Magnetic memory for regulating and controlling exchange bias field based on electric field

Abstract

The invention provides a magnetic memory for regulating and controlling an exchange bias field based on an electric field, which relates to the field of magnetic memories and comprises an antiferromagnetic layer, an insulating insertion layer, a free layer, a barrier layer and a fixed layer which are sequentially attached from bottom to top, wherein the insulating insertion layer maintains an exchange bias field generated between the antiferromagnetic layer and the free layer; when longitudinal voltage is applied to the insulation insertion layer, a longitudinal electric field is formed between the free layer and the antiferromagnetic layer, the exchange bias field is overturned, the magnetic moment of the free layer is overturned, and information writing is achieved. The states of atoms or ions on the upper interface and the lower interface of the insulating insertion layer can be regulated and controlled through the electric field, the magnetic neighbor effect is changed, and therefore the exchange bias field is changed in size and direction, and the free layer is driven to achieve information writing.

Description

Technical Field

[0001] The present application relates to the field of magnetic memory, and in particular to a magnetic memory based on electric field regulation of exchange bias field. Background Art

[0002] Magnetic Random Access Memory (MRAM) has the characteristics of high speed, non-volatility, and compatibility with CMOS technology, and has important application prospects in the field of storage. Its basic unit, the magnetic tunnel junction (MTJ), is a tunneling magnetoresistance (TMR) device composed of a sandwich structure of free layer (ferromagnetic layer) / insulating layer (tunneling layer, barrier layer) / reference layer (ferromagnetic layer). The parallel (anti-parallel) magnetic moment of the free layer and the magnetic moment of the reference layer make the device have a low resistance state (high resistance state), which becomes the basis of information storage.

[0003] In order to pursue the capacity of magnetic random access memory, it is necessary to miniaturize the size of the magnetic tunnel junction as much as possible. However, when the device size is miniaturized to less than 100 nanometers, the in-plane magnetic tunnel junction relying on shape anisotropy is difficult to maintain sufficient thermal stability. Subsequently, the introduction of perpendicular magnetic anisotropy makes the thermal stability of the magnetic tunnel junction no longer rely on shape anisotropy, but can be maintained by perpendicular magnetic anisotropy. However, as the size of the magnetic tunnel junction is further miniaturized, the strength of the perpendicular magnetic anisotropy of the interface is also difficult to maintain a sufficiently high thermal stability. To solve this problem, the exchange bias field is introduced into the magnetic tunnel junction, relying on the exchange bias field generated by the antiferromagnetic and ferromagnetic interface to stabilize the free layer in one direction. The thermal stability of the free layer no longer relies solely on shape anisotropy and perpendicular magnetic anisotropy of the interface, but depends on the exchange bias field of the antiferromagnetic / ferromagnetic interface. It is precisely because of the high stability of antiferromagnetism that this exchange bias-based magnetic tunnel junction has the potential for further device miniaturization. However, this exchange bias-based magnetic tunnel junction relies on spin-orbit moment or thermal effect to change the direction of the exchange bias field, which requires extremely high current density, which is not conducive to the widespread application of the device.

[0004] The latest scientific research shows that not only can the spin-orbit distance current flip the exchange bias field, but the electric field is also an effective way to regulate the exchange bias field, and it has unique advantages in terms of write power consumption. Among them, the electric field can change the state of the antiferromagnetic and ferromagnetic interface at the interface by adjusting the movement of atoms or ions, thereby changing the size and direction of the exchange bias field. In addition, the electric field can also change the coupling strength of the ferromagnetic and antiferromagnetic layers through the movement of atoms or ions and the magnetic proximity effect, and it is hoped that the exchange bias field can be changed. Introducing the electric field regulation mechanism into the exchange bias-based magnetic tunnel junction to solve the problems of high current density and write power consumption is of great significance to promoting the development of spintronic devices in the field of ultra-low power storage and computing. Summary of the invention

[0005] In response to the problems in the prior art, the present application provides a magnetic storage device based on electric field regulation of exchange bias field, which can regulate the state of atoms or ions at the upper and lower interfaces of the insulating insertion layer through the electric field, change the magnetic proximity effect, and thus cause the exchange bias field to change in size and direction, thereby driving the free layer to realize information writing.

[0006] In order to solve the above technical problems, this application provides the following technical solutions:

[0007] In the first aspect, the present application provides a magnetic memory based on electric field regulation of exchange bias field, comprising: an antiferromagnetic layer, an insulating insertion layer, a free layer, a barrier layer and a fixed layer sequentially laminated from bottom to top; wherein the insulating insertion layer maintains the exchange bias field generated between the antiferromagnetic layer and the free layer; when a longitudinal voltage is applied to the insulating insertion layer, a longitudinal electric field is formed between the free layer and the antiferromagnetic layer, the exchange bias field is reversed, and the magnetic moment of the free layer is reversed, thereby realizing information writing.

[0008] Furthermore, the material of the antiferromagnetic layer is one of platinum manganese, iridium manganese, palladium manganese, and iron manganese, or any combination thereof.

[0009] Furthermore, the thickness of the antiferromagnetic layer is 1 nm to 10 nm.

[0010] Furthermore, the material of the insulating insertion layer is one of gadolinium oxide, aluminum oxide, and magnesium oxide, or any combination thereof; the oxygen component fraction in the gadolinium oxide, the aluminum oxide, or the magnesium oxide is 0.1 to 3.

[0011] Furthermore, the thickness of the insulating insertion layer is 0.2 nm to 4 nm.

[0012] Furthermore, the free layer is a ferromagnetic material; wherein the magnetization direction of the ferromagnetic material can be reversed, and the coercive field of the free layer is smaller than the exchange bias field.

[0013] Furthermore, the material of the barrier layer is magnesium oxide, and the thickness is 0.6 nm to 2 nm.

[0014] Furthermore, the fixed layer is a ferromagnetic material; wherein the coercive field of the fixed layer is higher than the coercive field of the free layer.

[0015] Furthermore, a heavy metal layer is provided at the bottom of the antiferromagnetic layer, which is used to change the exchange bias field by using the longitudinal voltage, and to flip the antiferromagnetic magnetic moment by using the spin-orbit moment generated by the transverse current in the heavy metal, thereby flipping the exchange bias field.

[0016] Furthermore, an electrode is disposed at one end of the free layer, so that the information writing voltage is only distributed on two sides of the insulating insertion layer but not on the barrier layer.

[0017] In view of the problems in the prior art, the present application provides a magnetic memory based on electric field regulation of exchange bias field, in which the fixed layer, barrier layer and free layer can achieve high tunneling magnetoresistance by optimizing materials and processes to ensure the accuracy of information reading in applications; since the exchange bias field between the antiferromagnetic layer and the free layer is greater than the coercive field of the free layer, the direction of the magnetic moment of the free layer can be controlled, so that the magnetic order of the antiferromagnetic layer is associated with the magnetic order of the ferromagnetic layer, and at the same time, due to the high stability of the antiferromagnetic layer, the stability of the magnetic moment of the free layer is greatly improved; in addition, by regulating the thickness and material of the insulating insertion layer, the exchange bias field between the antiferromagnetic layer and the free layer can still be greater than the coercive field of the free layer, and the state of atoms or ions at the upper and lower interfaces of the insulating insertion layer can be regulated by the electric field to change the magnetic proximity effect, so that the exchange bias field changes in size and direction, thereby driving the free layer to write information. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 Structural diagram of a magnetic memory based on electric field regulation of exchange bias field in an embodiment of the present application.

[0020] Figure 2 One of the improved structural diagrams of the magnetic memory based on electric field regulation of exchange bias field in the embodiment of the present application.

[0021] Figure 3 Schematic diagram of a high-density storage method of a magnetic tunnel junction based on electric field and spin-orbit moment regulation of exchange bias field in an embodiment of the present application.

[0022] Figure 4 The second improved structural diagram of the magnetic memory based on electric field regulation of exchange bias field in the embodiment of the present application. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] In one embodiment, see Figure 1 In order to be able to regulate the states of atoms or ions at the upper and lower interfaces of the insulating insertion layer through an electric field, change the magnetic proximity effect, and thereby change the size and direction of the exchange bias field, thereby driving the free layer to achieve information writing, the present application provides a magnetic memory based on electric field regulation of the exchange bias field, comprising: an antiferromagnetic layer, an insulating insertion layer, a free layer, a barrier layer and a fixed layer sequentially bonded from bottom to top; wherein the insulating insertion layer maintains the exchange bias field generated between the antiferromagnetic layer and the free layer; when a longitudinal voltage is applied to the insulating insertion layer, a longitudinal electric field is formed between the free layer and the antiferromagnetic layer, the exchange bias field is reversed, and the magnetic moment of the free layer is reversed, thereby achieving information writing.

[0025] It can be understood that the magnetic memory based on electric field regulation of exchange bias field in the present invention is a spin electronic device, which comprises five layers, from bottom to top, respectively, an antiferromagnetic layer, an insulating insertion layer, a free layer, a barrier layer and a fixed layer, such as Figure 1 As shown. Among them, the extremely thin insulating insertion layer is located between the free layer and the antiferromagnetic layer, which can not only maintain the original exchange bias field between the antiferromagnetic layer and the free layer to a certain extent, but also form a strong longitudinal electric field between the free layer and the antiferromagnetic layer when a certain longitudinal voltage is applied to the device, causing the displacement of atoms or ions, thereby changing the magnetic proximity effect, causing the exchange bias field to flip, driving the magnetic moment of the free layer to flip, and realizing information writing. Among them, Figure 1 Schematic diagram of the magnetic tunnel junction structure based on electric field regulation of the exchange bias field.

[0026] E is the electric field in the vertical direction.

[0027] In one embodiment, the material of the antiferromagnetic layer is one of platinum manganese, iridium manganese, palladium manganese, and iron manganese, or any combination thereof.

[0028] In one embodiment, the antiferromagnetic layer has a thickness of 1 nm (nanometer) to 10 nm (nanometer).

[0029] It is understood that the antiferromagnetic layer is one of platinum manganese (PtMn), iridium manganese (IrMn), palladium manganese (PdMn), iron manganese (FeMn) or a combination of any two, three or four thereof, and the thickness may be 1 nm (nanometer) to 10 nm (nanometer). The commonly used element ratio of PtMn may be Pt 50 Mn 50 , Pt 20 Mn 80 , Pt 25 Mn 75 or Pt 75 Mn 25 etc.; the common element ratio of IrMn can be Ir 50 Mn 50 , Ir 20 Mn 80 or Ir 25 Mn 75 etc.; the common element ratio of PdMn is Pd 50 Mn 50 , Pd 90 Mn 10 or Pd 75 Mn 25 etc.; the common element ratio of FeMn is Fe 50 Mn 50 or Fe 80 Mn 20 The numbers in the above materials represent the percentage of the elements. In addition, the material of the antiferromagnetic layer can also be nickel oxide (NiO), ruthenium oxide (RuO x ), chromium trioxide (Cr 2 O 3 ), iridium manganese oxide (YMnO 3 ), bismuth iron oxide (BiFeO3), or any combination thereof. The value of x in the above materials can be 0.1 to 3, and the thickness of the antiferromagnetic layer can be 3nm (nanometer) to 100nm (nanometer). The antiferromagnetic layer based on the above materials has high thermal stability and can still maintain a stable antiferromagnetic magnetic order and anti-external magnetic properties at room temperature. Through the selection and optimization of the substrate, the above antiferromagnetic materials can have good single crystal properties and a relatively consistent magnetic moment orientation, so that a larger exchange bias field can be provided for the neighboring (ferromagnetic) free layer, so that it is greater than the coercive field of the (ferromagnetic) free layer, and then the exchange bias field is used to achieve complete control of the magnetic moment direction of the (ferromagnetic) free layer, laying the foundation for the subsequent voltage-controlled exchange bias field writing method.

[0030] In one embodiment, the material of the insulating insertion layer is one of gadolinium oxide, aluminum oxide, and magnesium oxide, or any combination thereof; the oxygen component fraction in the gadolinium oxide, the aluminum oxide, or the magnesium oxide is 0.1 to 3.

[0031] In one embodiment, the thickness of the insulating insertion layer is 0.2 nm to 4 nm.

[0032] It is understood that the insulating insertion layer is gadolinium oxide (GdO x ), aluminum oxide (AlO x ), magnesium oxide (MgO x ) or a combination of any two or three of them. In the above materials, the value of x can be 0.1 to 3, and the thickness of the insulating insertion layer can be 0.2nm (nanometer) to 4nm (nanometer). Different metals and their ratios with oxygen elements can affect the magnetic proximity effect of the insulating insertion layer and its equivalent thickness, and can also affect the efficiency of voltage-controlled exchange bias field. Reasonable selection of element ratios and thicknesses in this range can ensure that there is still a sufficient exchange bias field value between the (ferromagnetic) free layer and the antiferromagnetic layer, and at the same time, the direction of the exchange bias field between the antiferromagnetic layer and the (ferromagnetic) free layer can be switched by voltage regulation, thereby realizing the writing of the ferromagnetic free layer state.

[0033] In addition, the insulating insertion layer can effectively prevent the migration of elements in the antiferromagnetic material at high temperatures, thereby increasing the applicable annealing temperature and improving the performance of the overall device. Further, by inserting a specific insulating insertion layer between the antiferromagnetic layer and the (ferromagnetic) free layer, the exchange bias field reversal controlled by the electric field can be achieved. Furthermore, the insulating insertion layer can also limit the diffusion of elements during high temperature annealing.

[0034] In one embodiment, the free layer is a ferromagnetic material; wherein the magnetization direction of the ferromagnetic material can be flipped, and the coercive field of the free layer is smaller than the exchange bias field.

[0035] It is understood that the free layer is a ferromagnetic material, whose magnetization direction can be reversed, and whose coercive field is smaller than the exchange bias field. For example, the material of the free layer can use a single metal including only one of chromium (Cr), manganese (Mn), cobalt (Co), iron (Fe) or nickel (Ni), or a metal alloy containing one or more of the above five metals and exhibiting ferromagnetism, or an alloy containing the above metals and at least one of the following elements (boron (B), carbon (C) and nitrogen (N)). Specifically, for example, Co-Fe, Co-Fe-B, Ni-Fe, CoNi, CoPt, etc.

[0036] In terms of writing, since the exchange bias field formed with the antiferromagnetic layer is greater than the coercive field of the magnetic layer, the direction of the magnetic moment of the (ferromagnetic) free layer can be completely determined by the exchange bias field, and the information writing to the (ferromagnetic) free layer can be achieved by voltage-controlled exchange bias field. In terms of information reading, the sandwich structure composed of the (ferromagnetic) free layer, barrier layer and fixed layer can produce a strong tunneling magnetoresistance effect and has a high tunneling magnetoresistance ratio, which is convenient for reading the high and low resistance states of the device.

[0037] In one embodiment, the material of the barrier layer is magnesium oxide, and the thickness is 0.6nm (nanometer) to 2nm (nanometer). It can be understood that the material of the barrier layer is magnesium oxide (MgO). At present, the barrier layers in the magnetic tunnel junction film layer with higher tunneling magnetoresistance in the industry are all magnesium oxide (MgO). Due to its more consistent lattice structure, the tunneling magnetoresistance effect can be enhanced.

[0038] In one embodiment, the fixed layer is a ferromagnetic material; wherein the coercive field of the fixed layer is higher than the coercive field of the free layer.

[0039] It is understandable that the material of the fixed layer is a ferromagnetic (composite) material, which has a coercive field much higher than that of the free layer. The ferromagnetic (composite) material can be artificially synthesized. For example, the fixed layer can use a single metal including only one of chromium (Cr), manganese (Mn), cobalt (Co), iron (Fe) or nickel (Ni), or a metal alloy containing one or more of the above five metals and exhibiting ferromagnetism, or an alloy containing the above metals and at least one of the following elements (boron (B), carbon (C) and nitrogen (N)). Specifically, for example, Co-Fe, Co-Fe-B, Ni-Fe, CoNi, CoPt, can also be composed of a single-layer film or a multi-layer film structure of the above alloys.

[0040] In one embodiment, a heavy metal layer is provided at the bottom of the antiferromagnetic layer, which is used to utilize the longitudinal voltage to achieve the change of the exchange bias field, and utilize the spin-orbit moment generated by the transverse current in the heavy metal to flip the antiferromagnetic magnetic moment, thereby realizing the flipping of the exchange bias field.

[0041] It is understandable that based on Figure 1 The basic structure shown in FIG. 1 can add heavy metal at the bottom of the antiferromagnetic layer, so that the longitudinal voltage can be used to change the exchange bias field, and the spin-orbit moment generated by the transverse current in the heavy metal can be used to flip the antiferromagnetic magnetic moment, thereby realizing the flipping of the exchange bias field. Figure 2 This structure can be used to explore the synergistic effect of two exchange bias field reversals and construct a three-port device, which has application prospects in the field of NAND-SPIN high-density storage, such as Figure 3 As shown. Among them, Figure 2Schematic diagram of the structure of a magnetic tunnel junction that controls the exchange bias field based on electric field and spin-orbit moment. Figure 3 It is a high-density storage method of magnetic tunnel junction based on electric field and spin-orbit moment regulation of exchange bias field.

[0042] In one embodiment, an electrode is disposed at one end of the free layer so that the information writing voltage is distributed only on two sides of the insulating insertion layer but not on the barrier layer.

[0043] It is understandable that based on Figure 1 The basic structure shown in FIG. 1 can be provided with an additional electrode at the (ferromagnetic) free layer, so that the write voltage is only distributed on both sides of the insulating insertion layer, and no longer distributed on the barrier layer. This arrangement is beneficial to protecting the barrier layer, thereby increasing the service life of the device, and is also beneficial to further reducing the write voltage. The specific device structure is shown in FIG. Figure 4 As shown. Among them, Figure 4 Schematic diagram of a magnetic tunnel junction structure with efficient writing characteristics based on electric field-controlled exchange bias field.

[0044] In summary, the present invention has at least the following beneficial effects:

[0045] First, the insulating insertion layer can provide a large electric field strength between the antiferromagnetic layer and the ferromagnetic (free) layer, so that the exchange bias field is reversed under the movement of atoms or ions and the magnetic proximity effect. In this way, on the one hand, the scheme uses voltage to regulate the magnetic proximity effect at the interface of the antiferromagnetic / insulating insertion layer and the insulating insertion layer / (ferromagnetic) free layer to achieve the change of the direction of the exchange bias field, so that only the interface properties need to be changed, and the internal structure of the film layer does not need to be changed. Therefore, the required voltage is small and it is easy to be compatible with CMOS technology; on the other hand, the writing method is voltage effect writing, which does not require current input and has ultra-low power consumption properties.

[0046] Second, the insulating insertion layer can effectively prevent the diffusion of elements at high temperatures, which is beneficial to increasing the annealing temperature and is compatible with the CMOS back-end process.

[0047] From the above description, it can be seen that the magnetic storage device based on electric field regulation of exchange bias field provided by the present application can achieve high tunneling magnetoresistance in its fixed layer, barrier layer and free layer by optimizing materials and processes to ensure the accuracy of information reading in applications; since the exchange bias field between the antiferromagnetic layer and the free layer is greater than the coercive field of the free layer, the direction of the magnetic moment of the free layer can be controlled, so that the magnetic order of the antiferromagnetic layer is associated with the magnetic order of the ferromagnetic layer, and at the same time, due to the high stability of the antiferromagnetic layer, the stability of the magnetic moment of the free layer is greatly improved; in addition, by regulating the thickness and material of the insulating insertion layer, the exchange bias field between the antiferromagnetic layer and the free layer can still be greater than the coercive field of the free layer, and the state of atoms or ions at the upper and lower interfaces of the insulating insertion layer can be regulated by the electric field to change the magnetic proximity effect, so that the exchange bias field changes in size and direction, thereby driving the free layer to write information.

[0048] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0049] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0050] Each embodiment in this specification is described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In the description of this specification, the description of reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of this specification. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradiction.

[0051] The above is only an example of the embodiment of the present specification and is not intended to limit the embodiment of the present specification. For those skilled in the art, the embodiment of the present specification may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiment of the present specification shall be included in the scope of the claims of the embodiment of the present specification.

Claims

1. A magnetic memory based on electric field regulation of exchange bias field, It is characterized in that include: An antiferromagnetic layer, an insulating insertion layer, a free layer, a barrier layer and a fixed layer are sequentially attached from bottom to top; wherein the insulating insertion layer maintains the exchange bias field generated between the antiferromagnetic layer and the free layer; when a longitudinal voltage is applied to the insulating insertion layer, a longitudinal electric field is formed between the free layer and the antiferromagnetic layer, the exchange bias field is reversed, and the magnetic moment of the free layer is reversed, thereby realizing information writing.

2. The magnetic memory based on electric field regulation of exchange bias field according to claim 1, It is characterized in that The material of the antiferromagnetic layer is one of platinum manganese, iridium manganese, palladium manganese, and iron manganese, or any combination thereof.

3. The magnetic memory based on electric field regulation of exchange bias field according to claim 1, It is characterized in that The thickness of the antiferromagnetic layer is 1 nm to 10 nm.

4. The magnetic memory based on electric field regulation of exchange bias field according to claim 1, It is characterized in that The material of the insulating insertion layer is one of gadolinium oxide, aluminum oxide, and magnesium oxide, or any combination thereof; the oxygen component in the gadolinium oxide, the aluminum oxide, or the magnesium oxide is 0.1 to 3.

5. The magnetic memory based on electric field regulation of exchange bias field according to claim 4, It is characterized in that The thickness of the insulating insertion layer is 0.2 nm to 4 nm.

6. The magnetic memory based on electric field regulation of exchange bias field according to claim 1, It is characterized in that The free layer is a ferromagnetic material, wherein the magnetization direction of the ferromagnetic material can be reversed, and the coercive field of the free layer is smaller than the exchange bias field.

7. The magnetic memory based on electric field regulation of exchange bias field according to claim 1, It is characterized in that The barrier layer is made of magnesium oxide and has a thickness of 0.6 nm to 2 nm.

8. The magnetic memory based on electric field regulation of exchange bias field according to claim 1, It is characterized in that The fixed layer is made of ferromagnetic material; wherein the coercive field of the fixed layer is higher than the coercive field of the free layer.

9. The magnetic memory based on electric field regulation of exchange bias field according to claim 1, It is characterized in that A heavy metal layer is arranged at the bottom of the antiferromagnetic layer, which is used to realize the change of the exchange bias field by using the longitudinal voltage, and to realize the reversal of the exchange bias field by using the spin-orbit moment generated by the transverse current in the heavy metal to flip the antiferromagnetic magnetic moment.

10. The magnetic memory based on electric field regulation of exchange bias field according to claim 1, It is characterized in that An electrode is disposed at one end of the free layer so that the information writing voltage is only distributed on two sides of the insulating insertion layer but not on the barrier layer.

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