Magnetic storage unit writing method and magnetic storage unit

Abstract

The invention provides a magnetic storage unit write-in method, which comprises the following steps of: applying a write-in current greater than a preset current threshold to a spin-orbit layer of a magnetic storage unit, so that a resistor of the magnetic storage unit oscillates; reading the resistance of the magnetic storage unit in real time; when a difference value between the resistance of the magnetic storage unit and a target write-in resistance is smaller than a preset difference value, applying a holding current smaller than a preset current threshold value to the spin-orbit layer; and when a difference value between the resistance of the magnetic storage unit and a target write-in resistance is greater than a preset difference value, applying a holding current greater than a preset current threshold value to the spin-orbit layer. According to the magnetic storage unit writing method provided by the invention, accurate writing of data can be realized under the condition of not depending on an external auxiliary magnetic field.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic storage, and particularly to a method for writing a magnetic storage unit and a magnetic storage unit. Background Art

[0002] Compared with the spin transfer torque magnetic random access memory (STT-MRAM), the spin orbit torque magnetic random access memory (SOT-MRAM) has a higher writing speed and lower power consumption, and is considered as the main writing method for the next generation of magnetic random access memories. The principle of SOT-MRAM is to utilize the spin Hall effect to realize the flipping of the free layer magnetic moment, thereby changing the magnetic tunnel junction resistance to achieve data storage. However, for a perpendicularly magnetized magnetic tunnel junction, only using the spin orbit torque cannot make the magnetic moment flip deterministically, and accurate data writing cannot be achieved. An external auxiliary magnetic field is required to achieve accurate writing. Summary of the Invention

[0003] The method for writing a magnetic storage unit and the magnetic storage unit provided by the present invention can achieve accurate data writing without relying on an external auxiliary magnetic field.

[0004] In a first aspect, the present invention provides a method for writing a magnetic storage unit, the method comprising:

[0005] Applying a write current greater than a preset current threshold to the spin orbit layer of the magnetic storage unit to cause the resistance of the magnetic storage unit to oscillate;

[0006] Reading the resistance of the magnetic storage unit in real time;

[0007] When the difference between the resistance of the magnetic storage unit and the target write resistance is less than a predetermined difference, applying a holding current less than the preset current threshold to the spin orbit layer.

[0008] Optionally, after reading the resistance of the magnetic storage unit in real time, the method further comprises:

[0009] When the difference between the resistance of the magnetic storage unit and the target write resistance is greater than the predetermined difference, applying a write current greater than the preset current threshold to the spin orbit layer.

[0010] Optionally, after applying the holding current less than the preset current threshold to the spin orbit layer, the method further comprises:

[0011] Obtaining the time for applying the holding current, and stopping applying the holding current when the time for applying the holding current exceeds a predetermined time threshold.

[0012] Optionally, the method further comprises:

[0013] Obtain the stable probability of a single oscillation period of the free layer of the magnetic storage unit and the period time of a single oscillation period;

[0014] Determine a predetermined time threshold according to the stable probability, the period time, and a preset write error rate.

[0015] Optionally, determining a predetermined time threshold according to the stable probability, the period time, and a preset write error rate includes:

[0016] Subtract the stable probability from 100% probability to determine the non-stable probability of a single oscillation period;

[0017] Calculate the logarithm of the preset write error rate with the non-stable probability as the base to obtain the minimum number of periods required for applying the holding current;

[0018] Calculate the product of the number of periods and the period time to obtain the shortest time required for applying the holding current;

[0019] Determine the predetermined time threshold according to the shortest time.

[0020] In a second aspect, the present invention provides a magnetic storage unit, including:

[0021] A magnetic storage unit body, including a magnetic tunnel junction stack and a spin orbit layer, the magnetic tunnel junction stack having a first resistance state and a second resistance state, and the spin orbit layer can change the resistance of the magnetic tunnel junction stack when passing a current greater than a preset current threshold;

[0022] A write control circuit, the write control circuit having a current output terminal and a resistance value input terminal, the current output terminal being electrically connected to the spin orbit layer, and the resistance value input terminal being electrically connected to the upper surface of the magnetic tunnel junction stack; the write control circuit is used to execute the magnetic storage unit write method as described in any one of the above to write a first resistance state or a second resistance state to the magnetic storage unit body.

[0023] Optionally, the magnetic tunnel junction stack includes a free layer, and the free layer is formed of a material with a magnetic moment oscillation frequency greater than a preset frequency.

[0024] Optionally, the free layer includes one or a combination of two of a synthetic antiferromagnetic film layer or an antiferromagnetic film layer.

[0025] Optionally, the synthetic antiferromagnetic film layer includes one or a combination of two of a composite film layer formed by CoFeB, Ru, and CoFeB in sequence and a composite film layer formed by CoFeB, Ir, and CoFeB in sequence; the antiferromagnetic film layer includes a single-layer or multi-layer thin film formed by one or a combination of two or more of Mn3Ir, Mn3Pt, Mn3Sn, and Mu2Au.

[0026] Optionally, the magnetic tunnel junction stack includes a free layer, a barrier layer, and a reference layer, and the magnetization directions of the free layer and the reference layer are perpendicular magnetization.

[0027] In the technical solution provided by the present invention, when the resistance of the magnetic storage unit approaches the target write resistance, a holding current is input to the spin-orbit layer, so that the resistance of the magnetic storage unit has a probability of stabilizing at the target resistance. Since the resistance of the magnetic storage unit may enter a stable state every time it oscillates, the longer the write time, the lower the write error rate. Therefore, maintaining the oscillation of the resistance of the magnetic storage unit can effectively reduce the write error rate. Description of the Drawings

[0028] Figure 1 is a flowchart of a method for writing a magnetic storage unit according to an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of different results of difference judgment in the flowchart of a method for writing a magnetic storage unit according to an embodiment of the present invention;

[0030] Figure 3 is a flowchart of determining a predetermined time threshold in a method for writing a magnetic storage unit according to another embodiment of the present invention;

[0031] Figure 4 is a flowchart of determining a predetermined time threshold in a method for writing a magnetic storage unit according to another embodiment of the present invention;

[0032] Figure 5 is a schematic structural diagram of a magnetic storage unit according to another embodiment of the present invention. Detailed Embodiments

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] An embodiment of the present invention provides a method for writing a magnetic storage unit, as Figure 1 shown, the method includes:

[0035] Step 100, applying a write current greater than a preset current threshold to the spin-orbit layer of the magnetic storage unit to cause the resistance of the magnetic storage unit to oscillate;

[0036] In some embodiments, when the current in the spin-orbit layer is greater than a preset current threshold, the free layer will oscillate under the action of the spin-orbit torque, thereby causing the resistance of the magnetic tunnel junction to oscillate continuously. The preset current threshold refers to the current threshold that can cause the resistance of the magnetic storage unit to oscillate.

[0037] Step 200, read the resistance of the magnetic storage unit in real time;

[0038] In some embodiments, when the resistance of the magnetic tunnel junction oscillates, the overall resistance of the magnetic tunnel junction will show a changing trend during the oscillation process and gradually approach the target write resistance. Therefore, it is necessary to detect the resistance of the magnetic tunnel junction in real time to determine when to maintain the oscillation.

[0039] Step 300, when the difference between the resistance of the magnetic storage unit and the target write resistance is less than a predetermined difference, apply a holding current less than the preset current threshold to the spin-orbit layer.

[0040] In some embodiments, if writing data 0, when the magnetoresistance approaches or reaches the first resistance state, reduce the write current so that it is less than the preset current threshold. At this time, the magnetic random access memory has a certain probability of stabilizing in the first resistance state or continuing to oscillate. When the magnetoresistance is far from the first resistance state, increase the write current so that it is greater than the preset current threshold. At this time, the magnetic random access memory maintains an oscillating state. If writing data 1, when the magnetoresistance approaches or reaches the second resistance state, reduce the write current so that it is less than the preset current threshold. At this time, the magnetic random access memory has a certain probability of stabilizing in the second resistance state or continuing to oscillate. When the magnetoresistance is far from the second resistance state, increase the write current so that it is greater than the preset current threshold. At this time, the magnetic random access memory maintains an oscillating state. The predetermined difference can be determined based on prior data. For example, the difference that can successfully write data in historical data is determined as the predetermined difference.

[0041] In the technical solution provided by the embodiments of the present invention, when the resistance of the magnetic storage unit approaches the target write resistance, a holding current is input to the spin-orbit layer, so that the resistance of the magnetic storage unit has a chance to stabilize at the target resistance. Since the resistance of the magnetic storage unit may enter a stable state every time it oscillates, the longer the write time, the lower the write error rate. Therefore, maintaining the oscillation of the resistance of the magnetic storage unit can effectively reduce the write error rate.

[0042] As an alternative embodiment, as Figure 2 shown, in step 200, after reading the resistance of the magnetic storage unit in real time, the method further includes:

[0043] Step 210, when the difference between the resistance of the magnetic storage unit and the target write resistance is greater than a predetermined difference, apply a write current greater than the preset current threshold to the spin-orbit layer.

[0044] In some embodiments, since a write current greater than a preset current threshold can drive the resistance of the entire magnetic storage unit to change towards a target write resistance, when the difference between the resistance of the magnetic storage unit and the target write resistance is greater than a predetermined difference, a write current needs to be applied to the spin-orbit layer.

[0045] As an alternative implementation, in step 300, after applying a holding current less than the preset current threshold to the spin-orbit layer, the method further includes:

[0046] Obtaining the time for which the holding current is applied, and when the time for which the holding current is applied exceeds a predetermined time threshold, stopping the application of the holding current.

[0047] In some embodiments, the predetermined time threshold is determined based on the write success rate. Generally, the longer the holding current is applied, the higher the write success rate. However, the write efficiency should also be considered. Therefore, a reasonable predetermined time threshold needs to be set.

[0048] As an alternative implementation, as Figure 3 shown, the method further includes:

[0049] Step 400, obtaining the stable probability of a single oscillation period of the free layer of the magnetic storage unit and the period time of a single oscillation period;

[0050] Step 500, determining a predetermined time threshold based on the stable probability, the period time, and a preset write error rate.

[0051] As an alternative implementation, as Figure 4 shown, in step 500, determining a predetermined time threshold based on the stable probability, the period time, and a preset write error rate includes:

[0052] Step 510, subtracting the stable probability from 100% to determine the non-stable probability of a single oscillation period;

[0053] Step 520, calculating the logarithm of the preset write error rate with the non-stable probability as the base to obtain the minimum number of periods required for applying the holding current;

[0054] Step 530, calculating the product of the number of periods and the period time to obtain the shortest time required for applying the holding current;

[0055] Step 540, determining the predetermined time threshold based on the shortest time.

[0056] In some embodiments, the probability that the free layer stabilizes in each oscillation period T is P. After a time t, the probability that the magnetic random access memory stabilizes in the expected data state is 1 - (1 - P)^(t / T), that is, the write error rate is (1 - P)^(t / T). The longer the current application time t is, the lower the write error rate is. Stopping the input of the write current after a preset time threshold can achieve data writing with a very low write error rate.

[0057] An embodiment of the present invention further provides a magnetic storage cell, as Figure 5 shown, including:

[0058] A magnetic storage cell body, including a magnetic tunnel junction stack and a spin-orbit layer. The magnetic tunnel junction stack has a first resistance state and a second resistance state. When the spin-orbit layer passes a current greater than a preset current threshold, it can change the resistance of the magnetic tunnel junction stack.

[0059] In some embodiments, the magnetic tunnel junction stack includes a free layer, a barrier layer, and a reference layer. The relative magnetic moments of the free layer and the reference layer determine the magnetoresistance of the magnetic tunnel junction. When the magnetic moments of the free layer and the reference layer are in opposite directions, it is the first resistance state, corresponding to data 0; when the magnetic moments of the free layer and the reference layer are in the same direction, it is the second resistance state, corresponding to data 1. When the spin-orbit layer applies a write current greater than a predetermined current threshold, it can use the spin Hall effect to change the magnetic moment direction of the free layer.

[0060] A write control circuit, which has a current output terminal and a resistance value input terminal. The current output terminal is electrically connected to the spin-orbit layer, and the resistance value input terminal is electrically connected to the upper surface of the magnetic tunnel junction stack. The write control circuit is used to execute the magnetic storage cell writing method described in any one of the above to write the first resistance state or the second resistance state to the magnetic storage cell body.

[0061] In some embodiments, the write control circuit is used to apply a write current to the spin-orbit moment layer, so that the magnetic moment of the free layer of the magnetic tunnel junction stack oscillates. At this time, the resistance of the magnetic storage cell body gradually approaches the target write resistance. At the same time, the write control circuit reads the resistance of the magnetic storage cell body in real time, and reduces the write current when the resistance value is close to the target write resistance, so that the resistance value has a certain probability of stabilizing at the target resistance. The write control circuit can receive external control signals, such as external control signals for writing data.

[0062] As an optional implementation manner, the magnetic tunnel junction stack includes a free layer, and the free layer is formed of a material with a magnetic moment oscillation frequency greater than a preset frequency.

[0063] In some embodiments, since each oscillation may stabilize the resistance of the magnetic storage unit body at the target write resistance, the free layer made of a material with a higher oscillation frequency has a higher write success rate within the same oscillation time. The preset frequency can be, for example, 1 GHz.

[0064] As an alternative implementation, the free layer includes one or a combination of two of a synthetic antiferromagnetic film layer or an antiferromagnetic film layer.

[0065] As an alternative implementation, the synthetic antiferromagnetic film layer includes one or a combination of two of a composite film layer formed by CoFeB, Ru, and CoFeB in sequence and a composite film layer formed by CoFeB, Ir, and CoFeB in sequence; the antiferromagnetic film layer includes a single-layer or multi-layer thin film formed by one or a combination of two or more of Mn3Ir, Mn3Pt, Mn3Sn, and Mu2Au.

[0066] As an alternative implementation, the magnetic tunnel junction stack includes a free layer, a barrier layer, and a reference layer, and the magnetization directions of the free layer and the reference layer are perpendicular magnetization.

[0067] Those of ordinary skill in the art can understand that all or part of the processes in the above method embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above method embodiments. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0068] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for writing a magnetic storage unit, characterized in that, The method includes: Applying a write current greater than a preset current threshold to the spin - orbit layer of the magnetic storage unit to cause the resistance of the magnetic storage unit to oscillate; Reading the resistance of the magnetic storage unit in real - time; When the difference between the resistance of the magnetic storage unit and the target write resistance is less than a predetermined difference, applying a holding current less than the preset current threshold to the spin - orbit layer.

2. The method according to claim 1, characterized in that After reading the resistance of the magnetic storage unit in real - time, the method further includes: When the difference between the resistance of the magnetic storage unit and the target write resistance is greater than a predetermined difference, applying a write current greater than the preset current threshold to the spin - orbit layer.

3. The method according to claim 1, wherein After applying the holding current less than the preset current threshold to the spin - orbit layer, the method further includes: Obtaining the time of applying the holding current, and when the time of applying the holding current exceeds a predetermined time threshold, stopping applying the holding current.

4. The method according to claim 3, wherein The method further includes: Obtaining the stable probability of a single oscillation period and the period time of a single oscillation period of the free layer of the magnetic storage unit; Determining the predetermined time threshold according to the stable probability, the period time, and a preset write error rate.

5. The method according to claim 4, wherein Determining the predetermined time threshold according to the stable probability, the period time, and a preset write error rate includes: Subtracting the stable probability from 100% to determine the unstable probability of a single oscillation period; Calculating the logarithm of the preset write error rate with the unstable probability as the base to obtain the minimum number of periods required for applying the holding current; Calculating the product of the number of periods and the period time to obtain the shortest time required for applying the holding current; Determining the predetermined time threshold according to the shortest time.

6. A magnetic storage unit, characterized in that, Includes: A magnetic storage unit body, including a magnetic tunnel junction stack and a spin - orbit layer, the magnetic tunnel junction stack having a first resistance state and a second resistance state, and the spin - orbit layer can change the resistance of the magnetic tunnel junction stack when passing a current greater than the preset current threshold; A write control circuit, the write control circuit having a current output terminal and a resistance value input terminal, the current output terminal being electrically connected to the spin - orbit layer, and the resistance value input terminal being electrically connected to the upper surface of the magnetic tunnel junction stack; the write control circuit is used to execute the magnetic storage unit write method as described in any one of claims 1 - 5 to write the first resistance state or the second resistance state to the magnetic storage unit body.

7. The magnetic storage unit according to claim 6, characterized in that, The magnetic tunnel junction stack includes a free layer, and the free layer is formed of a material with a magnetic moment oscillation frequency greater than a preset frequency.

8. The magnetic storage unit according to claim 7, characterized in that, The free layer includes one or a combination of two of a synthetic antiferromagnetic film layer or an antiferromagnetic film layer.

9. The magnetic storage unit according to claim 8, wherein, The synthetic antiferromagnetic film layer includes one or a combination of two of a composite film layer formed by CoFeB, Ru, and CoFeB in sequence and a composite film layer formed by CoFeB, Ir, and CoFeB in sequence; the antiferromagnetic film layer includes a single - layer or multi - layer thin film formed by one or a combination of two or more of Mn3Ir, Mn3Pt, Mn3Sn, and Mu2Au.

10. The magnetic storage cell according to claim 6, characterized in that, The magnetic tunnel junction stack includes a free layer, a barrier layer, and a reference layer, and the magnetization directions of the free layer and the reference layer are perpendicular magnetization.

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