JP5370907B2 - Magnetoresistive element and magnetic random access memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for easily introducing a magnetic domain wall, for preventing a pinning force of the magnetic domain wall from superfluously increasing, and for fully reducing a writing current with respect to an MRAM utilizing a current inducing magnetic domain wall movement phenomenon using a perpendicular magnetization film. <P>SOLUTION: A magneto-resistive element is equipped with a primary ferromagnetic layer 10 constituted by a ferromagnetic material having a vertical magnetic anisotropy. The primary ferromagnetic layer 10 is provided with: a magnetization fixed area 11a which has a magnetization fixed in a first direction; a magnetization fixed area 11b which has a magnetization fixed in an anti-parallel direction to the first direction; and a magnetization free region 12 which is joined to the magnetization fixed areas 11a, 11b and has a reversible magnetization. A top face 11aT of the magnetization fixed area 11a is formed in a position higher than a top face 12T of the magnetization free region 12 in a substrate perpendicular direction. A lower surface 11aB of the magnetization fixed area 11a is formed in a position lower than a lower surface 12B of the magnetization free region 12 in the substrate perpendicular direction. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a magnetoresistive effect element and a magnetic random access memory. In particular, the present invention relates to a domain wall motion type magnetoresistive effect element and a magnetic random access memory.

  Magnetic Random Access Memory (MRAM) is expected as a non-volatile memory capable of high-speed operation and infinite rewriting, and has been actively developed. In the MRAM, a magnetic material is used as a storage element, and data is stored in correspondence with the magnetization direction of the magnetic material. Several methods have been proposed as a method for switching the magnetization of the magnetic material, but all of them are common in that current is used. In putting MRAM into practical use, it is very important how much the write current can be reduced. According to Non-Patent Document 1, a reduction to 0.5 mA or less, more preferably a reduction to 0.2 mA or less. It has been demanded.

  The most common method of writing data to the MRAM is to arrange a wiring for writing around the magnetic memory element and to change the magnetization direction of the magnetic memory element by a magnetic field generated by passing a current through the wiring. It is a method of switching. Since this method uses magnetization reversal by a magnetic field, writing in 1 nanosecond or less is possible in principle, which is preferable for realizing a high-speed MRAM. However, the magnetic field for switching the magnetization of the magnetic material that has ensured thermal stability and disturbance magnetic field resistance is generally about several tens of Oe (Ehrstead). In order to generate such a magnetic field, about several mA is required. A current is required. In this case, the chip area is inevitably increased, and the power consumption required for writing increases, so that it is inferior in competitiveness compared to other random access memories. In addition to this, when the element is miniaturized, the write current further increases, which is not preferable in terms of scaling.

  In recent years, the following two methods have been proposed as means for solving such problems. The first is spin injection magnetization reversal. This is a laminated film composed of a first magnetic layer having reversible magnetization and a second magnetic layer electrically connected to and fixed in magnetization. This is a method of reversing the magnetization of the first magnetic layer by utilizing the interaction between spin-polarized conduction electrons and a localized electron in the first magnetic layer when a current is passed between the layers. . Since spin injection magnetization reversal occurs at a certain current density or higher, the current required for writing is reduced as the element size is reduced. That is, it can be said that the spin injection magnetization reversal method is excellent in scaling. However, generally, an insulating layer is provided between the first magnetic layer and the second magnetic layer, and a relatively large current must be passed through the insulating layer at the time of writing. Sex is an issue. In addition, since the current path for writing and the current path for reading are the same, there is a concern about erroneous writing during reading. Thus, although spin transfer magnetization reversal is excellent in scaling, there are some barriers to practical use.

  On the other hand, the magnetization reversal method using the current-induced domain wall motion phenomenon, which is the second method, can solve the above-described problems of spin injection magnetization reversal. An MRAM using the current-induced domain wall motion phenomenon is disclosed in Patent Document 1, for example. The MRAM using the current-induced domain wall motion phenomenon is generally fixed so that the magnetizations at both ends thereof are substantially antiparallel to each other in the first magnetic layer having reversible magnetization. In such a magnetization arrangement, a domain wall is introduced into the first magnetic layer. Here, as reported in Non-Patent Document 2, when a current is passed in the direction penetrating the domain wall, the domain wall moves in the direction of conduction electrons, so that a current flows in the first magnetic layer. Can be written. Since current-induced domain wall motion also occurs when the current density is higher than a certain current density, it can be said that there is scaling as in spin injection magnetization reversal. In addition to this, in the MRAM element using current-induced domain wall motion, the write current does not flow through the insulating layer, and the write current path and the read current path are different, so that the spin injection magnetization reversal can be mentioned. The above problem will be solved.

Non-Patent Document 2 requires about 1 × 10 ⁸ [A / cm ² ] as the current density necessary for current-induced domain wall motion. In this case, for example, when the width of the layer in which the domain wall motion occurs is 100 nm and the film thickness is 10 nm, the write current is 1 mA. This cannot satisfy the above-mentioned conditions concerning the write current. However, as described in Non-Patent Document 3, it has been reported that the write current can be reduced sufficiently by using a material having perpendicular magnetic anisotropy as a ferromagnetic layer in which current-induced domain wall motion occurs. For this reason, when manufacturing MRAM using current-induced domain wall motion, it can be said that it is preferable to use a ferromagnetic material having perpendicular magnetic anisotropy as a layer in which domain wall motion occurs. Non-Patent Document 4 reports observation of current-induced domain wall motion in a perpendicular magnetization film. In addition, when manufacturing an MRAM using a perpendicular magnetization film, it is necessary to introduce a domain wall into a layer where domain wall movement occurs. However, in Non-Patent Document 4, a domain wall is introduced by providing a step in a layer where domain wall movement occurs. doing.

However, when the domain wall is introduced by a simple step as used in Non-Patent Document 4, there is a concern that the current density required for writing is not sufficiently reduced. This is because, as will be described later with reference to FIG. 7, a magnetic field generated by the magnetic flux in the film surface direction is applied to the domain wall near the step, and this magnetic field becomes the pinning force of the domain wall. The pinning force caused by the in-plane magnetic field generated by such a step becomes excessively large according to the calculation, and this can be an obstacle to the reduction of the write current.
JP 2005-191032 A IEEE Journal of Solid-State Circuits, vol. 42, p.830 (2007). Physical Review Letters, vol. 92, number 7, p.077205, (2004). 52nd Annual Conference on Magnetism and Magnetic Materials, Abstracts, FE-06, p.352, (2007). Applied Physics Express, vol. 1, p.011301, (2008).

  Therefore, an object of the present invention is to introduce a domain wall easily for an MRAM using a current-induced domain wall motion phenomenon using a perpendicular magnetization film, to prevent excessive increase of the domain wall pinning force, and to sufficiently reduce a write current. It is to provide a technique for doing this.

  The magnetoresistive effect element of the present invention includes a first ferromagnetic layer made of a ferromagnetic material having perpendicular magnetic anisotropy. The first ferromagnetic layer includes a first magnetization fixed region having a magnetization fixed in a first direction, a second magnetization fixed region having a magnetization fixed in an antiparallel direction to the first direction, and the first magnetization layer. And a magnetization free region having reversible magnetization joined to the first and second magnetization fixed regions. The upper surface of one of the first magnetization fixed region and the magnetization free region is formed at a position higher in the direction perpendicular to the substrate than the other upper surface, and the one of the first magnetization fixed region and the magnetization free region The lower surface is formed at a lower position in the substrate vertical direction than the other lower surface.

  According to the present invention, it is possible to easily introduce a domain wall in an MRAM using a current-induced domain wall motion phenomenon using a perpendicular magnetization film, prevent an excessive increase in the pinning force of the domain wall, and reduce a write current. .

  A magnetic random access memory according to the present invention will be described with reference to the accompanying drawings. In general, a magnetic random access memory has a plurality of magnetic memory cells arranged in an array, and each magnetic memory cell has a magnetoresistive element. Below, various suitable forms of a magnetoresistive effect element are explained.

(First embodiment)
1A to 1C schematically show the structure of a first ferromagnetic layer 10 (a ferromagnetic layer into which data is written) of the magnetoresistive effect element according to the first embodiment of the invention. 1A is a perspective view, and FIGS. 1B and 1C are an xy plan view and an xz sectional view in the xyz coordinate system shown in FIG. 1A. In the figure, the z-axis is defined as being perpendicular to the substrate, and the x-axis and y-axis are defined as being parallel to the substrate.

  The first ferromagnetic layer 10 includes a magnetization free region 12 and a plurality of magnetization fixed regions 11. In the present embodiment, two magnetization fixed regions 11 are provided, and in the following, one of them is described as a magnetization fixed region 11a and the other as a magnetization fixed region 11b. The magnetization fixed region 11a is connected to one end of the magnetization free region 12, and the magnetization fixed region 11b is connected to the other end.

  At least one of the magnetization fixed regions 11a and 11b has an upper surface formed at a position higher than the upper surface 12T of the magnetization free region 12, and a lower surface formed at a position lower than the lower surface 12B of the magnetization free region 12. Has been. In the present embodiment, such a structure is employed for both the magnetization fixed regions 11a and 11b. That is, the upper surface 11aT of the magnetization fixed region 11a is formed at a position higher than the upper surface 12T of the magnetization free region 12, and the lower surface 11aB of the magnetization fixed region 11a is formed at a position lower than the lower surface 12B of the magnetization free region 12. Similarly, the upper surface 11bT of the magnetization fixed region 11b is formed at a position higher than the upper surface 12T of the magnetization free region 12, and the lower surface 11bB of the magnetization fixed region 11b is formed at a position lower than the lower surface 12B of the magnetization free region 12. .

  The first ferromagnetic layer 10 is made of a ferromagnetic material having perpendicular magnetic anisotropy. Specifically, as shown in FIG. 2, the magnetization fixed region 11a has an upward fixed magnetization, and the magnetization fixed region 11b has a downward fixed magnetization. On the other hand, the magnetization of the magnetization free region 12 can be reversed in the vertical direction. In the case of such a magnetization arrangement, a domain wall is formed at the boundary between the magnetization free region 12 and the magnetization fixed region 11a or 11b according to the magnetization direction of the magnetization free region 12. The magnetization direction of the magnetization free region 12 corresponds to data stored in the magnetoresistive effect element. An example of a material that can be used for the first ferromagnetic layer 10 is a Co—Pt alloy.

  The first ferromagnetic layer 10 having such a structure can be formed by various methods. For example, the first ferromagnetic layer 10 can be formed by forming a ferromagnetic film after forming the groove and then patterning the formed ferromagnetic film. As another method, after forming the ferromagnetic film, patterning is performed to form a part of the magnetization fixed region 11, and after burying the formed part, cueing is performed by a method such as CMP or milling, The first ferromagnetic layer 10 can also be formed by forming and patterning the remaining portion of the magnetization fixed region 11.

  Next, a method of writing data to the first ferromagnetic layer 10 in the present embodiment will be described with reference to FIGS. 3A and 3B. A domain wall is formed in the first ferromagnetic layer 10 at a location corresponding to the magnetization direction of the magnetization free region 12. In the magnetoresistive effect element of this embodiment, data is written by driving the domain wall with current. 3A and 3B show an example of the method. In this embodiment, the electrode layers 40a and 40b are joined to the magnetization fixed regions 11a and 11b, respectively, and a current for driving the domain wall is supplied using the electrode layers 40a and 40b.

  In the following, as shown in FIG. 3A, the magnetization of the magnetization fixed region 11a is fixed upward, the magnetization of the magnetization fixed region 11b is fixed downward, and the magnetization of the magnetization free region 12 is directed downward. The state is defined as “0” state. Further, as shown in FIG. 3B, a state where the magnetization of the magnetization free region 12 is directed upward is defined as a “1” state. FIG. 3A shows a method of writing data “1” to the first ferromagnetic layer 10 in the “0” state, and FIG. 3B shows a method of writing data “0” to the first ferromagnetic layer 10 in the “1” state. Show. However, those skilled in the art will readily understand that the definitions of the “0” state and the “1” state are not limited to this.

  Specifically, in the “0” state of FIG. 3A, a domain wall (DW) is formed at the boundary between the magnetization fixed region 11 a and the magnetization free region 12. Here, as shown by a dotted line in FIG. 3A, when a write current is introduced from the magnetization fixed region 11b to the magnetization fixed region 11a via the magnetization free region 12, the conduction electrons are transferred from the magnetization fixed region 11a to the magnetization free region. 12 flows in a direction toward the magnetization fixed region 11 b via 12. This conduction electron causes current-induced domain wall movement, and the domain wall (DW) moves from the boundary between the magnetization fixed region 11 a and the magnetization free region 12 to the boundary between the magnetization fixed region 11 b and the magnetization free region 12. As a result, a magnetization arrangement as shown in FIG. 3B appears. In this way, data “1” is written. A mechanism in which the domain wall (DW) stops at the boundary between the magnetization fixed region 11b and the magnetization free region 12 will be described later.

  On the other hand, in the “1” state of FIG. 3B, a domain wall (DW) is formed at the boundary between the magnetization fixed region 11 b and the magnetization free region 12. Here, as indicated by a dotted line in FIG. 3B, a write current is introduced in a direction from the magnetization fixed region 11a to the second magnetization fixed region 11b via the magnetization free region 12. At this time, conduction electrons flow in the direction from the second magnetization fixed region 11b to the first magnetization fixed region 11a via the magnetization free region 12, and current conduction domain wall motion occurs due to the conduction electrons, and the domain wall (DW) It moves from the boundary between the two magnetization fixed region 11b and the magnetization free region 12 to the boundary between the first magnetization fixed region 11a and the magnetization free region 12, resulting in a magnetization arrangement as shown in FIG. 3A. In this way, “0” is written.

  Although not shown, it should be noted that according to the above write operation, overwrite (write operation without changing data) is also possible. That is, data “0” can be written to the first ferromagnetic layer 10 in the “0” state, and data “1” can be written to the “1” state.

  It should be noted that when writing, the domain wall cannot pass through the boundary between the magnetization fixed region 11 and the magnetization free region 12 and enter the magnetization fixed region 11. This is because the current density in the magnetization fixed region 11 is smaller than that in the magnetization free region 12. Specifically, it will be described as follows. When a write current is passed between the electrode layers 40 a and 40 b, the cross-sectional area in the direction perpendicular to the current direction increases outside the boundary between the magnetization fixed region 11 and the magnetization free region 12. Accordingly, the current density in the magnetization fixed region 11 is reduced. If the thickness in the z-axis direction of the magnetization fixed region 11 is adjusted so that the current density in the magnetization fixed region 11 is smaller than the threshold current density necessary for current-induced domain wall motion, the domain wall motion does not occur in the magnetization fixed region 11. Instead, the domain wall stops at the boundary between the magnetization fixed region 11 and the magnetization free region 12.

  Such a reduction in current density due to an increase in cross-sectional area can also be controlled by the xy planar shape. For example, the current density outside the boundary between the magnetization fixed region 11 and the magnetization free region 12 can be reduced by setting the width of the magnetization fixed region 11 wider than the width of the magnetization free region 12. A suitable shape for this will be described later.

  The domain wall stopped at the boundary between the magnetization fixed region 11 and the magnetization free region 12 can stably remain in place. This is because in a material having perpendicular magnetic anisotropy, there are innumerable pinning sites and they have sufficiently large thermal stability.

(Reading method)
Next, a method of reading data from the magnetoresistive effect element in the present embodiment will be described with reference to FIGS. 4A and 4B. As described above, in the magnetoresistive effect element of this embodiment, data is stored according to the magnetization direction of the magnetization free region 12 of the first ferromagnetic layer 10. In the magnetoresistive effect element of this embodiment, data is read by detecting the magnetization of the magnetization free region 12 using the magnetoresistive effect.

  4A and 4B show an example of a data reading method. In the present embodiment, the first nonmagnetic layer 20 and the second ferromagnetic layer 30 are provided to read data. The second ferromagnetic layer 30 is provided so as to face the magnetization free region 12 of the first ferromagnetic layer 10, and the first nonmagnetic layer 20 includes the second ferromagnetic layer 30 and the first ferromagnetic layer 10. Are provided between the magnetization free regions 12. The first ferromagnetic layer 10, the first nonmagnetic layer 20, and the second ferromagnetic layer 30 form a magnetic tunnel junction (MTJ).

The first nonmagnetic layer 20 is made of a nonmagnetic and insulating material. Specific examples of the material of the first nonmagnetic layer 20 include aluminum oxide (AlO _x ). Instead, the first nonmagnetic layer 20 may be formed of a nonmagnetic semiconductor or metal material. In this case, the first ferromagnetic layer 10, the first nonmagnetic layer 20, and the second ferromagnetic layer 30 constitute a GMR element exhibiting a GMR effect (Giant Magnetoresistance effect).

  The second ferromagnetic layer 30 is made of a ferromagnetic material having perpendicular magnetic anisotropy. The magnetization of the second ferromagnetic layer 30 is substantially fixed in one direction at least in part. The second ferromagnetic layer 30 is illustrated as a single-layer ferromagnetic layer in FIGS. 4A and 4B, but may actually be formed of a laminated film including a plurality of ferromagnetic layers. A nonmagnetic layer may be inserted between them. Adjacent ferromagnetic layers may be magnetically coupled in the antiparallel direction by a nonmagnetic layer disposed in the middle. Furthermore, the magnetization can be more firmly fixed by bonding an antiferromagnetic layer to the second ferromagnetic layer 30. Examples of the laminated structure of the second ferromagnetic layer 30 include Co—Pt / Ru / Co—Pt / PtMn.

  4A shows a method of reading data from the first ferromagnetic layer 10 in the “0” state, and FIG. 4B shows a method of reading data from the first ferromagnetic layer 10 in the “1” state. . Now, as shown in FIGS. 4A and 4B, the magnetization of the second ferromagnetic layer 30 (or the magnetization of the portion of the second ferromagnetic layer 30 near the interface with the first nonmagnetic layer 20) is downward. It shall be fixed to. Data reading is performed by introducing a current in a direction penetrating the first ferromagnetic layer 10, the first nonmagnetic layer 20, and the second ferromagnetic layer 30.

  As shown in FIG. 4A, when data “0” is stored in the first ferromagnetic layer 10 (that is, when the magnetization free region 12 is magnetized downward), the magnetization free region 12 and the second magnetization layer 12 Since the magnetization of the ferromagnetic layer 30 is parallel, the MTJ resistance in this case is (relatively) low. On the other hand, as shown in FIG. 4B, when data “1” is stored in the first ferromagnetic layer 10 (that is, when the magnetization free region 12 is magnetized upward), the first ferromagnetic layer Since the magnetizations of 10 and the second ferromagnetic layer 30 are antiparallel, the MTJ resistance in this case is (relatively) high. Thus, by detecting the difference in resistance when a current is passed through the MTJ, the magnetization direction of the magnetization free region 12 can be detected, and data is read from the magnetoresistive effect element. Can do.

  Next, a method for initializing the memory state of the magnetoresistive effect element according to the present embodiment will be described with reference to FIGS. 5A and 5B. As described above, in the magnetoresistive effect element according to this embodiment, one of the magnetization fixed regions 11a and 11b of the first ferromagnetic layer 10 needs to be directed upward and the other must be directed downward. Such a magnetized state can be realized by the following steps.

First, in the first ferromagnetic layer 10 as shown in FIG. 5A, the coercive force of the magnetization fixed region 11a (that is, the magnetic field necessary for the reversal of the magnetization of the magnetization fixed region 11a) is Hc_11a, and the coercivity of the magnetization fixed region 11b. Is Hc_11b, and the coercive force of the magnetization free region 12 is Hc_12. Here, between the coercive forces Hc_11a, Hc_11b, and Hc_12,
Hc_11a> Hc_11b,
Hc_11a> Hc_12
Is assumed to hold. The magnitude relationship between the coercive forces Hc_11b and Hc_12 is arbitrary.
Hc_11b> Hc_12
Is assumed to hold.

At this time, first, H ₁ > Hc — 11a in the upward direction
By applying the magnetic field H, the magnetization of the entire region can be aligned upward as shown in FIG. 5A. next,
Hc — 11a> H ₂ > Hc — 11b (> Hc — 12)
When the composed field H ₂ is applied in the downward direction, the magnetization free region 12 and the magnetization only inverts the second magnetization fixed region 11b, as shown in Figure 5B, the first ferromagnetic layer 10, the initial to the "0" state It becomes.

  It should be noted that as long as the coercivity of the magnetization fixed regions 11a and 11b is different, the magnitude relationship of the coercivity of the magnetization fixed regions 11a and 11b and the magnetization free region 12 is arbitrary. As long as the threshold magnetic fields of the magnetization fixed region 11a and the magnetization fixed region 11b are different from each other, the magnetization of the magnetization fixed region 11a and the magnetization fixed region 11b can be directed in the antiparallel direction by applying the two-stage magnetic field as described above. it can.

  One feature of the magnetoresistive effect element of the present embodiment is that at least one of the magnetization fixed regions 11a and 11b is formed such that the upper surface is higher than the upper surface 12T of the magnetization free region 12, and the lower surface is the upper surface of the magnetization free region 12. A structure formed at a position lower than 12T is employed. Below, the advantage of such a structure and the principle from which the advantage is obtained will be described.

  As a method for introducing a domain wall into a perpendicular magnetization film, as described in Non-Patent Document 4, it is known to provide a step in the perpendicular magnetization film. FIG. 6A and FIG. 6B show a general structure when a method of introducing a domain wall by a step as used in Non-Patent Document 4 is applied to a domain wall displacement type element. 6A is a perspective view, and FIG. 6B is an xz sectional view in the xyz coordinate system shown in FIG. 6A.

  However, in the configuration shown in FIGS. 6A and 6B, there is a concern that the domain wall is excessively pinned at the boundary between the magnetization fixed region 11 and the magnetization free region 12. FIG. 7 schematically shows this. In FIG. 7, a region that is not at the same height as the magnetization free region 12 in the magnetization fixed region 11 a is hatched. In addition, a magnetic field generated in the periphery when this region is magnetized upward is indicated by an arrow 13. As shown in FIGS. 6A and 6B, a rightward magnetic field is generated at the boundary 14 between the magnetization free region 12 and the magnetization fixed region 11a due to the edge effect. According to the inventor's calculations, this magnetic field can be locally 1 kOe or more. When the domain wall is pinned by such a local magnetic field, it cannot be depinned by the intrinsic threshold current density required for current-induced domain wall movement in the perpendicular magnetization film, and a larger current density is required. I learned from the tics calculation. That is, even if a perpendicular magnetic anisotropic material is used for the layer where domain wall motion occurs, the write current density can be reduced within a certain range when a structure having a simple step as shown in FIGS. 6A and 6B is used. It will stay.

  According to the structure of the first ferromagnetic layer 10 of the present embodiment, the above-described problems can be solved, and a magnetic random access memory capable of writing data with a sufficiently reduced current density can be provided. . FIG. 8 schematically shows this. In the present invention, the upper surface of at least one magnetization fixed region 11 is formed at a position higher than the upper surface of the magnetization free region 12, and the lower surface of the at least one magnetization fixed region 11 is lower than the lower surface of the magnetization free region 12. Formed in position. In other words, the magnetization fixed region 11 has a region protruding above the magnetization free region 12 and a region protruding below. In FIG. 8, the region that protrudes upward and the region that protrudes downward of the magnetization fixed region 11 a are shaded. Further, in FIG. 8, the magnetic field formed by the hatched region is schematically indicated by an arrow 13. As can be seen from FIG. 8, unlike FIG. 7, the in-plane component of the magnetic field from the hatched region at the boundary 14 between the magnetization free region 12 and the magnetization fixed region 11 is canceled between the upper and lower regions, and is zero or small. It can be seen that the size can be controlled. As a result, the excessive pinning force as described above is not generated, and an increase in write current can be suppressed.

  Next, an example of a circuit configuration of a magnetic memory cell including the magnetoresistive effect element according to this embodiment will be described. FIG. 9 shows a configuration example of a circuit for one bit of the magnetic memory cell in the present embodiment. As shown in FIG. 9, the second ferromagnetic layer 30 is connected to the ground line 101 for reading. On the other hand, the magnetization fixed region 11a is connected to one source / drain of the MOS transistor 100a. The other source / drain of MOS transistor 100a is connected to bit line 102a for writing. Similarly, the magnetization fixed region 11b is connected to one source / drain of the MOS transistor 100a. The other source / drain of MOS transistor 100a is connected to bit line 102b for writing. The gate electrodes of the MOS transistors 100 a and 100 b are connected to the common word line 103. The magnetic random access memory (MRAM) is configured by arranging the magnetic memory cells shown in FIG. 9 in a matrix in a memory array, and the memory array is connected to a peripheral circuit.

  The write operation and read operation of the magnetic memory cell shown in FIG. 9 are as follows. When performing the write operation, the word line 103 is pulled up to the “High” level, thereby turning on the MOS transistors 100a and 100b. One of the bit lines 102a and 102b is pulled up to the “High” level, and the other is pulled down to the “Low” level. The direction of the current flowing through the first ferromagnetic layer 10 changes depending on which of the bit lines 102a and 102b is set to "High" level and which is set to "Low" level, whereby desired data is transferred to the magnetoresistive element. Can be written on.

In the read operation, the word line 103 is pulled up to the “High” level, thereby turning on the MOS transistors 100a and 100b. In addition, the bit line 102a is set to a high impedance state, and the bit line 102b is pulled up to the “High” level. As a result, the current passing through the magnetoresistive effect element from the bit line 102b flows to the ground line 101 via the first ferromagnetic layer 10, the first nonmagnetic layer 20, and the second ferromagnetic layer 30, so that the magnetoresistance High-speed reading using the effect is possible.
The magnetic memory cells shown in FIG. 9 are arranged in an array, and these are connected to a peripheral circuit to form a magnetic random access memory.

  However, the operation of the circuit shown in FIG. 9 and the circuit described here is merely an example of a method for carrying out the present invention, and can be implemented by other circuit configurations.

  Next, the material of each layer of the magnetoresistive effect element of this embodiment is illustrated. Note that all the materials shown here are examples, and any material may be used in practice as long as the above-described magnetization state can be realized.

  The first ferromagnetic layer 10 and the second ferromagnetic layer 30 are made of a ferromagnetic material including at least one material selected from Fe, Co, and Ni. Moreover, perpendicular magnetic anisotropy can be stabilized by including Pt and Pd. In addition to this, B, C, N, O, Al, Si, P, Ti, V, Cr, Mn, Cu, Zn, Zr, Nb, Mo, Tc, Ru, Rh, Ag, Hf, Ta, W, By adding Re, Os, Ir, Au, Sm or the like, it is possible to adjust so that desired magnetic properties are expressed. Specifically, Co, Co—Pt, Co—Pd, Co—Cr, Co—Pt—Cr, Co—Cr—Ta, Co—Cr—B, Co—Cr—Pt—B, Co—Cr—Ta— B, Co-V, Co-Mo, Co-W, Co-Ti, Co-Ru, Co-Rh, Fe-Pt, Fe-Pd, Fe-Co-Pt, Fe-Co-Pd, Sm-Co, Examples include Gd—Fe—Co, Tb—Fe—Co, and Gd—Tb—Fe—Co. In addition, the magnetic anisotropy in the perpendicular direction can also be exhibited by laminating a layer containing any one material selected from Fe, Co, and Ni with different layers. Specifically, a laminated film of Co / Pd, Co / Pt, Co / Ni, Fe / Au, and the like are exemplified.

  The first nonmagnetic layer 20 is preferably made of a nonmagnetic and insulating material. Specifically, Mg-O, Al-O, Al-N, Ni-O, Hf-O, etc. are illustrated. However, when the magnetoresistive element is configured as a GMR element, a semiconductor or a metal material may be used for the first nonmagnetic layer 20. In this case, the first nonmagnetic layer 20 is made of, for example, Al, Cr, Cu, or the like.

  As described above, the magnetization can be more firmly fixed by making the antiferromagnetic layer adjacent to the second ferromagnetic layer 30. Specific examples of the antiferromagnetic material include Pt—Mn, Ir—Mn, and Fe—Mn.

(Second Embodiment)
10A and 10B schematically show the structure of the first ferromagnetic layer 10 of the magnetoresistive effect element according to the second embodiment of the present invention. The second embodiment relates to the structure of the magnetization fixed regions 11a and 11b. 10A is a perspective view, and FIG. 10B is an xz sectional view in the xyz coordinate system shown in FIG. 10A.

  10A and 10B, the upper surface of the magnetization fixed region is formed at a position higher than the upper surface 12T of the magnetization free region 12, and the lower surface is formed at a position lower than the upper surface 12T of the magnetization free region 12. This structure can be adopted only in one of the magnetization fixed regions 11a and 11b. 10A and 10B, the upper surface 11aT of the first magnetization fixed region 11a is formed at a position higher than the upper surface 12T of the magnetization free region 12, and is formed at a position lower than the lower surface 12B of the first magnetization fixed region 11b. On the other hand, the upper surface 11bT of the second magnetization fixed region 11b and the lower surface 11bB of the second magnetization fixed region 11b are formed at the same height as the upper surface 12T and the lower surface 12B of the magnetization free region 12, respectively. Even in this case, an excessive pinning force is not generated at the boundary between the magnetization fixed region 11a and the magnetization free region 12, so that an increase in write current can be suppressed.

  Also in the structure shown in FIGS. 10A and 10B, by providing the electrode layer 40b adjacent to the magnetization fixed region 11b as shown in FIG. 10C, the domain wall is reduced during writing due to the decrease in the current density described above. It can be stopped at the boundary between the magnetization free region 12 and the second magnetization fixed region 11b. In order to more actively reduce the current density of the second magnetization fixed region 11b (as will be described later with reference to FIGS. 20A and 20B), the planar shape, particularly the width, of the first ferromagnetic layer 10 is used. It is also effective to have these changes. In addition, in order to stop the domain wall more stably, the first ferromagnetic layer 10 may have a local shape change, as will be described later with reference to FIG. 19A.

(Third embodiment)
11A, 11B, 12A, and 12B schematically show the structure of the first ferromagnetic layer 10 of the magnetoresistive effect element according to the third embodiment of the present invention. The third embodiment relates to a stacked configuration of the magnetization fixed region 11. 11A and 12A are perspective views, and FIGS. 11B and 12B show xz sectional views in the xyz coordinate system shown in FIGS. 11A and 12A.

  In the first and second embodiments, it has been described that the first ferromagnetic layer 10 is made of a ferromagnetic material having perpendicular magnetic anisotropy. May include a non-magnetic layer. 11A, 11B, 12A, and 12B show examples in which the first ferromagnetic layer 10 includes second nonmagnetic layers 15a and 15b. The position of the second nonmagnetic layer 15 is arbitrary. 11A and 11B show an example in which the second nonmagnetic layer 15 is provided at a position lower than the height of the magnetization free region 12, and FIGS. 12A and 12B are higher than the height of the magnetization free region 12. An example in which the second nonmagnetic layer 15 is provided at the position is shown.

  That is, in the first ferromagnetic layer 10 illustrated in FIGS. 11A and 11B, the magnetization fixed region 11a includes the ferromagnetic film 16a, the second nonmagnetic layer 15a, the ferromagnetic portion 17a, and the ferromagnetic film 18a. It has. Similarly, the magnetization fixed region 11b includes a ferromagnetic film 16b, a second nonmagnetic layer 15b, a ferromagnetic portion 17b, and a ferromagnetic film 18b. The ferromagnetic portions 17 a and 17 b are portions formed integrally with the magnetization free region 12, and the ferromagnetic portions 17 a and 17 b are formed in the same process as the magnetization free region 12. The second nonmagnetic layer 15a is provided between the ferromagnetic film 16a and the ferromagnetic portion 17a so as to be bonded to the lower surface of the ferromagnetic portion 17a. Similarly, the second nonmagnetic layer 15b is provided between the ferromagnetic film 16b and the ferromagnetic portion 17b so as to be bonded to the lower surface of the ferromagnetic portion 17b.

  On the other hand, in the first ferromagnetic layer 10 shown in FIGS. 12A and 12B, the second nonmagnetic layer 15a is bonded to the upper surface of the ferromagnetic portion 17a between the ferromagnetic film 16a and the ferromagnetic portion 17a. Is provided. Similarly, the second nonmagnetic layer 15b is provided between the ferromagnetic film 16b and the ferromagnetic portion 17b so as to be bonded to the upper surface of the ferromagnetic portion 17b.

  As shown in FIG. 12C, the first nonmagnetic layer 20 and the second ferromagnetic layer 30 are provided on the magnetization free region 12, and the first ferromagnetic layer 10, the first nonmagnetic layer 20, and the first ferromagnetic layer 30 are provided. The MTJ (or GMR element) is formed by the two ferromagnetic layers 30.

  Even if the second nonmagnetic layers 15a and 15b are provided in the first ferromagnetic layer 10, the effect of reducing the write current by controlling the pinning force of the domain wall in the present invention can be obtained. This is because the principle described with reference to FIG. 8 applies to the first ferromagnetic layer 10 even if the hatched region in FIG. 8 is located away from the magnetization free region 12. is there.

  Providing the second nonmagnetic layer 15 in the first ferromagnetic layer 10 facilitates production and also facilitates the development of more preferable material characteristics. In order to form the first ferromagnetic layer 10 as described above, it is necessary to go through several steps. In this case, it is easier to manufacture by inserting a nonmagnetic layer for the convenience of the manufacturing process. There is. For example, when a nonmagnetic layer is used as an underlayer, a cap layer, or a protective layer of a ferromagnetic layer having perpendicular magnetic anisotropy, these may remain in the first ferromagnetic layer 10 during the integration process. Though conceivable, even in such a case, an effect of suppressing an excessive pinning force can be obtained.

  The position and film thickness of the second nonmagnetic layer 15 can be variously changed. Further, the second nonmagnetic layer 15 may be provided on both the upper and lower sides of the magnetization free region 12.

  Various materials can be selected for the material of the second nonmagnetic layer 15. A conductive material such as Ta, W, Ti, Ti—N, or Zr—N, or an insulating material such as SiO 2, SiN, Al—O, or Mg—O can be used. 12C, the second nonmagnetic layer 15a may be formed at the same height as the first nonmagnetic layer 20. As a result, it can be formed by the same process as the MTJ tunnel barrier, and the manufacturing process is simplified.

(Fourth embodiment)
13A to 13C schematically show the structure of the magnetoresistive element according to the fourth embodiment of the present invention. The fourth embodiment relates to data reading from the first ferromagnetic layer 10. 13A is a perspective view, and FIGS. 13B and 13C respectively show an xy plan view and an xz cross-sectional view in the xyz coordinate system shown in FIG. 13A.

  In the fourth embodiment, an MTJ is provided separately from the first ferromagnetic layer 10 in which data is stored, and the MTJ is used for data reading. More specifically, in the fourth embodiment, in addition to the first ferromagnetic layer 10, a third ferromagnetic layer 210, a third nonmagnetic layer 220, and a fourth ferromagnetic layer 230 are provided. The third ferromagnetic layer 210 and the first ferromagnetic layer 10 are connected by a contact layer 240. The third nonmagnetic layer 220 is provided between the third ferromagnetic layer 210 and the fourth ferromagnetic layer 230. The third ferromagnetic layer 210, the third nonmagnetic layer 220, and the fourth ferromagnetic layer 230 form a magnetic tunnel junction (MTJ).

  The center of gravity of the third ferromagnetic layer 210 is provided so as to be shifted in the xy plane with respect to the center of gravity of the magnetization free region 12 of the first ferromagnetic layer 10. The direction of this shift is now defined as the “shift direction”.

  The third ferromagnetic layer 210 and the fourth ferromagnetic layer 230 are made of a ferromagnetic material having magnetic anisotropy in the in-plane direction. The direction of the magnetic anisotropy of the third ferromagnetic layer 210 is arbitrary in the in-plane direction. On the other hand, the magnetization of the fourth ferromagnetic layer 230 is substantially fixed in one direction. This direction is preferably parallel to the “shift direction”.

  In the fourth embodiment, the data stored as the magnetization direction in the direction perpendicular to the magnetization free region 12 of the first ferromagnetic layer 10 is the third ferromagnetic layer 210, the third nonmagnetic layer 220, and the fourth ferromagnetic layer. Reading is performed using an MTJ having in-plane magnetization composed of the layer 230. Specifically, the magnetization free region 12 of the first ferromagnetic layer 10 is magnetically coupled to the third ferromagnetic layer 210, and the direction of magnetization in the perpendicular direction of the magnetization free region 12 of the first ferromagnetic layer 10 is The third ferromagnetic layer 210 appears in the in-plane direction of magnetization. The direction of magnetization in the in-plane direction of the third ferromagnetic layer 210 is detected as a change in MTJ resistance, and data is identified from the change in MTJ resistance.

  The principle of the read operation in the fourth embodiment will be described in detail with reference to FIGS. 14A and 14B. FIG. 14A shows the magnetization state of each layer when the first ferromagnetic layer 10 is in the “0” state, and FIG. 14B shows the magnetization state when the first ferromagnetic layer 10 is in the “1” state. Indicates the state. The magnetizations of the magnetization fixed region 11a, the magnetization fixed region 11b, and the fourth ferromagnetic layer 230 are depicted as being fixed in the positive z-axis direction, the negative direction, and the negative y-axis direction, respectively. The magnetization directions of the magnetization fixed region 11a, the second magnetization fixed region 11b, and the fourth ferromagnetic layer 230 are arbitrary. This optionality will be apparent to those skilled in the art.

  As shown in FIG. 14A, when the first ferromagnetic layer 10 is in the “0” state in which the magnetization free region 12 is magnetized downward, the magnetization of the third ferromagnetic layer 210 is changed to the magnetization free region 12. The y-axis negative direction is directed by the leakage magnetic flux generated by the downward magnetization. This is because the third ferromagnetic layer 210 is disposed below the magnetization free region 12 (in the negative z-axis direction), and the center of gravity of the third ferromagnetic layer 210 is in the negative y-axis direction with respect to the magnetization free region 12. This is because they are provided in a shifted manner. As a result, the magnetizations of the third ferromagnetic layer 210 and the fourth ferromagnetic layer 230 become parallel, and the MTJ enters a low resistance state.

  On the other hand, as shown in FIG. 14B, when the first ferromagnetic layer 10 is in the “1” state in which the magnetization free region 12 is magnetized upward, the magnetization of the third ferromagnetic layer 210 is changed to the magnetization free region 12. It faces in the y-axis positive direction by the leakage magnetic flux generated by the upward magnetization. As a result, the magnetizations of the third ferromagnetic layer 210 and the fourth ferromagnetic layer 230 become antiparallel, and the MTJ enters a high resistance state.

  Thus, the data stored as the magnetization in the perpendicular direction of the magnetization free region 12 is transferred to the magnetization of the third ferromagnetic layer 210 having in-plane magnetization, and the third ferromagnetic layer 210, the third nonmagnetic layer 220, the fourth It is read by the MTJ composed of the ferromagnetic layer 230.

  In general, a high magnetoresistive effect ratio (MR ratio) can be obtained in an MTJ constituted by a ferromagnetic layer having in-plane magnetization. Therefore, the magnetoresistive effect element according to the fourth embodiment can obtain a large read signal.

  13A to 13C, the third ferromagnetic layer 210, the third nonmagnetic layer 220, and the fourth ferromagnetic layer 230 are disposed on the lower side (z-axis negative direction) with respect to the first ferromagnetic layer 10. Although depicted as a thing, this position is arbitrary and may be, for example, the upper side. Further, the “shift direction”, which is the shift direction of the centroid of the third ferromagnetic layer 210 from the centroid of the magnetization free region 12, is drawn as a negative y-axis direction in the figure, but this is also arbitrary. And may be in the positive y-axis direction or may contain an x component.

(Fifth embodiment)
15A and 15B schematically show the structure of the fifth embodiment of the magnetoresistance effect element according to the present invention. The fifth embodiment relates to the configuration of the magnetization fixed region. FIG. 15A is a perspective view, and FIG. 15B is an xz sectional view in the xyz coordinate system shown in FIG. 15A.

  Now, as shown in FIG. 15B, a region located at the same height as the magnetization free region 12 in the first magnetization fixed region 11a is a region 11a-0, a region located higher than that is 11a-1, and a lower region. Is defined as region 11a-2. Similarly, in the second magnetization fixed region 11b, a region located at the same height as the magnetization free region 12 is a region 11b-0, a region located higher than that is a region 11b-1, and a lower region is designated a region 11b-2. Define. At this time, the material, characteristics, and film thickness of the region 11b-1 and the region 11b-2 can be variously changed. For example, the region 11b-1 and the region 11b-2 may have different film thicknesses, and may have different materials and characteristics (for example, magnetization).

  As an example, FIG. 16 shows a case where the magnetization of the region 11a-1 is larger than the magnetization of the region 11a-2. In FIG. 16, the magnetic field formed by the magnetization of the region 11 a-1 and the region 11 a-2 in the region 11 a-0 and the magnetization free region 12 is schematically indicated by an arrow 13. When the magnetization magnitudes of the region 11a-1 and the region 11a-2 are different as shown in FIG. 16, a finite magnetic field remains at the boundary 14 between the magnetization free region 12 and the first magnetization fixed region 11a. In this way, the pinning force of the domain wall can be adjusted by intentionally adjusting the film thickness and material characteristics.

(Sixth embodiment)
17A and 17B schematically show the structure of the magnetoresistive effect element according to the sixth embodiment of the present invention. The sixth embodiment also relates to the configuration of the magnetization fixed region. FIG. 17A is a perspective view, and FIG. 17B shows an xz cross-sectional view in the xy coordinate system shown in FIG. 17A.

  In the sixth embodiment, unlike the first embodiment, at least one of the magnetization fixed regions 11a and 11b is formed such that the upper surface is higher than the upper surface 12T of the magnetization free region 12, and the lower surface is A structure formed at a position lower than the lower surface 12B of the magnetization free region 12 is adopted. In the sixth embodiment, such a structure is adopted for both the magnetization fixed regions 11a and 11b. That is, the upper surfaces 11aT and 11bT of the magnetization fixed region 11a and the magnetization fixed region 11b are formed at positions lower than the upper surface 12T of the magnetization free region 12, while the lower surfaces 11aB and 11bB of the magnetization fixed region 11a and the second magnetization fixed region 11b. Is formed at a position higher than the lower surface 12B of the magnetization free region 12.

  Also in the configuration shown in FIGS. 17A and 17B, an effect equivalent to the effect of the present invention described with reference to FIG. 8 can be obtained. FIG. 18 schematically shows such a state. In FIG. 18, the magnetic field formed around the magnetization of the first magnetization fixed region 11 a is indicated by an arrow 13. As shown in FIG. 18, at the boundary 14 between the magnetization free region 12 and the first magnetization fixed region 11a, a positive magnetic field and a negative magnetic field of the x axis are generated, and these cancel each other to prevent a large domain wall pinning force. I understand.

  One of the magnetization fixed regions 11 a and 11 b has the structure of the first embodiment (that is, the upper surface is formed at a position higher than the upper surface 12 T of the magnetization free region 12, and the lower surface is the lower surface of the magnetization free region 12. The other is formed in the structure of the sixth embodiment (that is, the upper surface is formed in a position lower than the upper surface 12T of the magnetization free region 12). The lower surface may be formed at a position higher than the lower surface 12B of the magnetization free region 12).

  When writing, it is necessary to stop the domain wall at the boundary 14, which is provided with the electrode layers 40a and 40b as described above, or the plane of the first ferromagnetic layer 10 as described later. This can be realized by adjusting the shape.

(Seventh embodiment)
19A to 19E, 20A, 20B, and 21A, 21B schematically show the structure of the seventh embodiment of the magnetoresistance effect element of the seventh embodiment of the present invention. The seventh embodiment relates to the planar shape of the first ferromagnetic layer 10.

  1A-1C, the first ferromagnetic layer 10 is depicted as being rectangular in the xy plane, but as shown in FIGS. 19A-19E, 20A, 20B, and 21A, 21B. The planar shape of the first ferromagnetic layer 10 can be variously changed. 19A to 19E, FIGS. 20A, 20B, and 21B are xy plan views. FIG. 21A shows a perspective view of the first ferromagnetic layer 10 having a planar shape as shown in FIG. 21B.

  As shown in FIG. 19A, the first ferromagnetic layer 10 may be provided with a notch. This notch is provided at the boundary between the first magnetization fixed region 11 a and the magnetization free region 12 and at the boundary between the second magnetization fixed region 11 b and the magnetization free region 12. Thereby, the pinning position of the domain wall can be clearly defined. A protrusion may be provided instead of the notch.

  Moreover, as FIG. 19B-19E shows, the 1st ferromagnetic layer 10 may be formed so that a center part may become thick. In order to lower the energy of the entire system, the domain wall has the property of moving as thin as possible, but by forming the center part thick as shown in FIGS. 19B to 19E, the domain wall is less likely to stop at the center part and is stable. This binary state is realized.

  20A and 20B, the first ferromagnetic layer 10 may be formed so that the width of the magnetization fixed region 11 is larger than the width of the magnetization free region 12. FIG. 20A shows an example where both the magnetization fixed region 11a and the magnetization fixed region 11b are formed thick, and FIG. 20B shows an example where only the magnetization fixed region 11b is formed thick. By forming the magnetization fixed region 11 wider than the magnetization free region 12, it is possible to prevent the domain wall from passing through the magnetization free region 12 and entering the magnetization fixed region 11. This is because the current density decreases in the magnetization fixed region because the width increases.

  21A and 21B, the first ferromagnetic layer 10 may be formed in a Y shape. In the structures of FIGS. 21A and 21B, the first ferromagnetic layer 10 has a magnetization free region 12 provided extending in the x direction, and a magnetization fixed region provided connected to one end (−x side) thereof. 11 a and a magnetization fixed region 11 b provided similarly connected to one end. That is, the first ferromagnetic layer 10 forms a three-way path. Also in this case, the magnetizations of the magnetization fixed region 11a and the magnetization fixed region 11b are fixed to each other in an antiparallel direction in the vertical direction. The magnetization of the magnetization free region 12 can be reversed up and down in the vertical direction.

  A writing method when the first ferromagnetic layer 10 has a Y-shape as shown in FIGS. 21A and 21B will be described with reference to FIGS. 22A and 22B. FIG. 22A schematically shows an operation of writing data “1” when the first ferromagnetic layer 10 is in the “0” state, and FIG. 22B shows that the first ferromagnetic layer 10 is in the “1” state. In this case, an operation of writing data “0” is shown.

  As shown in FIG. 22A, when the first ferromagnetic layer 10 is in the “0” state in which the magnetization free region 12 is magnetized downward, a domain wall (DW) is formed at the boundary between the magnetization fixed region 11 a and the magnetization free region 12. It is formed. Here, if a current is passed in the direction of the dotted line in FIG. 22A, the domain wall (DW) moves to the opposite side of the end of the magnetization free region 12 connected to the magnetization fixed region 11a due to the phenomenon of current induced domain wall movement. One ferromagnetic layer 10 transitions to the “1” state as shown in FIG. 22B. Similarly, when the first ferromagnetic layer 10 is in the “1” state in which the magnetization free region 12 is magnetized upward as shown in FIG. 22B, the domain wall is located at the boundary between the second magnetization fixed region 11 b and the magnetization free region 12. (DW) is formed. Here, if a current is passed in the direction of the dotted line in FIG. 22B, the domain wall (DW) moves to the opposite side of the end of the magnetization free region 12 connected to the second magnetization fixed region 11b due to the phenomenon of current induced domain wall movement. The first ferromagnetic layer 10 transitions to the “0” state as shown in FIG. 22A. In this way, data can be rewritten.

  When the first ferromagnetic layer 10 is formed in a three-way shape as shown in FIGS. 21A and 21B, writing is performed by extracting the domain wall at the end of the magnetization free region 12. By such a writing process, a more stable writing operation can be realized.

  Although various embodiments of the present invention are described above, the present invention should not be construed as being limited to the above-described embodiments. It will be apparent to those skilled in the art that the present invention can be implemented with various modifications from the above-described embodiments. It should be noted that a plurality of the structures of the above-described embodiments may be employed in combination with one magnetoresistive element as long as there is no contradiction.

FIG. 1A is a perspective view showing the configuration of the magnetoresistive effect element according to the first embodiment of the present invention. FIG. 1B is a plan view showing the configuration of the magnetoresistive effect element according to the first embodiment. FIG. 1C is a cross-sectional view showing the configuration of the magnetoresistive effect element according to the first embodiment. FIG. 2 is a cross-sectional view showing the magnetization arrangement of the magnetoresistive element of FIG. FIG. 3A is a cross-sectional view conceptually showing the write operation of the magnetoresistive effect element according to the first exemplary embodiment. FIG. 3B is a cross-sectional view conceptually showing the write operation of the magnetoresistive effect element according to the first exemplary embodiment. FIG. 4A is a cross-sectional view conceptually showing the read operation of the magnetoresistive effect element according to the first exemplary embodiment. FIG. 4B is a cross-sectional view conceptually showing the read operation of the magnetoresistive effect element according to the first exemplary embodiment. FIG. 5A is a sectional view conceptually showing an initialization operation of the magnetoresistive effect element according to the first exemplary embodiment. FIG. 5B is a cross-sectional view conceptually showing an initialization operation of the magnetoresistive effect element according to the first exemplary embodiment. FIG. 6A is a perspective view showing a structure of a magnetoresistive effect element in which a step is provided in a ferromagnetic layer. FIG. 6B is a cross-sectional view showing the structure of the magnetoresistive effect element in which a step is provided in the ferromagnetic layer. FIG. 7 is a conceptual diagram showing a magnetic field generated in the ferromagnetic layer having the structure shown in FIGS. 6A and 6B. FIG. 8 is a conceptual diagram showing a magnetic field generated in the first ferromagnetic layer of the magnetoresistive effect element according to the first embodiment. FIG. 9 is a circuit diagram showing a circuit configuration of a magnetic memory cell in which the magnetoresistive effect element according to the first embodiment is integrated. FIG. 10A is a perspective view showing the configuration of the magnetoresistive effect element according to the second embodiment of the present invention. FIG. 10B is a plan view showing the configuration of the magnetoresistive effect element according to the second embodiment. FIG. 10C is a cross-sectional view illustrating the configuration of the magnetoresistive effect element according to the second embodiment. FIG. 11A is a perspective view showing a configuration of a magnetoresistive effect element according to a third embodiment of the present invention. FIG. 11B is a cross-sectional view showing the configuration of the magnetoresistive effect element according to the third embodiment of the present invention. FIG. 12A is a perspective view illustrating a configuration of a magnetoresistive effect element according to a third embodiment. FIG. 12B is a cross-sectional view illustrating the configuration of the magnetoresistive effect element according to the third embodiment. FIG. 12C is a cross-sectional view illustrating the configuration of the magnetoresistive effect element according to the third embodiment. FIG. 13A is a perspective view illustrating a configuration of a magnetoresistive effect element according to a fourth embodiment. FIG. 13B is a plan view showing the configuration of the magnetoresistive effect element according to the fourth embodiment. FIG. 13C is a cross-sectional view showing the configuration of the magnetoresistive effect element according to the fourth embodiment. FIG. 14A is a sectional view conceptually showing the read operation of the magnetoresistive effect element of the fourth exemplary embodiment. FIG. 14B is a cross-sectional view conceptually showing the read operation of the magnetoresistive effect element of the fourth exemplary embodiment. FIG. 15A is a perspective view showing a configuration of a magnetoresistive effect element according to a fifth embodiment of the present invention. FIG. 15B is a cross-sectional view showing the configuration of the magnetoresistive effect element according to the fifth embodiment of the present invention. FIG. 16 is a conceptual diagram showing a magnetic field generated in the first ferromagnetic layer of the magnetoresistive effect element according to the fifth embodiment. FIG. 17A is a perspective view showing the configuration of the magnetoresistive element of the sixth exemplary embodiment. FIG. 17B is a cross-sectional view illustrating the configuration of the magnetoresistive effect element according to the sixth embodiment. FIG. 18 is a conceptual diagram illustrating a magnetic field generated in the first ferromagnetic layer of the magnetoresistive effect element according to the sixth embodiment. FIG. 19A is a plan view illustrating an example of a planar shape of a first ferromagnetic layer of the magnetoresistive effect element according to the seventh embodiment. FIG. 19B is a plan view showing another example of the planar shape of the first ferromagnetic layer of the magnetoresistance effect element of the seventh exemplary embodiment. FIG. 19C is a plan view illustrating another example of the planar shape of the first ferromagnetic layer of the magnetoresistance effect element according to the seventh exemplary embodiment. FIG. 19D is a plan view illustrating another example of the planar shape of the first ferromagnetic layer of the magnetoresistance effect element according to the seventh exemplary embodiment. FIG. 19E is a plan view illustrating another example of the planar shape of the first ferromagnetic layer of the magnetoresistance effect element according to the seventh exemplary embodiment. FIG. 20A is a plan view illustrating another example of the planar shape of the first ferromagnetic layer of the magnetoresistance effect element according to the seventh exemplary embodiment. FIG. 20B is a plan view illustrating another example of the planar shape of the first ferromagnetic layer of the magnetoresistive effect element according to the seventh embodiment. FIG. 21A is a perspective view showing another example of the configuration of the magnetoresistance effect element of the seventh exemplary embodiment. FIG. 21B is a plan view showing a planar shape of the configuration of the magnetoresistive element shown in FIG. 21A. FIG. 22A is a plan view conceptually showing a write operation to the magnetoresistive effect element shown in FIGS. 21A and 21B. FIG. 22B is a plan view conceptually showing a write operation to the magnetoresistive effect element shown in FIGS. 21A and 21B.

Explanation of symbols

10: First ferromagnetic layer 11, 11a, 11b: Fixed magnetization region 11aT, 11bT: Upper surface 11aB, 11bB: Lower surface 11a-0, 11a-1, 11a-2: Region 11b-0, 11b-1, 11b-2 : Region 12: magnetization free region 12T: upper surface 12B: lower surface 13: arrow 14: boundaries 15, 15a, 15b: second nonmagnetic layers 16a, 16b: ferromagnetic films 17a, 17b: ferromagnetic portions 18a, 18b: ferromagnetic Film 20: first nonmagnetic layer 30: second ferromagnetic layer 40a, 40b: electrode layer 100a, 100b: MOS transistor 101: ground line 102a, 102b: bit line 103: word line 210: third ferromagnetic layer 220: Third nonmagnetic layer 230: Fourth ferromagnetic layer 240: Contact layer

Claims (10)

A first ferromagnetic layer composed of a ferromagnetic material having perpendicular magnetic anisotropy ;
A third ferromagnetic layer provided magnetically coupled to the first ferromagnetic layer;
A fourth ferromagnetic layer provided to face the third ferromagnetic layer;
A second nonmagnetic layer provided between the third ferromagnetic layer and the fourth ferromagnetic layer
And
The first ferromagnetic layer includes
A first magnetization fixed region having magnetization fixed in a first direction;
A second magnetization fixed region having magnetization fixed in a direction antiparallel to the first direction;
A magnetization free region having reversible magnetization joined to the first and second magnetization fixed regions,
One upper surface of the first magnetization fixed region and the magnetization free region is formed at a higher position in the substrate vertical direction than the other upper surface,
The one lower surface of the first magnetization fixed region and the magnetization free region is formed at a lower position in the substrate vertical direction than the other lower surface ,
The center of gravity of the third ferromagnetic layer is provided so as to be shifted in a second direction that is an in-plane direction with respect to the center of gravity of the magnetization free region,
The third ferromagnetic layer has magnetization that can be reversed in an in-plane direction,
The fourth ferromagnetic layer is a magnetoresistive element having magnetization fixed substantially parallel to the second direction . The magnetoresistive element according to claim 1,
The first magnetization fixed region has an upper surface formed at a position higher in the substrate vertical direction than an upper surface of the magnetization free region, and a lower surface formed at a position lower in the substrate vertical direction than the lower surface of the magnetization free region. Magnetoresistive effect element. The magnetoresistive element according to claim 1 or 2,
A second ferromagnetic layer provided to face the magnetization free region;
A first nonmagnetic layer provided between the second ferromagnetic layer and the magnetization free region;
The second ferromagnetic layer has a magnetization fixed in a vertical direction in at least a part of the second ferromagnetic layer. The magnetoresistive effect element according to any one of claims 1 to 3 ,
The first magnetization fixed region is bonded to one end of the magnetization free region;
The magnetoresistive effect element, wherein the second magnetization fixed region is joined to the other end of the magnetization free region. The magnetoresistive effect element according to any one of claims 1 to 3 ,
The first magnetization fixed region is bonded to one end of the magnetization free region;
The magnetoresistive effect element, wherein the second magnetization fixed region is joined to the one end of the magnetization free region. The magnetoresistive effect element according to any one of claims 1 to 3 ,
A magnetoresistive element in which at least one of the first and second magnetization fixed regions is formed wider than the magnetization free region in an in-plane direction. Comprising a first ferromagnetic layer composed of a ferromagnetic material having perpendicular magnetic anisotropy;
The first ferromagnetic layer includes
A first magnetization fixed region having magnetization fixed in a first direction;
A second magnetization fixed region having magnetization fixed in a direction antiparallel to the first direction;
Magnetization free region having reversible magnetization joined to the first and second magnetization fixed regions
And
The upper surface of the first magnetization fixed region is formed at a position higher in the substrate vertical direction than the upper surface of the magnetization free region, and the lower surface is formed at a position lower in the substrate vertical direction than the lower surface of the magnetization free region,
The first magnetization fixed region is
A first region located at a higher position in the direction perpendicular to the substrate than the magnetization free region;
A second region located at a lower position in the direction perpendicular to the substrate than the free magnetization region,
The first region and the second region differ in at least one of magnetization and film thickness. The magnetoresistive effect element according to any one of claims 1 to 7 ,
A magnetoresistive element in which at least one of the first and second magnetization fixed regions is joined to an electrode layer. The magnetoresistive effect element according to any one of claims 1 to 8 ,
At least one of the first and second magnetization fixed regions includes a nonmagnetic layer. Magnetic random access memory comprising a magneto-resistance effect element according to any one of claims 1 to 9.

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