WO2010128615A1 - Storage element and storage method - Google Patents

Storage element and storage method Download PDF

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Publication number
WO2010128615A1
WO2010128615A1 PCT/JP2010/056650 JP2010056650W WO2010128615A1 WO 2010128615 A1 WO2010128615 A1 WO 2010128615A1 JP 2010056650 W JP2010056650 W JP 2010056650W WO 2010128615 A1 WO2010128615 A1 WO 2010128615A1
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layer
value
free layer
magnetization
free
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PCT/JP2010/056650
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French (fr)
Japanese (ja)
Inventor
幸男 菊地
健一 今北
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株式会社アルバック
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices
    • G01R33/093—Magnetoresistive devices using multilayer structures, e.g. giant magnetoresistance sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
    • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
    • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
    • G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/10—Magnetoresistive devices

Definitions

  • the present invention relates to a storage element and a storage method.
  • a memory element using a magnetic multilayer film that exhibits a tunneling magnetoresistive (TMR) effect is applied to a nonvolatile memory such as an MRAM.
  • the multilayer film of the tunnel magnetoresistive element has two magnetic layers and an insulating layer sandwiched therebetween.
  • the insulating layer is made of a material such as alumina or MgO.
  • the insulating layer is thin, and when a sense current is passed vertically on the multilayer film surface to operate as a memory element, each film is stacked through an insulating layer sandwiched between two magnetic layers by the tunnel effect. A tunnel current flows vertically.
  • the resistance value of the tunnel magnetoresistive element is small when the magnetization directions of the two magnetic layers are the same, and large when they are opposite. In a conventionally used rectangular or elliptical tunnel magnetoresistive element, it is possible to fabricate a memory element adopting the binary method by making the resistance value large and small correspond to “0” and “1”.
  • a ternary or quaternary memory element may be manufactured instead of a binary memory element.
  • a multi-layered film in which three or more magnetic layers having different coercive forces are stacked and a plurality of magnetoresistive elements having different tunnel resistance values are connected in series can be considered. There is a problem that the cost is high.
  • the present invention was created to solve the above-described disadvantages of the prior art, and an object of the present invention is to provide a storage element and a storage method for storing ternary or quaternary values with a conventional simple multilayer film structure. is there.
  • the present invention is magnetized in a direction perpendicular to the film thickness direction and has a fixed layer having a predetermined coercive force, and is magnetized in a direction parallel to the magnetization direction of the fixed layer.
  • the fixed layer has a free layer smaller than the fixed layer, and an insulating layer sandwiched between the fixed layer and the free layer.
  • the magnetization of the fixed layer A storage element in which a first and a second magnetoresistive element in which a tunnel current flows in the insulating layer with a resistance value corresponding to a difference between a direction and a magnetization direction of the free layer, the first magnetoresistance
  • the length of the free layer of the element along the magnetization direction is longer than the length of the second magnetoresistive element along the magnetization direction of the second magnetoresistive element, with respect to an external magnetic field opposite to the magnetization direction.
  • the coercivity of the free layer of the second magnetoresistive element is the first magnetism.
  • resistive element is greater than the coercive force of the free layer, ternary or 4 values by the magnitude of the resistance value of the memory element to be stored.
  • a fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force, and magnetized in a direction parallel to the magnetization direction of the fixed layer, the coercive force is smaller than that of the fixed layer.
  • the free layer is formed in a shape having a planar shape having a width and a longitudinal direction longer than the width, and the longitudinal directions of the free layers of the first and second magnetoresistive elements are arranged at right angles to each other.
  • the free layer of the first magnetoresistive element is the free layer Magnetized parallel to the longitudinal direction
  • the free layer of the second magnetoresistive element is magnetized parallel to the length direction of the width of the free layer, and an external magnetic field opposite to the magnetization direction is applied.
  • the coercive force of the free layer of the second magnetoresistive element is made larger than the coercive force of the free layer of the first magnetoresistive element, and a ternary value or a quaternary value is stored as the resistance value. Storage element.
  • a fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force, and magnetized in a direction parallel to the magnetization direction of the fixed layer, the coercive force is smaller than that of the fixed layer.
  • the length along the magnetization direction is longer than the length along the magnetization direction of the free layer of the second magnetoresistive element, and the second magnetic field is applied to a spin injection current that reverses the magnetization direction.
  • the strength of the first magnetoresistive element is greater than the strength against magnetization reversal when the spin injection current of the free layer flows, and the memory stores 3 or 4 values as the resistance value. It is an element.
  • a fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force, and magnetized in a direction parallel to the magnetization direction of the fixed layer, the coercive force is smaller than that of the fixed layer.
  • the free layer is formed in a shape having a planar shape having a width and a longitudinal direction longer than the width, and the longitudinal directions of the free layers of the first and second magnetoresistive elements are arranged at right angles to each other.
  • the free layer of the first magnetoresistive element is the free layer A spin injection current that is magnetized parallel to the longitudinal direction
  • the free layer of the second magnetoresistive element is magnetized parallel to the length direction of the width of the free layer to reverse the magnetization direction
  • the strength against magnetization reversal when the spin injection current of the free layer of the second magnetoresistive element flows is that when the spin injection current of the free layer of the first magnetoresistive element flows.
  • This is a storage element that is larger than the strength against magnetization reversal and stores three or four values in terms of the resistance value.
  • the present invention is a memory element, wherein the free layers of the first and second magnetoresistive elements are connected to each other.
  • the present invention is a memory element, wherein the fixed layers of the first and second magnetoresistive elements are connected to each other.
  • the present invention is a memory element, wherein the insulating layers of the first and second magnetoresistive elements are connected to each other.
  • the present invention is a storage method for storing first, second, and third values using the storage element, wherein the first and second magnetoresistors are used for storing the first value.
  • the first and second magnetoresistive elements are oriented in the same direction as the magnetization direction of the fixed layer, so that both elements exhibit the same magnetization direction resistance value. In order to store the parallel resistance value of the second magnetoresistive element in correspondence with the first value, and to store the second value, both the first and second magnetoresistive elements have opposite magnetization directions.
  • the magnetization direction of the free layer of the first and second magnetoresistive elements is directed to the opposite direction to the magnetization direction of the fixed layer, respectively.
  • the magnetization direction of the free layer of the one magnetoresistive element is oriented in the same direction as the magnetization direction of the fixed layer so that the magnetoresistive element exhibits the same magnetization direction resistance value, and the other magnetoresistive element
  • the parallel resistance of the first and second magnetoresistive elements is set so that the magnetization direction of the free layer of the other magnetoresistive element is directed to the opposite direction to the magnetization direction of the fixed layer so as to indicate a magnetization unidirectional resistance value.
  • a storage method for storing a value in association with the third value is a storage method for rewriting a first value, a second value, and a third value, and storing the rewritten value, wherein only the magnetization direction of the free layer of the first magnetoresistive element is reversed.
  • an external magnetic field larger than the coercive force of the free layer of the first magnetoresistive element and smaller than the coercive force of the free layer of the second magnetoresistive element is applied to the first magnetoresistive element.
  • the storage method stores the rewritten value by applying in the direction opposite to the magnetization direction of the free layer.
  • the present invention is a storage method for rewriting a first value, a second value, and a third value, and storing the rewritten value, wherein only the magnetization direction of the free layer of the first magnetoresistive element is reversed.
  • the magnetization direction of the free layer of the first magnetoresistive element is reversed, and the strength of the first magnetoresistive element against the magnetization reversal when the spin injection current of the free layer flows is greater than
  • the storage method stores a rewritten value by supplying a spin injection current smaller than the strength against magnetization reversal when the spin injection current of the free layer of the second magnetoresistive element flows.
  • the present invention is a storage method for measuring a resistance value of the storage element and reading a value stored from the resistance value, measuring the resistance value of the storage element and comparing it with a reference value, and The case where it is determined that the resistance value of the resistance element is the magnetization direction resistance value is the first value, and the case where it is determined that the resistance value of both the magnetoresistance elements is the magnetization direction resistance value
  • the magnetization direction of the magnetic layer when the magnetization direction of the magnetic layer is parallel to the direction of the external magnetic field and the major axis is longer than the minor axis (here, 1.5 times or longer), the magnetization direction is parallel to the major axis.
  • the layer pays attention to the fact that the magnetization direction can be reversed with an external magnetic field smaller than that of the magnetic layer whose magnetization direction is parallel to the minor axis (referred to as magnetic shape anisotropy).
  • the state in which the magnetic layer is magnetized is a state in which the N pole and the S pole appear at both ends of the magnetization direction of the magnetic layer. Create a magnetic field (demagnetizing field) in the opposite direction.
  • the size of the internal demagnetizing field is proportional to the size of the magnetization, and at the same time, depends on the shape of the magnetization direction. Magnetic field becomes 0).
  • the magnetic field acting inside the magnetic layer is considered to be given by the difference between the external magnetic field and the demagnetizing field.
  • FIG. 3 (a) and 3 (b) show the strength and magnetism of an external magnetic field when an external magnetic field parallel to and opposite to the magnetization direction is applied to a magnetic layer magnetized in a direction parallel to the major axis and minor axis. It is the result of having measured the relationship of the magnetization of the layer.
  • the magnetic layer magnetized in the direction parallel to the long axis is inverted by a weak external magnetic field ⁇ H 1 to saturate the magnetization (FIG. 3A), but the magnetic layer magnetized in the direction parallel to the short axis is Since the magnetization changes linearly until it is inverted at ⁇ H 2 larger than ⁇ H 1 , the magnetization is not saturated unless a large external magnetic field is applied (FIG. 3B).
  • the present invention controls the area ratio of the free layers of the first and second magnetoresistive elements so that the magnetization directions of the free layer and the fixed layer of one magnetoresistive element are the same and the other magnetoresistive is The resistance value when the magnetization directions of the free layer and the fixed layer of the element are opposite directions, the resistance value when the magnetization directions of the free layer and the fixed layer of both magnetoresistive elements are the same direction, and the resistance value of both magnetoresistive elements
  • This is a memory element that can control the resistance value when the magnetization directions of the free layer and the fixed layer are opposite to each other.
  • the resistance value is not the maximum or minimum value, but the magnetic fields of the two magnetic layers of one element are in the same direction.
  • An intermediate value can be taken when the magnetic fields of the two magnetic layers of the other element are in opposite directions, and a ternary or quaternary storage element can be obtained by discriminating the maximum value, intermediate value, and minimum value. .
  • the storage capacity can be increased as compared with the binary storage medium without increasing the density of the storage elements.
  • a multilayer film conventionally used can be used, there is no need to newly create a multilayer film having a complicated laminated structure, and a ternary or quaternary memory element can be obtained at low cost.
  • FIG. 1 The top view of the memory element of this invention Sectional view taken along the line AA of the memory element of the present invention.
  • Reference numeral 10 in FIG. 1 is a plan view of a memory element according to the present invention.
  • the memory element 10 has first and second magnetoresistive elements 11 and 12.
  • FIG. 2 is a cross-sectional view of the memory element 10 taken along the line AA.
  • the first and second magnetoresistive elements 11 and 12 are magnetized in a direction parallel to the magnetization direction of the fixed layer 48 having a predetermined coercive force, the insulating layer 43, and the fixed layer 48, and the coercive force has a fixed layer 48. It has smaller free layers 22, 32.
  • First and second magnetoresistive elements 11 and 12 are formed. After the free layers 22 and 32 are etched, a SiO 2 layer 41 is laminated from the free layers 22 and 32 side, and then the SiO 2 layer 41 is etched to expose the surfaces of the free layers 22 and 32.
  • the second electrode 62 is formed so as to be in close contact with the surfaces of the free layers 22 and 32.
  • the insulating layer 43 is thin, and when a voltage is applied between the free layers 22 and 32 and the fixed layer 48, a tunnel current flows in a direction perpendicular to each layer due to the tunnel effect.
  • the conductance values of the first and second magnetoresistive elements 11 and 12 are large when the magnetization directions of the free layers 22 and 32 are the same as the magnetization direction of the fixed layer 48, and vice versa. Small in the direction (conductance value is the reciprocal of the resistance value). Accordingly, the first and second magnetoresistive elements 11 and 12 function as tunnel magnetoresistive elements.
  • the planar shapes of the free layers 22 and 32 (hereinafter referred to as the first and second free layers) of the first and second magnetoresistive elements 11 and 12 are as follows. It has a width direction 52, 54 that is vertical and shorter than the length in the longitudinal direction.
  • the length of the first free layer 22 in the longitudinal direction 51 is 1.5 times or more the length of the width direction 52.
  • the first and second free layers 22 and 32 are magnetized in directions parallel to each other.
  • the length along the magnetization direction of the first free layer 22 is longer than the length along the magnetization direction of the second free layer 32, where the first and second free layers 22, 32 are longitudinal.
  • the directions 51 and 53 are arranged so as to be perpendicular to each other.
  • the coercive force (hereinafter referred to as the first coercive force) of the first free layer 22 magnetized in the longitudinal direction 51 against the external magnetic field opposite to the magnetization direction is the first magnetized in the width direction 54. It is smaller than the coercive force of the second free layer 32 (hereinafter referred to as the second coercive force).
  • the strength against magnetization reversal when the spin injection current of the first free layer 22 magnetized in the longitudinal direction 51 flows against the spin injection current that reverses the magnetization direction is magnetized in the width direction 54.
  • the second free layer 32 is made smaller than the strength against magnetization reversal when the spin injection current flows.
  • first and second free layers 22 and 32 are arranged so that the longitudinal directions 51 and 53 are perpendicular to each other.
  • the present invention is not limited to this, and the first and second free layers 22 and 32 are arranged.
  • the layers 22 and 32 are included in the present invention when the straight lines extending along the longitudinal directions 51 and 53 are arranged so as to intersect each other.
  • the fixed layer 48 is in contact with and electrically connected to the first electrode 61, and the first and second free layers 22 and 32 are respectively connected to the second electrode 62. Is in contact with and electrically connected. Therefore, the memory element 10 forms a parallel connection circuit in which the first and second magnetoresistive elements 11 and 12 are connected in parallel.
  • the minimum conductance values of the first and second magnetoresistive elements 11 and 12 are C1 and C2, respectively, and the maximum values are C1 + ⁇ C1 and C2 + ⁇ C2, respectively.
  • FIG. 4A to 4D show changes in the magnetization directions F 1 and F 2 of the first and second free layers 22 and 32 with respect to the magnetization direction F 0 of the fixed layer 48 inside the memory element 10. ing.
  • the conductance value is a maximum value close to the value represented by C1 + C2 + ⁇ C1 + ⁇ C2. (Because the current that originally flows through the low conductance portion flows into the high conductance portion, the change in the conductance of the entire element is not accurately ⁇ C1 + ⁇ C2, Close to that).
  • the conductance of the memory element 10 has four conductance values of the maximum value C1 + C2 + ⁇ C1 + ⁇ C2, the first intermediate value C1 + C2 + ⁇ C1, the second intermediate value C1 + C2 + ⁇ C2, and the minimum value C1 + C2.
  • the first conductance difference ⁇ C1 is larger than the second conductance difference ⁇ C2 ( ⁇ C1> ⁇ C2)
  • the first intermediate value becomes a large intermediate value
  • the second intermediate value becomes a small intermediate value.
  • the second conductance difference ⁇ C2 ⁇ C1 ⁇ C2
  • the second intermediate value becomes a large intermediate value
  • the first intermediate value becomes a small intermediate value.
  • the first reference value is placed between the maximum value and the large intermediate value
  • the second reference value is placed between the small intermediate value and the minimum value
  • the three conductances of maximum value, minimum value, and intermediate value are set.
  • a ternary memory element can be obtained.
  • a third reference value is placed between the large intermediate value and the small intermediate value, and the maximum value, the large intermediate value, the small intermediate value, and the minimum value are set.
  • a four-value memory element is obtained by discriminating the four conductance values.
  • FIG. 5 is a cross-sectional view showing an example of the storage device 1 such as an MRAM.
  • the storage device 1 has a plurality of first and second wirings 5 and 6.
  • the first wiring 5 is arranged parallel to each other with a predetermined interval, and the second wiring 6 intersects the first wiring 5 in a plane parallel to the plane where the first wiring 5 is arranged.
  • the first and second wirings 5 and 6 are embedded in an insulating layer 2 such as SiO 2 .
  • the memory element 10 of the present invention is disposed in the vicinity of the three-dimensional intersection position of the first and second wirings 5 and 6. Since the intersection positions of the first and second wirings 5 and 6 are arranged in a matrix, the memory elements 10 are arranged in a matrix.
  • the first and second electrodes 61 and 62 of the memory element 10 are respectively connected to first and second wirings 5 and 6 that intersect in the vicinity of the memory element 10.
  • the first and second wirings 5 and 6 are connected to the control device 8.
  • the control device 8 selects the first and second wirings 5 and 6 to pass a current through the desired storage element 10, and the measurement device 9 stores the current flowing through the storage device 10.
  • the conductance value is measured from the voltage and current between the electrodes of the element 10, and the measurement result is transmitted to the control device 8.
  • the conductance value of the memory element 10 of the present invention can be obtained in three ways of the maximum value, the minimum value, and the intermediate value, and at least the maximum value and the minimum value of the conductance are set as the reference values in the control device 8. ing.
  • the control device 8 compares the measurement result of the measurement device 9 with the set conductance value (reference value), and the measurement result corresponds to the maximum value, the minimum value, or between the maximum value and the minimum value (intermediate value). Judge whether to do.
  • the control device 8 associates the determined result with information such as “0”, “1”, “2”, etc., and reads it as information. Therefore, in the storage device 1, the first and second wirings 5 and 6, the control device 8, and the measurement device 9 constitute a reading unit that reads information.
  • the rewrite wiring 4 is extended along the wiring of the first wiring 5. Since the first wiring 5 intersects with the second wiring 6, the rewrite wiring 4 also intersects with the second wiring 6. Each memory element 10 is disposed between the rewrite wiring 4 and the second wiring 6 at the intersection of the rewrite wiring 4 and the second wiring 6. The rewrite wiring 4 is not in contact with the memory element 10 and the first and second wirings 5 and 6 and is insulated.
  • the rewrite wiring 4 is connected to the control device 8.
  • the positional relationship between the rewrite wiring 4 and the second wiring 6 and the memory element 10 is set in the control device 8.
  • the control device 8 selects one of the target storage elements 10 among the rewrite wirings 4 and the second wirings 6 arranged in a lattice shape and energizes them.
  • a magnetic field is generated around the rewrite wiring 4 and the second wiring 6, a composite magnetic field is generated near the intersection of the rewriting wiring 4 and the second wiring 6, and other elements are affected by the magnetic field. Absent. Therefore, only the memory elements 10 at the intersection of the selected wirings 4 and 6 among the plurality of memory elements 10 arranged in a matrix are exposed to the synthesized magnetic field.
  • the energization conditions such as the direction and strength of the current flowing through the rewrite wiring 4 and the second wiring 6 are changed, the direction and strength of the synthetic magnetic field change.
  • the energization conditions for creating each combined magnetic field that sets the conductance of the storage element 10 to the maximum value, the minimum value, and the intermediate value are obtained in advance and set in the control device 8.
  • the control device 8 associates the information to be stored with the conductance of the storage element 10, and allows current to flow through the rewrite wiring 4 and the second wiring 6 under the energization condition that sets the conductance to an associated value, and stores desired storage information in the storage element 10. Memorize as conductance.
  • the second wiring 6, the rewriting wiring 4, and the control device 8 serve as a rewriting means for rewriting information, but the rewriting means is not limited to this.
  • the rewriting means may be composed of only the rewrite wiring 4 and the control device 8.
  • the control device 8 selects the rewrite wiring 4 and energizes it, and rewrites the information in the storage element 10 on the selected rewrite wiring 4.
  • the rewriting means may be constituted by the first and second wirings 5 and 6 and the control device 8 without providing the rewriting wiring 4.
  • the control device 8 selects and energizes the first and second wirings 5 and 6, generates a synthetic magnetic field at the crossing position of the selected first and second wirings 5 and 6, and Information in the memory element 10 in the vicinity of the position is rewritten.
  • the control device 8 selects the first and second wirings 5 and 6 and spins to reverse the magnetization.
  • the information in the memory element 10 may be rewritten by flowing an injection current.
  • the magnetization direction of the first free layer is reversed and is greater than the strength against magnetization reversal when the spin injection current of the first free layer flows.
  • the information in the memory element 10 is rewritten by applying a spin injection current smaller than the strength against magnetization reversal when the spin injection current of the second free layer flows.
  • the rewriting means has the control device 8 and the wiring, and the control device 8 rewrites the information of the memory element 10 on the wiring by selecting the wiring and energizing it.
  • Rewriting means for example, a magnetic field forming means such as a very small electromagnet
  • Rewriting means may be provided outside the storage device 1 and information may be rewritten by bringing the rewriting means close to the storage element 10 that needs rewriting from the outside.
  • the conductance value is determined from the voltage and current between the electrodes of the memory element 10 to determine the ternary value or the quaternary value. included. Further, the ternary value or the quaternary value may be determined from the voltage value or current value between the electrodes of the memory element 10.
  • the resistance values of the first and second magnetoresistive elements 11 and 12 when the magnetization directions of the first and second free layers 22 and 32 are the same as the magnetization direction of the fixed layer 48 are the same. It is called the direction resistance value, and the resistance value in the reverse direction is called the magnetization opposite direction resistance value.
  • the present invention is not limited to the case where the first and second free layers 22 and 32 are separated.
  • N pole (+) and S pole ( ⁇ ) appear at both ends of the magnetization direction as shown in FIG.
  • the first and second free layers 22 and 32 are connected because the distance between the N pole and the S pole is related to the strength against magnetization reversal when a coercive force or a spin injection current flows
  • the first free layer 22 magnetized in the longitudinal direction and the second free layer 32 magnetized in the width direction can be discriminated.
  • the free layers of the first and second magnetoresistive elements 11 and 12 are separated and the insulating layer and the fixed layer are connected, and the free layer, the insulating layer, and the fixed layer are all connected.
  • the case where the free layer and the insulating layer are separated and the fixed layer is connected, and the case where the free layer, the insulating layer, and the entire fixed layer are separated are also included.
  • the fixed layer is separated and the free layer and the insulating layer are connected.
  • the case includes a case where the free layer and the fixed layer are separated and the insulating layer is connected, and a case where the insulating layer and the fixed layer are separated and the free layer is connected.
  • the fixed layer 48 has an antiferromagnetic layer 47 and a magnetic layer 46, and is formed on a Si substrate 49 in the order of a first electrode 61, an antiferromagnetic layer 47, and a magnetic layer 46.
  • the coercive force of the magnetic layer 46 is increased when the magnetic layer 46 and the antiferromagnetic layer 47 are brought into contact with each other.
  • the present invention is not limited to the case where the magnetization direction of the fixed layer 48 is fixed by providing the antiferromagnetic layer 47, and the coercive force of the magnetic layer 46 is sufficiently higher than both the first and second coercive forces.
  • the antiferromagnetic layer 47 may not be provided.
  • the coercive force of the magnetic layer 46 is usually about several tens of gauss, whereas when the magnetization direction is fixed by the antiferromagnetic layer 47, the coercive force increases to about 600 to 800 gauss.
  • the difference from the first and second coercive forces can be made larger.
  • the constituent material of the antiferromagnetic layer 47 is, for example, PtMn.
  • the constituent material of the magnetic layer 46 is, for example, a ferrimagnetic material in which CoFeB / Ru / CoFe is laminated.
  • the constituent material of the free layers 22 and 32 is, for example, CoFeB whose coercive force differs by about one digit.
  • the constituent material of the insulating layer 43 is not particularly limited. For example, either or both of MgO and alumina (Al 2 O 3 ) can be used. However, when MgO is used, the resistance change rate of the memory element 10 is increased. Particularly preferred.

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Abstract

Disclosed are a storage element having a large storage capacity, and a storage method. The storage element is configured such that first and second magnetoresistive elements are connected in parallel. The first and the second magnetoresistive elements have a common fixed layer, first and second free layers (22, 32) having coercive forces smaller than the coercive force of the fixed layer, and a common insulating layer sandwiched between the fixed layer and the free layers. Each of the first and the second free layers (22, 32) has a shape having a longitudinal direction length and a width direction length shorter than the longitudinal direction length, and the free layers are disposed such that the straight lines extending in the respective longitudinal directions are perpendicular to each other. The magnetization direction (F0) of the fixed layer and the magnetization directions (F1, F2) of the first and the second free layers (22, 32) are parallel to the longitudinal direction of the first free layer (22). The coercive force of the first free layer (22) which is magnetized in the longitudinal direction is smaller than that of the second free layer (32) magnetized in the width direction. Therefore, ternary or quaternary storage is made possible by inverting the magnetization direction (F1) of the first free layer without changing the magnetization direction (F2) of the second free layer (32).

Description

記憶素子及び記憶方法Storage element and storage method
　本発明は、記憶素子及び記憶方法に関する。 The present invention relates to a storage element and a storage method.
　現在、トンネル磁気抵抗（ＴＭＲ：Ｔｕｎｎｅｌｉｎｇ　Ｍａｇｎｅｔｏ－Ｒｅｓｉｓｔｉｖｅ）効果を発現する磁性多層膜を用いた記憶素子（トンネル磁気抵抗素子）は、ＭＲＡＭ等の不揮発性メモリー等に応用されている。
　トンネル磁気抵抗素子の多層膜は、二層の磁性層と、その間に挟まれる絶縁層を有している。絶縁層はアルミナあるいはＭｇＯなどの材料が使用される。 At present, a memory element (tunnel magnetoresistive element) using a magnetic multilayer film that exhibits a tunneling magnetoresistive (TMR) effect is applied to a nonvolatile memory such as an MRAM.
The multilayer film of the tunnel magnetoresistive element has two magnetic layers and an insulating layer sandwiched therebetween. The insulating layer is made of a material such as alumina or MgO.
　絶縁層の膜厚は薄く、記憶素子として動作させるために多層膜面上に垂直にセンス電流を流すと、トンネル効果により、二層の磁性層の間に挟まれる絶縁層を通して各膜の積層に垂直にトンネル電流が流れる。
　トンネル磁気抵抗素子の抵抗値は、二層の磁性層の磁化方向が互いに同じ向きの場合に小さく、逆向きの場合に大きい。
  従来採用されている矩形あるいは楕円形のトンネル磁気抵抗素子では、大小の抵抗値を『０』『１』に対応させることにより二進法を採用した記憶素子を作製することが可能であった。 The insulating layer is thin, and when a sense current is passed vertically on the multilayer film surface to operate as a memory element, each film is stacked through an insulating layer sandwiched between two magnetic layers by the tunnel effect. A tunnel current flows vertically.
The resistance value of the tunnel magnetoresistive element is small when the magnetization directions of the two magnetic layers are the same, and large when they are opposite.
In a conventionally used rectangular or elliptical tunnel magnetoresistive element, it is possible to fabricate a memory element adopting the binary method by making the resistance value large and small correspond to “0” and “1”.
特開２００３－１９７８７５JP 2003-197875 A 特開２００６－０１３４３０JP 2006-013430 A
  現在研究開発が進められている不揮発性メモリーのＭＲＡＭにしても、あるいは量産され更に微細化が進められているＤＲＡＭにしても、情報の基本となるビットは『０』『１』の二進法を基本としている。そのためそれが揮発であれ不揮発であれ、容量という観点から見れば優位性はない。 Whether it is a non-volatile memory MRAM that is currently being researched or developed, or a DRAM that is mass-produced and further miniaturized, the basic bits of information are based on the binary system of “0” and “1”. It is said. Therefore, whether it is volatile or non-volatile, there is no advantage from the viewpoint of capacity.
　これらの記憶容量を増やすためには記憶素子の個数（密度）を増やすこと以外に解はなく、そのためには微細化をより進める以外に方法はないが、記憶素子の微細化には限界がある。従って、微細化以外の方法で記録密度を向上させるための手段が必要である。 In order to increase these storage capacities, there is no solution other than increasing the number (density) of storage elements. For that purpose, there is no method other than further miniaturization, but there is a limit to miniaturization of storage elements. . Therefore, a means for improving the recording density by a method other than miniaturization is necessary.
　微細化以外の方法として、２値の記憶素子に代わり３値又は４値の記憶素子を作製することが考えられる。一例として、異なる保磁力の磁性層を三層以上積層した多層膜で、異なるトンネル抵抗値を持った磁気抵抗素子を複数直列に接続する方法が考えられるが、その方法では新たに複雑な多層膜を作製する必要があり、コストが高いという問題があった。
　本発明は上記従来技術の不都合を解決するために創作されたものであり、その目的は、従来の単純な多層膜構造で３値又は４値を記憶する記憶素子及び記憶方法を提供することにある。 As a method other than miniaturization, a ternary or quaternary memory element may be manufactured instead of a binary memory element. As an example, a multi-layered film in which three or more magnetic layers having different coercive forces are stacked and a plurality of magnetoresistive elements having different tunnel resistance values are connected in series can be considered. There is a problem that the cost is high.
The present invention was created to solve the above-described disadvantages of the prior art, and an object of the present invention is to provide a storage element and a storage method for storing ternary or quaternary values with a conventional simple multilayer film structure. is there.
  上記課題を解決するために、本発明は膜厚方向とは垂直な方向に磁化され、所定の保磁力を有する固定層と、前記固定層の磁化方向と平行な方向に磁化され、保磁力が前記固定層よりも小さい自由層と、前記固定層と前記自由層とで挟まれた絶縁層とを有し、前記固定層と前記自由層との間に電圧を印加すると、前記固定層の磁化方向と前記自由層の磁化方向の異同に応じた抵抗値で前記絶縁層にトンネル電流が流れる第一、第二の磁気抵抗素子が並列接続された記憶素子であって、前記第一の磁気抵抗素子の前記自由層の前記磁化方向に沿った長さは、前記第二の磁気抵抗素子の前記自由層の前記磁化方向に沿った長さより長くされ、磁化方向とは逆向きな外部磁界に対し、前記第二の磁気抵抗素子の前記自由層の保磁力は、前記第一の磁気抵抗素子の前記自由層の保磁力よりも大きくされ、抵抗値の大きさで３値又は４値が記憶される記憶素子である。
　本発明は、膜厚方向とは垂直な方向に磁化され、所定の保磁力を有する固定層と、前記固定層の磁化方向と平行な方向に磁化され、保磁力が前記固定層よりも小さい自由層と、前記固定層と前記自由層とで挟まれた絶縁層とを有し、前記固定層と前記自由層との間に電圧を印加すると、前記固定層の磁化方向と前記自由層の磁化方向の異同に応じた抵抗値で前記絶縁層にトンネル電流が流れる第一、第二の磁気抵抗素子が並列接続された記憶素子であって、前記第一、第二の磁気抵抗素子がそれぞれ有する前記自由層は、平面形状が、幅と、前記幅よりも長い長手方向とを有する形状に形成され、前記第一、第二の磁気抵抗素子の前記自由層の前記長手方向は互いに直角に配置され、前記第一の磁気抵抗素子の前記自由層は、その前記自由層の前記長手方向と平行に磁化され、前記第二の磁気抵抗素子の前記自由層は、その前記自由層の前記幅の長さ方向と平行に磁化されて、磁化方向とは逆向きな外部磁界に対し、前記第二の磁気抵抗素子の前記自由層の保磁力は、前記第一の磁気抵抗素子の前記自由層の保磁力よりも大きくされ、抵抗値の大きさで３値又は４値が記憶される記憶素子である。
　本発明は、膜厚方向とは垂直な方向に磁化され、所定の保磁力を有する固定層と、前記固定層の磁化方向と平行な方向に磁化され、保磁力が前記固定層よりも小さい自由層と、前記固定層と前記自由層とで挟まれた絶縁層とを有し、前記固定層と前記自由層との間に電圧を印加すると、前記固定層の磁化方向と前記自由層の磁化方向の異同に応じた抵抗値で前記絶縁層にトンネル電流が流れる第一、第二の磁気抵抗素子が並列接続された記憶素子であって、前記第一の磁気抵抗素子の前記自由層の前記磁化方向に沿った長さは、前記第二の磁気抵抗素子の前記自由層の前記磁化方向に沿った長さより長くされ、磁化方向を逆向きにするスピン注入電流に対し、前記第二の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さは、前記第一の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも大きくされ、抵抗値の大きさで３値又は４値が記憶される記憶素子である。
　本発明は、膜厚方向とは垂直な方向に磁化され、所定の保磁力を有する固定層と、前記固定層の磁化方向と平行な方向に磁化され、保磁力が前記固定層よりも小さい自由層と、前記固定層と前記自由層とで挟まれた絶縁層とを有し、前記固定層と前記自由層との間に電圧を印加すると、前記固定層の磁化方向と前記自由層の磁化方向の異同に応じた抵抗値で前記絶縁層にトンネル電流が流れる第一、第二の磁気抵抗素子が並列接続された記憶素子であって、前記第一、第二の磁気抵抗素子がそれぞれ有する前記自由層は、平面形状が、幅と、前記幅よりも長い長手方向とを有する形状に形成され、前記第一、第二の磁気抵抗素子の前記自由層の前記長手方向は互いに直角に配置され、前記第一の磁気抵抗素子の前記自由層は、その前記自由層の前記長手方向と平行に磁化され、前記第二の磁気抵抗素子の前記自由層は、その前記自由層の前記幅の長さ方向と平行に磁化されて、磁化方向を逆向きにするスピン注入電流に対し、前記第二の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さは、前記第一の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも大きくされ、抵抗値の大きさで３値又は４値が記憶される記憶素子である。
　本発明は記憶素子であって、前記第一、第二の磁気抵抗素子がそれぞれ有する前記自由層は互いに接続されている記憶素子である。
　本発明は記憶素子であって、前記第一、第二の磁気抵抗素子がそれぞれ有する前記固定層は互いに接続されている記憶素子である。
　本発明は記憶素子であって、前記第一、第二の磁気抵抗素子がそれぞれ有する前記絶縁層は互いに接続されている記憶素子である。
　本発明は、前記記憶素子を用いて、第一、第二、第三の値を記憶する記憶方法であって、前記第一の値を記憶するために、前記第一、第二の磁気抵抗素子の両方が磁化同方向抵抗値を示すように、前記第一、第二の磁気抵抗素子の前記自由層の磁化方向をそれぞれ前記固定層の磁化方向と同じ方向に向けて、前記第一、第二の磁気抵抗素子の並列抵抗値を前記第一の値と対応させて記憶し、前記第二の値を記憶するために、前記第一、第二の磁気抵抗素子の両方が磁化反対方向抵抗値を示すように、前記第一、第二の磁気抵抗素子の前記自由層の磁化方向をそれぞれ前記固定層の磁化方向と反対方向に向けて、前記第一、第二の磁気抵抗素子の並列抵抗値を前記第二の値と対応させて記憶し、前記第三の値を記憶するために、いずれか一方の前記磁気抵抗素子が前記磁化同方向抵抗値を示すように当該一方の前記磁気抵抗素子の前記自由層の磁化方向を前記固定層の磁化方向と同じ方向に向け、他方の前記磁気抵抗素子が前記磁化同方向抵抗値を示すように当該他方の前記磁気抵抗素子の前記自由層の磁化方向を前記固定層の磁化方向と反対方向に向けて、前記第一、第二の磁気抵抗素子の並列抵抗値を前記第三の値と対応させて記憶する記憶方法である。
　本発明は、第一、第二、第三の値を相互に書き換えて、書き換えた値を記憶する記憶方法であって、前記第一の磁気抵抗素子の前記自由層の磁化方向だけを反転させる場合には、前記第一の磁気抵抗素子の前記自由層の保磁力よりも大きく、前記第二の磁気抵抗素子の前記自由層の保磁力よりも小さい外部磁界を、前記第一の磁気抵抗素子の前記自由層の磁化方向と逆向きに印加して、書き換えた値を記憶する記憶方法である。
　本発明は、第一、第二、第三の値を相互に書き換えて、書き換えた値を記憶する記憶方法であって、前記第一の磁気抵抗素子の前記自由層の磁化方向だけを反転させる場合には、前記第一の磁気抵抗素子の前記自由層の磁化方向を逆向きにし、前記第一の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも大きく、前記第二の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも小さいスピン注入電流を流して、書き換えた値を記憶する記憶方法である。
　本発明は、前記記憶素子の抵抗値を測定し、前記抵抗値から記憶された値を読み取る記憶方法であって、前記記憶素子の抵抗値を測定して基準値と比較し、両方の前記磁気抵抗素子の抵抗値が前記磁化同方向抵抗値であると判別した場合を前記第一の値とし、両方の前記磁気抵抗素子の抵抗値が前記磁化反対方向抵抗値であると判別した場合を前記第二の値とし、一方の前記磁気抵抗素子が前記磁化同方向抵抗値であり他方の前記磁気抵抗素子が前記磁化反対方向抵抗値であると判別した場合を第三の値とする記憶方法である。 In order to solve the above problems, the present invention is magnetized in a direction perpendicular to the film thickness direction and has a fixed layer having a predetermined coercive force, and is magnetized in a direction parallel to the magnetization direction of the fixed layer. The fixed layer has a free layer smaller than the fixed layer, and an insulating layer sandwiched between the fixed layer and the free layer. When a voltage is applied between the fixed layer and the free layer, the magnetization of the fixed layer A storage element in which a first and a second magnetoresistive element in which a tunnel current flows in the insulating layer with a resistance value corresponding to a difference between a direction and a magnetization direction of the free layer, the first magnetoresistance The length of the free layer of the element along the magnetization direction is longer than the length of the second magnetoresistive element along the magnetization direction of the second magnetoresistive element, with respect to an external magnetic field opposite to the magnetization direction. , The coercivity of the free layer of the second magnetoresistive element is the first magnetism. It said resistive element is greater than the coercive force of the free layer, ternary or 4 values by the magnitude of the resistance value of the memory element to be stored.
In the present invention, a fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force, and magnetized in a direction parallel to the magnetization direction of the fixed layer, the coercive force is smaller than that of the fixed layer. And an insulating layer sandwiched between the fixed layer and the free layer, and when a voltage is applied between the fixed layer and the free layer, the magnetization direction of the fixed layer and the magnetization of the free layer A memory element in which a first and a second magnetoresistive element in which a tunnel current flows in the insulating layer with a resistance value corresponding to a difference in direction is connected in parallel, each of the first and second magnetoresistive elements having The free layer is formed in a shape having a planar shape having a width and a longitudinal direction longer than the width, and the longitudinal directions of the free layers of the first and second magnetoresistive elements are arranged at right angles to each other. The free layer of the first magnetoresistive element is the free layer Magnetized parallel to the longitudinal direction, the free layer of the second magnetoresistive element is magnetized parallel to the length direction of the width of the free layer, and an external magnetic field opposite to the magnetization direction is applied. On the other hand, the coercive force of the free layer of the second magnetoresistive element is made larger than the coercive force of the free layer of the first magnetoresistive element, and a ternary value or a quaternary value is stored as the resistance value. Storage element.
In the present invention, a fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force, and magnetized in a direction parallel to the magnetization direction of the fixed layer, the coercive force is smaller than that of the fixed layer. And an insulating layer sandwiched between the fixed layer and the free layer, and when a voltage is applied between the fixed layer and the free layer, the magnetization direction of the fixed layer and the magnetization of the free layer A memory element in which a first and a second magnetoresistive element in which a tunnel current flows in the insulating layer with a resistance value corresponding to a difference in direction is connected in parallel, and the free layer of the first magnetoresistive element is the memory element The length along the magnetization direction is longer than the length along the magnetization direction of the free layer of the second magnetoresistive element, and the second magnetic field is applied to a spin injection current that reverses the magnetization direction. For magnetization reversal when the spin injection current of the free layer of the resistance element flows The strength of the first magnetoresistive element is greater than the strength against magnetization reversal when the spin injection current of the free layer flows, and the memory stores 3 or 4 values as the resistance value. It is an element.
In the present invention, a fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force, and magnetized in a direction parallel to the magnetization direction of the fixed layer, the coercive force is smaller than that of the fixed layer. And an insulating layer sandwiched between the fixed layer and the free layer, and when a voltage is applied between the fixed layer and the free layer, the magnetization direction of the fixed layer and the magnetization of the free layer A memory element in which a first and a second magnetoresistive element in which a tunnel current flows in the insulating layer with a resistance value corresponding to a difference in direction is connected in parallel, each of the first and second magnetoresistive elements having The free layer is formed in a shape having a planar shape having a width and a longitudinal direction longer than the width, and the longitudinal directions of the free layers of the first and second magnetoresistive elements are arranged at right angles to each other. The free layer of the first magnetoresistive element is the free layer A spin injection current that is magnetized parallel to the longitudinal direction, and the free layer of the second magnetoresistive element is magnetized parallel to the length direction of the width of the free layer to reverse the magnetization direction On the other hand, the strength against magnetization reversal when the spin injection current of the free layer of the second magnetoresistive element flows is that when the spin injection current of the free layer of the first magnetoresistive element flows. This is a storage element that is larger than the strength against magnetization reversal and stores three or four values in terms of the resistance value.
The present invention is a memory element, wherein the free layers of the first and second magnetoresistive elements are connected to each other.
The present invention is a memory element, wherein the fixed layers of the first and second magnetoresistive elements are connected to each other.
The present invention is a memory element, wherein the insulating layers of the first and second magnetoresistive elements are connected to each other.
The present invention is a storage method for storing first, second, and third values using the storage element, wherein the first and second magnetoresistors are used for storing the first value. The first and second magnetoresistive elements are oriented in the same direction as the magnetization direction of the fixed layer, so that both elements exhibit the same magnetization direction resistance value. In order to store the parallel resistance value of the second magnetoresistive element in correspondence with the first value, and to store the second value, both the first and second magnetoresistive elements have opposite magnetization directions. In order to indicate the resistance value, the magnetization direction of the free layer of the first and second magnetoresistive elements is directed to the opposite direction to the magnetization direction of the fixed layer, respectively. In order to store the parallel resistance value in association with the second value, and to store the third value, The magnetization direction of the free layer of the one magnetoresistive element is oriented in the same direction as the magnetization direction of the fixed layer so that the magnetoresistive element exhibits the same magnetization direction resistance value, and the other magnetoresistive element The parallel resistance of the first and second magnetoresistive elements is set so that the magnetization direction of the free layer of the other magnetoresistive element is directed to the opposite direction to the magnetization direction of the fixed layer so as to indicate a magnetization unidirectional resistance value. A storage method for storing a value in association with the third value.
The present invention is a storage method for rewriting a first value, a second value, and a third value, and storing the rewritten value, wherein only the magnetization direction of the free layer of the first magnetoresistive element is reversed. In this case, an external magnetic field larger than the coercive force of the free layer of the first magnetoresistive element and smaller than the coercive force of the free layer of the second magnetoresistive element is applied to the first magnetoresistive element. The storage method stores the rewritten value by applying in the direction opposite to the magnetization direction of the free layer.
The present invention is a storage method for rewriting a first value, a second value, and a third value, and storing the rewritten value, wherein only the magnetization direction of the free layer of the first magnetoresistive element is reversed. In this case, the magnetization direction of the free layer of the first magnetoresistive element is reversed, and the strength of the first magnetoresistive element against the magnetization reversal when the spin injection current of the free layer flows is greater than The storage method stores a rewritten value by supplying a spin injection current smaller than the strength against magnetization reversal when the spin injection current of the free layer of the second magnetoresistive element flows.
The present invention is a storage method for measuring a resistance value of the storage element and reading a value stored from the resistance value, measuring the resistance value of the storage element and comparing it with a reference value, and The case where it is determined that the resistance value of the resistance element is the magnetization direction resistance value is the first value, and the case where it is determined that the resistance value of both the magnetoresistance elements is the magnetization direction resistance value A storage method in which a second value is used, and when one of the magnetoresistive elements is determined to have the same magnetization resistance value and the other magnetoresistive element has the opposite magnetization direction resistance value, the third value is used. is there.
　本発明は、磁性層の磁化方向が外部磁界の方向と平行であり、長軸が短軸より長い（ここでは１．５倍以上長いとする）場合に、磁化方向が長軸に平行な磁性層は、磁化方向が短軸に平行な磁性層よりも小さな外部磁界で磁化方向を反転させることができること（磁気形状異方性という）に着目している。 In the present invention, when the magnetization direction of the magnetic layer is parallel to the direction of the external magnetic field and the major axis is longer than the minor axis (here, 1.5 times or longer), the magnetization direction is parallel to the major axis. The layer pays attention to the fact that the magnetization direction can be reversed with an external magnetic field smaller than that of the magnetic layer whose magnetization direction is parallel to the minor axis (referred to as magnetic shape anisotropy).
　磁性層が磁化した状態は磁性層の磁化方向の両端にＮ極とＳ極が現れた状態であり、この磁極は磁性層外部に磁力線を発生させるのと同時に、磁性層内部にも外部とは反対方向に磁場（反磁場）を作る。内部の反磁場の大きさは、磁化の大きさに比例すると同時に、磁化方向の形状に依存し、長矩形状の磁性層では長軸方向に磁化した場合が一番小さい（無限に長い棒では反磁場が０になる）。磁性層の内部に働く磁場は、外部磁界と反磁場の差で与えられると考えられる。 The state in which the magnetic layer is magnetized is a state in which the N pole and the S pole appear at both ends of the magnetization direction of the magnetic layer. Create a magnetic field (demagnetizing field) in the opposite direction. The size of the internal demagnetizing field is proportional to the size of the magnetization, and at the same time, depends on the shape of the magnetization direction. Magnetic field becomes 0). The magnetic field acting inside the magnetic layer is considered to be given by the difference between the external magnetic field and the demagnetizing field.
　図３（ａ）、（ｂ）は、長軸、短軸に平行な方向に磁化された磁性層に、磁化方向と平行で逆向きの外部磁界を印加したときの、外部磁界の強度と磁性層の磁化の関係を測定した結果である。
　長軸に平行な方向に磁化された磁性層は、弱い外部磁界±Ｈ1で反転して磁化が飽和するが（図３（ａ））、短軸に平行な方向に磁化された磁性層は、±Ｈ1よりも大きな±Ｈ2で反転するまで直線的に磁化が変化するので、大きな外部磁界をかけないと磁化が飽和しない（図３（ｂ））。 3 (a) and 3 (b) show the strength and magnetism of an external magnetic field when an external magnetic field parallel to and opposite to the magnetization direction is applied to a magnetic layer magnetized in a direction parallel to the major axis and minor axis. It is the result of having measured the relationship of the magnetization of the layer.
The magnetic layer magnetized in the direction parallel to the long axis is inverted by a weak external magnetic field ± H 1 to saturate the magnetization (FIG. 3A), but the magnetic layer magnetized in the direction parallel to the short axis is Since the magnetization changes linearly until it is inverted at ± H 2 larger than ± H 1 , the magnetization is not saturated unless a large external magnetic field is applied (FIG. 3B).
　また、本発明は、第一、第二の磁気抵抗素子の自由層の面積比を制御することにより、一方の磁気抵抗素子の自由層と固定層の磁化方向が同方向で、他方の磁気抵抗素子の自由層と固定層の磁化方向が逆方向のときの抵抗値を、両方の磁気抵抗素子の自由層と固定層の磁化方向が同方向のときの抵抗値と、両方の磁気抵抗素子の自由層と固定層の磁化方向が逆方向のときの抵抗値に対して制御できる記憶素子である。 In addition, the present invention controls the area ratio of the free layers of the first and second magnetoresistive elements so that the magnetization directions of the free layer and the fixed layer of one magnetoresistive element are the same and the other magnetoresistive is The resistance value when the magnetization directions of the free layer and the fixed layer of the element are opposite directions, the resistance value when the magnetization directions of the free layer and the fixed layer of both magnetoresistive elements are the same direction, and the resistance value of both magnetoresistive elements This is a memory element that can control the resistance value when the magnetization directions of the free layer and the fixed layer are opposite to each other.
　磁化形状異方性を持つ形状のトンネル磁気抵抗素子を二個並列に接続することで、抵抗値は最大値、最小値以外に、一方の素子の二層の磁性層の磁場が互いに同方向で他方の素子の二層の磁性層の磁場が互いに逆方向のときに中間値を取ることができ、最大値、中間値、最小値を判別することで３値又は４値の記憶素子が得られる。 By connecting two tunnel magnetoresistive elements with magnetization shape anisotropy in parallel, the resistance value is not the maximum or minimum value, but the magnetic fields of the two magnetic layers of one element are in the same direction. An intermediate value can be taken when the magnetic fields of the two magnetic layers of the other element are in opposite directions, and a ternary or quaternary storage element can be obtained by discriminating the maximum value, intermediate value, and minimum value. .
　従って、記憶素子の密度を増やさなくても、２値の記憶媒体よりも記憶容量を増やすことができる。
　また従来から使用されている多層膜が利用できるため、新たに複雑な積層構造の多層膜を作製する必要はなく、低コストで３値又は４値の記憶素子が得られる。 Therefore, the storage capacity can be increased as compared with the binary storage medium without increasing the density of the storage elements.
In addition, since a multilayer film conventionally used can be used, there is no need to newly create a multilayer film having a complicated laminated structure, and a ternary or quaternary memory element can be obtained at low cost.
本発明の記憶素子の平面図The top view of the memory element of this invention 本発明の記憶素子のＡ－Ａ切断断面図Sectional view taken along the line AA of the memory element of the present invention. （ａ），（ｂ）：磁化形状異方性を説明する模式図(A), (b): Schematic diagram explaining magnetization shape anisotropy （ａ）～（ｄ）：磁化方向の向きの組合せを説明する模式図(A) to (d): Schematic diagrams illustrating combinations of magnetization directions 本発明の記憶素子を用いた記憶媒体の一例を説明する断面図Sectional drawing explaining an example of the storage medium using the memory element of this invention （ａ）～（ｄ）：自由層が接続している場合の例を示す図(A)-(d): The figure which shows the example in case the free layer is connected 自由層が接続している場合の磁化を説明する模式図Schematic explaining the magnetization when the free layer is connected
　１……記憶装置
１０……記憶素子
１１……第一の磁気抵抗素子
１２……第二の磁気抵抗素子
２２……第一の磁気抵抗素子の自由層
３２……第二の磁気抵抗素子の自由層
４３……絶縁層
４８……固定層
５１……第一の磁気抵抗素子の自由層の長手方向
５２……第一の磁気抵抗素子の自由層の幅の長さ方向
５３……第二の磁気抵抗素子の自由層の長手方向
５４……第二の磁気抵抗素子の自由層の幅の長さ方向 DESCRIPTION OF SYMBOLS 1 ... Memory | storage device 10 ... Memory element 11 ... 1st magnetoresistive element 12 ... 2nd magnetoresistive element 22 ... Free layer 32 of 1st magnetoresistive element ... 2nd magnetoresistive element Free layer 43 ... insulating layer 48 ... fixed layer 51 ... longitudinal direction 52 of the free layer of the first magnetoresistive element 52 length direction 53 of the free layer width of the first magnetoresistive element ... second Longitudinal direction 54 of the free layer of the second magnetoresistive element ... the length direction of the width of the free layer of the second magnetoresistive element
　図１の符号１０は本発明である記憶素子の平面図である。記憶素子１０は第一、第二の磁気抵抗素子１１、１２を有している。
　図２は記憶素子１０のＡ－Ａ切断断面図である。
　第一、第二の磁気抵抗素子１１、１２は、所定の保磁力を有する固定層４８と、絶縁層４３と、固定層４８の磁化方向と平行な方向に磁化され、保磁力が固定層４８より小さい自由層２２、３２を有している。 Reference numeral 10 in FIG. 1 is a plan view of a memory element according to the present invention. The memory element 10 has first and second magnetoresistive elements 11 and 12.
FIG. 2 is a cross-sectional view of the memory element 10 taken along the line AA.
The first and second magnetoresistive elements 11 and 12 are magnetized in a direction parallel to the magnetization direction of the fixed layer 48 having a predetermined coercive force, the insulating layer 43, and the fixed layer 48, and the coercive force has a fixed layer 48. It has smaller free layers 22, 32.
　第一の電極６１と固定層４８と絶縁層４３と自由層２２、３２とをこの順序でＳｉ基板４９上に積層した後、自由層２２、３２部分だけを後述の形状にエッチングして、第一、第二の磁気抵抗素子１１、１２が形成されている。
　自由層２２、３２のエッチング後、自由層２２、３２側からＳｉＯ2層４１を積層し、その後にＳｉＯ2層４１をエッチングして自由層２２、３２の表面を露出させる。自由層２２、３２の表面に密着するように第二の電極６２を形成する。 After laminating the first electrode 61, the fixed layer 48, the insulating layer 43, and the free layers 22 and 32 on the Si substrate 49 in this order, only the free layers 22 and 32 are etched into the shapes described later, First and second magnetoresistive elements 11 and 12 are formed.
After the free layers 22 and 32 are etched, a SiO 2 layer 41 is laminated from the free layers 22 and 32 side, and then the SiO 2 layer 41 is etched to expose the surfaces of the free layers 22 and 32. The second electrode 62 is formed so as to be in close contact with the surfaces of the free layers 22 and 32.
　絶縁層４３の膜厚は薄く、自由層２２、３２と固定層４８との間に電圧が印加されると、トンネル効果により、各層に対して垂直な方向にトンネル電流が流れる。
　トンネル電流が流れるときの第一、第二の磁気抵抗素子１１、１２のコンダクタンス値は、固定層４８の磁化方向に対して、自由層２２、３２の磁化方向が同じ向きの場合に大きく、逆向きの場合に小さい（コンダクタンス値は抵抗値の逆数である）。従って、第一、第二の磁気抵抗素子１１、１２はトンネル磁気抵抗素子として機能する。 The insulating layer 43 is thin, and when a voltage is applied between the free layers 22 and 32 and the fixed layer 48, a tunnel current flows in a direction perpendicular to each layer due to the tunnel effect.
When the tunnel current flows, the conductance values of the first and second magnetoresistive elements 11 and 12 are large when the magnetization directions of the free layers 22 and 32 are the same as the magnetization direction of the fixed layer 48, and vice versa. Small in the direction (conductance value is the reciprocal of the resistance value). Accordingly, the first and second magnetoresistive elements 11 and 12 function as tunnel magnetoresistive elements.
　第一、第二の磁気抵抗素子１１、１２の自由層２２、３２（以下第一、第二の自由層と呼ぶ）の平面形状は、図１に示すように、長手方向５１、５３とそれに垂直で長手方向の長さより短い幅方向５２、５４を有している。ここでは、第一の自由層２２の長手方向５１の長さは、幅方向５２の長さの１．５倍以上とする。
　第一、第二の自由層２２、３２は互いに平行な方向に磁化されている。
　第一の自由層２２の磁化方向に沿った長さは、第二の自由層３２の磁化方向に沿った長さより長くされ、ここでは、第一、第二の自由層２２、３２は、長手方向５１、５３が互いに直角になるように配置されている。
　そのため、磁化方向とは逆向きな外部磁界に対し、長手方向５１に磁化された第一の自由層２２の保磁力（以下第一の保磁力と呼ぶ）は、幅方向５４に磁化された第二の自由層３２の保磁力（以下第二の保磁力と呼ぶ）より小さくされている。また、磁化方向を逆向きにするスピン注入電流に対し、長手方向５１に磁化された第一の自由層２２のスピン注入電流が流れたときの磁化反転に対する強さは、幅方向５４に磁化された第二の自由層３２のスピン注入電流が流れたときの磁化反転に対する強さより小さくされている。
　ここでは、第一、第二の自由層２２、３２は、長手方向５１、５３が互いに直角になるように配置されているが、本発明はこれに限定されず、第一、第二の自由層２２、３２は、長手方向５１、５３に沿って延びる直線が互いに交差するように配置されている場合は本発明に含まれる。 As shown in FIG. 1, the planar shapes of the free layers 22 and 32 (hereinafter referred to as the first and second free layers) of the first and second magnetoresistive elements 11 and 12 are as follows. It has a width direction 52, 54 that is vertical and shorter than the length in the longitudinal direction. Here, the length of the first free layer 22 in the longitudinal direction 51 is 1.5 times or more the length of the width direction 52.
The first and second free layers 22 and 32 are magnetized in directions parallel to each other.
The length along the magnetization direction of the first free layer 22 is longer than the length along the magnetization direction of the second free layer 32, where the first and second free layers 22, 32 are longitudinal. The directions 51 and 53 are arranged so as to be perpendicular to each other.
Therefore, the coercive force (hereinafter referred to as the first coercive force) of the first free layer 22 magnetized in the longitudinal direction 51 against the external magnetic field opposite to the magnetization direction is the first magnetized in the width direction 54. It is smaller than the coercive force of the second free layer 32 (hereinafter referred to as the second coercive force). The strength against magnetization reversal when the spin injection current of the first free layer 22 magnetized in the longitudinal direction 51 flows against the spin injection current that reverses the magnetization direction is magnetized in the width direction 54. Further, the second free layer 32 is made smaller than the strength against magnetization reversal when the spin injection current flows.
Here, the first and second free layers 22 and 32 are arranged so that the longitudinal directions 51 and 53 are perpendicular to each other. However, the present invention is not limited to this, and the first and second free layers 22 and 32 are arranged. The layers 22 and 32 are included in the present invention when the straight lines extending along the longitudinal directions 51 and 53 are arranged so as to intersect each other.
　記憶素子１０内部では、図２に示すように、固定層４８は第一の電極６１に接触して電気的に接続され、第一、第二の自由層２２、３２はそれぞれ第二の電極６２に接触して電気的に接続されている。
　従って、記憶素子１０は、第一、第二の磁気抵抗素子１１、１２を並列に接続した並列接続回路を形成している。 Inside the memory element 10, as shown in FIG. 2, the fixed layer 48 is in contact with and electrically connected to the first electrode 61, and the first and second free layers 22 and 32 are respectively connected to the second electrode 62. Is in contact with and electrically connected.
Therefore, the memory element 10 forms a parallel connection circuit in which the first and second magnetoresistive elements 11 and 12 are connected in parallel.
　第一、第二の電極６１、６２の間に電圧を印加すると、電流は第一、第二の磁気抵抗素子１１、１２の両方を膜厚方向と平行な方向に流れるように配線されているが、よりコンダクタンス値の高い部分を流れる傾向を持つ。
　第一、第二の磁気抵抗素子１１、１２のコンダクタンスの最小値をそれぞれＣ１、Ｃ２、最大値をそれぞれＣ１＋ΔＣ１、Ｃ２＋ΔＣ２とする。 When a voltage is applied between the first and second electrodes 61 and 62, the current is wired so as to flow in both the first and second magnetoresistive elements 11 and 12 in a direction parallel to the film thickness direction. However, it tends to flow through a portion with a higher conductance value.
The minimum conductance values of the first and second magnetoresistive elements 11 and 12 are C1 and C2, respectively, and the maximum values are C1 + ΔC1 and C2 + ΔC2, respectively.
　図４（ａ）～（ｄ）は、記憶素子１０内部の、固定層４８の磁化方向Ｆ0に対する、第一、第二の自由層２２、３２の磁化方向Ｆ1、Ｆ2の変化を示している。
　図４（ａ）を参照し、第一、第二の自由層２２、３２の磁化方向Ｆ1、Ｆ2の両方が、固定層４８の磁化方向Ｆ0と同じ向きの場合、記憶素子１０のコンダクタンス値はＣ１＋Ｃ２＋ΔＣ１＋ΔＣ２で表される値に近い最大値となる（低コンダクタンスになった部分を本来流れる電流が高コンダクタンス部に流れ込むため、素子全体としてのコンダクタンス変化は正確にはΔＣ１＋ΔＣ２とはならず、それに近い値となる）。 4A to 4D show changes in the magnetization directions F 1 and F 2 of the first and second free layers 22 and 32 with respect to the magnetization direction F 0 of the fixed layer 48 inside the memory element 10. ing.
Referring to FIG. 4A, when both the magnetization directions F 1 and F 2 of the first and second free layers 22 and 32 are the same as the magnetization direction F 0 of the fixed layer 48, The conductance value is a maximum value close to the value represented by C1 + C2 + ΔC1 + ΔC2. (Because the current that originally flows through the low conductance portion flows into the high conductance portion, the change in the conductance of the entire element is not accurately ΔC1 + ΔC2, Close to that).
　次に、第一の保磁力以上第二の保磁力未満の外部磁界Ｈrを固定層４８の磁化方向Ｆ0と逆向きに印加すると、第一の自由層２２の磁化方向Ｆ1だけが反転し、記憶素子１０のコンダクタンス値はＣ１＋Ｃ２＋ΔＣ２になる（図４（ｂ））。
　次に、第二の保磁力以上の外部磁界Ｈrを固定層４８の磁化方向Ｆ0と逆向きに印加すると、第二の自由層３２の磁化方向Ｆ2も反転し、記憶素子１０のコンダクタンス値は最小値Ｃ１＋Ｃ２になる（図４（ｃ））。
　次に、第一の保磁力以上第二の保磁力未満の外部磁界Ｈrを固定層４８の磁場方向Ｆ0と同じ向きに印加すると、第一の自由層２２の磁化方向Ｆ1が再度反転して、記憶素子１０のコンダクタンス値はＣ１＋Ｃ２＋ΔＣ１になる（図４（ｄ））。 Next, when an external magnetic field H r that is greater than or equal to the first coercive force and less than the second coercive force is applied in a direction opposite to the magnetization direction F 0 of the fixed layer 48, only the magnetization direction F 1 of the first free layer 22 is reversed. The conductance value of the memory element 10 is C1 + C2 + ΔC2 (FIG. 4B).
Then, upon application of a second coercive force more external magnetic field H r to the magnetization direction F 0 and opposite the fixed layer 48, the magnetization direction F 2 of the second layer 32 is also reversed, the conductance of the memory element 10 The value becomes the minimum value C1 + C2 (FIG. 4C).
Next, when an external magnetic field H r that is greater than or equal to the first coercive force and less than the second coercive force is applied in the same direction as the magnetic field direction F 0 of the fixed layer 48, the magnetization direction F 1 of the first free layer 22 is reversed again. Thus, the conductance value of the memory element 10 becomes C1 + C2 + ΔC1 (FIG. 4D).
　このように、記憶素子１０のコンダクタンスは、最大値Ｃ１＋Ｃ２＋ΔＣ１＋ΔＣ２、第一の中間値Ｃ１＋Ｃ２＋ΔＣ１、第二の中間値Ｃ１＋Ｃ２＋ΔＣ２、最小値Ｃ１＋Ｃ２の４通りのコンダクタンス値をとる。
　第一のコンダクタンス差ΔＣ１が第二のコンダクタンス差ΔＣ２より大きい場合（ΔＣ１＞ΔＣ２）には、第一の中間値が大なる中間値になり、第二の中間値が小なる中間値になる。第一のコンダクタンス差ΔＣ１が第二のコンダクタンス差ΔＣ２より小さい場合（ΔＣ１＜ΔＣ２）には、第二の中間値が大なる中間値になり、第一の中間値が小なる中間値になる。 As described above, the conductance of the memory element 10 has four conductance values of the maximum value C1 + C2 + ΔC1 + ΔC2, the first intermediate value C1 + C2 + ΔC1, the second intermediate value C1 + C2 + ΔC2, and the minimum value C1 + C2.
When the first conductance difference ΔC1 is larger than the second conductance difference ΔC2 (ΔC1> ΔC2), the first intermediate value becomes a large intermediate value, and the second intermediate value becomes a small intermediate value. When the first conductance difference ΔC1 is smaller than the second conductance difference ΔC2 (ΔC1 <ΔC2), the second intermediate value becomes a large intermediate value, and the first intermediate value becomes a small intermediate value.
　最大値と大なる中間値の間に第一の基準値を置き、小なる中間値と最小値の間に第二の基準値を置いて、最大値、最小値、中間値の３通りのコンダクタンス値を判別することで３値の記憶素子が得られる。
　更に、第一、第二の基準値に加えて、大なる中間値と小なる中間値の間に第三の基準値を置いて、最大値、大なる中間値、小なる中間値、最小値の４通りのコンダクタンス値を判別することで４値の記憶素子が得られる。 The first reference value is placed between the maximum value and the large intermediate value, and the second reference value is placed between the small intermediate value and the minimum value, and the three conductances of maximum value, minimum value, and intermediate value are set. By determining the value, a ternary memory element can be obtained.
Furthermore, in addition to the first and second reference values, a third reference value is placed between the large intermediate value and the small intermediate value, and the maximum value, the large intermediate value, the small intermediate value, and the minimum value are set. A four-value memory element is obtained by discriminating the four conductance values.
　次に、本発明の記憶素子１０を用いた記憶装置を説明する。図５はＭＲＡＭ等の記憶装置１の一例を示す断面図である。
　記憶装置１は第一、第二の配線５、６を複数本ずつ有している。第一の配線５は所定間隔を空けて互いに平行に配置され、第二の配線６は第一の配線５が配置された平面と平行な平面内で、第一の配線５と交差するように配置されている。ここでは、第一、第二の配線５、６はＳｉＯ2等の絶縁層２に埋設されている。 Next, a memory device using the memory element 10 of the present invention will be described. FIG. 5 is a cross-sectional view showing an example of the storage device 1 such as an MRAM.
The storage device 1 has a plurality of first and second wirings 5 and 6. The first wiring 5 is arranged parallel to each other with a predetermined interval, and the second wiring 6 intersects the first wiring 5 in a plane parallel to the plane where the first wiring 5 is arranged. Has been placed. Here, the first and second wirings 5 and 6 are embedded in an insulating layer 2 such as SiO 2 .
　第一、第二の配線５、６の立体交差位置の近傍には、本発明の記憶素子１０が配置されている。第一、第二の配線５、６の交差位置は行列状に配置されているから、記憶素子１０は行列状に配置されている。
　記憶素子１０の第一、第二の電極６１、６２は、記憶素子１０の近傍で交差する第一、第二の配線５、６にそれぞれ接続されている。
　第一、第二の配線５、６は制御装置８に接続されている。記憶素子１０から記憶された情報を読み出す場合、制御装置８は、第一、第二の配線５、６を選択して所望の記憶素子１０に電流を流し、測定装置９は電流が流れた記憶素子１０の電極間の電圧と電流から、ここではコンダクタンス値を測定し、測定結果を制御装置８へ伝送する。 The memory element 10 of the present invention is disposed in the vicinity of the three-dimensional intersection position of the first and second wirings 5 and 6. Since the intersection positions of the first and second wirings 5 and 6 are arranged in a matrix, the memory elements 10 are arranged in a matrix.
The first and second electrodes 61 and 62 of the memory element 10 are respectively connected to first and second wirings 5 and 6 that intersect in the vicinity of the memory element 10.
The first and second wirings 5 and 6 are connected to the control device 8. When reading the stored information from the storage element 10, the control device 8 selects the first and second wirings 5 and 6 to pass a current through the desired storage element 10, and the measurement device 9 stores the current flowing through the storage device 10. Here, the conductance value is measured from the voltage and current between the electrodes of the element 10, and the measurement result is transmitted to the control device 8.
　上述したように、本発明の記憶素子１０のコンダクタンス値は、最大値、最小値、中間値の３通りが得られ、制御装置８には少なくともコンダクタンスの最大値と最小値が基準値として設定されている。
　制御装置８は測定装置９の測定結果と設定されたコンダクタンス値（基準値）とを比較し、測定結果が最大値、最小値、又は最大値と最小値の間（中間値）のいずれに相当するか判断する。制御装置８は、判断した結果をそれぞれ『０』『１』『２』等の情報に関連付け、情報として読み出す。
　従って、この記憶装置１では、第一、第二の配線５、６と、制御装置８と、測定装置９とで、情報を読み出す読み出し手段が構成される。 As described above, the conductance value of the memory element 10 of the present invention can be obtained in three ways of the maximum value, the minimum value, and the intermediate value, and at least the maximum value and the minimum value of the conductance are set as the reference values in the control device 8. ing.
The control device 8 compares the measurement result of the measurement device 9 with the set conductance value (reference value), and the measurement result corresponds to the maximum value, the minimum value, or between the maximum value and the minimum value (intermediate value). Judge whether to do. The control device 8 associates the determined result with information such as “0”, “1”, “2”, etc., and reads it as information.
Therefore, in the storage device 1, the first and second wirings 5 and 6, the control device 8, and the measurement device 9 constitute a reading unit that reads information.
　次に、情報の書き換えについて説明する。この記憶装置１では、第一の配線５の配線に沿って書き換え配線４が延設されている。第一の配線５は第二の配線６と交差するから、書き換え配線４も第二の配線６と交差する。
　各記憶素子１０は書き換え配線４と第二の配線６の交差位置で、書き換え配線４と第二の配線６の間に配置されている。書き換え配線４は記憶素子１０及び第一、第二の配線５、６と非接触であり、絶縁されている。 Next, information rewriting will be described. In the storage device 1, the rewrite wiring 4 is extended along the wiring of the first wiring 5. Since the first wiring 5 intersects with the second wiring 6, the rewrite wiring 4 also intersects with the second wiring 6.
Each memory element 10 is disposed between the rewrite wiring 4 and the second wiring 6 at the intersection of the rewrite wiring 4 and the second wiring 6. The rewrite wiring 4 is not in contact with the memory element 10 and the first and second wirings 5 and 6 and is insulated.
　書き換え配線４は制御装置８に接続されている。制御装置８には、書き換え配線４及び第二の配線６と、記憶素子１０との位置関係が設定されている。
　制御装置８は格子状に配置された書き換え配線４と第二の配線６との間に配置されている中で目的とする記憶素子１０の一つを選択し、通電する。通電により、書き換え配線４と第二の配線６の周囲に磁場が発生し、書き換え配線４と第二の配線６の交差位置近傍に合成磁場が発生し、他の素子には磁場の影響を与えない。従って、行列状に配置された複数の記憶素子１０のうち、選択した配線４、６の交差位置にある記憶素子１０だけが合成磁場に曝される。 The rewrite wiring 4 is connected to the control device 8. The positional relationship between the rewrite wiring 4 and the second wiring 6 and the memory element 10 is set in the control device 8.
The control device 8 selects one of the target storage elements 10 among the rewrite wirings 4 and the second wirings 6 arranged in a lattice shape and energizes them. When energized, a magnetic field is generated around the rewrite wiring 4 and the second wiring 6, a composite magnetic field is generated near the intersection of the rewriting wiring 4 and the second wiring 6, and other elements are affected by the magnetic field. Absent. Therefore, only the memory elements 10 at the intersection of the selected wirings 4 and 6 among the plurality of memory elements 10 arranged in a matrix are exposed to the synthesized magnetic field.
　書き換え配線４と第二の配線６に流す電流の向きや強さ等の通電条件を変えると、合成磁場の向きや強さが変わる。記憶素子１０のコンダクタンスを最大値、最小値、中間値にする各合成磁場を作る通電条件は予め求められ、制御装置８に設定されている。
　制御装置８は記憶したい情報と記憶素子１０のコンダクタンスを関連付け、コンダクタンスを関連付けた値にする通電条件で、書き換え配線４と第二の配線６に電流を流し、記憶素子１０に所望の記憶情報をコンダクタンスとして記憶する。 When the energization conditions such as the direction and strength of the current flowing through the rewrite wiring 4 and the second wiring 6 are changed, the direction and strength of the synthetic magnetic field change. The energization conditions for creating each combined magnetic field that sets the conductance of the storage element 10 to the maximum value, the minimum value, and the intermediate value are obtained in advance and set in the control device 8.
The control device 8 associates the information to be stored with the conductance of the storage element 10, and allows current to flow through the rewrite wiring 4 and the second wiring 6 under the energization condition that sets the conductance to an associated value, and stores desired storage information in the storage element 10. Memorize as conductance.
　このように、第二の配線６と、書き換え配線４と、制御装置８とが情報を書き換える書き換え手段となるが、書き換え手段はこれに限定されない。例えば、書き換え手段を書き換え配線４と制御装置８だけで構成してもよい。この場合、制御装置８は書き換え配線４を選択して通電し、選択した書き換え配線４上にある記憶素子１０の情報を書き換える。 Thus, the second wiring 6, the rewriting wiring 4, and the control device 8 serve as a rewriting means for rewriting information, but the rewriting means is not limited to this. For example, the rewriting means may be composed of only the rewrite wiring 4 and the control device 8. In this case, the control device 8 selects the rewrite wiring 4 and energizes it, and rewrites the information in the storage element 10 on the selected rewrite wiring 4.
　また、書き換え配線４を設けず、第一、第二の配線５、６と制御装置８で書き換え手段を構成してもよい。この場合、制御装置８は、第一、第二の配線５、６を選択して通電し、選択された第一、第二の配線５、６の交差位置で合成磁場を発生させ、当該交差位置近傍の記憶素子１０の情報を書き換える。 Further, the rewriting means may be constituted by the first and second wirings 5 and 6 and the control device 8 without providing the rewriting wiring 4. In this case, the control device 8 selects and energizes the first and second wirings 5 and 6, generates a synthetic magnetic field at the crossing position of the selected first and second wirings 5 and 6, and Information in the memory element 10 in the vicinity of the position is rewritten.
　また、第一、第二の配線５、６と制御装置８で書き換え手段を構成する場合には、制御装置８は、第一、第二の配線５、６を選択し、磁化を反転させるスピン注入電流を流して、記憶素子１０の情報を書き換えてもよい。
　第一の自由層の磁化方向だけを反転させる場合には、第一の自由層の磁化方向を逆向きにし、第一の自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも大きく、第二の自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも小さいスピン注入電流を流して、記憶素子１０の情報を書き換える。
　スピン注入電流を用いることにより、書き換えのために外部磁場を発生させる必要がなく、装置設計の自由度が上がる。
　要するに、書き換え手段は制御装置８と配線とを有し、制御装置８が配線を選択して通電することにより、配線上の記憶素子１０の情報を書き換える。 When the rewriting means is configured by the first and second wirings 5 and 6 and the control device 8, the control device 8 selects the first and second wirings 5 and 6 and spins to reverse the magnetization. The information in the memory element 10 may be rewritten by flowing an injection current.
When only the magnetization direction of the first free layer is reversed, the magnetization direction of the first free layer is reversed and is greater than the strength against magnetization reversal when the spin injection current of the first free layer flows. The information in the memory element 10 is rewritten by applying a spin injection current smaller than the strength against magnetization reversal when the spin injection current of the second free layer flows.
By using the spin injection current, it is not necessary to generate an external magnetic field for rewriting, and the degree of freedom in device design is increased.
In short, the rewriting means has the control device 8 and the wiring, and the control device 8 rewrites the information of the memory element 10 on the wiring by selecting the wiring and energizing it.
　書き換え手段は記憶装置１に設ける必要も無い。書き換え手段（例えばごく微少な電磁石等の磁界形成手段）を記憶装置１の外側に設け、書き換えの必要な記憶素子１０に外部から書き換え手段を近づけることで、情報の書き換えを行ってもよい。
　上記説明では記憶素子１０の電極間の電圧と電流から、コンダクタンス値を測定して３値又は４値を判別したが、抵抗値を測定して３値又は４値を判別する場合も本発明に含まれる。また、記憶素子１０の電極間の電圧値又は電流値から、３値又は４値を判別してもよい。
　なお、固定層４８の磁化方向に対して、第一、第二の自由層２２、３２の磁化方向が同じ向きの場合の第一、第二の磁気抵抗素子１１、１２の抵抗値を磁化同方向抵抗値と呼び、逆向きの場合の抵抗値を磁化反対方向抵抗値と呼ぶ。 There is no need to provide the rewriting means in the storage device 1. Rewriting means (for example, a magnetic field forming means such as a very small electromagnet) may be provided outside the storage device 1 and information may be rewritten by bringing the rewriting means close to the storage element 10 that needs rewriting from the outside.
In the above description, the conductance value is determined from the voltage and current between the electrodes of the memory element 10 to determine the ternary value or the quaternary value. included. Further, the ternary value or the quaternary value may be determined from the voltage value or current value between the electrodes of the memory element 10.
The resistance values of the first and second magnetoresistive elements 11 and 12 when the magnetization directions of the first and second free layers 22 and 32 are the same as the magnetization direction of the fixed layer 48 are the same. It is called the direction resistance value, and the resistance value in the reverse direction is called the magnetization opposite direction resistance value.
　本発明は、第一、第二の自由層２２、３２が分離されている場合に限定されず、例えば図６（ａ）～（ｄ）に示すＬ型パターン、Ｔ型パターン、クロスパターン、凹型パターンのように、接続されている場合も含まれる。
　例えばクロスパターンの磁性層が磁化されている場合は、図７に示すように磁化方向の両端にＮ極（＋）とＳ極（－）が現れる。Ｎ極とＳ極との間の距離が保磁力又はスピン注入電流が流れたときの磁化反転に対する強さと関係しているため、第一、第二の自由層２２、３２が接続されている場合でも、長手方向に磁化された第一の自由層２２と幅方向に磁化された第二の自由層３２が判別できる。 The present invention is not limited to the case where the first and second free layers 22 and 32 are separated. For example, an L-shaped pattern, a T-shaped pattern, a cross pattern, and a concave shape shown in FIGS. The case where it is connected like a pattern is also included.
For example, when a cross-pattern magnetic layer is magnetized, N pole (+) and S pole (−) appear at both ends of the magnetization direction as shown in FIG. When the first and second free layers 22 and 32 are connected because the distance between the N pole and the S pole is related to the strength against magnetization reversal when a coercive force or a spin injection current flows However, the first free layer 22 magnetized in the longitudinal direction and the second free layer 32 magnetized in the width direction can be discriminated.
　本発明は、第一、第二の磁気抵抗素子１１、１２の自由層が分離し、絶縁層と固定層が接続している場合と、自由層と絶縁層と固定層の全層が接続している場合に限定されず、自由層と絶縁層が分離し、固定層が接続している場合と、自由層と絶縁層と固定層の全層が分離している場合も含まれる。
　また、第一、第二の磁気抵抗素子１１、１２の絶縁層が分離し、自由層と固定層が接続されている場合と、固定層が分離し、自由層と絶縁層が接続されている場合と、自由層と固定層が分離し、絶縁層が接続されている場合と、絶縁層と固定層が分離し、自由層が接続されている場合も含まれる。 In the present invention, the free layers of the first and second magnetoresistive elements 11 and 12 are separated and the insulating layer and the fixed layer are connected, and the free layer, the insulating layer, and the fixed layer are all connected. The case where the free layer and the insulating layer are separated and the fixed layer is connected, and the case where the free layer, the insulating layer, and the entire fixed layer are separated are also included.
In addition, when the insulating layers of the first and second magnetoresistive elements 11 and 12 are separated and the free layer and the fixed layer are connected, the fixed layer is separated and the free layer and the insulating layer are connected. The case includes a case where the free layer and the fixed layer are separated and the insulating layer is connected, and a case where the insulating layer and the fixed layer are separated and the free layer is connected.
　ここでは、固定層４８は反強磁性層４７と磁性層４６を有しており、Ｓｉ基板４９上に第一の電極６１，反強磁性層４７、磁性層４６の順で形成されている。磁性層４６を磁性層の表面と平行な方向に磁化させる場合、磁性層４６と反強磁性層４７を接触させると磁性層４６の保磁力が増大される。
　本発明は、固定層４８の磁化方向を反強磁性層４７を設けて固定する場合に限定されず、磁性層４６の保磁力が、第一、第二の保磁力の両方より十分高いのであれば、反強磁性層４７を設けなくてもよい。 Here, the fixed layer 48 has an antiferromagnetic layer 47 and a magnetic layer 46, and is formed on a Si substrate 49 in the order of a first electrode 61, an antiferromagnetic layer 47, and a magnetic layer 46. When magnetizing the magnetic layer 46 in a direction parallel to the surface of the magnetic layer, the coercive force of the magnetic layer 46 is increased when the magnetic layer 46 and the antiferromagnetic layer 47 are brought into contact with each other.
The present invention is not limited to the case where the magnetization direction of the fixed layer 48 is fixed by providing the antiferromagnetic layer 47, and the coercive force of the magnetic layer 46 is sufficiently higher than both the first and second coercive forces. For example, the antiferromagnetic layer 47 may not be provided.
　しかし、通常、磁性層４６の保磁力は数十ガウス程度であるのに対し、反強磁性層４７で磁化方向を固定した場合には、保磁力が６００ガウス～８００ガウス程度に上昇するので、反強磁性層４７で磁化方向を固定した方が、第一、第二の保磁力との差をより大きくできる。 However, the coercive force of the magnetic layer 46 is usually about several tens of gauss, whereas when the magnetization direction is fixed by the antiferromagnetic layer 47, the coercive force increases to about 600 to 800 gauss. When the magnetization direction is fixed by the antiferromagnetic layer 47, the difference from the first and second coercive forces can be made larger.
　反強磁性層４７の構成材料は例えばＰｔＭｎ等である。磁性層４６の構成材料は例えばＣｏＦｅＢ/Ｒｕ/ＣｏＦｅを積層したフェリ磁性体等である。自由層２２、３２の構成材料は保磁力が１桁程度異なる、例えばＣｏＦｅＢである。
　絶縁層４３の構成材料は特に限定されず、例えばＭｇＯやアルミナ（Ａｌ2Ｏ3）のいずれか一方又は両方を用いることができるが、ＭｇＯを用いると記憶素子１０の抵抗変化率が高くなるから特に好ましい。
  The constituent material of the antiferromagnetic layer 47 is, for example, PtMn. The constituent material of the magnetic layer 46 is, for example, a ferrimagnetic material in which CoFeB / Ru / CoFe is laminated. The constituent material of the free layers 22 and 32 is, for example, CoFeB whose coercive force differs by about one digit.
The constituent material of the insulating layer 43 is not particularly limited. For example, either or both of MgO and alumina (Al 2 O 3 ) can be used. However, when MgO is used, the resistance change rate of the memory element 10 is increased. Particularly preferred.

Claims (11)

  1. 　膜厚方向とは垂直な方向に磁化され、所定の保磁力を有する固定層と、
    　前記固定層の磁化方向と平行な方向に磁化され、保磁力が前記固定層よりも小さい自由層と、
    　前記固定層と前記自由層とで挟まれた絶縁層とを有し、
    　前記固定層と前記自由層との間に電圧を印加すると、前記固定層の磁化方向と前記自由層の磁化方向の異同に応じた抵抗値で前記絶縁層にトンネル電流が流れる第一、第二の磁気抵抗素子が並列接続された記憶素子であって、
    　前記第一の磁気抵抗素子の前記自由層の前記磁化方向に沿った長さは、前記第二の磁気抵抗素子の前記自由層の前記磁化方向に沿った長さより長くされ、
    　磁化方向とは逆向きな外部磁界に対し、前記第二の磁気抵抗素子の前記自由層の保磁力は、前記第一の磁気抵抗素子の前記自由層の保磁力よりも大きくされ、抵抗値の大きさで３値又は４値が記憶される記憶素子。     A fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force;
    A free layer magnetized in a direction parallel to the magnetization direction of the fixed layer, and having a coercive force smaller than that of the fixed layer;
    An insulating layer sandwiched between the fixed layer and the free layer;
    When a voltage is applied between the fixed layer and the free layer, a first and second tunnel current flows through the insulating layer with a resistance value corresponding to the difference between the magnetization direction of the fixed layer and the magnetization direction of the free layer. Storage elements connected in parallel,
    The length of the free layer of the first magnetoresistive element along the magnetization direction is longer than the length of the free layer of the second magnetoresistive element along the magnetization direction;
    For an external magnetic field opposite to the magnetization direction, the coercivity of the free layer of the second magnetoresistive element is made larger than the coercivity of the free layer of the first magnetoresistive element, and the resistance value A storage element that stores three or four values in size.
  2. 　膜厚方向とは垂直な方向に磁化され、所定の保磁力を有する固定層と、
    　前記固定層の磁化方向と平行な方向に磁化され、保磁力が前記固定層よりも小さい自由層と、
    　前記固定層と前記自由層とで挟まれた絶縁層とを有し、
    　前記固定層と前記自由層との間に電圧を印加すると、前記固定層の磁化方向と前記自由層の磁化方向の異同に応じた抵抗値で前記絶縁層にトンネル電流が流れる第一、第二の磁気抵抗素子が並列接続された記憶素子であって、
    　前記第一、第二の磁気抵抗素子がそれぞれ有する前記自由層は、平面形状が、幅と、前記幅よりも長い長手方向とを有する形状に形成され、前記第一、第二の磁気抵抗素子の前記自由層の前記長手方向は互いに直角に配置され、
    　前記第一の磁気抵抗素子の前記自由層は、その前記自由層の前記長手方向と平行に磁化され、
    　前記第二の磁気抵抗素子の前記自由層は、その前記自由層の前記幅の長さ方向と平行に磁化されて、
    　磁化方向とは逆向きな外部磁界に対し、前記第二の磁気抵抗素子の前記自由層の保磁力は、前記第一の磁気抵抗素子の前記自由層の保磁力よりも大きくされ、抵抗値の大きさで３値又は４値が記憶される記憶素子。     A fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force;
    A free layer magnetized in a direction parallel to the magnetization direction of the fixed layer, and having a coercive force smaller than that of the fixed layer;
    An insulating layer sandwiched between the fixed layer and the free layer;
    When a voltage is applied between the fixed layer and the free layer, a first and second tunnel current flows through the insulating layer with a resistance value corresponding to the difference between the magnetization direction of the fixed layer and the magnetization direction of the free layer. Storage elements connected in parallel,
    Each of the free layers of the first and second magnetoresistive elements has a planar shape having a width and a longitudinal direction longer than the width, and the first and second magnetoresistive elements. The longitudinal directions of the free layers are arranged at right angles to each other,
    The free layer of the first magnetoresistive element is magnetized parallel to the longitudinal direction of the free layer;
    The free layer of the second magnetoresistive element is magnetized parallel to the length direction of the width of the free layer,
    For an external magnetic field opposite to the magnetization direction, the coercivity of the free layer of the second magnetoresistive element is made larger than the coercivity of the free layer of the first magnetoresistive element, and the resistance value A storage element that stores three or four values in size.
  3. 　膜厚方向とは垂直な方向に磁化され、所定の保磁力を有する固定層と、
    　前記固定層の磁化方向と平行な方向に磁化され、保磁力が前記固定層よりも小さい自由層と、
    　前記固定層と前記自由層とで挟まれた絶縁層とを有し、
    　前記固定層と前記自由層との間に電圧を印加すると、前記固定層の磁化方向と前記自由層の磁化方向の異同に応じた抵抗値で前記絶縁層にトンネル電流が流れる第一、第二の磁気抵抗素子が並列接続された記憶素子であって、
    　前記第一の磁気抵抗素子の前記自由層の前記磁化方向に沿った長さは、前記第二の磁気抵抗素子の前記自由層の前記磁化方向に沿った長さより長くされ、
    　磁化方向を逆向きにするスピン注入電流に対し、前記第二の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さは、前記第一の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも大きくされ、抵抗値の大きさで３値又は４値が記憶される記憶素子。     A fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force;
    A free layer magnetized in a direction parallel to the magnetization direction of the fixed layer, and having a coercive force smaller than that of the fixed layer;
    An insulating layer sandwiched between the fixed layer and the free layer;
    When a voltage is applied between the fixed layer and the free layer, a first and second tunnel current flows through the insulating layer with a resistance value corresponding to the difference between the magnetization direction of the fixed layer and the magnetization direction of the free layer. Storage elements connected in parallel,
    The length of the free layer of the first magnetoresistive element along the magnetization direction is longer than the length of the free layer of the second magnetoresistive element along the magnetization direction;
    The strength against magnetization reversal when the spin injection current of the free layer of the second magnetoresistive element flows against the spin injection current that reverses the magnetization direction is the free resistance of the first magnetoresistive element. A memory element in which a ternary value or a quaternary value is stored as a resistance value, which is greater than the strength against magnetization reversal when a spin injection current of a layer flows.
  4. 　膜厚方向とは垂直な方向に磁化され、所定の保磁力を有する固定層と、
    　前記固定層の磁化方向と平行な方向に磁化され、保磁力が前記固定層よりも小さい自由層と、
    　前記固定層と前記自由層とで挟まれた絶縁層とを有し、
    　前記固定層と前記自由層との間に電圧を印加すると、前記固定層の磁化方向と前記自由層の磁化方向の異同に応じた抵抗値で前記絶縁層にトンネル電流が流れる第一、第二の磁気抵抗素子が並列接続された記憶素子であって、
    　前記第一、第二の磁気抵抗素子がそれぞれ有する前記自由層は、平面形状が、幅と、前記幅よりも長い長手方向とを有する形状に形成され、前記第一、第二の磁気抵抗素子の前記自由層の前記長手方向は互いに直角に配置され、
    　前記第一の磁気抵抗素子の前記自由層は、その前記自由層の前記長手方向と平行に磁化され、
    　前記第二の磁気抵抗素子の前記自由層は、その前記自由層の前記幅の長さ方向と平行に磁化されて、
    　磁化方向を逆向きにするスピン注入電流に対し、前記第二の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さは、前記第一の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも大きくされ、抵抗値の大きさで３値又は４値が記憶される記憶素子。     A fixed layer magnetized in a direction perpendicular to the film thickness direction and having a predetermined coercive force;
    A free layer magnetized in a direction parallel to the magnetization direction of the fixed layer, and having a coercive force smaller than that of the fixed layer;
    An insulating layer sandwiched between the fixed layer and the free layer;
    When a voltage is applied between the fixed layer and the free layer, a first and second tunnel current flows through the insulating layer with a resistance value corresponding to the difference between the magnetization direction of the fixed layer and the magnetization direction of the free layer. Storage elements connected in parallel,
    Each of the free layers of the first and second magnetoresistive elements has a planar shape having a width and a longitudinal direction longer than the width, and the first and second magnetoresistive elements. The longitudinal directions of the free layers are arranged at right angles to each other,
    The free layer of the first magnetoresistive element is magnetized parallel to the longitudinal direction of the free layer;
    The free layer of the second magnetoresistive element is magnetized parallel to the length direction of the width of the free layer,
    The strength against magnetization reversal when the spin injection current of the free layer of the second magnetoresistive element flows against the spin injection current that reverses the magnetization direction is the free resistance of the first magnetoresistive element. A memory element in which a ternary value or a quaternary value is stored as a resistance value, which is greater than the strength against magnetization reversal when a spin injection current of a layer flows.
  5. 　前記第一、第二の磁気抵抗素子がそれぞれ有する前記自由層は互いに接続されている請求項１乃至請求項４のいずれか１項記載の記憶素子。 The memory element according to any one of claims 1 to 4, wherein the free layers of the first and second magnetoresistive elements are connected to each other.
  6. 　前記第一、第二の磁気抵抗素子がそれぞれ有する前記固定層は互いに接続されている請求項１乃至請求項５のいずれか１項記載の記憶素子。 6. The memory element according to claim 1, wherein the fixed layers of the first and second magnetoresistive elements are connected to each other.
  7. 　前記第一、第二の磁気抵抗素子がそれぞれ有する前記絶縁層は互いに接続されている請求項１乃至請求項６のいずれか１項記載の記憶素子。 The memory element according to any one of claims 1 to 6, wherein the insulating layers of the first and second magnetoresistive elements are connected to each other.
  8. 　請求項１乃至請求項７のいずれか１項記載の記憶素子を用いて、第一、第二、第三の値を記憶する記憶方法であって、
    　前記第一の値を記憶するために、前記第一、第二の磁気抵抗素子の両方が磁化同方向抵抗値を示すように、前記第一、第二の磁気抵抗素子の前記自由層の磁化方向をそれぞれ前記固定層の磁化方向と同じ方向に向けて、前記第一、第二の磁気抵抗素子の並列抵抗値を前記第一の値と対応させて記憶し、
    　前記第二の値を記憶するために、前記第一、第二の磁気抵抗素子の両方が磁化反対方向抵抗値を示すように、前記第一、第二の磁気抵抗素子の前記自由層の磁化方向をそれぞれ前記固定層の磁化方向と反対方向に向けて、前記第一、第二の磁気抵抗素子の並列抵抗値を前記第二の値と対応させて記憶し、
    　前記第三の値を記憶するために、いずれか一方の前記磁気抵抗素子が前記磁化同方向抵抗値を示すように当該一方の前記磁気抵抗素子の前記自由層の磁化方向を前記固定層の磁化方向と同じ方向に向け、他方の前記磁気抵抗素子が前記磁化同方向抵抗値を示すように当該他方の前記磁気抵抗素子の前記自由層の磁化方向を前記固定層の磁化方向と反対方向に向けて、前記第一、第二の磁気抵抗素子の並列抵抗値を前記第三の値と対応させて記憶する記憶方法。     A storage method for storing a first value, a second value, and a third value using the storage element according to any one of claims 1 to 7,
    In order to store the first value, the magnetization of the free layer of the first and second magnetoresistive elements so that both the first and second magnetoresistive elements exhibit a magnetization unidirectional resistance value. With each direction directed in the same direction as the magnetization direction of the fixed layer, the parallel resistance values of the first and second magnetoresistive elements are stored in correspondence with the first value,
    In order to store the second value, the magnetization of the free layer of the first and second magnetoresistive elements such that both the first and second magnetoresistive elements exhibit opposite magnetization resistance values. The direction is directed in the direction opposite to the magnetization direction of the fixed layer, and the parallel resistance values of the first and second magnetoresistive elements are stored in correspondence with the second value,
    In order to store the third value, the magnetization direction of the free layer of the one magnetoresistive element is set to the magnetization of the fixed layer so that any one of the magnetoresistive elements exhibits the same magnetization resistance value. The magnetization direction of the free layer of the other magnetoresistive element is directed to the opposite direction to the magnetization direction of the fixed layer so that the other magnetoresistive element exhibits the same magnetization resistance value. And storing the parallel resistance values of the first and second magnetoresistive elements in correspondence with the third value.
  9. 　第一、第二、第三の値を相互に書き換えて、書き換えた値を記憶する請求項８記載の記憶方法であって、
    　前記第一の磁気抵抗素子の前記自由層の磁化方向だけを反転させる場合には、前記第一の磁気抵抗素子の前記自由層の保磁力よりも大きく、前記第二の磁気抵抗素子の前記自由層の保磁力よりも小さい外部磁界を、前記第一の磁気抵抗素子の前記自由層の磁化方向と逆向きに印加して、書き換えた値を記憶する記憶方法。     The storage method according to claim 8, wherein the first value, the second value, and the third value are mutually rewritten, and the rewritten value is stored.
    When only the magnetization direction of the free layer of the first magnetoresistive element is reversed, the coercivity of the free layer of the first magnetoresistive element is greater than the free magnetic field of the second magnetoresistive element. A storage method for storing a rewritten value by applying an external magnetic field smaller than the coercive force of a layer in a direction opposite to the magnetization direction of the free layer of the first magnetoresistive element.
  10. 　第一、第二、第三の値を相互に書き換えて、書き換えた値を記憶する請求項８記載の記憶方法であって、
    　前記第一の磁気抵抗素子の前記自由層の磁化方向だけを反転させる場合には、前記第一の磁気抵抗素子の前記自由層の磁化方向を逆向きにし、前記第一の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも大きく、前記第二の磁気抵抗素子の前記自由層のスピン注入電流が流れたときの磁化反転に対する強さよりも小さいスピン注入電流を流して、書き換えた値を記憶する記憶方法。     The storage method according to claim 8, wherein the first value, the second value, and the third value are mutually rewritten, and the rewritten value is stored.
    When reversing only the magnetization direction of the free layer of the first magnetoresistive element, the magnetization direction of the free layer of the first magnetoresistive element is reversed and the direction of the first magnetoresistive element is A spin injection current that is greater than the strength against magnetization reversal when the free layer spin injection current flows and smaller than the strength against magnetization reversal when the free magnetoresistive element spin injection current flows. A storage method for storing and rewriting the stored value.
  11. 　前記記憶素子の抵抗値を測定し、前記抵抗値から記憶された値を読み取る請求項８記載の記憶方法であって、
    　前記記憶素子の抵抗値を測定して基準値と比較し、
    　両方の前記磁気抵抗素子の抵抗値が前記磁化同方向抵抗値であると判別した場合を前記第一の値とし、
    　両方の前記磁気抵抗素子の抵抗値が前記磁化反対方向抵抗値であると判別した場合を前記第二の値とし、
    　一方の前記磁気抵抗素子が前記磁化同方向抵抗値であり他方の前記磁気抵抗素子が前記磁化反対方向抵抗値であると判別した場合を第三の値とする記憶方法。     The storage method according to claim 8, wherein a resistance value of the storage element is measured and a stored value is read from the resistance value.
    Measuring the resistance value of the memory element and comparing it to a reference value;
    The case where it is determined that the resistance values of both the magnetoresistive elements are the magnetization co-directional resistance values as the first value,
    The case where it is determined that the resistance value of both the magnetoresistive elements is the resistance value opposite to the magnetization, the second value,
    A storage method in which the third value is determined when one of the magnetoresistive elements has the same magnetization direction resistance value and the other of the magnetoresistive elements has the opposite magnetization direction resistance value.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000195251A (en) * 1998-12-28 2000-07-14 Yamaha Corp Magnetoresistance random access memory
JP2005340468A (en) * 2004-05-26 2005-12-08 Fujitsu Ltd Semiconductor device
JP2008243933A (en) * 2007-03-26 2008-10-09 Nippon Hoso Kyokai <Nhk> Magnetic random access memory and recording device equipped with the same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000195251A (en) * 1998-12-28 2000-07-14 Yamaha Corp Magnetoresistance random access memory
JP2005340468A (en) * 2004-05-26 2005-12-08 Fujitsu Ltd Semiconductor device
JP2008243933A (en) * 2007-03-26 2008-10-09 Nippon Hoso Kyokai <Nhk> Magnetic random access memory and recording device equipped with the same

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