JP5679690B2 - Spin injection magnetization reversal device, magnetic random access memory and spatial light modulator using the same - Google Patents

Description

  The present invention relates to a spin-injection magnetization reversal element, a magnetic random access memory, or a spatial light modulator that uses the properties of a magnetic film.

  The film surface vertical conduction type magnetoresistive element (magnetoresistance effect element) includes two or more layers of magnetic films, and current is supplied perpendicularly to the film surface from vertically connected electrodes (wiring). Due to the spin injection magnetization reversal, the magnetization direction of a part of the magnetic film is rotated (reversed) by 180 °, and becomes the same direction or the opposite direction to another magnetic film that does not change the magnetization direction. In this magnetoresistive element, the resistance between the upper and lower electrodes changes depending on whether the magnetizations of the magnetic films are in the same direction or in different directions, so that 1-bit data is written / read using this. be able to. That is, the magnetoresistive element constitutes a magnetic random access memory (MRAM) by arranging memory cells including the magnetoresistive element in a matrix. Since the magnetoresistive element is extremely small in size and operates at a high speed of magnetization reversal, research and development of an MRAM and a magnetoresistive element as a large-capacity magnetic memory are underway.

  As a magnetic material of the magnetoresistive element, a Co—Fe alloy or the like that exhibits magnetization in the film surface direction has been conventionally studied, but recently, in order to further increase the capacity and power saving of the MRAM, Attention has been focused on magnetic materials that exhibit magnetization in the direction perpendicular to the film surface (having perpendicular magnetic anisotropy) that can further miniaturize the magnetoresistive element and reduce the current required for magnetization reversal. Among such perpendicular magnetic anisotropy materials, an alloy of rare earth metal and transition metal (RE-TM alloy) is attracting attention as a ferrimagnetic perpendicular magnetic anisotropy material. It is promising as a magnetic material for elements (see, for example, Patent Document 1).

  Another application of the magnetoresistive element is a light modulation element mounted on a pixel of a spatial light modulator. The magnetoresistive element as the light modulation element reverses the magnetization direction of the magnetic film by the magneto-optic effect in which the direction of polarization of the light reflected or transmitted by the magnetic film changes (rotates). Is changed to a binary value. Also in the spatial light modulator, research and development are being conducted in the same manner as the MRAM as a material replacing the conventional liquid crystal in order to achieve high definition and high speed (for example, see Patent Document 2). It is desirable that the magnetoresistive element used as the light modulation element has a large change in polarization direction (a large degree of light modulation). Therefore, it is desirable for the light modulation element to increase the degree of light modulation by the polar Kerr effect by using a magnetoresistive element having perpendicular magnetic anisotropy and making light enter the film surface almost perpendicularly (for example, non-polarity effect). Patent Document 1).

JP 2008-283207 A (Claim 6, Claim 11, Paragraph 0027) JP 2008-83686A (Claim 1, FIG. 1A)

K. Aoshima et. Al, “Magneto-optical and spin-transfer switching properties of current-perpendicular-to plane spin valves with perpendicular magnetic anisotropy.”, IEEE Transactions on Magnetics, Vol.44, No.11, pp.2491- 2495 (2008)

  Magnetism is reversed by applying a magnetic field of a specific magnitude or more in the opposite direction to its own magnetization from the outside, but in spin injection magnetization reversal, the spin in the direction opposite to the electrons of the magnetic substance is reversed. Is injected, that is, the current is supplied in the opposite direction, thereby reversing the magnetization. The current required for spin injection magnetization reversal (reversal current) increases as the coercivity of the magnetic material increases, as in the case of magnetization reversal by an external magnetic field (external magnetic field). The magnitude of the external magnetic field, ie the coercive force, for reversing the magnetization of a single magnetic body in one direction and in the opposite direction has the same absolute value. However, in a magnetoresistive element that performs spin injection magnetization reversal, a magnetic film (magnetization fixed layer) in which magnetization is fixed (magnetization reversal) is extremely thin, apart from a magnetic film (magnetization free layer) that undergoes magnetization reversal. They are stacked with a nonmagnetic film (intermediate layer) in between. In such a configuration, since the magnetic field leaked from the magnetization fixed layer acts on the magnetization free layer, the magnetization of the magnetization free layer is in the same direction as the magnetization fixed layer even in the absence of external magnetic field application or current supply. There is a tendency to try. Therefore, in the magnetoresistive element, the reversal current that makes the magnetization of the magnetization free layer the same direction as the magnetization fixed layer (makes the magnetization parallel) or the opposite direction (makes the magnetization antiparallel) is absolute. The value increases.

  In a device including a magnetoresistive element (MRAM, spatial light modulator, etc.), supplying each current for making the magnetization of the magnetoresistive element parallel and antiparallel so that their absolute values are different from each other is This is not preferable because the drive circuit becomes complicated. In addition, increasing the supply current to make the magnetization antiparallel prevents the power saving of the device and may cause the magnetization of the magnetization fixed layer to be reversed, resulting in unstable operation of the magnetoresistive element. Become. Therefore, the apparatus is provided with magnetic field applying means such as arranging magnets around the arrangement of the magnetoresistive elements so that the reversal currents that make the magnetization of the magnetoresistive elements parallel and antiparallel are almost the same in absolute value. It is necessary to apply a magnetic field (bias magnetic field) in the direction opposite to the leakage magnetic field of the magnetization fixed layer. However, in order to reduce the size of the apparatus and reduce the cost, a magnetoresistive element that does not require a magnetic field applying unit is desirable.

  The present invention was devised in view of the above problems, and provides a spin injection magnetization reversal element that does not require application of a bias magnetic field, and a magnetic random access memory and a spatial light modulator provided with this spin injection magnetization reversal element. With the goal.

  In order to solve the above-mentioned problems, the present inventors have recorded a magneto-optical (MO) disk among RE-TM alloys, which are ferrimagnetic materials that are preferable as a perpendicular magnetic anisotropic material and have a low apparent saturation magnetization. It has been found that a Tb—Fe—Co alloy, which is widely used as a material, is applied to the magnetization fixed layer of the spin-injection magnetization reversal element, and further its composition is limited to suppress magnetic field leakage.

That is, the spin injection magnetization reversal element according to the present invention includes a magnetization fixed layer, an intermediate layer, and a magnetization free layer stacked, and a spin injection magnetization reversal to which a current is supplied via a pair of upper and lower electrodes. In the element, the magnetization fixed layer includes a Tb—Fe—Co alloy, and the composition of the Tb—Fe—Co alloy is Tb _x (Fe, Co) _1-x ( 0.226 ≦ x ≦ 0.25). ). Furthermore, the composition of the Tb—Fe—Co alloy is Tb _x (Fe _1−y Co _y ) _1−x ( 0.226 ≦ x ≦ 0.25, 0.4 <y <0.67). Is preferred.

  With this configuration, the Tb—Fe—Co alloy exhibiting strong perpendicular magnetic anisotropy can be applied to the magnetization fixed layer of the spin-injection magnetization reversal element, and miniaturization can be achieved, and the content of Tb, which is a rare earth metal, is limited. As a result, the saturation magnetization is controlled to suppress the leakage of the magnetic field from the magnetization fixed layer, and the magnetization reversal operation of the magnetization free layer is stabilized. In addition, by including Fe and Co as transition metals, the Curie temperature of the magnetization fixed layer is increased, and a spin-injection magnetization reversal element having excellent heat resistance is obtained.

  Furthermore, in the spin injection magnetization switching element according to the present invention, it is preferable that the magnetization free layer contains two or more elements selected from Tb, Gd, Fe, Co, Ni, Pt, and Pd. With this configuration, the magnetization reversal operation is stabilized because the magnetization free layer also exhibits strong perpendicular magnetic anisotropy similar to the magnetization fixed layer.

  The magnetic random access memory according to the present invention comprises a memory cell including the spin injection magnetization reversal element and a pair of electrodes connected to the upper and lower sides thereof, and a plurality of the memory cells are two-dimensionally arranged. With this configuration, the magnetic random access memory can miniaturize the spin-injection magnetization reversal element that records 1 bit as perpendicular magnetic anisotropy, and the data write / read operation is stable.

  Further, the spatial light modulator according to the present invention is such that the spin injection magnetization reversal element is a light modulation element, and the spin injection magnetization reversal element and a pair of electrodes connected to the top and bottom thereof are provided in the pixel. Is done. That is, the spatial light modulator supplies a predetermined current to a plurality of pixels arranged two-dimensionally, a pixel selection unit that selects one or more pixels from the plurality of pixels, and a pixel selected by the pixel selection unit. Current supply means, and changes the polarization direction of the light incident on the pixel selected by the pixel selection means in a specific direction and emits the light. With this configuration, the spatial light modulator can increase the light modulation degree by the polar Kerr effect by using the magnetoresistive element constituting the light modulation element provided in the pixel as the perpendicular magnetic anisotropy, and can perform the pixel selection operation. Stabilize.

  According to the spin-injection magnetization reversal element according to the present invention, a perpendicular magnetic anisotropy magnetoresistive element with stable magnetization reversal operation can be obtained without application of a bias magnetic field. According to the magnetic random access memory according to the present invention, it is possible to achieve a large capacity and stable data writing / reading operation at high speed. Further, according to the spatial light modulator according to the present invention, the pixel selectivity can be improved with high definition and high speed response.

It is sectional drawing of the magnetoresistive element which concerns on one Embodiment of this invention. It is a perspective view explaining typically operation of a magnetoresistive element concerning one embodiment of the present invention. In the magnetization curve of the magnetoresistive element, (a) is an ideal model and (b) is an actual model. It is a top view which shows typically the structure of the spatial light modulator which concerns on one Embodiment of this invention. FIG. 5 is a schematic diagram of a display device using the spatial light modulator shown in FIG. 4 and corresponds to a cross-sectional view taken along the line AA in FIG. 4. It is a top view which shows typically the structure of the recording device provided with the magnetic random access memory which concerns on one Embodiment of this invention. FIG. 7 is a cross-sectional view of the magnetoresistive element according to the embodiment of the present invention and a memory cell including the magnetoresistive element, and is a cross-sectional view taken along line BB of FIG.

  Hereinafter, embodiments for realizing a spin transfer magnetization reversal element, a magnetic random access memory, and a spatial light modulator according to the present invention will be described with reference to the drawings.

[Magnetic resistance element]
(Constitution)
As shown in FIGS. 1 and 2, a magnetoresistive element (spin injection magnetization reversal element) 1 according to an embodiment of the present invention includes a magnetization fixed layer 11, an intermediate layer 12, a magnetization free layer 13, and a protective layer 14 (FIG. 2 is omitted), and is connected to the upper electrode 2 and the lower electrode 3 (hereinafter referred to as electrodes 2 and 3 as appropriate), which are a pair of electrodes, and is supplied with a current perpendicular to the film surface. The The magnetoresistive element 1 is a CPP-GMR having a magnetization fixed layer 11 whose magnetization is fixed in one direction and a magnetization free layer 13 whose magnetization direction is rotatable, with an intermediate layer 12 which is nonmagnetic or an insulator interposed therebetween. A spin-injection magnetization reversal element such as a (Current Perpendicular to the Plane Giant MagnetoResistance) element or a TMR (Tunnel MagnetoResistance) element. Furthermore, in order to protect these layers from damage in the manufacturing process, a protective layer 14 is provided as the uppermost layer. It should be noted that the stacking order of the magnetization fixed layer 11 and the magnetization free layer 13 may be switched. Each layer constituting the magnetoresistive element 1 is formed with a lower electrode 3 and is continuously formed and laminated by a known method such as a sputtering method or a molecular beam epitaxy (MBE) method. And it is processed into a desired planar view shape by an ion beam milling method or the like. In FIG. 2, the shape of the magnetoresistive element 1 in plan view is rectangular, but this is not restrictive. Hereinafter, details of each layer constituting the magnetoresistive element 1 will be described.

The magnetization fixed layer 11 is made of a Tb—Fe—Co alloy (hereinafter referred to as a TbFeCo alloy) which is an amorphous alloy, and its composition is 0.20 ≦ x ≦ when expressed by Tb _x (Fe, Co) _1-x. 0.25. Moreover, it is preferable that the thickness shall be 1-50 nm. While transition metals (TM) Fe and Co exhibit a uniform magnetic moment in one direction (+ z direction), rare earth metal (RE) Tb has a reverse direction (−z The magnetic moment is distributed so as to form a conical side surface extending in the center (axis), and the magnetic moment as a whole is canceled in the x and y directions and becomes only the −z direction. In a RE-TM alloy such as a TbFeCo alloy, a difference in magnitude occurs between the magnetic moment of Fe and Co in the + z direction and the magnetic moment of Tb in the -z direction, resulting in ferrimagnetism that exhibits magnetization as a whole. . In particular, when the rare earth metal is Tb, the magnetic moment tends to be dominant, and strong perpendicular magnetic anisotropy is exhibited. Further, since a part of the magnetic moment is canceled out in the ferrimagnetic material, the saturation magnetization is apparently lowered. By suppressing the saturation magnetization Ms _pin of the magnetization fixed layer 11, the leakage magnetic field from the magnetization fixed layer 11 can be reduced and the magnetization reversal of the magnetization free layer 13 can be stabilized. On the other hand, the magnetization fixed layer 11 has a sufficiently large coercive force Hc _pin , preferably 5 kOe or more, and preferably 0.5 kOe or more larger than the coercive force Hc of the magnetization free layer 13 (1 Oe≈79.577 A / m). Such a coercive force Hc _pin can be obtained by adjusting the composition and film thickness of the TbFeCo alloy. As described above, since the coercive force Hc _pin is sufficiently larger than the coercive force Hc of the magnetization free layer 13, the magnetization of the magnetization fixed layer 11 is not easily rotated by current supply or the like, and is fixed in one direction. The magnetization fixed layer 11 may have a multilayer structure or the like laminated with other materials in addition to the TbFeCo alloy.

When the TbFeCo alloy constituting the magnetization fixed layer 11 is less than Tb: 20 at%, the magnetic moment in the + z direction of Fe and Co is dominant, the magnitude of the perpendicular magnetic anisotropy energy Ku is insufficient, and the strong perpendicular Magnetic anisotropy cannot be obtained. On the other hand, when Tb exceeds 25 at%, the magnetic moment in the −z direction of Tb is too large, and the saturation magnetization Ms _pin is not sufficiently lowered, and the leakage magnetic field is increased. Accordingly, Tb: 20 to 25 at%, that is, 0.20 ≦ x ≦ 0.25 when expressed by Tb _x (Fe _1−y Co _y ) _1−x . Further, since the Curie temperature is increased by containing two kinds of transition metals, Fe and Co, the magnetization of the magnetization fixed layer 11 is maintained even at a high temperature, and the operation of the magnetoresistive element 1 is stabilized. Further, since the magnetic Kerr effect can be increased, the magnetoresistive element 1 suitable as an optical modulation element is obtained. Specifically, it is preferable that 0.4 <y <0.67 in the composition.

The intermediate layer 12 is provided between the magnetization fixed layer 11 and the magnetization free layer 13. If the magnetoresistive element 1 is a TMR element, the intermediate layer 12 is made of an insulator such as MgO, Al ₂ O ₃ , HfO ₂ or a laminated film containing an insulator such as Mg / MgO / Mg. The thickness is preferably 0.1 to 2 nm. If the magnetoresistive element 1 is a CPP-GMR element, the intermediate layer 12 is made of a nonmagnetic metal such as Cu, Ag, or Al, and the thickness is preferably 1 to 10 nm.

  The magnetization free layer 13 can be made of a known magnetic material as a magnetization free layer such as a CPP-GMR element or a TMR element having perpendicular magnetic anisotropy, and the thickness is preferably 1 to 20 nm. . Specifically, for example, a CoPt, CoPd alloy, or a multilayer film of [Co / Pt] × n, [Co / Pd] × n, or MnBi containing a transition metal such as Fe, Co, or Ni and Pt, Pd, or the like. Mn-containing magnetic alloys such as PtMnSb alloy. Further, similarly to the magnetization fixed layer 11, it may be composed of a RE-TM alloy including a TbFeCo alloy, and examples of rare earth metals include Sm, Eu, and Gd in addition to Tb. Among these materials, alloys and multilayer films containing two or more elements selected from Tb, Gd, Fe, Co, Ni, Pt, and Pd are particularly strong because they have a large perpendicular magnetic anisotropy energy Ku. Showing perpendicular magnetic anisotropy. Furthermore, as will be described later, when the magnetoresistive element 1 is applied to a light modulation element, a GdFe, GdFeCo alloy having a high degree of light modulation is preferable.

The magnetization free layer 13 is also preferably made of a material having a low saturation magnetization Ms such as a RE-TM alloy. Since the reversal current density is proportional to the square of the saturation magnetization, if the saturation magnetization Ms of the magnetization free layer 13 is low, the reversal current Ic (of the magnetization free layer 13) of the magnetoresistive element 1 can be reduced. On the other hand, the coercive force Hc is set to a certain level or more so that the magnetization direction of the magnetization free layer 13 is maintained even when the magnetoresistive element 1 is not constantly supplied with current, and the magnetization can be easily reversed. The coercive force Hc _pin of the magnetization fixed layer 11 is made sufficiently smaller. Specifically, it is preferably in the range of 0.2 to 1 kOe. The coercive force Hc also depends on the composition and composition of the material constituting the magnetization free layer 13, but the magnetization free layer 13 is made thinner than the magnetization fixed layer 11 to be smaller than the coercivity Hc _pin of the magnetization fixed layer 11. Can do.

  The protective layer 14 is composed of a single layer of Ta, Ru, Cu, or two layers of Cu / Ta, Cu / Ru. In addition, when setting it as the said 2 layer structure, all make Cu inside (lower layer). When the thickness of the protective layer 14 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 free layer 13 and the like in the manufacturing process is further improved. do not do. Therefore, the thickness of the protective layer 14 is preferably 1 to 10 nm.

(Operation)
The magnetization reversal operation of the magnetoresistive element 1 will be described with reference to FIGS. As shown in FIG. 3A as an ideal model of the magnetization curve of the ferromagnetic material, when the magnetic field (magnetic field) H is applied while changing, the magnetization fixed layer 11 and the magnetization free layer 13 each change the magnetization M. When the magnetic field H exceeds the respective coercive forces + Hc _pin and + Hc in the positive direction, the magnetization M rises sharply and changes from negative to positive. On the other hand, when the magnetic field H exceeds the coercive force −Hc _pin , −Hc in the negative direction, the magnetization M drops sharply and changes from positive to negative. The magnetization M is positive and negative and the magnetization direction is different by 180 °. Since the magnetization fixed layer 11 and the magnetization free layer 13 have perpendicular magnetic anisotropy, the magnetization is upward or downward. In the present embodiment, when the magnetization M shown in FIG. 3 is positive, the magnetization is downward in FIG. When the magnetic field H is H ≦ −Hc _pin , since the magnetization fixed layer 11 and | Hc | <| Hc _pin |, the magnetization free layer 13 is magnetized upward (see FIG. 2A). When this is initially applied and thereafter the magnetic field H is changed in the range of −Hc _pin <H <+ Hc _pin and from H ≦ −Hc to H ≧ + Hc, the magnetization M of the magnetization fixed layer 11 is negative, that is, FIG. As shown in a) and (b), only the magnetization free layer 13 is fixed in the upward direction, and the magnetization M changes between positive and negative along the hysteresis loop (magnetization curve) shown in FIG. Thus, the magnetization direction is reversed up and down. In particular, when the initial application is made sufficiently large in the negative direction with respect to the −Hc _pin and thereafter the magnetic field H is changed so as not to approach the + Hc _pin , the magnetization M of the magnetization fixed layer 11 is the saturation magnetization− _Stays near the Ms _pin .

The magnetoresistive element 1 that is a spin injection magnetization reversal element changes the magnetization direction of the magnetization free layer 13 by injecting electrons having spins in the opposite direction instead of applying a magnetic field, that is, by supplying current in the opposite direction. Inversion (spin injection magnetization reversal, hereinafter referred to as magnetization reversal as appropriate) is performed in the same direction as the magnetization direction of the magnetization fixed layer 11 or in a direction different by 180 °. In FIG. 2A, the magnetization of the magnetization free layer 13 shows the same upward direction as the magnetization direction of the magnetization fixed layer 11. Hereinafter, this state is referred to as that the magnetization of the magnetoresistive element 1 is parallel (P: Parallel). When the current I ₁ is supplied from the magnetization fixed layer 11 side to the magnetization free layer 13 with the upper electrode 2 set to “−” and the lower electrode 3 set to “+” to the magnetoresistive element 1 in this state, the magnetization free layer As shown in FIG. 2B, the magnetization of 13 is reversed and becomes the downward direction opposite to the magnetization direction of the magnetization fixed layer 11. Hereinafter, this state is referred to as anti-parallel (AP) in which the magnetization of the magnetoresistive element 1 is antiparallel. On the contrary, when the current I ₀ is supplied downward from the magnetization free layer 13 side to the magnetization fixed layer 11 with the upper electrode 2 set to “+” and the lower electrode 3 set to “−”, the magnetization of the magnetization free layer 13 is reversed again. Then, it returns to the upper direction and becomes the state shown in FIG.

The magnitudes of the supply currents I ₀ and I ₁ for reversing the magnetization of the magnetoresistive element 1 in parallel and antiparallel are equal to or greater than the current (reversal current) required for spin injection magnetization reversal in the negative and positive directions, respectively. In the spin injection magnetization reversal characteristics of the magnetoresistive element 1, the horizontal axis (magnetic field axis) in FIG. 3A corresponds to the current axis, and the magnitude of the reversal current corresponds to the coercivity of the magnetization free layer 13. . Therefore, if the magnitudes (absolute values) of the negative and positive coercivity of the magnetization free layer 13 are the same as shown by -Hc and + Hc in FIG. 3A, the reversal current is also positive and negative. Are the same. When indicating this reversal current -Ic, at _{+ Ic, I 0 ≦ -Ic,} I 1 ≧ + Ic becomes, | I ₀ | = | can be set as | I _1.

If the magnetization of the magnetoresistive element 1 indicates either parallel or antiparallel magnetization, the coercive force of the magnetization free layer 13 is supplied until a current (I ₀ , I ₁ ) for reversing the magnetization is supplied. Magnetization is maintained by Hc. Thus, since the magnetization is retained in the magnetoresistive element 1, a current that temporarily reaches the current value that reverses the magnetization direction, such as a pulse current, is used as the current supplied to the magnetoresistive element 1. Can do.

However, in the actual magnetoresistive element 1, a magnetic field leaks from the magnetization fixed layer 11 and acts on the magnetization free layer 13 via the intermediate layer 12. In FIG. 2, as described above, the magnetization M of the magnetization fixed layer 11 is in the vicinity of the saturation magnetization -Ms _pin , and a leakage magnetic field acts in the negative direction. For this reason, in the magnetization free layer 13, the magnetization M does not change positively unless a larger magnetic field H is applied in the positive direction, and conversely, the magnetization free layer 13 easily changes negatively with the small magnetic field H in the negative direction. Since the limit value of the magnetization M of the magnetization free layer 13 does not change from the saturation magnetic fields −Ms and + Ms, therefore, the magnetization curve of the magnetization free layer 13 shifts to the positive in the magnetic field H direction as shown in FIG. At this time, since the coercive forces Hc ₀ and Hc ₁ are also shifted in the positive direction from −Hc and + Hc, respectively, a deviation occurs between the absolute values (| Hc ₀ | <| Hc ₁ |). This shift amount increases as the leakage magnetic field from the magnetization fixed layer 11 increases, that is, as the saturation magnetization Ms _pin of the magnetization fixed layer 11 increases.

As described above, since the magnitude of the switching current of the magnetoresistive element 1 corresponds to the magnitude of the coercive force of the magnetization free layer 13, if the coercive force Hc _0, Hc ₁ of the magnetization free layer 13, the inversion of the respective positive and negative The magnitude of the current is also different. Coercive force Hc _0, Hc ₁ shift amount _{ΔHc (ΔHc = | Hc 1 |} -Hc, Hc- | Hc 0 |) is large beyond 10Oe, | Hc ₀ | a | Hc ₁ | difference (.DELTA.Hc × 2) is large, the reversal current is positive and negative, and the difference in absolute value is large. With respect to such a magnetoresistive element 1, if | I ₀ | = | I ₁ | with respect to the supply currents I ₀ and I ₁ , there is a possibility that problems such as lack of stability in the magnetization reversal operation may occur. Therefore, in such a case, a magnetic field applying means such as a magnet is provided in the vicinity of the magnetoresistive element 1, and a magnetic field (bias magnetic field) is applied in the reverse positive direction in order to cancel the leakage magnetic field of the magnetization fixed layer 13. It is necessary to operate while. The magnetoresistive element 1 according to the present embodiment reduces the leakage magnetic field by limiting the composition of the TbFeCo alloy constituting the magnetization fixed layer 13 as described above so that the saturation magnetization Ms _pin does not become high, and the magnetization free layer The amount of shift of the coercive force Hc of 13 is made sufficiently small (close to 0 Oe). That is, it is possible to suppress a phenomenon in which the spin injection magnetization reversal characteristics of the magnetoresistive element 1 are shifted to one side in the current axis direction. As a result, the positive magnetization reversal current and the negative magnetization reversal current are set to substantially the same magnitude (+ Ic, −Ic), and a stable spin injection magnetization reversal operation can be obtained without applying a bias magnetic field.

  As described above, the magnetoresistive element according to the present embodiment can provide a magnetoresistive element with stable magnetization reversal operation. As will be described later, the magnetoresistive element 1 generally has a pixel array of a magnetic random access memory (MRAM) or a spatial light modulator by two-dimensionally arranging a plurality of elements in the film surface direction. By supplying a predetermined current from 2 and 3, any one or more magnetoresistive elements 1 can be selectively reversed in magnetization.

  Note that the magnetoresistive element according to the present embodiment is configured to include one magnetization fixed layer, one intermediate layer, and one magnetization free layer. However, the present invention is not limited to this. For example, as in the dual pin structure, A magnetoresistive element including two magnetization fixed layers with an intermediate layer interposed between the upper and lower sides may be used.

[Spatial light modulator]
Hereinafter, an embodiment of a spatial light modulator provided in a pixel using the magnetoresistive element according to the present invention as a light modulation element will be described. In addition, the pixel in this specification refers to a means for displaying information (bright / dark) in the minimum unit of display by the spatial light modulator.

  A spatial light modulator 10 according to an embodiment of the present invention includes a pixel array 40 composed of pixels 4 arranged in a two-dimensional array on a substrate (see FIG. 5) as shown in FIG. Are provided with a current control unit 80 that selects and drives one or more pixels 4. The plane (upper surface) in this specification is a light incident surface of the spatial light modulator, and the spatial light modulator 10 reflects light incident on the pixel 4 (pixel array 40) from above and modulates the light. Thus, the reflective spatial light modulator is emitted upward.

  As shown in FIG. 4, the pixel array 40 includes a plurality of upper electrodes 2, 2... Striped in plan view, and a plurality of lower electrodes 3, 3 that are also striped and orthogonal to the upper electrode 2 in plan view. ,..., And one pixel 4 is provided at each intersection of the upper electrode 2 and the lower electrode 3. Accordingly, the pixels 4 are arranged in a two-dimensional array on the light incident surface of the spatial light modulator 10 to constitute the pixel array 40. In the present embodiment, the pixel array 40 is exemplified by a configuration including 16 pixels 4 of 4 rows × 4 columns. 4 and 5, the pixel 4 includes an upper electrode 2 and a lower electrode 3 as a pair of electrodes in the pixel 4, and a magnetoresistive element 1 sandwiched between these electrodes 2 and 3 from above and below. Is provided. Further, the insulating layers 6 are filled between the adjacent upper electrodes 2 and 2, the magnetoresistive elements 1 and 1, and the lower electrodes 3 and 3.

  As shown in FIG. 4, the current control unit 80 controls the upper electrode selection unit 82 that selects the upper electrode 2, the lower electrode selection unit 83 that selects the lower electrode 3, and the electrode selection units 82 and 83. A pixel selection section (pixel selection means) 84 and a power supply (current supply means) 81 that supplies current to the electrodes 2 and 3 are provided. These may be known ones and supply appropriate voltages and currents to reverse the magnetization of the magnetoresistive element 1.

  The upper electrode selection unit 82 selects one or more of the upper electrodes 2, and the lower electrode selection unit 83 selects one or more of the lower electrodes 3, and each supplies a predetermined current from the power source 81. The pixel selection unit 84 selects one or more specific pixels 4 of the pixel array 40 based on, for example, an external signal (not shown), and connects the electrodes 2 and 3 connected to the selected pixel 4 to the electrode selection units 82 and 83. To select. The power supply 81 supplies an appropriate voltage / current to reverse the magnetization of the magnetoresistive element 1 provided in the selected pixel 4. With such a configuration, a specific pixel 4 is selected, and a predetermined current is supplied to the magnetoresistive element 1 of this pixel 4 to reverse the magnetization. In FIG. 4, the power supply 81 is connected to one end of each of the electrodes 2 and 3 via the electrode selection units 82 and 83, but may be connected to both ends. By connecting to both ends, the response speed can be increased and the operation variation between pixels can be reduced.

  Details of the configuration of the pixel 4 of the spatial light modulator 10 will be described with reference to FIGS. 4 and 5. The upper electrode 2 is disposed on the magnetoresistive element 1 as shown in FIG. 5, and extends in a strip shape in the lateral direction as shown in FIG. One upper electrode 2 supplies a current to each of the magnetoresistive elements 1 of the plurality of pixels 4, 4,... Arranged in one horizontal row. On the other hand, the lower electrode 3 is disposed under the magnetoresistive element 1 and extends in a strip shape in the vertical direction. One lower electrode 3 supplies a current to each of the magnetoresistive elements 1 of the plurality of pixels 4, 4,... Arranged in one vertical column. The upper electrode 2 is made of a transparent electrode material so as not to block incident light and outgoing light of the magnetoresistive element 1. On the other hand, the lower electrode 3 is made of an electrode metal material having excellent conductivity. The pixels 4 are formed on the pixel array 40 by being arranged on a known substrate such as a Si substrate whose surface is thermally oxidized.

  As shown in FIG. 4, the magnetoresistive element 1 is arranged in a portion where the upper electrode 2 and the lower electrode 3 overlap in a plan view, and is sandwiched and connected to the electrodes 2 and 3 from above and below. The magnetoresistive element 1 has a function as a light modulating element in the spatial light modulator 10, but its configuration is the same as the magnetoresistive element 1 according to the present invention shown in FIGS. Description is omitted. The planar view shape of the magnetoresistive element 1 is a square in the present embodiment, but is not limited to this. In addition, one magnetoresistive element 1 is arranged for one pixel 4. For example, a plurality of magnetoresistive elements such as (1 × 3), (2 × 2), and the like are provided in one pixel 4 in the surface direction. Element 1 may be provided.

The upper electrode 2 is made of a transparent electrode material so that light can pass therethrough. Transparent electrode materials include, for example, indium zinc oxide (IZO), indium tin oxide (ITO), tin oxide (SnO ₂ ), antimony oxide-tin oxide system (ATO), oxidation zinc (ZnO), fluorine-doped tin oxide (FTO), consisting of a known transparent electrode material such as indium oxide (in ₂ O _3). In particular, IZO is most preferable in terms of specific resistance and ease of film formation. These transparent electrode materials are formed into a film by a known method such as a sputtering method, a vacuum deposition method, or a coating method.

  When the electrode (wiring) is made of a transparent electrode material, it is preferable to provide a metal film between the electrode and the magnetoresistive element 1 connected to the electrode. That is, in the upper electrode 2 made of a transparent electrode material, it is preferable to laminate a metal film as a base layer between the magnetoresistive element 1 (not shown). By interposing a metal film between the magnetoresistive element 1 and the upper electrode 2 made of a transparent electrode material having a resistance higher than that of the electrode metal material, the contact resistance between the upper electrode 2 and the magnetoresistive element 1 is reduced. To increase the response speed.

  As the metal constituting the underlayer, for example, Au, Ru, Ta, or an alloy composed of two or more of these metals can be used, and these metals are formed by a known method such as a sputtering method. The Then, in order to further reduce the contact resistance by improving the adhesion between the underlayer and the layer above it, that is, the transparent electrode, the metal film serving as the underlayer is continuously formed in the vacuum processing chamber with the transparent electrode material. It is preferred that If the thickness of the underlayer is less than 1 nm, it is difficult to form a continuous film, while if it exceeds 10 nm, the amount of transmitted light is reduced. Therefore, the preferable thickness of the underlayer is 1 to 10 nm.

  The lower electrode 3 is made of a general electrode metal material such as a metal such as Cu, Al, Au, Ag, Ta, Cr, or an alloy thereof. Then, it is processed into a stripe shape by a known method such as a sputtering method, by film formation, photolithography, etching, lift-off method, or the like.

The insulating layer 6 is arranged between the adjacent upper electrodes 2 and 2 (not shown in FIG. 5) and between the lower electrodes 3 and 3 to insulate them from each other, and is a region without the magnetoresistive element 1 in plan view. In order to insulate between the electrodes 2 and 3 and to seal the side surface of the magnetoresistive element 1, the magnetoresistive elements 1 and 1 are disposed. Here, when an oxide such as SiO ₂ is disposed as the insulating layer 6 between the magnetoresistive elements 1 and 1, an oxygen (O) -containing film such as an oxide is usually supplied with an atmospheric gas containing oxygen. While forming the film. At this time, if the exposed end surface (side surface) of the magnetoresistive element 1 includes a TbFeCo alloy constituting the magnetization fixed layer 11 and further a RE-TM alloy in the magnetization free layer 13, these alloys are oxidized and the magnetic field is increased. The characteristics may change and affect the magnetization reversal operation or the like of the magnetoresistive element 1. Specifically, when the rare earth metal such as Tb of the RE-TM alloy is oxidized and changed to a composition having a high proportion of transition metals such as Fe and Co, the coercive force Hc _pin is lowered and the saturation magnetization Ms _pin When the oxidation increases and the oxidation further proceeds, the properties as a ferrimagnetic material cannot be maintained, and the perpendicular magnetic anisotropy is lost. Further, the heat treatment in the process after the film formation of SiO ₂ and the heat generated during the operation cause the RE-TM alloy to be oxidized by the oxygen (O) of SiO ₂ from the interface or side surface in contact with SiO ₂ of the magnetoresistive element 1. There is a risk of progress.

Therefore, in the spatial light modulator 10 to which the magnetoresistive element 1 according to the present invention is applied, a non-oxide is formed between the magnetoresistive elements 1 and 1 as the insulating layer 6, in particular, between the magnetoresistive elements 1 and 1. It is preferable to apply an insulating material. As such an insulating material, for example, silicon nitride (the main composition is Si ₃ N ₄ , hereinafter referred to as Si—N) can be given. Note that a general insulating material such as SiO ₂ or Al ₂ O ₃ is applied to an insulating material disposed in a region not in contact with the magnetoresistive element 1 such as between the upper electrodes 2 and 2 and between the lower electrodes 3 and 3. May be.

  After the magnetoresistive element 1 is processed into a desired plan view shape, the insulating layer 6 is formed by sputtering Si-N or chemical vapor deposition (CVD) before forming the upper electrode 2 (forming an electrode material). ) And the like, and deposited between the magnetoresistive elements 1 and 1, and then Si—N on the magnetoresistive element 1 is removed by etching, CMP (Chemical Mechanical Polishing), or the like. Can be formed. Alternatively, Si-N may be deposited with the resist used as a mask remaining in the processing of the magnetoresistive element 1, and the entire Si-N may be removed (lift-off).

(Spatial light modulator pixel selection operation)
Next, the pixel selection operation of the spatial light modulator 10 will be described as a display device using the spatial light modulator 10 with reference to FIG. The electrodes 2 and 3 are connected to the current control unit 80 as described above. Further, as shown in FIG. 5, a light source 93 that irradiates light toward the pixel array 40 and a light source 93 that irradiates light above the pixel 4 (pixel array 40) of the spatial light modulator 10 according to the present embodiment. An incident polarization filter 91 that converts the emitted light into polarized light before entering the pixel array 40, an output polarization filter 92 that transmits only polarized light in a specific direction from the light reflected and emitted from the pixel array 40, and an output polarization filter A detector 94 for detecting the light transmitted through 92 is disposed.

  The light source 93 includes, for example, a laser light source, a beam expander that is optically connected to the laser light source and expands the laser light, and a lens that converts the expanded laser light into parallel light (not shown). Since the light (laser light) emitted from the light source 93 is so-called natural light including various polarization components, the light is transmitted through the incident polarization filter 91 in front of the pixel array 40 to be light of one polarization component. . Hereinafter, light of one polarization component is referred to as polarization. This polarized light (incident polarized light) is incident on all the pixels 4 of the pixel array 40 at a predetermined incident angle. In each pixel 4, the incident polarized light passes through the upper electrode 2 and enters the magnetoresistive element 1, is reflected by the magnetization free layer 13 of the magnetoresistive element 1, is emitted as outgoing polarized light, and passes through the upper electrode 2 again. Then, the light is emitted from the pixel 4. All outgoing polarized light emitted from each pixel 4 reaches the outgoing polarization filter 92. The outgoing polarization filter 92 transmits only specific polarized light, here polarized light whose angle θap is rotated with respect to incident polarized light, and this transmitted outgoing polarized light is incident on the detector 94. Each of the polarizing filters 91 and 92 is a polarizing plate, and the detector 94 is an image display means such as a screen, a camera, or the like.

When light incident on the magnetoresistive element 1 is reflected by the magnetization free layer 13 which is a magnetic material and emitted, the polarization direction of the incident light changes (rotation) due to the Kerr effect (magnetic Kerr effect). As described above, the magnetization of the magnetoresistive element 1 is reversed according to the direction of the current supplied from the electrodes 2 and 3, and the magnetization is parallel / antiparallel for each pixel 4, that is, the magnetization of the magnetization free layer 13 is An upward / downward direction is shown (see FIGS. 2A and 2B). As described above, when the magnetization direction of the magnetization free layer 13 is different by 180 °, the incident light is emitted by rotating in the opposite directions at the same rotation angle, that is, the Kerr rotation angle θ _K of the magnetization free layer 13. When the optical rotation angles in the magnetoresistive element 1 having magnetization parallel and antiparallel are respectively expressed as θp and θap, θp = + θ _K and θap = −θ _{K are obtained} , and the magnetoresistive element 1 depends on the direction of the current from the electrodes 2 and 3. difference or the difference in angle of rotation of the polarization direction of the light emitted from | θp-θap | becomes 2 [Theta] _K.

Alternatively, the polarized light incident on the magnetoresistive element 1 passes through the magnetization free layer 13, the intermediate layer 12, and the magnetization fixed layer 11, is reflected on the upper surface of the lower electrode 3, and is again reflected in the magnetization fixed layer 11, the intermediate layer 12, and the magnetization The structure which permeate | transmits and emits the free layer 13 may be sufficient. In this case, by passing through the magnetization free layer 13 and the magnetization fixed layer 11 which are magnetic materials, the direction of polarized light depends on the respective predetermined angles (optical rotation) of the magnetization free layer 13 and the magnetization fixed layer 11 due to the Faraday effect. Rotate (rotate) to (angle). However, since the magnetization direction of the magnetization fixed layer 11 is constant, the change in the polarization of the emitted light from the magnetoresistive element 1 is determined by the Faraday rotation angle θ _F of the magnetization free layer 13. Since the emitted light is transmitted through the magnetization free layer 13 twice, the difference between the optical rotation angle | θp-θap | becomes 4? _F.

  The outgoing polarized light from the left and right pixels 4 and 4 in FIG. 4 rotated by an angle θap with respect to the incident polarized light passes through the outgoing polarizing filter 92 and reaches the detector 94, so that the pixel 4 is bright (white). ) Is displayed on the detector 94. On the other hand, since the outgoing polarized light from the central pixel 4 is blocked by the outgoing polarizing filter 92, the pixel 4 is dark (black) and displayed on the detector 94. Thus, light / dark (white / black) can be separated for each pixel, and light / dark can be switched by switching the direction of the current. As an initial state of the spatial light modulator 10, for example, all the upper electrodes 2 are “-” so that the magnetizations of the magnetoresistive elements 1 of all the pixels 4 are anti-parallel so that the whole is displayed white. All of the lower electrode 3 may be set to “+” to supply an upward current.

Here, the Kerr rotation angle θ _K and the Faraday rotation angle θ _F of the magnetization free layer 13 are larger as the incident angle of light is closer to the magnetization direction of the magnetization free layer 13 as described above. Therefore, it is desirable to make the incident angle perpendicular to the film surface, that is, 0 °, in order to maximize the optical rotation angle difference | θp−θap |. However, in this case, the optical path of the outgoing polarized light coincides with the optical path of the incident polarized light. To do. Therefore, the incident angle is slightly inclined so that the outgoing polarization filter 92, the detector 94, the light source 93, and the incoming polarization filter 91 are arranged so as not to block the optical paths of the incident polarized light and the outgoing polarized light, respectively. Specifically, the incident angle of polarized light is preferably 5 ° to 30 °. Alternatively, a half mirror may be disposed between the incident polarizing filter 91 and the pixel array 40 with an incident angle of 0 °, and only the outgoing polarized light may be reflected to the side. In this case, the output polarization filter 92 and the detector 94 are arranged on the side of the pixel array 40. Since the RE-TM alloy, particularly the GdFe alloy, has a large Kerr rotation angle and Faraday rotation angle, the magnetoresistive element 1 includes such an alloy in the magnetization free layer 13 so that the difference in optical rotation angle can be obtained. | θp−θap | can be made larger.

In another embodiment, the spatial light modulator according to the present invention may be a reflective spatial light modulator that enters from below as a configuration in which the top and bottom are switched. That is, the lower electrode is made of a transparent electrode material and the upper electrode is made of an electrode metal material. Light incident from below is transmitted through the lower electrode and reflected by the magnetoresistive element 1 or the upper electrode, and the lower electrode is again formed. Transmits and exits. Accordingly, the polarizing filters 91 and 92, the light source 93, and the detector 94 are disposed below the pixel array 40. In this case, the lower electrode is preferably provided with a base layer, which is a metal film, between the magnetoresistive element 1 and the contact resistance is reduced as in the case where the upper electrode is made of a transparent electrode material. In addition, the magnetoresistive element 1 is laminated by switching the positions of the magnetization fixed layer 11 and the magnetization free layer 13. Further, the substrate is made of a transparent substrate material such as SiO ₂ , Al ₂ O ₃ , MgO or the like so that light enters the pixel 4 from below and light emitted from the pixel 4 is irradiated again downward. Apply.

  As yet another embodiment, both the upper electrode and the lower electrode may be made of a transparent electrode material to form a transmissive spatial light modulator. At this time, the substrate is made of the transparent substrate material so that light transmitted through the pixel from above is further irradiated downward. In addition, the magnetoresistive element 1 may be laminated by switching the positions of the magnetization fixed layer 11 and the magnetization free layer 13. In such a spatial light modulator, the light source 93 and the incident polarizing filter 91 are disposed immediately above the pixel array 40, and the outgoing polarizing filter 92 and the detector 94 are disposed immediately below the pixel array 40, respectively, with an incident angle of 0 °. can do. Alternatively, a transmissive spatial light modulator that emits light from below and emits upward may be used.

  Furthermore, as a modification of each of these embodiments, for the upper electrode and the lower electrode that are made of a transparent electrode material and transmit light, the wiring portion is a hole in a region overlapping with the magnetoresistive element 1 in plan view as a metal material for an electrode The transparent electrode material may be provided only inside the hole (not shown). By using such an electrode, light can be incident on the magnetoresistive element 1 using a low-resistance metal material, so that a voltage drop due to wiring resistance is suppressed to save power and reduce operation variation between pixels. it can.

  As described above, according to the spatial light modulators according to the embodiments of the present invention and the modifications thereof, a pixel (pixel) using a magnetoresistive element including a TbFeCo alloy having a predetermined composition in a magnetization fixed layer as a light modulation element. Even if no magnetic field applying means is provided around the array, a spatial light modulator with stable pixel selection operation is obtained.

[Magnetic random access memory]
A magnetic random access memory (MRAM) 70 according to an embodiment of the present invention is a component that constitutes the recording device 9 together with the current control unit 80A, as shown in FIG. The MRAM 70 includes a plurality of bit lines 2A, 2A,... Striped in plan view, and a plurality of word lines 5, 5,... That are also striped and orthogonal to the bit line 2A in plan view. One memory cell 7 is provided for each intersection of 2A and the word line 5. In the present embodiment, the MRAM 70 is exemplified by a configuration including 16 memory cells 7 of 4 rows × 4 columns.

  As shown in FIG. 6, the current control unit 80A includes a bit line selection unit 82A that selects the bit line 2A, a word line selection unit 85 that selects the word line 5, and cells that control the selection units 82A and 85. A selection unit 84A and a power supply 81A for supplying current to the bit line 2A and the word line 5 are provided. The cell selection unit 84A selects, for example, one or more specific memory cells 7 of the MRAM 70 based on an external signal (not shown), and selects the bit line 2A and the word line 5 connected to the selected memory cell 7 as a bit line. The part 82A and the word line selection part 85 are selected. The power supply 81A supplies an appropriate voltage / current for operating the magnetoresistive element 1 and the MOSFET provided in the selected memory cell 7.

  As shown in FIG. 7, one memory cell 7 includes one magnetoresistive element 1 on the MOSFET. Specifically, the lower electrode 3A of the magnetoresistive element 1 is connected to the drain of the MOSFET via a wiring layer. In the memory cell 7, the upper electrode of the magnetoresistive element 1 constitutes the bit line 2 </ b> A of the MRAM 70. The configuration of the magnetoresistive element 1 is the same as that of the magnetoresistive element 1 according to the present invention shown in FIGS. Therefore, in the MRAM 70, in the layered direction region where the magnetoresistive element 1 and the bit line 2A and the lower electrode 3A connected to the upper and lower sides thereof are formed, the lower electrode 3A is not extended in the vertical direction in plan view. Otherwise, the configuration is the same as the pixel array 40 of the spatial light modulator 10 shown in FIG.

  In the MOSFET, for example, a source and a drain are formed on a p-type substrate made of silicon (Si). On the p-type substrate between the source and the drain, a gate electrode is formed via an insulating layer 6. In addition, contacts are formed and connected between the drain-wiring layer and between the wiring layer-lower electrode 3A. On the other hand, the word line 5 is connected to the source via a contact, and the word line 5 is grounded.

  These wirings, that is, the bit line (upper electrode) 2A, the lower electrode 3A, the wiring layer, the gate electrode, and the word line 5 are general metals such as Cu, Al, Au, Ag, Ta, Cr, and alloys thereof. It is made of a typical electrode metal material. Therefore, in the MRAM 70, unlike the pixel array 40 of the spatial light modulator 10, both electrodes connected to the top and bottom of the magnetoresistive element 1 are made of a metal material.

The insulating layer 6 is disposed between the blank portion in FIG. 7 and between the adjacent bit lines 2A and 2A (not shown in FIG. 7) to insulate the wirings from each other, and seals the side surface of the magnetoresistive element 1 To do. Here, the insulating layer 6 disposed at least between the magnetoresistive elements 1, 1, that is, between the bit line 2 </ b> A and the lower electrode 3 </ b> A is oxygenated like Si—N, like the pixel array 40 of the spatial light modulator 10. It is preferable to apply an insulating material that does not contain. Thereby, when the TbFeCo alloy constituting the magnetization fixed layer 11 of the magnetoresistive element 1 and further the RE-TM alloy in the magnetization free layer 13 are formed, these alloys are formed or formed during the formation (film formation) of the insulating layer 6. Later, the side surface of the magnetoresistive element 1 is not oxidized, and the characteristics such as the magnetization reversal operation of the magnetoresistive element 1 can be maintained. It should be noted that a general insulating material such as SiO ₂ or Al ₂ O ₃ is applied to the insulating material disposed between the bit lines 2A and 2A, the lower electrodes 3A and 3A, the other wirings, and the MOSFET region. Also good.

(Memory cell operation)
Next, the operation of the magnetoresistive element 1 in the memory cell 7 will be described with reference to FIGS. In the memory cell 7 (MRAM 70), the magnetization of the magnetoresistive element 1 is reversed in parallel / antiparallel by the current supply from the bit line 2A and the word line 5. As shown in FIG. 2A, the magnetoresistive element 1 having parallel magnetization has a low resistance in the direction perpendicular to the film surface, and a value of “0” is recorded at this time. On the other hand, as shown in FIG. 2B, the magnetoresistive element 1 having the antiparallel magnetization has a high resistance and a value of “1” is recorded. In the initial state of the memory cell 7, the magnetoresistive element 1 is in a state in which this magnetization is antiparallel.

In this initial state, when a predetermined voltage is applied to the gate electrode to turn on the MOSFET and the current control unit 80A causes the current I ₀ to flow downward from the bit line 2A to the MOSFET, Magnetization reversal of the magnetoresistive element 1 causes the magnetization to become parallel, and a value of “0” is written. On the contrary, when the current I ₁ flows to the magnetoresistive element 1 upward from the word line 5 to the bit line 2A via the MOSFET, the magnetization of the magnetoresistive element 1 becomes antiparallel again and a value of “1” is written. . In reading the value, a predetermined voltage may be applied between the bit line 2A and the word line 5 to detect the magnitude of the current flowing through the magnetoresistive element 1.

  As described above, according to the magnetic random access memory according to the embodiment of the present invention, using a magnetoresistive element including a TbFeCo alloy having a predetermined composition in a magnetization fixed layer, writing or the like can be performed without a magnetic field applying unit. Can be obtained.

  As mentioned above, although each embodiment for implementing the magnetoresistive element, the spatial light modulator, and the magnetic random access memory of the present invention has been described, the present invention is not limited to these embodiments. Various modifications are possible within the range shown in.

  In order to confirm the effect of the present invention, a sample of the magnetoresistive element (see FIG. 1) according to the embodiment of the present invention was produced. The magnetoresistive element is a CPP-GMR element in which a magnetization fixed layer: TbFeCo (10 nm), an intermediate layer: Cu (3 nm), a magnetization free layer: GdFeCo (10 nm), and a protective layer: Ru (3 nm) are stacked from the lower electrode side. It was. The composition of the TbFeCo alloy constituting the magnetization fixed layer was changed as shown in Table 1. In the sample, only one magnetoresistive element was provided, the shape in plan view was a rectangle of 100 nm × 300 nm, and Cu was applied to the upper electrode and the lower electrode. Specifically, first, Cu as the lower electrode and each layer of the magnetoresistive element are sequentially formed on the Si substrate whose surface is thermally oxidized by DC magnetron sputtering in an Ar atmosphere and 0.1 Pa in order. Laminated. Next, in order to simulate the heat treatment in the subsequent process, a heat treatment at 190 ° C. for 1 hour is performed in a vacuum to form a resist mask having a shape in plan view of the magnetoresistive element, and the magnetoresistive resistance is formed by an ion beam milling method. After processing each layer of the element and the vicinity of the surface of Cu (lower electrode), a Si—N film is formed on the resist, and the resist is removed together with the Si—N (lift-off). A surrounding (side) insulating layer was formed. And Cu was formed into a film as an upper electrode on the magnetoresistive element, and it was set as the sample of the Example.

A uniform magnetic field was applied from the outside to the manufactured sample so that the magnetization of the magnetoresistive element was parallel as an initial state. In this sample, while measuring the resistance of the magnetoresistive element between the upper and lower electrodes, a magnetic field is gradually increased from the outside and applied in one direction, and the magnetic field at which the magnetization of the magnetization free layer and the magnetization fixed layer is inverted is measured and maintained. The magnetic force was determined. Next, a magnetic field was applied in the opposite direction, and the coercive force was obtained by measuring again the magnetic field at which the magnetization of the magnetization free layer and further the magnetization fixed layer was reversed. Further, saturation magnetization was also measured for the magnetization fixed layer. Table 1 shows the coercive force −Hc _pin and + Hc _pin and saturation magnetization Ms _pin of the magnetization fixed layer and the coercivity Hc ₁ and Hc ₀ of the magnetization free layer for each sample of the magnetoresistive element. Further, the coercive force shift amount ΔHc (ΔHc = (| Hc ₁ | − | Hc ₀ |) / 2) is calculated from the difference between the coercive forces Hc ₀ and Hc ₁ of the magnetization free layer and shown in Table 1. .

As shown in Table 1, sample numbers of magnetoresistive elements 1 and 2 are examples in which the composition of the TbFeCo alloy constituting the magnetization fixed layer is within the scope of the present invention, and the saturation magnetization Ms _pin of the magnetization fixed layer was sufficiently suppressed. Therefore, the leakage magnetic field from the magnetization fixed layer is small, the coercivity shift amount ΔHc of the magnetization free layer satisfies the target of 10 Oe or less, and the magnetoresistive element exhibits a stable spin injection magnetization reversal operation. In contrast, sample no. 3 and 4 are comparative examples in which the Tb content in the TbFeCo alloy is excessive, so that the saturation magnetization Ms _pin of the magnetization fixed layer was large. As a result, the coercive force Hc ₀ , Hc ₁ of the magnetization free layer is shifted in the same direction by the leakage magnetic field, and the shift amount ΔHc is increased, resulting in a magnetoresistive element that requires application of a bias magnetic field for stable operation. .

10 Spatial light modulator 1 Magnetoresistive element (spin injection magnetization reversal element)
11 magnetization fixed layer 12 intermediate layer 13 magnetization free layer 14 protective layer 2 upper electrode 2A bit line (upper electrode)
3, 3A Lower electrode 40 Pixel array 4 Pixel 5 Word line 6 Insulating layer 70 MRAM (magnetic random access memory)
7 Memory cell 80 Current control unit 81 Power supply (current supply means)
84 Pixel selection unit (pixel selection means)
9 Recording device

Claims (5)

A spin-injection magnetization reversal element comprising a magnetization fixed layer, an intermediate layer, and a magnetization free layer stacked and supplied with current through a pair of electrodes connected vertically.
The magnetization fixed layer includes a Tb—Fe—Co alloy, and the composition of the Tb—Fe—Co alloy is Tb _x (Fe, Co) _1-x ( 0.226 ≦ x ≦ 0.25). A spin-injection magnetization reversal element. The composition of the Tb—Fe—Co alloy is Tb _x (Fe _1-y Co _y ) _1-x ( 0.226 ≦ x ≦ 0.25, 0.4 <y <0.67). The spin injection magnetization reversal element according to claim 1.   The spin injection magnetization reversal element according to claim 1 or 2, wherein the magnetization free layer contains two or more elements selected from Tb, Gd, Fe, Co, Ni, Pt, and Pd. . A magnetic random access memory comprising a plurality of memory cells arranged two-dimensionally,
A magnetic random access memory comprising: the spin injection magnetization reversal element according to any one of claims 1 to 3; and a pair of electrodes connected to the top and bottom of the spin injection magnetization reversal element. . A plurality of pixels arranged two-dimensionally, pixel selection means for selecting one or more pixels from the plurality of pixels, and current supply means for supplying a predetermined current to the pixels selected by the pixel selection means. A spatial light modulator that emits light by changing the polarization direction of the light incident on the pixel selected by the pixel selection means to a specific direction,
The spatial light modulator comprising: the spin injection magnetization reversal element according to any one of claims 1 to 3; and a pair of electrodes connected above and below the spin injection magnetization reversal element.