatial light modulator 10, an optical system OPS having a light source or the like that irradiates light (laser light) toward the pixel array 80, and the light emitted from the optical system OPS is applied to the pixel array 80. A polarizer (polarization filter) PFi that makes light of one polarization component (hereinafter referred to as incident light) before entering, and outgoing light that is incident and incident on the pixel array 80 from below is emitted from the pixel array 80. A polarizer (polarization filter) PFo that shields light of a specific polarization component and a detector PD that detects light transmitted through the polarizer PFo are disposed. In FIG. 6, the spatial light modulator 10 omits the current control unit 90 and shows only the pixel array 80.

  The optical system OPS includes, for example, a laser light source, a beam expander that is optically connected to the laser light source and expands the laser light onto the entire surface of the pixel array 80, and a lens that converts the expanded laser light into parallel light. (Not shown). Since the light (laser light) emitted from the optical system OPS contains various polarization components, this light is transmitted through the polarizer PFi in front of the pixel array 80 to be one polarization component light. The polarizers PFi and Pfo are polarizing plates, respectively, and the detector PD is an image display means such as a screen.

  The optical system OPS irradiates the pixel array 80 with a parallel laser beam. Here, the magneto-optical effect of the magnetization free layer 3 of the light modulation element 1 increases as the incident angle of light becomes closer to the magnetization direction of the magnetization free layer 3. Therefore, it is desirable that the incident angle be perpendicular to the film surface, that is, 0 °, in order to maximize the degree of light modulation. However, in this case, the optical path of the emitted light coincides with the optical path of the incident light. Therefore, the incident angle is slightly inclined so that the polarizer PF0, the detector PD, the optical system OPS, and the polarizer PFi are arranged so as not to block the optical paths of the incident light and the outgoing light, respectively. Specifically, the incident angle of incident light is preferably set to 30 ° or less. The laser light passes through the polarizer PFi and becomes incident light of one polarization component, and is incident on all the pixels 8 from below the pixel array 80. Incident light passes through the substrate 7, is reflected by the light modulation element 1 of each pixel 8, exits from the pixel 8 as outgoing light, and passes through the substrate 7 again.

  Outgoing light is light of a specific polarization component by the polarizer PFo, here, light that has been rotated by θθ relative to the incident light is shielded, and light that has passed through the polarizer PFo enters the detector PD. Accordingly, since the light emitted from the pixel 8 whose magnetization direction of the magnetization free layer 3 of the light modulation element 1 is upward is blocked by the polarizer PFo, the pixel 8 is dark (black) and is displayed on the detector PD. . On the other hand, light that has been rotated by −θk with respect to incident light, that is, light emitted from the pixel 8 in which the magnetization direction of the magnetization free layer 3 of the light modulation element 1 is downward passes through the polarizer PFo and reaches the detector PD. Therefore, this pixel 8 is displayed brightly (white) on the detector PD.

As described above, the spatial light modulator 10 according to the present invention switches between light / dark (white / black) for each pixel 8 and switches the direction of current supplied to each pixel 8 (+ I _W / −I _W ). Light / dark will switch. The initial state of the spatial light modulator 10 is all from the power source 95 so that the magnetization direction of the magnetization free layer 3 of the light modulation elements 1 of all the pixels 8 is downward, for example, so that the whole is displayed white. The current + I _W may be supplied to the pixel 8 (see FIGS. 4D and 4A).

[Method for detecting pixel write error in spatial light modulator]
As shown in FIG. 7, when the spatial light modulator according to the present invention is represented by an equivalent circuit diagram (a pixel array shows only pixels of 2 rows × 2 columns), the first element structure MR1 of the light modulation element 1 and the first element structure MR1 Since the combined resistance with the three-element structure MR3 is represented as one magnetoresistive element, the first electrode (X electrode) 51 is a bit line, the third electrode (Z electrode) 53 is a word line, and the pixel array 80 is It can be said that the circuit structure is the same as that of the cross point type MRAM. Therefore, the spatial light modulator according to the present invention can check whether the magnetization reversal operation (writing) of the light modulation element has been normally performed for the selected pixel by performing a reading operation similar to that of the MRAM. A method for detecting a write error in a pixel of the spatial light modulator will be described with reference to FIGS. 1 and 5 and FIG. 4 as appropriate.
First, the relationship between the voltage between the electrodes 51 and 53 connected to the light modulation element 1 and the magnetization direction of the magnetization free layer 3 will be described.

(Relationship between magnetization direction and voltage of magnetization free layer in light modulator)
As shown in FIGS. 5A and 5B, when a current _ITST having a predetermined magnitude is supplied from the sub power source 96 to the light modulation element 1, a voltmeter connected in parallel with the sub power source 96 is used. The measured voltage is proportional to the resistance of the light modulation element 1. At this time, the current (resistance measurement current) I _TST supplied to the light modulation element 1 does not change the magnetization direction of the magnetization free layer 3, that is, is smaller than the magnetization reversal current I _STS of the light modulation element 1. In FIG. 5, the resistance measurement current I _TST is supplied with the first electrode 51 set to “+”, but the direction of the current is not limited, and for the magnetization reversal operation of the light modulation element 1. Unlike the currents −I _W and + I _W , the direction of the current may be one direction. Thus, even if the light modulation element 1 is supplied with a current smaller than the magnetization reversal current I _STS , the magnetization direction of the magnetization free layer 3 does not change. The voltage measured by supplying such a constant current I _TST to the light modulation element 1 varies depending on the magnetization direction of the magnetization free layer 3 of the light modulation element 1.

As shown in FIG. 5A, in the light modulation element 1 in which the magnetization free layer 3 exhibits downward magnetization, the resistance value between the electrodes 51 and 53 is R13 _D , so that the voltage value V _D is I _TST · R13 _D. On the other hand, as shown in FIG. 5B, the light modulation element 1 in which the magnetization free layer 3 exhibits upward magnetization has a voltage value of R13 _U because the resistance value between the electrodes 51 and 53 is R13U. V _U becomes I _TST · R13 _U. As described above, in the light modulation element 1, the resistance between the electrodes 51 and 53 is higher when the magnetization free layer 3 exhibits downward magnetization. From the above equations (5) to (7), R13 _D > R13 _U , so V _D > V _U. That is, whether the magnetization of the magnetization free layer 3 of the light modulation element 1 is upward or downward is detected from the value of the voltage measured by a voltmeter connected in parallel with the sub power source 96, in other words, connected to the electrodes 51 and 53. can do. For example, threshold values Vref _L and Vref _H (V _U <Vref _L <Vref _H <V _D ) are set as limit values in the allowable ranges of the voltages V _D and V _U. If the measured voltage value is Vref _H or more, the magnetization of the magnetization free layer 3 can be detected downward, and if it is Vref _L or less, it can be detected that the magnetization of the magnetization free layer 3 is upward. Therefore, in the light modulation element 1, the larger the resistance change ΔR13 between the electrodes 51 and 53, the larger the difference between the voltages V _D and V _{U that} change due to magnetization reversal, and the magnetization free layer 3 by the thresholds Vref _L and Vref _H. Detection of the magnetization direction is easy and accurate.

(Pixel writing error detection method)
From this, the spatial light modulator 10 compares the voltage between the electrodes 51 and 53 of the light modulation element 1 with the thresholds Vref _L and Vref _H for the selected pixel 8, and the magnetization free layer of the light modulation element 1. 3 is detected and collated with the selection direction of the magnetization reversal operation by the pixel selection unit 94 which determines whether the magnetization direction of the magnetization free layer 3 of the light modulation element 1 is upward or downward. Can be checked to see if it was successful. Here, description will be made assuming that the detection of the write error is performed on the pixel 8 immediately after the magnetization reversal operation is performed on the light modulation element 1 of the selected pixel 8.

In the light modulation element 1, the power source 95 connected to the electrodes 51, 53 and the electrode 52 supplies a current + I _{W according} to a command from the pixel selection unit 94, so that the magnetization free layer 3 is formed as shown in FIG. The downward magnetization is shown. Here, the pixel selection unit 94 notifies the determination unit 97 that the magnetization of the magnetization free layer 3 is directed downward when instructing the current supply to the power source 95 for the magnetization reversal operation of the light modulation element 1. (See FIG. 1). Then, after supplying the current + I _W from the power source 95 (after the supply is stopped), the electrodes 51 and 53 and the electrode 52 of the light modulation element 1 are connected to the power source 95 according to a command from the pixel selecting unit 94. 51 and 53 and the sub power supply 96 are switched to each other, and a resistance measurement current I _TST is supplied from the sub power supply 96 as shown in FIG.

The determination unit 97 previously sets the reference potential (threshold value) that the voltage comparator 97a uses as a reference for comparison to Vref _H based on the selection direction of the magnetization reversal operation input from the pixel selection unit 94: downward, and inspection unit 97b is set to determine that a pass (pASS) if more than the threshold value Vref _H. Then, in accordance with the start of supply of the resistance measurement current I _TST by the sub power source 96, the voltage comparator 97a compares the voltage between the electrodes 51 and 53 with the threshold value Vref _{H in} the determination unit 97, and is equal to or higher than Vref _H. Is output to the inspection unit 97b. If the value of the voltage between the electrodes 51 and 53 is Vref _H or more, as shown in FIG. 5A, the magnetization of the magnetization free layer 3 is downward, and the magnetization reversal operation of the light modulation element 1 is normally performed. I understand that. On the other hand, if the value of the voltage is less than Vref _H, the magnetization reversal operation of the optical modulation element 1 is not properly done (FAIL), ie it can be seen that a write error.

On the other hand, as shown in FIG. 4C, when the current -I _W is supplied from the power source 95 and the magnetization of the magnetization free layer 3 is directed upward, the connection is switched in the same manner, as shown in FIG. As described above, the resistance measurement current I _TST is supplied from the auxiliary power source 96. At this time, the determination unit 97 sets the reference potential (threshold value) to Vref _L in advance based on the selection direction of the magnetization reversal operation input from the pixel selection unit 94: upward, and the inspection unit 97b has the threshold Vref _L or less. If so, it is set so as to be determined as passing (PASS). Result of the voltage comparator 97a to compare the value of the voltage between the electrodes 51 and 53 and the threshold value Vref _L, if the value of the voltage is below Vref _L, as shown in FIG. 5 (b), the magnetization of the magnetization free layer 3 is It can be seen that the magnetization reversal operation of the light modulation element 1 was normally performed. On the other hand, when the voltage value exceeds Vref _L , it can be seen that the magnetization reversal operation of the light modulation element 1 is not properly performed (FAIL), that is, a write error.

If the inspection unit 97b of the determination unit 97 determines that the magnetization reversal operation of the light modulation element 1 has been performed normally, the pixel selection unit 94 performs the next operation, that is, selection and writing of another pixel 8, or Command to move to next write to same pixel 8. On the other hand, when detecting a write error, the inspection unit 97b instructs the pixel selection unit 94 to execute the previous magnetization reversal operation on the same pixel 8 again (see FIG. 1). In this way, the spatial light modulator 10 can accurately display in all the pixels 8 of the pixel array 80 by performing the magnetization reversal operation (writing) by the pixel selection unit 94 while performing the determination by the determination unit 97. Can do. Note that a program for setting threshold values Vref _L and Vref _H , a determination method by the inspection unit 97b of the determination unit 97, a command to the pixel selection unit 94, and the like is stored in, for example, a storage device ( (Not shown) may be stored in advance.

(Another embodiment of write error detection method)
As a voltage threshold for detecting the magnetization direction of the magnetization free layer 3 of the light modulation element 1, only one value (Vref) may be set as Vref _L = Vref _H (V _U <Vref <V _D ). That is, the determination unit 97 detects whether the magnetization of the magnetization free layer 3 is downward or upward depending on whether the voltage value between the electrodes 51 and 53 is larger or smaller than the threshold value Vref. Specifically, the reference potential (threshold value) used as a reference for comparison by the voltage comparator 97a is fixed to Vref, and the determination unit 97 determines whether the inspection unit 97b is based on the selection direction of the magnetization reversal operation input from the pixel selection unit 94. What is necessary is just to set whether the case where it is larger than this threshold value Vref and the case where it is smaller is set to pass (PASS). Further, as the voltage threshold, only one of the limit values of the voltages V _D and V _U , that is, not the lower limit value Vref _H of the voltage V _D and the upper limit value Vref _L of the voltage V _U , but the voltage V _D , V _U The determination may be made more strictly by setting a total of four values, the lower limit value and the upper limit value of each allowable range.

  Further, in the above-described method, every time the pixel selection unit 94 selects the pixel 8 and performs writing, the determination unit 97 repeats the operation of detecting the writing error for the pixel 8, but is not limited thereto. . For example, when writing to all the pixels 8 in the pixel array 80 is completed, the writing error can be detected in order for all the pixels 8.

  In addition, when two or more pixels 8 are selected at the same time and the same magnetization reversal operation is performed on each of the light modulation elements 1, the write error detection may be performed on these pixels 8 collectively. Since the light modulation elements 1 of two or more pixels 8 selected at the same time are connected in parallel to the sub-power supply 96, the threshold value of the voltage based on the combined resistance can be preset or calculated by the determination unit 97. Write error detection can be performed in the same manner as in the case of the individual light modulation elements 1. In this case, the determination unit 97 determines whether the magnetization reversal operation has been normally performed for all the light modulation elements 1 of the selected pixel 8 or a write error has occurred for any one or more of the light modulation elements 1. Can be determined.

When the current I _TST is supplied to the electrodes 51 and 53, the spatial light modulator 10 connects all the Y electrodes 52 and the Z electrodes 53 in the non-selected pixels 8 to the third magnetization fixed layer 13 (Z electrode 53). You may connect to the "-" side of the sub power supply 96 which is the tip. Thereby, leakage current is reduced.

  As described above, according to the spatial light modulator according to the first embodiment, the conventional spin-injection magnetization reversal element is optically enlarged while the effective area of the pixel is widened by the light modulation element having a large area to increase the aperture ratio. Similar to the spatial light modulator used as the modulation element, the write error can be detected using the driving wiring, and the pixel can be further miniaturized.

(Second Embodiment)
Next, with reference to FIG. 11, a spatial light modulator according to the second embodiment of the invention will be described. In addition, in this embodiment and 3rd Embodiment mentioned later, the same code | symbol is attached | subjected about the element same as 1st Embodiment (refer FIGS. 1-6), and description is abbreviate | omitted.

  The spatial light modulator 10 according to the first embodiment has a configuration in which one pixel 8 includes one light modulation element 1, but is not limited thereto, and one pixel includes two or more light modulation elements. Also good. That is, as shown in FIG. 11, the pixel 8A of the spatial light modulator according to the second embodiment includes three light modulation elements 1A. In FIG. 11, similarly to FIG. 3A, shaded regions are the magnetization fixed layers 11, 12, and 13 (the protective film 4 is not shown). The light modulation element 1A has the same structure as that of the light modulation element 1 of the spatial light modulator 10 according to the first embodiment, except that the light modulation element 1A is a horizontally long rectangle in plan view extended in the X direction (lateral direction in FIG. 11). is there. In the pixel 8A, the three light modulation elements 1A are arranged in the short side direction (Y direction) of the light modulation element 1A and connected in parallel to the same set of electrodes 51, 52, and 53. Such pixels 8 </ b> A are two-dimensionally arranged on the substrate 7 to form a pixel array as in the first embodiment, and can be operated by the current control unit 90. Since the pixel array and current control unit 90 have the same configuration as in the first embodiment, illustration and description thereof are omitted.

  As described above, according to the spatial light modulator according to the second embodiment, even if the pixel size is increased, one size of the light modulation element is sufficiently small, so that the magnetization is appropriately reversed and the aperture ratio is high. It can be a pixel.

(Third embodiment)
Next, a spatial light modulator according to the third embodiment of the invention will be described with reference to FIG. In the present embodiment, the same elements as those in the first embodiment (see FIGS. 1 to 7) are denoted by the same reference numerals, and description thereof is omitted.

  The pixel array of the spatial light modulator according to the first embodiment has the same structure as the cross-point type MRAM circuit as described with reference to FIG. In this cross-point type MRAM, the current leaks also to the non-selected magnetoresistive effect element. Therefore, as the number of mounted magnetoresistive effect elements increases, the resistance change amount of one magnetoresistive effect element detected at the time of data reading is increased. Is smaller than the actual value, a magnetoresistance effect element having a sufficiently large resistance change is applied. That is, in the spatial light modulator 10 according to the first embodiment, the voltage between the electrodes 51 and 53 is the light of the non-selected pixel 8 depending on the number of mounted light modulation elements 1 (number of pixels) in the pixel array 80. The light modulation element 1 is designed so that the amount of change in resistance increases to such an extent that the voltage comparator 97a of the determination unit 97 can determine whether the threshold value is high or low even if affected by the resistance component of the modulation element 1. ing.

  However, when such a light modulation element 1 is applied, the spatial light modulator 10 requires time for reading, that is, determination (writing error detection). Therefore, as is often applied to MRAM, a select transistor type may be used. That is, as shown in FIG. 12, the spatial light modulator 10A according to this embodiment includes at least one of the electrodes connected to each light modulation element 1 when a write error is detected, here, the third electrode 53A and the third magnetization fixed. A transistor Tr1 is connected between the layer 13 as an element selection circuit. Specifically, the transistor Tr1 has a drain connected to the third magnetization fixed layer 13 of the light modulation element 1, a source connected to the third electrode 53A, and a gate (element selection electrode 58) newly provided with a gate. . The element selection electrode 58 is provided non-parallel to the third electrode 53A in order to select the pixel 8B independently of the third electrode 53A.

  Here, the spatial light modulator 10 (see FIG. 1) according to the first embodiment includes the third electrode (Z electrode) 53, the second electrode (Y electrode) 52 during the magnetization reversal operation, and the first electrode when the write error is detected. One electrode (X electrode) 51 is provided in a diagonal direction (Z direction) different from both the X and Y directions in plan view so as to be non-parallel to each other. However, in the present embodiment, the supply of current to the third magnetization fixed layer 13 can be selected for each pixel 8B (light modulation element 1) by the third electrode 53A and the element selection electrode 58. Therefore, the spatial light modulator 10A uses the third electrode 53A as the second Y electrode (Y2 electrode) 53A in parallel to the Y electrode (Y1 electrode) 52, that is, extends in the X direction, and the element selection electrode 58 is It extends in the Y direction so as to be orthogonal to the Y2 electrode 53A, that is, parallel to the X electrode 51. The spatial light modulator 10A newly includes an element selection unit 98 that selects the element selection electrode 58. The element selection electrode 58 is supplied with a current from a power source for driving the transistor Tr1 built in the element selection unit 98 (see FIG. 12). Supplied. In the magnetization reversal operation, the spatial light modulator 10A selects the specific pixel 8B by selecting the electrodes 51 and 58 in the X direction and the electrodes 52 and 53A in the Y direction, respectively. On the other hand, when a write error is detected, the electrodes 51 and 58 are selected in the X direction and the electrode 53A is selected in the Y direction.

  The spatial light modulator 10 </ b> A configured in this way selects the pixel 8 </ b> B not only with the electrodes 51, 52, 53 </ b> A that supply current to the light modulation element 1 but also with the element selection electrode 58. Then, in the spatial light modulator 10A, in the write error detection, the light modulation element 1 of the non-selected pixel 8B is not connected to the third magnetization fixed layer 13 (in the open state), and thus the spatial light modulator 10A (No. 3rd element structure MR3) during which no leakage current flows. As a result, the resistance of the light modulation element 1 of the selected pixel 8B is suppressed from being affected by the resistance component of the light modulation element 1 of the other pixel 8B in the non-selected state, and the amount of change in resistance due to magnetization reversal is not large. However, it is possible to distinguish between high and low. Further, the pixel array 80 of the spatial light modulator 10 according to the first embodiment requires a three-layer wiring structure in order to make the electrodes 51, 52, and 53 non-parallel to each other. In the pixel array 80B, each of the first electrode (X electrode) 51 and the element selection electrode 58, the second electrode (Y1 electrode) 52, and the third electrode (Y2 electrode) 53A is provided in parallel. It can be a structure.

  For example, a MOSFET (metal oxide semiconductor field effect transistor) can be applied to the transistor Tr1 provided for each pixel 8B. Here, the MOSFET is generally formed using a Si (silicon) substrate as a material. However, if a normal crystalline Si film that requires heat treatment at about 800 ° C. is formed on the light modulation element 1, the optical modulation element 1 is formed. The modulation element 1 is damaged. Therefore, polycrystalline silicon (poly-Si) that can be formed at a low temperature of about 150 ° C. is applied to the spatial light modulator 10A. Specifically, as an example, after the light modulation element 1 is formed on the substrate 7 and an interlayer insulating layer (insulating member 6) is formed thereon (see FIG. 9C), a poly-Si film is formed. A film is formed to form a MOSFET (transistor Tr1). Then, a contact hole is formed in the interlayer insulating layer on the magnetization fixed layers 11, 12, 13 of the light modulation element 1, and the third magnetization fixed layer 13 and the drain of the transistor Tr 1 are connected with a metal electrode material, and the first An X electrode 51 is connected to the magnetization fixed layer 11 and a Y1 electrode 52 is connected to the second magnetization fixed layer 12. Further, an element selection electrode 58 and a Y2 electrode 53A are connected to the gate and the source of the transistor Tr1, respectively. Note that the transistor Tr1 is formed in a region without the light modulation element 1 in a plan view so as not to hinder the connection to the magnetization fixed layers 11, 12, and 13.

The spatial light modulator 10A may connect all the Y1 electrodes 52 to the “−” side of the sub power supply 96 when supplying the current I _TST to the X electrode 51 (not shown). In the write error detection, the current I _TST supplied from the sub power source 96 to the light modulation element 1 via the selected X electrode 51 also flows from the second magnetization fixed layer 12 to the Y1 electrode 52, and this Y electrode 52 Flows into the light modulation element 1 of the non-selected pixel 8B sharing the same. Then, the light passes through the light modulation element 1 of the non-selected pixel 8B sharing the X pixel 51 or the Y1 electrode 52 with the selected pixel 8B, and merges with the selected X electrode 51. As described above, even when the transistor Tr1 is connected to the third magnetization fixed layer 13 (third element structure MR3), the Y1 electrode 52 forms a leakage current circuit that flows through the light modulation element 1 of the non-selected pixel 8B. This affects the resistance of the light modulation element 1 of the selected pixel 8 to some extent.

  On the other hand, when the Y1 electrode 52 is connected to the “−” side of the sub power supply 96, the leakage current is not affected by the resistance of the light modulation element 1 of the non-selected pixel 8B and becomes “−” of the sub power supply 96. Flowing. At this time, in the light modulation element 1 of the selected pixel 8B, the electrodes 52 and 53A are both connected to the “−” side of the sub power source 96, that is, in a state of being connected to the same polarity. As described above, a change amount smaller than the sum of the change amounts of the resistances of the element structures MR1 and MR3 and larger than one change amount of the resistance of the first element structure MR1 is measured. Therefore, although the amount of change in resistance is smaller than that in the case where the second electrode (Y1 electrode) 52 is open, the accuracy of write error detection is improved when the influence of leakage current is greater than that. .

  The spatial light modulator 10A connects the transistor Tr1 to the first magnetization fixed layer 11 (first element structure MR1) instead of the third magnetization fixed layer 13 (third element structure MR3) of the light modulation element 1. However, the same effect can be obtained. In this case, the transistor has a drain connected to the first magnetization fixed layer 11 of the light modulation element 1, a source connected to the X electrode 51, and a gate orthogonal to the X electrode 51 in a plan view (corresponding to the element selection electrode 58). , Each connected.

  As shown in FIG. 12, the spatial light modulator 10A is configured such that the X electrode 51 and the element selection electrode 58 of the pixels 8 in the same column are simultaneously selected by the pixel selection unit 94, but independently. It is good also as composition chosen. In the pixel array 80B of the spatial light modulator 10A, XY may be interchanged between the third electrode 53A and the element selection electrode 58. That is, the element selection electrode 58 is extended in parallel with the Y electrode 52, while the third electrode 53A is extended in parallel with the first electrode (X electrode) 51, and the X electrode 51 of the pixel 8B in the same column. It is configured to be selected at the same time (not shown).

  As described above, according to the spatial light modulator according to the third embodiment, even when a light modulation element having a small resistance change amount is applied, the same write error detection as that of the spatial light modulator according to the first embodiment is performed. Since this is possible, the response speed can be increased.

(Fourth embodiment)
In the pixel of the spatial light modulator according to the present invention, selection elements may be connected to two locations selected from the magnetization fixed layers 11, 12, and 13. For example, a transistor can be connected to each of the magnetization fixed layers 11 and 13 (not shown). The transistor connection method is the same as in the third embodiment. By connecting the selection element to two places of the light modulation element 1, in non-selected pixels, electrodes (wirings) 51, which are common to other pixels at two or more of the magnetization fixed layers 11, 12, and 13, 52 and 53 are not connected. Therefore, in the spatial light modulator, a leakage current does not flow through the light modulation element 1 of a non-selected pixel in the magnetization reversal operation and the write error detection.

  In the pixel of the spatial light modulator according to the present invention, a diode may be connected as a selection element. The diode can be formed in a poly-Si film as in the transistor Tr1. As shown in FIG. 13, the spatial light modulator 10C according to the fourth embodiment includes one transistor Tr1 in the pixel 8C as in the spatial light modulator 10A according to the third embodiment (see FIG. 12). The third magnetization fixed layer 53 (third element structure MR3) is connected and provided, and the first magnetization fixed layer 51 (first element structure MR1) is connected and provided with a diode Di1.

  The spatial light modulator 10C according to the present embodiment includes a unipolar drive type light modulation element 1D (element structures MR1 and MR2), and a power supply 95A is used to connect the first electrode 51A and the third electrode 53A to the second electrode 52. Current is supplied only in the direction to reverse magnetization (not shown). Therefore, the diode Di1 has the anode connected to the first electrode 51A and the cathode connected to the first magnetization fixed layer 51 of the light modulation element 1D. Alternatively, the spatial light modulator 10C supplies current to the light modulation element 1 only in one direction from the first electrode 51A and the third electrode 53A to the second electrode 52 in the magnetization reversal operation by supplying current from the power supply 95. Then, the magnetization direction of the magnetization free layer 3 is set downward (see FIGS. 4A and 4D). When making the magnetization direction of the magnetization free layer 3 upward, it can be reversed by applying a magnetic field to the pixel 8C (pixel array 80C), for example.

  The spatial light modulator 10C prevents a current from flowing through the light modulation element 1D of the non-selected pixel 8C even if one of the two selection elements is a diode. Specifically, when a current for a magnetization reversal operation as shown by a thick broken line is supplied to the upper left pixel 8C in FIG. 13, a circuit in which a leakage current as shown by a broken line flows is generated by providing the diode Di1. Absent. In the spatial light modulator 10C, in particular, by applying a diode having a small size in plan view to one of the two selection elements, an increase in the size of the pixel can be suppressed.

  Furthermore, as shown in FIG. 14, the spatial light modulator 10D according to the modification of the fourth embodiment includes a first magnetization fixed layer 51 (first element structure MR1) and a second magnetization of the unipolar drive type light modulation element 1D. Diodes Di1 and Di2 are connected to the magnetization fixed layer 52 (second element structure MR2), respectively. Similar to the spatial light modulator 10C shown in FIG. 13, the light modulation element 1D supplies current only in one direction from the first electrode 51A and the third electrode 53A to the second electrode 52A, and reverses magnetization. Therefore, the diode Di1 has the anode connected to the first electrode 51A and the cathode connected to the first magnetization fixed layer 51 of the light modulation element 1D. The diode Di2 has the anode connected to the second magnetization fixed layer 52 and the cathode connected to the second electrode. 52A is connected.

  In the spatial light modulator 10D according to this modification, in the magnetization reversal operation, all of the electrodes 51A, 52A, 53A are connected to the power source 95A, and the first electrode 51A (first magnetization) is also applied to the non-selected pixel 8D. Current can flow from the two directions of the fixed layer 11) and the third electrode 53A (third magnetization fixed layer 13) to the light modulation element 1D. Therefore, in the pixel array 80D of the spatial light modulator 10D, the electrodes 51A, 52A, and 53A are connected to the light modulation element 1D independently of each other as shown in FIG. Similar to the spatial light modulator 10 according to the first embodiment shown in FIG. 1 and FIG. 7, it extends in the XYZ directions.

  The spatial light modulator 10D prevents current from flowing through the light modulation element 1D of the non-selected pixel 8D even if the two selection elements are both diodes. Specifically, when a current for magnetization reversal operation as shown by a thick broken line is supplied to the upper left pixel 8D in FIG. 14, a circuit in which a leakage current as shown by a broken line flows by providing diodes Di1 and Di2 Does not occur. In the spatial light modulator 10D, a diode having a small size in plan view is applied to all of the selection elements, so that even if two selection elements are provided in one pixel, the size of the pixel does not increase. It is not necessary to provide wiring for supplying current to the power source.

  As described above, according to the spatial light modulator according to the fourth embodiment and the modification thereof, the current does not leak to the light modulation element of the non-selected pixel in both the write error detection and the magnetization reversal operation. In the detection, the response speed can be further increased. In the magnetization reversal operation, the loss due to the leakage current can be suppressed, so that the power can be saved.

  As mentioned above, although each embodiment for implementing the light modulation element and the spatial light modulator of the present invention has been described, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the claims. Can be changed.

10, 10A, 10C, 10D Spatial light modulator 1, 1A, 1B, 1C, 1D Light modulator 11 First magnetization fixed layer 12 Second magnetization fixed layer 13 Third magnetization fixed layer 21, 22, 23, 2 Intermediate layer 3 Magnetization free layer 51 1st electrode, X electrode (electrode)
52 Second electrode, Y electrode (electrode)
53 Third electrode, Z electrode (electrode)
7 Substrate 80, 80B, 80C, 80D Pixel array 8, 8A, 8B, 8C, 8D Pixel 90 Current control unit 94 Pixel selection unit (pixel selection means)
95,95A power supply (current supply means)
96 Sub power supply (sub current supply means)
97 determination unit (pixel determination means)

Claims (8)

A spin-injection magnetization reversal element structure in which a magnetization free layer, an intermediate layer, and a magnetization fixed layer are laminated in this order on a substrate, and the direction of polarization of light incident from the side on which the magnetization free layer is laminated is changed. A light modulation element that reflects and emits light,
The magnetization fixed layer includes a first magnetization fixed layer, a third magnetization fixed layer, and a second magnetization fixed layer disposed between the first magnetization fixed layer and the third magnetization fixed layer in a plane direction. And having the intermediate layer sandwiched between the magnetization free layers,
The first magnetization pinned layer and the second magnetization pinned layer are pinned to magnetization in antiparallel directions, the third magnetization pinned layer is pinned to magnetization in the same direction as the first magnetization pinned layer,
By connecting one of a pair of electrodes to the first magnetization fixed layer and the third magnetization fixed layer and connecting the other of the pair of electrodes to the second magnetization fixed layer, and supplying a current, the magnetization An optical modulation element characterized in that the magnetization direction of the free layer changes.   2. The light modulation element according to claim 1, wherein the second magnetization fixed layer has a coercive force different from that of the first magnetization fixed layer and the third magnetization fixed layer.   The at least one of the first magnetization fixed layer, the third magnetization fixed layer, and the second magnetization fixed layer has a multilayer structure including a magnetic film exchange-coupled. Light modulation element. A spatial light modulator comprising: a substrate that transmits light; and a plurality of pixels that are two-dimensionally arranged on the substrate, wherein the light that has passed through the substrate and is incident on the plurality of pixels is reflected and emitted. A pixel is connected to the light modulation element according to any one of claims 1 to 3, a first electrode connected to the first magnetization fixed layer of the light modulation element, and the second magnetization fixed layer. And a third electrode connected to the third magnetization fixed layer,
Pixel selection means for selecting one or more pixels from the plurality of pixels and further selecting which of the two different directions of magnetization directions of the magnetization free layer of the light modulation element for the selected pixels;
Supplying the current to the light modulation element of the pixel selected by the pixel selection means with the first electrode and the third electrode as one of a pair of electrodes and the second electrode as the other of the pair of electrodes; Current supply means for setting the magnetization direction of the magnetization free layer of the light modulation element to the direction selected by the pixel selection means;
The pixel determination for determining that the magnetization direction of the magnetization free layer of the light modulation element to which the current supply means has supplied current is the direction selected by the pixel selection means, and a change in the resistance of the light modulation element. A spatial light modulator comprising: a pixel determination unit that performs detection. Sub-current supply means for supplying a current of a predetermined magnitude to the light modulation element of the pixel selected by the pixel selection means,
The pixel determination unit calculates a value of a voltage between the first electrode and the third electrode connected to the light modulation element supplied with a current to the sub-current supply unit, as a magnetization of the magnetization free layer. The pixel determination is performed by comparing with a threshold set in advance based on a resistance of the light modulation element when the direction is a direction selected by the pixel selection unit. Spatial light modulator.   The pixel includes a selection element that can freely disconnect electrical connection between the first magnetization fixed layer and the first electrode or between the third magnetization fixed layer and the third electrode. The spatial light modulator according to claim 4 or 5, characterized in that:   The pixel is between the first magnetization fixed layer and the first electrode, between the second magnetization fixed layer and the second electrode, and between the third magnetization fixed layer and the third electrode. The spatial light modulator according to claim 4 or 5, further comprising a selection element that allows electrical connection to be freely disconnected at two selected locations.   8. The pixel according to claim 4, wherein the pixel includes two or more of the light modulation elements connected in parallel to the first electrode, the second electrode, and the third electrode. The spatial light modulator according to one item.

Images