JP2010098259A - Memory cell, and magnetic memory element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a memory cell using a magnetization inversion mechanism using a spin current. <P>SOLUTION: This memory cell 31 includes: a flat nonmagnetic layer 16; a ferromagnetic layer 12 installed on a surface of the nonmagnetic layer 16 and formed of a ferromagnetic substance with the direction of magnetization fixed; and a free layer 15 installed on a surface of the nonmagnetic layer 16 and formed of a ferromagnetic substance having a variable direction of magnetization. The memory cell 31 stores information depending on whether the direction of magnetization of the ferromagnetic layer 12 and that of the free layer 15 are nearly parallel with each other or nearly nonparallel with each other by changing the direction of a current flowing between the nonmagnetic layer 16 and the ferromagnetic layer 12 to change a spin quantization axis of a spin current flowing through the nonmagnetic layer 16 and thereby changing the direction of magnetization of the free layer 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a memory cell using a magnetization reversal mechanism using spin current, and a magnetic memory element.

  With the progress of the information society, it is possible to access high-speed and large-capacity communication networks, and the demand for higher performance of information terminals such as mobile phones and computers is increasing. In particular, the increase in the capacity of hard disks used for storing information and the speeding up of semiconductor elements such as CPUs used for processing information are steadily progressing. However, it is not always possible to improve the performance of the device as in the past. There are concerns that the physical limits will shift in the near future.

  Therefore, in recent years, magnetic random access memory (MRAM) using a magnetic material has attracted much attention.

  The MRAM uses at least two ferromagnetic layers and a nonmagnetic layer sandwiched between them as memory bits. The switching fields of the two ferromagnetic layers are designed to be different.

  A ferromagnetic layer whose magnetization is reversed by an information writing operation is called a free layer, and a ferromagnetic layer having a large switching magnetic field is called a pinned layer.

  Then, the state where the free layer and the pinned layer are in a parallel state and the state where the magnetic layer is in an antiparallel state are associated with one and the other of “memory state 0” and “memory state 1”, respectively. Remember. Typically, the parallel state is associated with “0” and the antiparallel state is associated with “1”.

  The read operation is performed by using the magnetoresistance effect, that is, the resistance difference due to the difference in relative magnetization between the two magnetic bodies. The resistance value differs between when the magnetic field is in a parallel state and when it is in an antiparallel state.

  On the other hand, a technique has been proposed in which the write operation is performed by causing magnetization reversal of the free layer by a magnetic field generated from a current flowing through write lines (word lines, bit lines) arranged above and below the memory bit.

  However, it is difficult to increase the capacity of the MRAM by the writing method using the current magnetic field. The reasons are roughly divided into the following two.

  First, since the magnitude of the magnetic field required for information writing, that is, the magnetization reversal of the free layer greatly increases as the size of the magnetic material decreases, the current density must be increased.

  Second, in order to increase the capacity of the MRAM, it is necessary to reduce the wiring width as well as the memory bit, and the current density required in the write operation greatly increases.

  When the current density increases, disconnection, electromigration, and the like occur, and the reliability of the memory element is significantly deteriorated.

  Techniques for solving this problem are proposed in Patent Documents 1 to 4 listed below.

  Here, Patent Document 1 proposes a magnetization reversal method using spin torque. In this method, spin-polarized electrons are injected from the outside into the free layer, and the magnetization of the free layer is reversed by transferring angular momentum between the injected spin and the magnetization moment of the free layer.

  If a current amount of a certain critical current density or more flows from the pinned layer to the free layer, the antiparallel state can be obtained, and if it flows from the free layer to the pinned layer, the parallel state can be obtained.

  When attempting to miniaturize an element using this technique, the current density flowing in the free layer increases by miniaturizing the memory bit. If this is viewed as a whole, the amount of current required for writing is reduced, so that scaling for large capacity is established, and it is considered an advantageous technique for realizing a large capacity MRAM.

  Various ideas have been proposed based on this technology.

  For example, a tunnel magnetoresistive (TMR) element has a large magnetoresistive effect, so there is an attempt to use it as a memory bit of MRAM. The TMR element is composed of a free layer, a pinned layer, and a dielectric layer of about several nanometers sandwiched between them.

Here, in order to cause magnetization reversal due to spin torque, a spin current density of about 10 ⁷ A / cm ² is usually required.

  However, when such a large current is passed through the TMR element, the dielectric breakdown of the ultrathin dielectric layer or the deterioration of the film quality becomes a problem. If there is variation between elements in the magnitude of the magnetoresistive effect due to deterioration and disconnection, the reliability as a memory element is greatly lost.

  In the technique disclosed in Patent Document 2, the wiring for reading and the wiring for writing are distinguished, and an attempt is made to solve the problem of dielectric breakdown of the TMR element.

  However, since current flows only in a part of the free layer in spin injection, and uniform spin torque is not generated in the magnetization of the free layer, there is a concern about non-uniform magnetization reversal due to generation of magnon or the like.

  On the other hand, in the technique disclosed in Patent Document 3, the wiring for reading and the wiring for writing are distinguished, and an attempt is made to solve the problem of dielectric breakdown of the TMR element.

  However, since a current flows between two antiparallel parallel fixed ferromagnetic layers in the write operation, there is a concern about magnetization reversal of the fixed ferromagnetic layers due to spin torque.

  Furthermore, in the technique disclosed in Patent Document 4, a stable write operation is attempted to be realized by using a spin current and distinguishing between a read wiring and a write wiring.

  However, in the read operation, since the thick non-magnetic layer is sandwiched between the free layer and the pin layer, the magnetoresistive effect is greatly reduced, and a sufficient signal necessary for reading cannot be obtained. When the nonmagnetic layer is made thin, a large current flows for writing, so there is a concern about element destruction.

US Pat. No. 5,695,864 JP-A-2005-116888 JP 2006-156477 A JP 2008-171945 A

  The present invention is intended to solve the above-described problems, and while using a magnetization reversal mechanism using a spin current, device deterioration and destruction due to a current during writing are suppressed, and reading speed is increased. An object is to provide a memory cell and a magnetic memory element.

  A memory cell according to a first aspect of the present invention includes a planar nonmagnetic material layer, a ferromagnetic material layer that is provided on the surface of the nonmagnetic material layer and is made of a ferromagnetic material having a fixed magnetization direction, A free layer made of a ferromagnetic material that is provided on the surface of the nonmagnetic material layer and whose magnetization direction is variable.

  Here, by changing the direction of the current flowing between the nonmagnetic layer and the ferromagnetic layer, the spin quantization axis of the spin current flowing between the nonmagnetic layer and the ferromagnetic layer is changed. Thus, the magnetization direction of the free layer is changed, and information is stored depending on whether the magnetization direction of the ferromagnetic layer and the magnetization direction of the free layer are substantially parallel or substantially antiparallel.

  Further, in the memory cell of the present invention, as the ferromagnetic layer, a plurality of ferromagnetic materials whose magnetization directions are fixed can be provided at different positions on the surface of the nonmagnetic layer.

  In the memory cell of the present invention, the ferromagnetic material forming the free layer can be configured to be an alloy or a compound containing at least one magnetic material.

  In the memory cell of the present invention, a free layer, an intermediate layer made of a non-magnetic material, and a pinned layer made of a ferromagnetic material whose magnetization direction is fixed in parallel to the ferromagnetic material layer are laminated. A difference in magnetization direction between the layer and the pinned layer can be detected by the tunnel magnetoresistive effect, and information stored in the free layer can be read out.

In the memory cell of the present invention, the contact area between the nonmagnetic material layer and the free layer can be configured to be 2.0 × 10 ⁴ nm ² or less.

  In the memory cell of the present invention, the interface between the nonmagnetic material layer and the free layer can be configured to be ohmic-bonded.

  In the memory cell of the present invention, the nonmagnetic layer can be configured to be Cu.

  In the memory cell of the present invention, the nonmagnetic layer can be configured to be Al.

  In the memory cell of the present invention, the nonmagnetic layer can be configured to be a semiconductor.

  In the memory cell of the present invention, the nonmagnetic layer can be configured to be a superconductor.

  In the memory cell of the present invention, the ferromagnetic material of the free layer can be configured to be a Co—Fe alloy.

  In the memory cell of the present invention, the ferromagnetic material of the free layer can be configured to be Co—Fe—B.

  In the memory cell of the present invention, the nonmagnetic material layer can be configured to have a thickness of 50 nm or more.

  A magnetic memory element according to another aspect of the present invention is configured such that a plurality of the memory cells are arranged in a matrix.

  According to the present invention, it is possible to provide a memory cell and a magnetic memory element in which the deterioration and destruction of an element due to a current during writing are suppressed and the reading speed is increased while using a magnetization reversal mechanism using a spin current. Can do.

  The best mode for carrying out the present invention will be described below. Note that the scope of the present invention is not limited to the following examples, and various modifications can be made based on the principle of the present invention, and these aspects are also included in the scope of the present invention.

  FIG. 1 is a cross-sectional view showing the structure of a memory cell of a magnetic memory element according to the first embodiment of the present invention. Hereinafter, a description will be given with reference to FIG.

  The memory cell 31 has a planar nonmagnetic layer 16. On one side of the non-magnetic layer 16, the write fixed magnetization terminal 1 and the read magnetoresistive effect element 2 are provided.

  The direct current source 19 allows a current to flow between the write magnetization fixed terminal 1 and the nonmagnetic layer 16, and designates information stored in the read magnetoresistive element 2 according to the direction of the current.

  The DC power source 18 and the ammeter 17 read information from the read magnetoresistive effect element 2 and determine the bit value of the stored information from the magnitude of the magnetoresistance of the read magnetoresistive effect element 2. The ammeter 17 is generally composed of an electronic element or an electronic circuit that obtains a bit value by comparison with a predetermined threshold value. However, when investigating the performance of the memory cell 31, particularly the hysteresis characteristic, Use the one that measures the size as it is.

  The writing fixed magnetization terminal 1 has a two-layer structure in which an antiferromagnetic layer 11 and a ferromagnetic layer 12 are laminated, and the ferromagnetic layer 12 is in contact with the nonmagnetic layer 16.

  The read magnetoresistive effect element 2 has a TMR element having a three-layer structure in which a pinned layer 13, a nonmagnetic intermediate layer 14, and a free layer 15 are stacked, and the free layer 15 is in contact with the nonmagnetic layer 16. .

  In this figure, the ferromagnetic layer 12 and the free layer 15 are disposed directly on the surface of the nonmagnetic layer 16, but a thin dielectric layer may be inserted between them to improve the spin injection efficiency. Is possible.

  In addition, when an ohmic junction having a small contact resistance is used between the free layer 15 and the nonmagnetic layer 16, it is possible to efficiently absorb the spin current in the free layer 15 and cause the spin torque magnetization reversal. .

  The magnetization direction of the magnetization fixed terminal 1 for writing has sufficiently high thermal stability and needs to be strongly fixed in one direction. In this example, the magnetization direction of the ferromagnetic layer 12 is strongly fixed by laminating the antiferromagnetic layer 11 and the ferromagnetic layer 12.

  Materials used for the ferromagnetic layer 12 include Ni, Fe, Co and alloys thereof, amorphous materials such as Co-Fe-B, Heusler materials such as Co-Mn-Si and Co-Cr-Fe-Al, It can be selected from ferromagnetic semiconductor materials such as GaMnAs.

  The ferromagnetic layer 12 is configured by selecting one of these as a thin film, or selecting a plurality of them as a multilayer film.

  In order to suppress the leakage magnetic field from the end of the ferromagnetic layer 12, a synthetic antiferromagnetic structure, that is, a ferromagnetic layer, a nonmagnetic layer, and a ferromagnetic layer are formed on the ferromagnetic layer 12. It is desirable to use a stacked structure in order.

  The material used for the antiferromagnetic material layer 11 can be selected from Ir—Mn, Pt—Mn, Fe—Mn, Ni—O, Co—O, and the like.

  When a ferromagnetic material having strong magnetic anisotropy such as Fe-Pd, Fe-Pt, Co-Pt or the like having an L10 structure is used as the ferromagnetic layer 12, an antiferromagnetic layer is used. It is also possible to configure the write fixed magnetization terminal 1 by omitting 11.

  On the other hand, as the magnetoresistive effect element 2 for reading, an anisotropic magnetoresistive effect element, a giant magnetoresistive effect element, a TMR element, or the like can be used, but the magnitude of the read signal affects the read speed of the element. Therefore, it is desirable to be as large as possible. In this case, a TMR element as shown in FIG.

  In the read magnetoresistive effect element 2 shown in this figure, the magnetoresistance changes depending on the relative angle of magnetization of the free layer 15 and the pinned layer 13. Therefore, when writing information, it represents a bit value that sets the relative angle of magnetization, and when reading, the bit value is obtained based on the value of the magnetoresistance.

  Here, the free layer 15 needs to have sufficient thermal stability in order to maintain the memory state, and the magnetization direction needs to be parallel and anti-parallel to the reference direction. It is necessary to use the one having the property.

  For this purpose, a material having high uniaxial magnetic anisotropy may be employed, or uniaxial anisotropy may be imparted to the element shape. For example, uniaxial magnetic anisotropy can be obtained by using the following materials as rectangular or elliptical shapes having a large aspect ratio representing the ratio between the length and width of the element.

Materials used for the free layer 15 include Ni, Fe, Co and alloys thereof, amorphous materials such as Co—Fe—B, Heusler materials such as Co—Mn—Si and Co—Cr—Fe—Al, and strong materials such as GaMnAs. magnetic semiconductor material, Fe-Pd, Fe-Pt , etc. L1 ₀ structure alloy such as Co-Pt can be used.

  In order to control magnetic properties and chemical properties, Ti, V, Cr, Mn, Cu, Zn, B, Al, Ga, C, Si, Ge, Sn, N, P, Sb, O, S, Mo , Ru, Ag, Hf, Ta, W, Ir, Pt, Au, and other nonmagnetic elements may be added as appropriate.

  Further, the free layer 15 may be selected from the above to be a ferromagnetic thin film, or a plurality of free layers 15 may be configured as a multilayer thin film.

  The film thickness of the free layer 15 is preferably 2 nm or more in consideration of noise and magnetic characteristics at the time of reading.

  On the other hand, the pinned layer 13 determines the reference magnetization direction, and therefore needs to have higher magnetic stability (coercive force) and higher thermal stability than the free layer 15.

  For example, the coercive force and the thermal stability can be improved by making the film thickness thicker than that of the free layer 15 or adopting a laminated film structure with an antiferromagnetic material and utilizing exchange interaction.

As the material of the pinned layer 13, Ni, Fe, Co and alloys thereof, amorphous materials such as Co-Fe-B, Heusler materials such as Co-Mn-Si and Co-Cr-Fe-Al, Fe-Pd, Fe -pt, it can be utilized such as L1 ₀ structure alloy such as Co-Pt.

  Moreover, in order to control magnetic characteristics and chemical characteristics, Ti, V, Cr, Mn, Cu, Zn, B, Al, Ga, C, Si, Ge, Sn, N, P, Sb, O, S, Mo , Ru, Ag, Hf, Ta, W, Ir, Pt, Au, and other nonmagnetic elements can be added as appropriate.

  In addition, the pinned layer 13 may be selected from the above to be a ferromagnetic thin film, or a plurality of pinned layers 13 may be configured as a multilayer thin film.

As shown in the figure, in the case of adopting the TMR element as a magneto-resistance effect element 2 for reading a non-magnetic intermediate layer _{14, SiO 2, Al 2 O} 3, MgO, SiN, AlN, BaF 2, MgF 2, CaF ₂ , insulators such as ZnO, TiO ₂ , Si, Ge, GaAs, ZnS, and ZnSe, and semiconductors can be used.

  Since the film thickness needs to be thin enough to allow tunneling current to flow, it is preferably 5 nm or less.

In order to uniformly absorb the spin current from the nonmagnetic material layer 16 into the free layer 15, it is desirable that the contact interface between them is 2.0 × 10 ⁴ nm ² or less.

  The distance between the magnetization fixed terminal 1 for writing and the magnetoresistive effect element 2 for reading needs to be less than or equal to the spin relaxation length of the nonmagnetic material. For example, at room temperature, Cu is about 500 nm, Au is about 50 nm, and Al is about 600 nm.

  In order to efficiently flow the spin accumulated in the nonmagnetic material layer 16 from the write magnetization fixed terminal 1 to the free layer 15 in the read magnetoresistive element 2, the nonmagnetic material layer 16 has a long spin relaxation length. Material is desirable. For example, in the case of a metal, it is Al, Cu, or Ag. Semiconductors and superconductors are more suitable because they have a longer spin relaxation length than metals.

Further, as described above, when the free layer 15 and the nonmagnetic material layer 16 are in ohmic contact, the nonmagnetic material layer 16 has a structure in order to efficiently absorb the spin accumulated in the nonmagnetic material into the free layer. The contact free layer 15 is preferably made of a material having a low spin resistance. The spin resistance R _S can be expressed as follows.
R _S = λ _SF / (σS (1-P ² ))

Here, λ _SF is the spin diffusion length in the ferromagnetic material, σ is the electrical conductivity, S is the contact area between the ferromagnetic layer and the nonmagnetic layer, and P is the spin polarization rate.

For example, when the contact area and 100 × 100 nm ^2, spin resistance becomes R _S = 0.46Ω in Ni-Fe alloy R _S = 0.15Ω, the Co.

  In general, since an alloy has a lower spin resistance than a single metal, the ferromagnetic material of the free layer 15 on the nonmagnetic material layer 16 is an alloy such as Ni—Fe or Co—Fe or Co—Fe—B. Are desirable.

  In order to realize stable spin torque magnetization reversal, the volume of the ferromagnetic layer 12 is desirably larger than the volume of the ferromagnetic material constituting the free layer 15 in contact with the nonmagnetic layer 16.

  Furthermore, the thickness of the nonmagnetic material layer 16 is desirably 50 nm or more for the purpose of reducing spin scattering on the surface or bottom surface of the nonmagnetic material layer 16.

  2A and 2B are explanatory views showing the operation of spin torque magnetization reversal by the spin current generated in the memory cell 31. FIG. Hereinafter, a description will be given with reference to FIG.

  In both figures, the arrows in the ferromagnetic layer 12, the pinned layer 13, and the free layer 15 indicate the directions of magnetization. Here, the magnetization directions of the ferromagnetic layer 12 and the pinned layer 13 are the same.

  In FIG. 2A, a current I flows from the nonmagnetic layer 16 to the write magnetization fixed terminal 1, and electrons move from the write magnetization fixed terminal 1 to the nonmagnetic layer 16.

  Then, many spins of the ferromagnetic layer 12 are injected and accumulated in the nonmagnetic layer 16. Thereafter, a large number of spins enter the free layer 15 while maintaining the spin quantization axis, and when a certain amount or more of spins flow into the free layer 15, the magnetization of the free layer 15 is the same as the spin quantization axis due to the torque. Aligned in the direction.

  On the other hand, in FIG. 2B, contrary to FIG. 2A, a current I flows from the write magnetization fixed terminal 1 to the nonmagnetic layer 16, and electrons move from the nonmagnetic layer 16 to the write magnetization fixed terminal 1. To do.

  Then, electrons in the same direction as many spins of the ferromagnetic layer 12 are absorbed from the nonmagnetic layer 16 to the ferromagnetic layer 12, so that the nonmagnetic layer 16 has a direction opposite to that of the ferromagnetic layer 12. Electrons having a spin quantization axis are accumulated.

  The accumulated electrons are absorbed by the free layer 15, and a certain amount or more of electrons flow into the free layer 15 from the nonmagnetic material layer 16, so that the magnetization direction of the free layer 15 is changed to a ferromagnetic material by spin torque magnetization reversal. It is in an antiparallel state with the layer 12.

  As described above, in this embodiment, it is possible to control the magnetization direction of the free layer 15 by changing the polarity of the current flowing through the write magnetization fixed terminal 1.

  On the other hand, the direction of magnetization of the free layer 15 can be read as the relative direction of magnetization of the free layer 15 and the pinned layer 13 in the read magnetoresistive element 2. For this reason, as described above, the magnetization directions of the ferromagnetic layer 12 and the pinned layer 13 are aligned in advance by the magnetic field.

  When the magnetization directions of the free layer 15 and the pinned layer 13 are in an antiparallel state, the resistance is high, and when the direction is parallel, the resistance is low. Typically, the former is associated with “1” and the latter is associated with “0”.

  As described above, the charge electron flow does not flow through the read magnetoresistive element 2 during the write operation. Therefore, it is not necessary to reduce the resistance. Further, when a TMR element is employed, a high resistance is desirable in order to realize a high magnetoresistance ratio. In this case, there is also an advantage that a sufficient output voltage can be secured.

  Hereinafter, the details of the memory cell 31 that is experimentally manufactured based on the above principle will be described.

  A Cu thin wire having a width of 170 nm and a film thickness of 65 nm was produced by an electron beam lithography apparatus and a thin film manufacturing apparatus (corresponding to the nonmagnetic layer 16).

A Ni—Fe alloy structure having a size of 170 × 75 nm ² and a thickness of 20 nm was formed on this Cu wire (corresponding to the ferromagnetic layer 12 of the magnetization fixed terminal 1 for writing).

Further, a Ni—Fe alloy structure having a size of 150 × 75 nm ² and a thickness of 20 nm was formed on this Cu thin wire (corresponding to the free layer 15 of the magnetoresistive effect element 2 for reading).

  The center-to-center distance between these two Ni—Fe alloy structures was 400 nm.

  And the spin accumulation effect in Cu nonmagnetic layer was confirmed using the nonlocal measurement method.

  The resistance difference between the two Ni—Fe alloy structures when the magnetization is in the parallel state and the antiparallel state is about 2 mΩ, and this resistance difference can be used as a spin signal.

  FIG. 3 is a graph depicting hysteresis showing the state of spin torque magnetization reversal obtained by experiment. Hereinafter, a description will be given with reference to FIG.

  In this figure, the direction in which the current flows from the Ni—Fe alloy structure to the Cu nonmagnetic layer is positive, the reverse direction is negative, and a pulse current having a width of 100 μs is used as a direct current source. After the application, the magnetization state of these two Ni—Fe alloy structures was detected by non-local measurement using AC lock-in. In the non-local measurement method, a high resistance state is exhibited when two ferromagnetic materials are in a parallel state, and a low resistance state is exhibited when the two ferromagnetic materials are in an antiparallel state.

  First, an external magnetic field was applied to the element, the magnetizations of both Ni—Fe alloy structures were made parallel, and then the magnitude of the current in the positive direction was gradually increased. Then, it was observed that the magnetization of the free layer 15 was reversed at about 5 mA.

  Subsequently, when the direct current was reversed from the positive direction to the negative direction, it was observed that the magnetization of the free layer 15 was reversed at about -3 mA.

  In this experiment, the spin torque magnetization reversal from the parallel state to the complete anti-parallel state was not performed because the film thickness was set to 20 nm for the purpose of sufficiently maintaining the thermal stability of the free layer 15. A complete spin torque magnetization reversal from the parallel state to the anti-parallel state is also possible by a method such as making the layer 15 thinner.

  It has been found that spin torque magnetization reversal is possible even with shorter pulses.

  FIG. 4 is a cross-sectional view showing the structure of the memory cell of the magnetic memory element according to the second embodiment of the present invention. Hereinafter, a description will be given with reference to FIG. The description of the same parts as those in the embodiment shown in FIG. 1 will be omitted as appropriate.

  The memory cell 51 has a nonmagnetic layer 16. On the surface of the nonmagnetic material layer 16, similarly to the first embodiment, the write magnetization fixed terminal 1 and the read magnetoresistive effect element 2 are installed, and further, the write magnetization fixed terminal 3 is installed. ing.

  Similar to the write magnetization fixed terminal 1, the write magnetization fixed terminal 3 has a two-layer structure in which a diamagnetic layer 20 and a ferromagnetic layer 21 are stacked, and the ferromagnetic layer 21 is a nonmagnetic layer. 16 is in contact.

  The configuration, material, bonding method, and the like of the write magnetization fixed terminal 1 and the write magnetization fixed terminal 3 can be the same as those in the first embodiment. Here, the magnetization directions of the ferromagnetic layer 12 and the ferromagnetic layer 21 included in both are the same.

  The configuration, material, joining method, etc. of the magnetoresistive effect element 2 for reading are typically the same as in the first embodiment.

  In the memory cell 51, spin injection is performed by the two write fixed magnetization terminals 1 and 3.

  When a current is passed from the nonmagnetic layer 16 to the write magnetization fixed terminal 1 and the write magnetization fixed terminal 3, a large number of spins of the ferromagnetic layer 12 and the ferromagnetic layer 21 are injected and accumulated in the nonmagnetic layer 16. The Since the ferromagnetic layer 12 and the ferromagnetic layer 21 have the same magnetization direction as described above, the directions of the majority spins injected from both are the same.

  In this way, the number of write fixed magnetization terminals for one read magnetoresistive effect element is two as in this embodiment, and the number may be increased further. By adopting such a configuration, even when the same voltage is applied, the number of accumulated spins in the nonmagnetic material layer 16 can be increased as compared with the first embodiment, so that spins flowing into the free layer 15 can be increased. The injection volume also increases.

  Contrary to the above, when a current is passed from the write fixed magnetization terminal 1 and the write fixed magnetization terminal 3 to the nonmagnetic layer 16, the ferromagnetic layer 12 and the ferromagnetic layer 21 are the same as in the first embodiment. Accepts spin electrons corresponding to the magnetization direction, the amount of spin outflow from the free layer 15 is increased as compared with the first embodiment.

  For example, when the critical current causing spin torque magnetization reversal in the free layer 15 is 5 mA, in the memory cell 51, 2.5 mA is supplied to the write magnetization fixed terminal 1 and 2.5 mA is supplied to the write magnetization fixed terminal 3. Thus, a write operation can be performed.

  As described above, in the magnetic memory element of this embodiment, by increasing the number of magnetization fixed terminals for writing, the current flowing through the wiring in the element is lowered, and the problem of element deterioration and destruction due to heat and electromigration is suppressed. This can improve the reliability of the memory element.

  FIG. 5 is an explanatory diagram for explaining an example of a circuit configuration of a magnetic memory element using the memory cell 31. Hereinafter, a description will be given with reference to FIG.

  One memory bit is composed of a memory cell 31 and a cell selection transistor 34 composed of an FET (Field Effect Transistor).

  The magnetization fixed terminal 1 for writing in the memory cell 31 is connected to the writing connection portion 32, and the magnetoresistive effect element 2 for reading is connected to the reading connection portion 33.

  The memory bits are arranged in a matrix, the write connection unit 32 is connected to the second bit line 36, and the read connection unit 33 is connected to the first bit line 35. The gate of the cell selection transistor 34 is connected to the word line 37.

  In writing data, first, a current sufficient to cause spin torque magnetization reversal is applied to the write magnetization fixed terminal 1 of the memory cell 31 in the second bit line 36 connected to the memory bit at the designated address. Apply a voltage that can be supplied.

  Next, a voltage is applied to the word line 37 on the designated address.

  Then, a current flows in the memory cell 31 at that address, and the magnetization reversal of the free layer 15 is performed according to the polarity of the injected spin electrons.

  In reading data, a voltage is applied to the first bit line 35 and the word line 37 at the designated address.

  Then, since the magnitude of the magnetoresistance effect of the memory cell 31 at the address can be acquired from the flowing current, data can be read out.

  FIG. 6 is a cross-sectional view showing the configuration of the memory bit of the magnetic memory element shown in FIG. Hereinafter, a description will be given with reference to FIG.

  As the cell selection transistor 34, an FET including a source 44, a drain 43, and a gate 42 is formed on a Si substrate.

  The gate 42 is connected to the word line 37. The drain 43 is connected to the nonmagnetic material layer 16 through the connection portion 41.

  The write magnetic fixed terminal 1 and the read magnetoresistive effect element 2 formed on the nonmagnetic layer 16 are connected to the write connection portion 32 and the read connection portion 33, respectively. A second bit line 36 is formed on the write connection portion 32, and a first bit line 35 is formed on the read connection portion 33.

  With such a configuration, a magnetic memory element composed of a plurality of memory cells 31 can be realized. In the present embodiment, one write magnetic fixed terminal 1 is provided for one memory cell 31. However, as in the second embodiment, a plurality of write magnetic fixed terminals are provided and each of the second magnetic fixed terminals is set to the second. It may be connected to the bit line 36.

  As described above, according to the present invention, while utilizing the magnetization reversal mechanism using spin current, the deterioration and destruction of the element due to the current at the time of writing are suppressed, and the reading speed is increased, and the magnetic memory An element can be provided.

1 is a cross-sectional view showing a structure of a memory cell of a magnetic memory element according to a first embodiment of the present invention. It is explanatory drawing which shows the operation | movement of the spin torque magnetization reversal by the spin flow which arises in a memory cell. It is explanatory drawing which shows the operation | movement of the spin torque magnetization reversal by the spin flow which arises in a memory cell. It is the graph which drew the hysteresis which shows the mode of spin torque magnetization reversal obtained by experiment. It is sectional drawing which shows the structure of the memory cell of the magnetic memory element based on the 2nd Embodiment of this invention. It is explanatory drawing explaining an example of the circuit structure of the magnetic memory element using a memory cell. It is sectional drawing which shows the structure of the memory bit of a magnetic memory element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Write magnetization fixed terminal 2 Read magnetoresistive effect element 3 Write magnetization fixed terminal 11 Antiferromagnetic material layer 12 Ferromagnetic material layer 13 Pin layer 14 Nonmagnetic intermediate | middle layer 15 Free layer 16 Nonmagnetic material layer 17 Ammeter 18 DC power supply 19 DC current source 20 Diamagnetic layer 21 Ferromagnetic layer 31 Memory cell 32 Write connection portion 33 Read connection portion 34 Cell selection transistor 35 First bit line 36 Second bit line 37 Word line 41 Connection portion 42 Gate 43 drain 44 source 51 memory cell

Claims (8)

A planar non-magnetic layer;
A ferromagnetic layer made of a ferromagnetic material installed on the surface of the nonmagnetic material layer and having a fixed magnetization direction;
A free layer made of a ferromagnetic material installed on the surface of the nonmagnetic material layer and having a variable magnetization direction;
A spin quantum of spin current flowing between the nonmagnetic layer and the ferromagnetic layer by changing a direction of a current flowing between the nonmagnetic layer and the ferromagnetic layer. Changing the magnetization axis changes the magnetization direction of the free layer,
Information is stored depending on whether the direction of magnetization of the ferromagnetic layer and the direction of magnetization of the free layer are substantially parallel or substantially antiparallel. The memory cell of claim 1,
A plurality of ferromagnetic materials whose magnetization directions are fixed as the ferromagnetic material layer are disposed at different positions on the surface of the nonmagnetic material layer. The memory cell according to claim 1 or 2,
The memory cell, wherein the ferromagnetic material forming the free layer is an alloy or a compound containing at least one magnetic material. The memory cell according to claim 1 or 2,
The contact area between the nonmagnetic layer and the free layer is 2.0 × 10 ⁴ nm ² or less. A memory cell according to any one of claims 1 to 4, wherein
The memory cell, wherein an interface between the non-magnetic layer and the free layer is ohmic-junction. A memory cell according to any one of claims 1 to 5,
A memory cell, wherein the nonmagnetic layer is a semiconductor or a superconductor. The memory cell according to any one of claims 1 to 6,
The memory cell, wherein the nonmagnetic layer has a thickness of 50 nm or more. A magnetic memory element comprising a plurality of memory cells according to claim 1 arranged in a matrix.

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