JP4666774B2 - Magnetic thin film memory element, magnetic thin film memory, and information recording / reproducing method - Google Patents

Magnetic thin film memory element, magnetic thin film memory, and information recording / reproducing method Download PDF

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JP4666774B2
JP4666774B2 JP2001003749A JP2001003749A JP4666774B2 JP 4666774 B2 JP4666774 B2 JP 4666774B2 JP 2001003749 A JP2001003749 A JP 2001003749A JP 2001003749 A JP2001003749 A JP 2001003749A JP 4666774 B2 JP4666774 B2 JP 4666774B2
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magnetic
layer
magnetic layer
recording
magnetization
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JP2002208680A (en
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貴司 池田
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キヤノン株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic thin film memory element utilizing a magnetoresistive effect, a magnetic thin film memory using the same, and an information recording / reproducing method thereof.
[0002]
[Prior art]
In recent years, semiconductor memory, which is a solid-state memory, has been widely used in information equipment, such as DRAM (Dynamic RAM (Random access Memory)), FeRAM (Ferroelectric RAM), and flash EEPROM (Electrically Erasable Programmable ROM (Read Only Memory)). There are various. The characteristics of these semiconductor memories have their merits and demerits, and there is no memory that satisfies all the specifications required for current information equipment. For example, DRAM has a high recording density and a large number of rewritable times, but since it is volatile, stored information is lost when the power is turned off. Further, although the flash EEPROM is non-volatile, it takes a long time to erase and is not suitable for high-speed information processing.
[0003]
In contrast to the current state of the semiconductor memory as described above, the memory (MRAM) using the magnetoresistive effect has specifications required by many information devices in terms of recording time, reading time, recording density, number of rewritable times, power consumption, and the like. It is promising as a memory that fills everything. In particular, MRAM using the spin-dependent tunneling magnetoresistance (TMR) effect is advantageous for high recording density or high-speed reading because a large read signal can be obtained. According to recent research reports, MRAM is feasible. Proven.
[0004]
The basic structure of the magnetoresistive film used for the memory element of the MRAM is a sandwich structure in which a magnetic layer is formed adjacent to a nonmagnetic layer. Nonmagnetic film materials include Cu and Al 2 O Three Is often used. A magnetoresistive film using a nonmagnetic layer made of a conductor such as Cu is called a giant magnetoresistive film (GMR film). 2 O Three Such a material using an insulator is called a spin-dependent tunnel effect film (TMR film). Since the TMR film shows a larger magnetoresistance effect than the GMR film, it is preferable as a memory element of MRAM.
[0005]
FIG. 13 is a diagram for explaining the electrical resistance of a magnetoresistive film using an in-plane magnetized film, wherein (a) is a cross-sectional view schematically showing a state in which the magnetization of the magnetoresistive film is parallel, and (b). These are sectional views schematically showing a state in which the magnetization of the magnetoresistive effect film is antiparallel. In FIG. 13, the arrow indicates the direction of magnetization. In the example of FIG. 13, the magnetoresistive film has a sandwich structure in which two magnetic layers 141 and 143 are stacked with a nonmagnetic layer 142 interposed therebetween. The magnetic layers 141 and 143 are both in-plane magnetization films.
[0006]
When the magnetization directions of the magnetic layers 141 and 143 are parallel as shown in FIG. 13A, the electric resistance of the magnetoresistive film is relatively small, and as shown in FIG. 13B, the magnetic layers 141 and 143 When the magnetization direction is antiparallel, the electrical resistance becomes relatively large. Therefore, it is possible to read out stored information by using the above-mentioned properties by using one of the magnetic layers 141 and 143 as a recording layer and the other as a reading layer.
[0007]
FIGS. 14A and 14B are diagrams for explaining the principle of recording / reproducing in a magnetoresistive film using an in-plane magnetization film. FIGS. 14A and 14B show the state of magnetization when reading recorded information “1”. Cross-sectional views schematically shown, (c) and (d) are cross-sectional views schematically showing the state of magnetization when recording information “0” is read. In FIG. 14, the arrow indicates the direction of magnetization, and the configuration of the magnetoresistive film is the same as that shown in FIG. Further, in this example, the magnetic layer 143 positioned below the nonmagnetic layer 142 is the recording layer, the magnetic layer 141 positioned above is the reading layer, and “1” is set when the magnetization direction of the recording layer is rightward. The case is set to “0”.
[0008]
As shown in FIG. 14A, when the magnetization directions of both magnetic layers are both rightward (parallel), the electric resistance of the magnetoresistive effect film is relatively small, and as shown in FIG. When the magnetization direction is leftward and the magnetization direction of the recording layer is rightward (antiparallel), the electric resistance is relatively large. As shown in FIG. 14C, when the magnetization direction of the reading layer is rightward and the magnetization direction of the recording layer is leftward (anti-parallel), the electric resistance becomes relatively large, as shown in FIG. As shown, when the magnetization directions of both magnetic layers are both leftward (parallel), the electrical resistance is relatively small. That is, when the magnetization direction of the reading layer is fixed to the right, if the electric resistance is large, “0” is recorded in the recording layer, and if the electric resistance is small, “1” is recorded. Will be. Further, when the magnetization direction of the reading layer is fixed to the left, if the electric resistance is large, “1” is recorded in the recording layer, and if the electric resistance is small, “0” is recorded. Will be.
[0009]
In the MRAM using the in-plane magnetization film as described above, when the element size is reduced in order to increase the recording density of the MRAM, the demagnetizing field (self-demagnetizing field) generated in the magnetic layer or the magnetization of the end face is reduced. There arises a problem that information cannot be held due to the effect of curling. As a method for avoiding this problem, for example, the shape of the magnetic layer may be rectangular, but in this case, since the element size cannot be reduced, improvement in recording density cannot be expected so much.
[0010]
Therefore, as described in Japanese Patent Laid-Open No. 11-213650, a proposal has been made to avoid the above problem by using a perpendicular magnetization film. According to this method, since the demagnetizing field does not increase even when the element size is reduced, it is possible to realize a magnetoresistive film having a smaller size than the MRAM using the in-plane magnetization film. Examples of the magnetic material exhibiting perpendicular magnetic anisotropy include transition metal-noble metal alloys and multilayer films, CoCr alloys, rare earth-transition metal alloys and multilayer films.
[0011]
Similar to the magnetoresistive film using the in-plane magnetization film, the MRAM using the perpendicular magnetization film has a sandwich structure in which the magnetic layers are stacked via the nonmagnetic layer, and the magnetization directions of both magnetic layers are parallel. The electric resistance of the magnetoresistive film is relatively small, and the electric resistance is relatively large when the magnetization directions are antiparallel.
[0012]
FIGS. 15A and 15B are diagrams for explaining the principle of recording / reproduction in a magnetoresistive film using a perpendicular magnetization film. FIGS. 15A and 15B schematically show the state of magnetization when recording information “1” is read. FIGS. 3C and 3D are cross-sectional views schematically showing the state of magnetization when recording information “0” is read. In FIG. 15, the arrow indicates the direction of magnetization, and the configuration of the magnetoresistive film is basically the same as that shown in FIG. 13 except that the magnetic layer is a perpendicular magnetization film. ing. In this example, the magnetic layer 143 located below the nonmagnetic layer 142 is the recording layer, the magnetic layer 141 located above is the readout layer, and the case where the magnetization direction of the recording layer is upward is set to “1”. Is “0”.
[0013]
When the magnetization directions of both magnetic layers are upward as shown in FIG. 15 (a), the electric resistance of the magnetoresistive film is relatively small, and the magnetization direction of the readout layer is downward as shown in FIG. 15 (b). When the magnetization direction of the recording layer is upward, the electrical resistance is relatively large. Further, when the magnetization direction of the reading layer is upward as shown in FIG. 15C and the magnetization direction of the recording layer is downward, the electric resistance is relatively large, and both magnetic properties are obtained as shown in FIG. When the magnetization directions of both layers are downward, the electrical resistance is relatively small. In other words, when the magnetization direction of the reading layer is fixed upward, if the electric resistance is large, “0” is recorded in the recording layer, and if the electric resistance is small, “1” is recorded. Will be. Further, when the magnetization direction of the reading layer is fixed downward, if the electric resistance is large, “1” is recorded in the recording layer, and if the electric resistance is small, “0” is recorded. Will be.
[0014]
[Problems to be solved by the invention]
In a memory element (magnetic thin film memory element) used in an MRAM, after applying a magnetic field during recording or reproduction, the magnitude of magnetization of each magnetic layer formed adjacently through a nonmagnetic layer is saturated. That is, it is preferable that the directions of all the spins are aligned in one direction in each magnetic layer. Magnetic materials often used in MRAM are Co, Fe, NiFe, or alloys thereof. For example, the coercivity of a magnetic layer made of Co (the intensity of a magnetic field with the magnetization of a ferromagnetic material in a magnetic saturation state being 0) is about 1 kA / m in a bulk type, but several tens of nm. In the case of this thin film, it is about several kA / m. Further, depending on the magnetic film forming conditions, the saturation magnetic field may be about several tens of kA / m. Further, in a magnetic thin film that has been finely processed, the saturation magnetic field may be further increased. On the other hand, recording of information in the MRAM is performed by passing a current through a conducting wire arranged near the memory element and reversing the magnetization direction of the magnetic layer by a magnetic field generated by this, but a current that can be passed through the conducting wire. Therefore, the strength of the magnetic field that can be applied to the memory element is up to about 10 kA / m. Therefore, in the recording method using a conducting wire, the magnetization of the magnetic layer cannot be completely reversed, and a sufficient magnetoresistance change may not be obtained. This can be a factor that limits the composition of the magnetic material, film formation conditions, film structure, and the like, or can cause a decrease in yield in manufacturing.
[0015]
In particular, the magnetization reversal magnetic field and the magnetization saturation magnetic field of the perpendicular magnetization film generally show larger values than the in-plane magnetization film. Therefore, when the perpendicular magnetization film is used for the MRAM, the composition and film formation conditions are further limited. Will be.
[0016]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a magnetic thin film memory element capable of stably recording and reading information even when using a magnetic material having a large magnetization reversal magnetic field and magnetization saturation magnetic field, and a magnetic thin film using the same An object of the present invention is to provide a memory and an information recording / reproducing method thereof.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, the magnetic thin film memory element of the present invention is a magnetic thin film memory element in which a read layer and a recording layer are laminated via a nonmagnetic layer, and the read layer has a magnetization direction in a predetermined direction. The recording layer includes a plurality of magnetic layers that are magnetically exchange-coupled to each other between adjacent layers, and the magnetization direction of the magnetic layer adjacent to the nonmagnetic layer depends on the recording temperature. Is reversible by the exchange coupling force generated in the recording layer.
[0018]
In the above case, at least the first to fourth magnetic layers are sequentially stacked in the recording layer, and the first to fourth magnetic layers have a Curie temperature of each magnetic layer,
Third magnetic layer <first magnetic layer <second magnetic layer <fourth magnetic layer
The magnetization direction of the fourth magnetic layer is fixed in a predetermined direction,
A 1-bit information may be recorded in the first magnetic layer according to the recording temperature.
[0019]
In the above case, a fifth magnetic layer having a predetermined magnitude and magnetization in a predetermined direction at a higher recording temperature and capable of reversing the magnetization of the second magnetic layer by a stray magnetic field generated by the magnetization is further provided. You may have.
[0020]
In addition, a sixth magnetic layer having a domain wall with a predetermined energy is formed between the first magnetic layer and the second magnetic layer when the magnetization directions of these magnetic layers are antiparallel. You may do it.
[0021]
Furthermore, an antiferromagnetic layer having a Neel temperature higher than the recording temperature may be provided adjacent to the fourth magnetic layer.
[0022]
Further, an antiferromagnetic layer having a Neel temperature higher than the recording temperature may be provided adjacent to the readout layer.
[0023]
A magnetic thin film memory according to the present invention is characterized in that a plurality of the magnetic thin film memory elements described above are provided, and heating means for selectively raising the temperature of the magnetic thin film memory elements is provided.
[0024]
The information recording / reproducing method of the present invention is an information recording / reproducing method for a magnetic thin film memory device in which a recording layer composed of a plurality of magnetic layers magnetically exchange-coupled to each other between adjacent layers and a reading layer are stacked via a nonmagnetic layer. In the reproducing method, the magnetization of the readout layer is fixed in a predetermined direction, and the magnetization direction of the magnetic layer adjacent to the nonmagnetic layer among the plurality of magnetic layers is set according to the level of recording temperature. Inverted by the exchange coupling force generated in the recording layer, 1-bit information is recorded, and the magnetization direction of the readout layer and the magnetization direction of the magnetic layer adjacent to the nonmagnetic layer are parallel and antiparallel, respectively. The method includes reading out the difference in magnetoresistance value of the magnetic thin film memory element in association with the 1-bit information.
[0025]
In the above case, the first to fourth magnetic layers are used as the plurality of magnetic layers, and the relationship between the Curie temperatures of the first to fourth magnetic layers is
Third magnetic layer <first magnetic layer <second magnetic layer <fourth magnetic layer
And In The magnetization direction of the fourth magnetic layer is fixed to a predetermined direction, the recording layer is heated to a first recording temperature higher than the Curie temperature of the third magnetic layer, and the third magnetic layer is The magnetization of the first magnetic layer and the magnetization reversal of the first magnetic layer by the exchange coupling force with the second magnetic layer. The first information is recorded as the magnetization direction, the recording layer is heated to a second recording temperature higher than the first recording temperature, and the fourth magnetic layer is compared with the second magnetic layer. By applying a magnetic field of a predetermined magnitude that is applied antiparallel to the magnetization direction, the magnetization direction of the second magnetic layer is aligned with the direction of the magnetic field, and the exchange coupling force with the second magnetic layer Second information is recorded with the magnetization direction of the first magnetic layer antiparallel to the magnetization direction of the fourth magnetic layer. It may also include a door.
[0026]
In addition, a fifth magnetic layer having a predetermined magnitude and magnetization in a predetermined direction at the second recording temperature is used, and a stray magnetic field generated by the fifth magnetic layer is used when information is recorded at the second recording temperature. You may use as a magnetic field of the predetermined magnitude | size applied.
[0027]
Further, a sixth magnetic layer is provided between the first magnetic layer and the second magnetic layer, and the magnetization direction of the first magnetic layer and the magnetization direction of the second magnetic layer are antiparallel. In this case, a domain wall having a predetermined energy may be formed in the sixth magnetic layer.
[0028]
Furthermore, the magnetization direction of the fourth magnetic layer may be fixed using an antiferromagnetic layer having a Neel temperature higher than the recording temperature.
[0029]
Furthermore, the magnetization direction of the readout layer may be fixed using an antiferromagnetic layer whose Neel temperature is higher than the recording temperature.
[0030]
In the present invention as described above, the recording layer is composed of a plurality of magnetic layers that are magnetically exchange-coupled to each other between adjacent layers, and the magnetization direction of the magnetic layer adjacent to the nonmagnetic layer depends on the recording temperature. By reversing, 1-bit information is recorded, but the reversal is performed by the exchange coupling force generated in the recording layer regardless of the external magnetic field. Therefore, even if a magnetic material having a large magnetization reversal magnetic field or magnetization saturation magnetic field is used for the recording layer, that is, the magnetic layer adjacent to the nonmagnetic layer, as in the prior art, a sufficient magnetoresistance change can be obtained.
[0031]
Specifically, the first to fourth magnetic layers are used as the plurality of magnetic layers constituting the recording layer, and the relationship between the Curie temperatures of the first to fourth magnetic layers is
Third magnetic layer <first magnetic layer <second magnetic layer <fourth magnetic layer
In the case where the magnetization direction of the fourth magnetic layer is fixed in a predetermined direction, it is higher than the Curie temperature of the third magnetic layer, and the magnetization direction of the first magnetic layer is the same as that of the second magnetic layer. At the first recording temperature that is easily reversed by the exchange coupling force, the magnetization of the third magnetic layer is degaussed and the magnetization reversal of the first magnetic layer is facilitated, and exchange coupling with the second magnetic layer is achieved. Due to the force, the magnetization direction of the first magnetic layer is changed to the magnetization direction of the fourth magnetic layer, and the first information is recorded, which is higher than the first recording temperature and the magnetization direction of the second magnetic layer is the fourth magnetization layer. At the second recording temperature, where the magnetization direction of the magnetic layer is easily aligned with the direction of the magnetic field of a predetermined magnitude applied in parallel to the magnetization direction of the magnetic layer, the magnetization direction of the second magnetic layer is aligned with the direction of the magnetic field, Due to the exchange coupling force with the second magnetic layer, the magnetization direction of the first magnetic layer becomes the magnetization direction of the fourth magnetic layer. Second information are antiparallel is recorded.
[0032]
In the above case, the application of the magnetic field is used to reverse the magnetization direction of the second magnetic layer, and the magnetization direction of the first magnetic layer on which information recording is performed does not reverse depending on the magnetic field. Inverted by the exchange coupling force with the second magnetic layer.
[0033]
In the present invention, the magnetization direction of the readout layer is fixed in a predetermined direction in advance. Whether the magnetization direction of the readout layer and the magnetization direction of the first magnetic layer are parallel or antiparallel. Thus, the resistance values of the magnetic thin film memory elements are different. Therefore, information recorded on the first magnetic layer as described above can be read without applying an external magnetic field.
[0034]
In the present invention, in the case of having the fifth magnetic layer having a predetermined magnitude of magnetization at the second recording temperature, the stray magnetic field generated by the fifth magnetic layer is the second at the second recording temperature. Since information recording is performed by being applied to the magnetic layer, it is not necessary to apply an external magnetic field during information recording.
[0035]
In the present invention, in the case where the sixth magnetic layer is formed between the first magnetic layer and the second magnetic layer, the magnetization directions of the first magnetic layer and the second magnetic layer are opposite to each other. It is possible to facilitate parallel orientation. In this case, the magnetic field applied to the second magnetic layer may be smaller.
[0036]
Furthermore, in the present invention, in the case where the antiferromagnetic layer whose Neel temperature is higher than the recording temperature is provided adjacent to the fourth magnetic layer, the fourth coupling layer is formed by the exchange coupling force with the antiferromagnetic layer. The magnetization direction of the magnetic layer is fixed. Therefore, it is not necessary to use a material having such a large coercive force for the fourth magnetic layer, and the degree of freedom of material selection regarding the fourth magnetic layer at the time of design is improved.
[0037]
Further, in the present invention, in the case where the antiferromagnetic layer having a Neel temperature higher than the recording temperature is provided adjacent to the first magnetic layer, the first coupling layer is formed by the exchange coupling force with the antiferromagnetic layer. The magnetization direction of the magnetic layer is fixed. Therefore, it is not necessary to use a material having such a large coercive force for the first magnetic layer, and the degree of freedom of material selection regarding the first magnetic layer at the time of design is improved.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0039]
FIG. 1 is a cross-sectional structure diagram of a magnetoresistive film used in a magnetic thin film memory element according to an embodiment of the present invention. This magnetoresistive film has a multilayer structure in which a magnetic layer 1, a nonmagnetic layer 2, and magnetic layers 3 to 6 are sequentially laminated. The magnetic layer 1 is a readout layer, and the magnetic layers 3 to 6 are recording layers (multilayer films). Magnetic exchange coupling is established between the magnetic layer 3 and the magnetic layer 4, between the magnetic layer 4 and the magnetic layer 5, and between the magnetic layer 5 and the magnetic layer 6. The magnetization direction of the magnetic layer 1 is fixed in a predetermined direction. Although not shown in FIG. 1, in order to fix the magnetization direction of the magnetic layer 1, an antiferromagnetic layer made of a material having a Neel temperature higher than the recording temperature is provided, and this and the magnetic layer 1 are exchange coupled. You may let them.
[0040]
Among the magnetic layers 3 to 6, the magnetic layer 6 has the highest Curie temperature, and the magnetization direction of the magnetic layer 6 is fixed within the operating temperature (recording temperature) range. The Curie temperature of the magnetic layer 4 is the second highest next to the Curie temperature of the magnetic layer 6, and the Curie temperature of the magnetic layer 5 is the lowest. Although not shown in FIG. 1, in order to fix the magnetization direction of the magnetic layer 6, an antiferromagnetic layer made of a material having a Neel temperature higher than the recording temperature is provided, and this and the magnetic layer 6 are exchange coupled. You may let them.
[0041]
The magnetoresistive film having the multilayer film structure as described above can be recorded by raising the temperature. Hereinafter, recording and reproduction of information when each magnetic layer of the magnetoresistive effect film is an in-plane magnetization film and when it is a perpendicular magnetization film will be described in detail.
[0042]
(1) In-plane magnetization film
(1-a) Information recording
FIG. 2 is a conceptual diagram for explaining an information recording process in the case where an in-plane magnetization film is used for each magnetic layer of the magnetoresistive effect film shown in FIG. 1, and (a) is recorded with “1”. (B) shows a relatively low recording temperature T L (C) is a schematic diagram showing the magnetization direction when the temperature is raised to a relatively high temperature. H (D) is a schematic diagram showing a magnetization direction when “0” is recorded. In FIG. 2, a white arrow indicates the direction of magnetization, and a black arrow (10) indicates a magnetic field applied from the outside.
[0043]
In the example shown in FIG. 2, all the magnetic layers 1, 3 to 6 are in-plane magnetized films in the magnetoresistive effect film, and an external magnetic field 10 is applied in the leftward direction in the film plane. In the following description, when the magnetization direction of the magnetic layer 3 is rightward, it is “1”, and when it is leftward, it is “0”.
[0044]
Now, for example, as shown in FIG. 2A, it is assumed that the magnetization directions of the magnetic layers 3 to 6 are all rightward and “1” is recorded. L The temperature rises to However, this relatively low recording temperature T L Is a temperature that is higher than the Curie temperature of the magnetic layer 5 and at which the magnetization direction of the magnetic layer 3 can be easily reversed by the exchange coupling force with the magnetic layer 4. The magnetic layer 4 has a relatively low recording temperature T. L In the state where the temperature has been raised to a level, the coercive force is such that magnetization does not reverse due to the influence of the externally applied magnetic field 10. Under such conditions, a relatively low recording temperature T L 2 (b), the magnetization of the magnetic layer 5 disappears macroscopically (or its coercive energy decreases), but the magnetization directions of the magnetic layers 3, 4, 6 All maintain the original magnetization state (rightward), and magnetization reversal by the externally applied magnetic field 10 does not occur.
[0045]
In the process of cooling the magnetoresistive film after the temperature rise, if the film temperature falls below the Curie temperature of the magnetic layer 5, the magnetization of the magnetic layer 5 is aligned in the same direction as the magnetization direction of the magnetic layer 6. It returns to the magnetized state of (a).
[0046]
Next, a relatively high recording temperature T from the state of FIG. H The temperature rises to This relatively high recording temperature T H Is a temperature at which the magnetization direction of the magnetic layer 4 easily aligns with the direction of the external magnetic field 10. Under such conditions, a relatively high recording temperature T H 2C, the magnetization of the magnetic layer 5 disappears macroscopically as shown in FIG. 2C, the magnetization direction of the magnetic layer 4 becomes leftward (magnetization reversal) by the externally applied magnetic field 10, and the magnetic layer 3 Are aligned in the magnetization direction (leftward) of the magnetic layer 4. However, the magnetic layer 6 maintains the original magnetization state (rightward direction).
[0047]
If the film temperature falls below the Curie temperature of the magnetic layer 5 in the process of cooling the magnetoresistive film after the temperature rise, the magnetization of the magnetic layer 5 is aligned with the magnetization direction (rightward) of the magnetic layer 6 and further exchanged. Due to the coupling force, the magnetization of the magnetic layer 4 is also aligned with the magnetization direction (rightward) of the magnetic layer 6. However, the domain wall energy at the interface between the magnetic layer 3 and the magnetic layer 4 at this time is set to be smaller than the coercive force energy of the magnetic layer 3. For this reason, the magnetization direction of the magnetic layer 3 is aligned with the direction of the external magnetic field 10, and a domain wall exists at the interface between the magnetic layer 3 and the magnetic layer 4.
[0048]
A relatively high recording temperature T as described above. H The magnetization state of the magnetoresistive film after the film temperature is lowered to the Curie temperature of the magnetic layer 5 is the magnetization state shown in FIG. 2D, and “0” is recorded. Become.
[0049]
Next, a relatively low recording temperature T from the magnetization state of FIG. 2D, that is, a state where “0” is recorded. L The temperature rises to Relatively low recording temperature T L In the subsequent cooling process, the magnetization of the magnetic layer 3 is aligned with the magnetization direction of the magnetic layer 4 by the exchange coupling force, and the magnetization state shown in FIG. When the film temperature falls below the Curie temperature of the magnetic layer 5, the magnetization of the magnetic layer 5 is aligned in the same direction as the magnetization direction of the magnetic layer 6 and returns to the magnetization state of FIG.
[0050]
Next, a relatively high recording temperature T from the state of FIG. H The temperature rises to Also in this case, the relatively high recording temperature T from FIG. H Since the magnetization of the magnetic layer 5 disappears macroscopically in the same way as when the temperature is raised to 1, the magnetization direction of the magnetic layer 4 is aligned with the direction of the external magnetic field 10, and the magnetization state shown in FIG.
[0051]
As is apparent from the above, the relatively low recording temperature T, regardless of whether the initial state is “0” or “1” is recorded. L If the temperature rises to 1 "Is recorded, and the recording temperature T is relatively high. H If the temperature rises to 0 "Is recorded. In this information recording, since the temperature of the magnetic layer is raised and recording is performed using the exchange coupling force, recording can be performed with a small applied magnetic field.
[0052]
(1-b) Information reproduction
Reading of recorded information utilizes the fact that the resistance value of the magnetoresistive film differs depending on whether the magnetization direction of the magnetic layer 1 (read layer) and the magnetization direction of the magnetic layer 3 are parallel or antiparallel. . In other words, the magnetization direction of the magnetic layer 1 is fixed in advance to the initialization direction, and the magnetization direction of the magnetic layer 3 depends on whether the recording information is “0” or “1”. Therefore, the resistance value of the magnetoresistive film varies depending on whether the recording information is “0” or “1”. Therefore, the recorded information can be read without applying an external magnetic field by detecting the magnitude of the resistance value of the magnetoresistive film.
[0053]
The magnetoresistive film described above is configured to record information by applying an external magnetic field 10, but by adding a function of applying a magnetic field for information recording to the magnetoresistive film itself, It is also possible to record information without applying the magnetic field 10.
[0054]
FIG. 3 is a cross-sectional view schematically showing a magnetization direction and a stray magnetic field direction in a magnetoresistive film capable of recording information without an external magnetic field. In the magnetoresistive film, a new magnetic layer 7 is provided on the magnetic layer 6 side in addition to the configuration shown in FIG. The magnetic layer 7 generates a stray magnetic field 20 necessary for information recording, has a large magnetization at a recording temperature, and is provided so as not to be in direct contact with the magnetic layer 6. The direction of magnetization of the magnetic layer 7 is fixed, and the direction is a relatively high recording temperature T. H This is a direction in which the stray magnetic field 20 is applied in anti-parallel to the magnetization direction of the magnetic layer 4 when the temperature is raised to. Also in this magnetoresistive film, the recording of information is the same as the recording of information shown in FIG. 2 except that the stray magnetic field 20 is used instead of the external magnetic field 10.
[0055]
In addition to the example of FIG. 3 described above, in order to prevent the recording direction from being lost by reversing the magnetization direction of the magnetic layer 3 due to the exchange coupling force with the magnetic layer 4, as shown in FIG. A magnetic layer 8 using a material having a small domain wall energy may be formed between the layers 4.
[0056]
In the configuration of the magnetoresistive film using the in-plane magnetization film described above, Co, Fe, Ni, and alloys thereof can be used as the magnetic layers 1 to 3 to 8. Furthermore, by adding an appropriate amount of Sb, V, Cr, Si, Al, Zn, Mn, Cu, Rh, Ru, Ir, Os, W, Mo, Nb, Re, Ga, Ge, Sn, Pt, Pd, etc. It is also possible to adjust magnetic properties such as a desired Curie temperature, domain wall energy, and coercive force.
[0057]
Further, the first antiferromagnetic layer may be formed to be exchange coupled with the magnetic layer 6 to fix the magnetization direction of the magnetic layer 6, or the second antiferromagnetic layer may be exchange coupled to the magnetic layer 1. The magnetization direction of the magnetic layer 1 may be fixed. As the antiferromagnetic material used for these antiferromagnetic layers, those having a high Neel temperature are preferable. For example, α-Fe 2 O Three NiO, MnIr, MnPt, MnCr, CrAl, CrGa, etc. can be used.
[0058]
(2) In case of perpendicular magnetization film
(2-a) Information recording
FIG. 5 is a conceptual diagram for explaining an information recording process in the case where a perpendicular magnetization film is used for each magnetic layer of the magnetoresistive film shown in FIG. 1, and (a) shows a case where “1” is recorded. (B) is a relatively low recording temperature T L (C) is a schematic diagram showing the magnetization direction when the temperature is raised to a relatively high temperature. H (D) is a schematic diagram showing a magnetization direction when “0” is recorded. In FIG. 5, a white arrow indicates the direction of magnetization, and a black arrow (10) indicates a magnetic field applied from the outside.
[0059]
In the example shown in FIG. 5, all the magnetic layers 1, 3 to 6 are perpendicular magnetization films in the magnetoresistive effect film, and an external magnetic field 10 is applied in the direction of perpendicular magnetization. Here, “1” is set when the magnetization direction of the magnetic layer 3 is upward, and “0” is set when the magnetization direction is downward. The recording process in this magnetoresistive film is the same as that in the case where the in-plane magnetization film shown in FIG. 2 is used, and the recording temperature T is relatively low. L When the temperature is raised to (in the state of FIG. 5B), “1” is recorded (in the state of FIG. 5A), and a relatively high recording temperature T H When the temperature is raised to (in the state of FIG. 5C), “0” is recorded (the state of FIG. 5D).
[0060]
Also in the magnetoresistive effect film using the perpendicular magnetization film of this example, the function of applying a magnetic field to the magnetoresistive effect film is added to the magnetoresistive effect film itself as in the case of using the in-plane magnetization film described above. Therefore, information can be recorded without applying the external magnetic field 10 during recording.
[0061]
FIG. 6 is a cross-sectional view schematically showing a magnetization direction and a stray magnetic field direction in a magnetoresistive film capable of recording information without an external magnetic field. In the magnetoresistive effect film, a new magnetic layer 7 is provided on the magnetic layer 6 side in addition to the configuration of the magnetoresistive effect film shown in FIG. The magnetic layer 7 generates a stray magnetic field 20 necessary for information recording, has a large magnetization at a recording temperature, and is provided so as not to be in direct contact with the magnetic layer 6. The direction of magnetization of the magnetic layer 7 is fixed, and the direction is a relatively high recording temperature T. H This is a direction in which the stray magnetic field 20 is applied in anti-parallel to the magnetization direction of the magnetic layer 4 when the temperature is raised to. In this magnetoresistive film, the recording of information is the same as the recording of information shown in FIG. 5 except that the stray magnetic field 20 is used instead of the external magnetic field 10.
[0062]
In the magnetoresistive effect film using the perpendicular magnetization film described above, the material used for each of the magnetic layers 1 and 3 to 7 is at least one element selected from rare earth metals such as Tb, Dy, Gd, and Nd. Rare earth transition metal alloys composed of at least one element selected from transition metals such as Fe, Co, Ni, alloys composed of transition metals and noble metals such as Pt / Co, Pd / Co, artificial lattice multilayer films, CoCr alloys, etc. Any material can be used as long as it has a Curie temperature higher than room temperature and exhibits perpendicular magnetization, but a rare earth transition metal alloy is particularly preferable because it can easily obtain desired magnetic properties by adjusting its composition. In order to obtain a large change in magnetoresistance, it is preferable to use a material having a high spin polarizability for the magnetic layer 1 and the magnetic layer 3.
[0063]
In the magnetic thin film memory element of this embodiment configured by the magnetoresistive effect film described above, the method for heating the magnetoresistive effect film is not particularly limited, but for example, a heating element is formed near the magnetoresistive effect film. There is a method of heating by heat conduction. In this case, a nickel chrome alloy, an iron chrome aluminum alloy, or the like can be used as the heating element.
[0064]
In a magnetic thin film memory, a plurality of magnetic thin film memory elements having a magnetic thin film resistive film and a heating element are arranged, and by selectively passing a current through the heating element, the magnetic thin film resistance film of the magnetic thin film memory element is heated to receive information. Record. A well-known MRAM selection circuit can be used as a circuit for selectively flowing a current to the heating element.
[0065]
In order to raise the temperature of the magnetic thin film resistive film of the magnetic thin film memory element efficiently, the heating element and the magnetic thin film resistive film need to be arranged as close as possible, but both must be electrically independent. . Therefore, the heating element and the magnetoresistive film are preferably formed adjacent to each other via an insulating layer having high thermal conductivity. An example of such an insulator is BeO. Further, even if the material is not a material having extremely high thermal conductivity, it can be used by reducing the film thickness as long as it has a high electrical resistivity and is difficult to cause dielectric breakdown. As such a material, for example, Al 2 O Three And Si Three N Four Etc.
[0066]
When electrically connecting a heating element or a magnetoresistive film to a semiconductor, in order to reduce thermal damage of the semiconductor or increase thermal efficiency, the heating element or the magnetoresistive film has a low electrical resistance, and It is preferable to connect to the semiconductor through a layer formed by a conductor having a low thermal conductivity. An example of such a material is Ti.
[0067]
The temperature of the magnetoresistive effect film can be raised by a method in which the magnetoresistive effect film is directly heated by irradiating the light emitted from the light emitter in addition to the heating by the heating element.
[0068]
【Example】
Next, the configuration of the magnetic thin film memory element of the present invention will be described with specific examples.
[0069]
Example 1
FIG. 7 is a sectional view showing a schematic configuration of the magnetic thin film memory element according to the first embodiment of the present invention, and FIG. 8 is a sectional view of a magnetoresistive effect film used in the magnetic thin film memory element.
[0070]
In this magnetic thin film memory element, a Si wafer is used as the substrate 21. By oxidizing the surface of the wafer, about 1 μm of SiO 2 is obtained. 2 A film 22 is formed. SiO 2 On top of the film 22 is a 50 nm thick Al film. 50 Cu 50 A word line 23 made of a film is formed, and an n-type semiconductor 24, a p-type semiconductor 25, and a heat blocking film 26 are sequentially stacked thereon. The heat blocking film 26 is made of Ti having a thickness of 100 nm.
[0071]
A magnetoresistive effect film 40 and an Al film with a thickness of 50 nm are formed on the heat blocking film 50 Cu 50 A bit line 27 made of a film is formed, and an insulating film 28, a lower electrode 29, and a heating element 30 are further formed thereon. The heating element 30 is used to raise the temperature of the magnetoresistive effect film 40, and is formed on the magnetoresistive effect film 40 via an electric insulating film 28 above the bit line 27, with a thickness of 50 nm below that. Al 50 Cu 50 It is electrically connected to the lower electrode 29 made of a film. Here, Ni having a thickness of 100 nm is formed on the heating element 30. 75 Cr twenty three Mn 2 Is used.
[0072]
A heat blocking film 31 made of a 100 nm-thickness Ti film is formed on the heating element 30, and a p-type semiconductor 32, an n-type semiconductor 33, and a 50 nm-thick Al film are further formed thereon. 50 Cu 50 An upper electrode 34 made of a film is formed. A conductive wire 36 made of Al having a thickness of 100 nm is formed on the upper electrode 34 through an insulating layer 35 in order to apply a magnetic field from the outside during reproduction of recorded information.
[0073]
The magnetoresistive effect film 40 is based on the magnetoresistive effect film shown in FIG. 1 described above. As shown in FIG. 8, the antiferromagnetic layer 50, the magnetic layer 41, the nonmagnetic layer 42, the magnetic layers 43˜ 46 and 48, and an antiferromagnetic layer 49 are sequentially laminated. The magnetic layer 41, the nonmagnetic layer 42, and the magnetic layers 43 to 46 correspond to the magnetic layer 1, the nonmagnetic layer 2, and the magnetic layers 3 to 6 shown in FIG. The magnetic layer 48 corresponds to the magnetic layer 8 shown in FIG. The antiferromagnetic layer 49 is for fixing the magnetization direction of the magnetic layer 46, and the direction of unidirectional anisotropy is fixed and exchange coupled with the magnetic layer 46. The antiferromagnetic layer 50 is for fixing the magnetization direction of the magnetic layer 1, the magnetization direction is fixed, and is exchange coupled with the magnetic layer 1.
[0074]
In this example, the antiferromagnetic layer 50 has a Mn thickness of 5 nm. 70 Ir 30 The film and magnetic layer 41 are 10 nm thick Co 50 Fe 50 The film and nonmagnetic layer 42 are made of Al with a thickness of 2 nm. 2 O Three The film and magnetic layer 43 are 5 nm thick Co. 50 Fe 50 The magnetic layer 44 is a 2 nm thick Co film, and the magnetic layer 45 is a 3 nm thick Ni film. 92 Cr 8 The magnetic layer 46 is a 5 nm thick Co film, and the magnetic layer 48 is a 5 nm thick Fe film. 80 Cr 20 The film, antiferromagnetic layer 49 is 5 nm thick Mn 70 Ir 30 A membrane was obtained. When each magnetic layer is formed, a magnetic field is applied in the right direction to induce uniaxial anisotropy in the magnetic layer, and the magnetization directions of the magnetic layer 1 and the magnetic layer 6 are fixed in the right direction. Yes.
[0075]
In the magnetic thin film memory element of this example configured as described above, information is recorded by passing a current through the heating element 30 formed above the magnetoresistive thin film 40 via the upper electrode 34 and the lower electrode 29. The magnetoresistive thin film 40 is heated appropriately. The temperature of the magnetoresistive thin film 40 can be set to a desired temperature by adjusting the magnitude of the current flowing through the heating element 30. At the time of information recording, a magnetic field is applied in the left direction in the film surface of the magnetoresistive thin film 40.
[0076]
The recorded information is read by passing a constant current through the word line 23 and the bit line 27 and detecting the voltage applied to the magnetic thin film memory element. The voltage value detected in this way is a value with information recorded in the magnetoresistive thin film 40.
[0077]
Due to heating by the heating element 30, the magnetoresistive thin film 40 is made to have a relatively high recording temperature T. H Then, a constant current is applied to the word line 23 and the bit line 27 to measure the voltage applied to the magnetic thin film memory element, and then the magnetoresistive thin film 40 is moved to a relatively low recording temperature T. L As a result of measuring the voltage applied to the magnetic thin film memory element by passing a constant current through the word line 23 and the bit line 27, the relatively high recording temperature T H The voltage value when the temperature is raised to a relatively low recording temperature T L It showed a value higher than the voltage value when the temperature was raised to. From this result, it can be seen that 1-bit information can be recorded according to the difference (high and low) in the recording temperature.
[0078]
FIG. 9 is a circuit diagram showing a schematic configuration of a magnetic thin film memory having a plurality of magnetic thin film memory elements shown in FIG. In FIG. 9, the same components as those shown in FIG.
[0079]
In this magnetic thin film memory, a plurality of word lines 23 and bit lines 27 are provided vertically and horizontally, and a magnetic thin film memory element 100 is provided at each intersection thereof. A magnetic field applying conductor 36 and an upper electrode 34 are provided along the word line 23, and a lower electrode 29 is provided along the bit line 27. A plurality of magnetic thin film memory elements 100 are arranged in a matrix, but all have the same configuration, and therefore, the configuration will be described in detail here by taking the magnetic thin film memory element positioned at the upper right in FIG. 9 as an example.
[0080]
The magnetic thin film memory element 100 has the structure shown in FIG. 7, and includes a magnetoresistive film 40, a heating element 30, a diode D1 (n-type semiconductor 24 and p-type semiconductor 25), and a diode D2 (n-type semiconductor 33 and p-type). Type semiconductor 32). The magnetoresistive film 40 has one end connected to the word line 23 via the diode D 1 and the other end connected to the bit line 27. The heating element 30 has one end connected to the upper electrode 34 via the diode D <b> 2 and the other end connected to the lower electrode 29.
[0081]
One end of the word line 23 is connected to one terminal of the transistor Tr3. The other terminal of the transistor Tr3 is connected to one end of the fixed resistor R and to one input terminal of the sense amplifier SA. The other end of the fixed resistor R is grounded via the power source 101. One end of the bit line 27 is connected to one terminal of each of the transistors Tr4 and Tr5. The other terminal of the transistor Tr5 is grounded, and the other terminal of the transistor Tr4 is grounded via the power supply 102.
[0082]
One end of the upper electrode 34 is connected to one terminal of the transistor Tr1. The other terminal of the transistor Tr1 is grounded via the power source 103. One end of the lower electrode 29 is grounded via the transistor Tr6, and one end of the conducting wire 36 is grounded via the transistor Tr2.
[0083]
Next, the information recording operation of this magnetic thin film memory will be described.
[0084]
By turning on the transistors Tr1 and Tr6, a current of a desired magnitude can be passed through the heating element 30 via the upper electrode 34 and the lower electrode 29, whereby the magnetoresistive thin film 40 can be recorded in a desired recording manner. Information can be recorded by raising the temperature. At the time of information recording, the transistor Tr2 is turned on, a current having a predetermined magnitude is passed through the conductor 36 in a predetermined direction, and a magnetic field generated by the conductor 36 is applied to the magnetoresistive thin film 40 of the magnetic thin film memory element 100. To do. In this example, a plurality of magnetic thin film memory elements 100 are arranged in a matrix, and the transistors Tr1 provided on the upper electrodes 34, the transistors Tr6 provided on the lower electrodes 29, and the conductors 36 are provided. By controlling on / off of each transistor Tr2, the current can be selectively passed to the heating element 30 of the specific magnetic thin film memory element 100, and a magnetic field can be applied to the magnetoresistive thin film 40. it can.
[0085]
Next, the read operation of recorded information will be described.
[0086]
(1) First, the transistor Tr5 of the bit line 27 connected to the magnetic thin film memory element 100 to be selected is turned on, and the transistor Tr4 is turned off. For the other bit lines, the opposite state, that is, the transistor Tr5 is turned off and the transistor Tr4 is turned on. Further, the transistor Tr3 of the word line 23 connected to the magnetic thin film memory element 100 to be selected is turned on. Here, the power supply voltage (power supply 101) on the word line 23 is slightly lower than the power supply voltage (power supply 102) connected to the bit line 27, and the voltage difference is a diode constituting the magnetic thin film memory device 100. It is set to be smaller than the Zener voltage of D1. Therefore, a positive voltage is applied to one end of the magnetoresistive film 40 of the magnetic thin film memory element 100 to be selected via the diode D1, and the other end falls to the ground. Current flows. In other magnetic thin film memory elements, since the transistor Tr4 is turned on, a high voltage is applied to the bit line side, and no current flows through the magnetoresistive film due to the action of the diode.
[0087]
(2) In the state where a constant current is passed through the magnetoresistive effect film 40 of the magnetic thin film memory element 100 selected as described above, a current is passed through the conducting wire 36 in a predetermined direction to generate a magnetic field. The magnetization direction of the reading layer (magnetic layer 41 (magnetization direction is fixed)) and the recording layer (magnetic layer 43) stacked via the nonmagnetic layer of the magnetoresistive film 40 of the selected magnetic thin film memory element 100 is The resistance of the magnetoresistive film 40 differs depending on whether it is antiparallel or parallel.
[0088]
(3) Since the magnetoresistive film 40 and the fixed resistance R of the selected magnetic thin film memory element 100 are connected in series, the potential difference applied to each resistance is proportional to the ratio of the resistance values, and the resistance The sum of the potential differences between the two power supplies (101, 102) is constant. Therefore, when the resistance value of the magnetoresistive effect film 40 is different, the potential difference applied to the magnetoresistive effect film 40 is also different. The recorded information is read by detecting the magnitude of this potential difference with the sense amplifier SA.
[0089]
(Example 2)
FIG. 10 is a sectional view showing a schematic configuration of a magnetic thin film memory element according to a second embodiment of the present invention, and FIG. 11 is a sectional view of a magnetoresistive film used for the magnetic thin film memory element.
[0090]
This magnetic thin film memory element is the same as that of the first embodiment described above except that the lead wire 36 and the insulating layer 35 are not provided and the configuration of the magnetoresistive film 40 is different.
[0091]
The magnetoresistive effect film 40 is based on the magnetoresistive effect film shown in FIG. 6 described above. As shown in FIG. 11, the magnetic layer 41, the nonmagnetic layer 42, and the magnetic layers 43, 48, 44 to 46 are formed. It has a multilayer structure in which a magnetic layer 47 is provided so as not to contact the magnetic layer 46 on the magnetic layer 46 side. The magnetic layer 41, the nonmagnetic layer 42, and the magnetic layers 43 to 47 correspond to the magnetic layer 1, the nonmagnetic layer 2, and the magnetic layers 3 to 7 shown in FIG. The magnetic layer 48 is provided in order to prevent the recording direction from being lost due to the magnetization direction of the magnetic layer 43 being reversed due to the exchange coupling force with the magnetic layer 44. The magnetic layer 48 includes the magnetic layer 8 shown in FIG. Do the same.
[0092]
In this example, the magnetic layer 41 has a Gd thickness of 10 nm. 26 Co 74 2 nm thick Al film on the nonmagnetic layer 42 2 O Three The film and magnetic layer 43 have a Tb thickness of 10 nm. twenty two Fe 75 Co Three Dy with a film thickness of 20 nm on the magnetic layer 44 20 Fe 62 Co 18 The film and magnetic layer 45 have a Tb thickness of 3 nm. 17 Fe 83 Tb with a film thickness of 30 nm on the magnetic layer 46 twenty two Co 78 The magnetic layer 47 has a Tb thickness of 20 nm. 18 Fe 41 Co 41 Gd with a film thickness of 5 nm on the magnetic layer 48 32 Co 68 A membrane was used. Here, the coercive force of the magnetic layer 43 for retaining information is remarkably increased to 6 MA / m or more.
[0093]
The magnetic thin film memory element manufactured under the above-described conditions is heated to 200 ° C., and simultaneously, a magnetic field having a magnitude of 1.6 MA / m is applied to the magnetoresistive thin film 40 in the direction normal to the film surface. Then, a magnetic field having a magnitude of 1 MA / m was applied downward at the normal direction of the film surface at room temperature to direct the magnetization direction of the magnetic layer 47 downward.
[0094]
In the magnetic thin film memory element subjected to the above processing, the magnetoresistive thin film 40 is heated to a relatively high recording temperature T by heating by the heating element 30 as in the case of the first embodiment. H Then, a constant current is applied to the word line 23 and the bit line 27 to measure the voltage applied to the magnetic thin film memory element, and then the magnetoresistive thin film 40 is moved to a relatively low recording temperature T. L As a result of measuring the voltage applied to the magnetic thin film memory element by passing a constant current through the word line 23 and the bit line 27, the relatively high recording temperature T H The voltage value when the temperature is raised to a relatively low recording temperature T L It showed a value higher than the voltage value when the temperature was raised to. From this result, it can be seen that 1-bit information can be recorded according to the difference (high and low) in the recording temperature.
[0095]
FIG. 12 is a circuit diagram showing a schematic configuration of a magnetic thin film memory having a plurality of magnetic thin film memory elements shown in FIG. This magnetic thin film memory is the same as that shown in FIG. 9 described above except that the lead wire 36 and the transistor TR2 are not provided and the configuration of the magnetic thin film memory element 100 is different. In FIG. 12, the same components as those shown in FIG. 9 are denoted by the same reference numerals.
[0096]
In this magnetic thin film memory, the magnetic thin film memory element shown in FIG. The information recording is basically the same as the operation in the magnetic thin film memory shown in FIG. 9, but the magnetic thin film memory element 100 is replaced with a magnetic field generated at the conducting wire 36 as a magnetic field applied during information recording. A stray magnetic field generated in the magnetic layer 47 is used. Therefore, in the recording operation in the magnetic thin film memory of this example, “the transistor Tr2 is turned on and a current having a predetermined magnitude in a predetermined direction is applied to the conductor 36, which is necessary in the recording operation in the magnetic thin film memory shown in FIG. And the operation of “applying the magnetic field generated by the conductor 36 to the magnetoresistive thin film 40 of the magnetic thin film memory element 100” is not necessary. The other recording operations are the same as those in the magnetic thin film memory shown in FIG.
[0097]
Also for reading of recorded information, a stray magnetic field generated in the magnetic layer 47 constituting the magnetic thin film memory element 100 is used in place of the magnetic field generated in the conducting wire 36. Therefore, in the magnetic thin film memory shown in FIG. Of the reading operations (1) to (3), the operation (2) is not necessary. Therefore, after the operation (1), the operation proceeds to the operation (3), and the magnitude of the potential difference applied to the magnetoresistive film 40 is detected by the sense amplifier SA, and the recorded information is read out.
[0098]
【The invention's effect】
As described above, according to the present invention, information is basically recorded by the exchange coupling force generated in the recording layer, so that it is difficult to reverse the magnetization direction with a small applied magnetic field. Even if it is used, recording is possible without increasing the applied magnetic field. Therefore, it is possible to improve the selectivity of the magnetic material of the recording layer, the film forming conditions, the film configuration, and the like, and as a result, it is possible to improve the manufacturing yield.
[Brief description of the drawings]
FIG. 1 is a cross-sectional structure diagram showing an embodiment of a magnetoresistive film used in a magnetic thin film memory element of the present invention.
FIG. 2 is a conceptual diagram for explaining an information recording process when the magnetoresistive film shown in FIG. 1 is used, (a) is a schematic diagram showing a magnetization direction when “1” is recorded; (B) is a relatively low recording temperature T. L (C) is a schematic diagram showing the magnetization direction when the temperature is raised to a relatively high temperature. H (D) is a schematic diagram showing a magnetization direction when “0” is recorded.
3 is a cross-sectional view schematically showing a magnetization direction and a stray magnetic field direction in a magnetoresistive film capable of recording information without an external magnetic field, which is a modification of the magnetoresistive film shown in FIG. FIG.
4 is a view showing a modification of the magnetoresistive film shown in FIG. 1. FIG.
5 is a conceptual diagram for explaining an information recording process in the case where a perpendicular magnetization film is used for each magnetic layer of the magnetoresistive film shown in FIG. 1. FIG. 5 (a) shows a case where “1” is recorded. (B) is a relatively low recording temperature T L (C) is a schematic diagram showing the magnetization direction when the temperature is raised to a relatively high temperature. H (D) is a schematic diagram showing a magnetization direction when “0” is recorded.
6 is a cross-sectional view schematically showing a magnetization direction and a stray magnetic field direction in a magnetoresistive film capable of recording information without an external magnetic field, which is a modification of the magnetoresistive film shown in FIG. FIG.
FIG. 7 is a cross-sectional view showing a schematic configuration of a magnetic thin film memory element according to a first embodiment of the present invention.
8 is a cross-sectional view of a magnetoresistive film used in the magnetic thin film memory element shown in FIG.
9 is a circuit diagram showing a schematic configuration of a magnetic thin film memory having a plurality of magnetic thin film memory elements shown in FIG. 7;
FIG. 10 is a sectional view showing a schematic configuration of a magnetic thin film memory element according to a second embodiment of the present invention.
11 is a cross-sectional view of a magnetoresistive film used in the magnetic thin film memory shown in FIG.
12 is a circuit diagram showing a schematic configuration of a magnetic thin film memory having a plurality of magnetic thin film memory elements shown in FIG. 10;
FIG. 13 is a diagram for explaining the electrical resistance of a conventional magnetoresistive film using an in-plane magnetized film; (B) is sectional drawing which shows typically the state by which the magnetization of a magnetoresistive effect film is antiparallel.
FIGS. 14A and 14B are diagrams for explaining a recording / reproducing principle in a conventional magnetoresistive film using an in-plane magnetization film, wherein FIGS. 14A and 12B are magnetizations when reading recorded information “1”; Sectional views schematically showing the state of (2), and (c) and (d) are sectional views schematically showing the state of magnetization when recording information “0” is read.
FIGS. 15A and 15B are diagrams for explaining the principle of recording / reproduction in a conventional magnetoresistive film using a perpendicular magnetization film. FIGS. 15A and 15B are diagrams illustrating magnetization when reading recorded information “1”. Sectional views schematically showing the state, (c) and (d) are sectional views schematically showing the state of magnetization when recording information “0” is read.
[Explanation of symbols]
1, 3-8, 41, 43-48, 141, 143 Magnetic layer
2, 42, 142 Nonmagnetic layer
49, 50 Antiferromagnetic layer
10 External magnetic field
20 stray magnetic field
21 Substrate
22 SiO 2 film
23 Word line
24, 33 n-type semiconductor
25, 32 p-type semiconductor
26, 31 Thermal barrier film
27 bit line
28, 35 Insulating film
29 Lower electrode
30 Heating element
34 Upper electrode
36 conductor
40 Magnetoresistive film
100 Magnetic thin film memory device
Tr1 to Tr6 transistors
101-103 power supply
SA sense amplifier
R Fixed resistance
D1, D2 diode

Claims (16)

  1. In a magnetic thin film memory element in which a reading layer and a recording layer are stacked via a nonmagnetic layer,
    The readout layer has its magnetization direction fixed in a predetermined direction,
    The recording layer includes a plurality of magnetic layers that are magnetically exchange-coupled to each other between adjacent layers, and the magnetization direction of the magnetic layer adjacent to the nonmagnetic layer varies depending on the recording temperature. Ri reversible der by exchange coupling force occurring in the layer,
    The plurality of magnetic layers are formed by sequentially laminating at least first to fourth magnetic layers, and each of the first to fourth magnetic layers has a Curie temperature of each magnetic layer,
    Third magnetic layer <first magnetic layer <second magnetic layer <fourth magnetic layer
    The magnetization direction of the fourth magnetic layer is fixed in a predetermined direction,
    A magnetic thin film memory element, wherein 1-bit information can be recorded in the first magnetic layer according to a recording temperature .
  2. It further has a fifth magnetic layer that has a predetermined magnitude and magnetization in a predetermined direction at a higher recording temperature and can reverse the magnetization of the second magnetic layer by a stray magnetic field generated by the magnetization. The magnetic thin film memory element according to claim 1 .
  3. Between the first magnetic layer and the second magnetic layer, there is a sixth magnetic layer in which a domain wall having a predetermined energy is formed in the layer when the magnetization directions of these magnetic layers are antiparallel. 2. The magnetic thin film memory element according to claim 1 , wherein
  4. 2. The magnetic thin film memory element according to claim 1 , wherein an antiferromagnetic layer having a Neel temperature higher than a recording temperature is provided adjacent to the fourth magnetic layer.
  5.   2. The magnetic thin film memory element according to claim 1, wherein an antiferromagnetic layer having a Neel temperature higher than a recording temperature is provided adjacent to the readout layer.
  6.   2. The magnetic thin film memory element according to claim 1, wherein the magnetic layer constituting the reading layer and the recording layer is an in-plane magnetization film.
  7.   2. The magnetic thin film memory element according to claim 1, wherein each magnetic layer constituting the reading layer and the recording layer is a perpendicular magnetization film.
  8. 8. The magnetic thin film memory element according to claim 7 , wherein the perpendicular magnetization film is made of an alloy of a rare earth and a transition metal.
  9.   2. The magnetic thin film memory element according to claim 1, wherein the magnetic layer constituting the reading layer and the recording layer is a spin-dependent tunnel effect film.
  10. The magnetic thin film memory element according to any one of claims 1 to 9 is provided with a plurality of magnetic thin film memory, characterized in that it comprises heating means for selectively heat a magnetic thin film memory element.
  11. An information recording / reproducing method for a magnetic thin film memory element in which a recording layer and a reading layer, which are composed of a plurality of magnetic layers magnetically exchange-coupled to each other between adjacent layers, are laminated via a nonmagnetic layer,
    Fixing the magnetization of the readout layer in a predetermined direction;
    One-bit information is recorded by reversing the magnetization direction of the magnetic layer adjacent to the nonmagnetic layer of the plurality of magnetic layers by the exchange coupling force generated in the recording layer according to the recording temperature. ,
    The difference in magnetoresistance value of the magnetic thin film memory element in the case where the magnetization direction of the readout layer and the magnetization direction of the magnetic layer adjacent to the nonmagnetic layer are parallel and antiparallel are associated with the 1-bit information. look at including that read,
    In recording the 1-bit information,
    Using the first to fourth magnetic layers as the plurality of magnetic layers, the relationship between the Curie temperatures of the first to fourth magnetic layers is
    Third magnetic layer <first magnetic layer <second magnetic layer <fourth magnetic layer
    And fixing the magnetization direction of the fourth magnetic layer in a predetermined direction,
    The recording layer is heated to a first recording temperature higher than the Curie temperature of the third magnetic layer, thereby demagnetizing the magnetization of the third magnetic layer and reversing the magnetization of the first magnetic layer. Recording the first information with the magnetization direction of the first magnetic layer as the magnetization direction of the fourth magnetic layer by the exchange coupling force with the second magnetic layer,
    The recording layer is heated to a second recording temperature higher than the first recording temperature, and is applied to the second magnetic layer in antiparallel to the magnetization direction of the fourth magnetic layer. Is applied so that the magnetization direction of the second magnetic layer is aligned with the direction of the magnetic field, and the magnetization direction of the first magnetic layer is changed by the exchange coupling force with the second magnetic layer. An information recording / reproducing method comprising recording the second information in antiparallel to the magnetization direction of the fourth magnetic layer .
  12. 12. The information recording / reproducing method according to claim 11 , wherein an external magnetic field is used as a magnetic field having a predetermined magnitude that is applied when information is recorded at the second recording temperature.
  13. A fifth magnetic layer having a predetermined magnitude and magnetization in a predetermined direction at a second recording temperature is used, and a stray magnetic field generated by the fifth magnetic layer is applied during information recording at the second recording temperature. 12. The information recording / reproducing method according to claim 11 , wherein the information recording / reproducing method is used as a magnetic field having a predetermined magnitude.
  14. When a sixth magnetic layer is provided between the first magnetic layer and the second magnetic layer, and the magnetization direction of the first magnetic layer and the magnetization direction of the second magnetic layer are antiparallel 12. The information recording / reproducing method according to claim 11 , wherein a domain wall having a predetermined energy is formed in the sixth magnetic layer.
  15. 12. The information recording / reproducing method according to claim 11 , wherein the magnetization direction of the fourth magnetic layer is fixed using an antiferromagnetic layer having a Neel temperature higher than the recording temperature.
  16. 12. The information recording / reproducing method according to claim 11 , wherein the magnetization direction of the readout layer is fixed using an antiferromagnetic layer having a Neel temperature higher than the recording temperature.
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