True random number generator and method of generating true random numbers

Abstract

The application provides a true random number generator and a method for generating a true random number. The random number generation module of the true random number generator comprises a spin current generation layer and two magnetic tunnel junctions arranged side by side on the spin current generation layer. The spin current generation layer is provided with a first electrode and a second electrode for passing a first current at both ends. The two magnetic tunnel junctions each comprise a free layer, an insulating layer, a reference layer, a pinned layer and a cap layer stacked in sequence. The free layers of the two magnetic tunnel junctions are configured to have opposite magnetization directions after magnetic field initialization. The spacing between the two magnetic tunnel junctions is configured to enable the free layers to produce antiferromagnetic coupling. The cap layer and the first electrode of one of the two magnetic tunnel junctions are used to pass a second current. The application reduces the influence of stray magnetic fields on randomness by designing the antiferromagnetic coupling of the free layer, and can effectively improve the randomness of the true random number generator based on the spin-orbit torque effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of information security and cryptography technology, and in particular to a true random number generator and a method for generating a true random number. BACKGROUND

[0002] The true random number generator based on the spin orbit torque effect (SOT) includes a vertical magnetization heterojunction composed of a heavy metal / ferromagnetic / non-magnetic, and in the vertical magnetization heterojunction, when an in-plane current flows through the heavy metal layer in the horizontal direction, due to the spin orbit coupling effect (SOC), a horizontally polarized pure spin current will be accumulated at the interface between the free layer and the heavy metal layer, and a torque (spin orbit torque) will be generated on the magnetic moment of the free layer, which will be pulled to the horizontal in-plane direction. Again, due to the existence of thermal disturbance, when the horizontal current is removed, the magnetic moment of the free layer of the vertical magnetization heterojunction will randomly flip up or down with equal probability (each 50%). When the magnetic moment direction of the free layer and the reference layer is consistent, it is in a low resistance state (logic "0"), and when it is opposite, it is in a high resistance state (logic "1") free layer, thereby generating a digital string with "0" and "1" randomly distributed with equal probability.

[0003] The magnetic heterojunction of the true random number generator based on the spin orbit torque effect (SOT) has a low coercivity and a small damping coefficient, and the randomness depends on the equal probability (50%) of the upward or downward flipping of the magnetic moment of the vertical magnetization ferromagnetic material under thermal disturbance. However, it is very sensitive to external small magnetic fields, and the action of the horizontal magnetic field and the spin orbit coupling effect will make the probability of the magnetic moment in a certain state larger, and the vertical magnetic field smaller than the coercivity of the magnetic layer will increase the flipping probability of the magnetic moment in the same direction as the magnetic field direction, and the vertical magnetic field larger than the coercivity of the magnetic layer will make the magnetic moment flip to the corresponding direction with 100% probability. When there is a small stray magnetic field in the external environment, the balance of the true random number generator based on the spin orbit torque effect (SOT) will be more easily destroyed. SUMMARY

[0004] In view of at least one defect of the prior art, the present application provides a true random number generator and a method for generating a true random number.

[0005] The true random number generator includes a random number generation module, wherein the random number generation module includes:

[0006] A spin current generation layer is provided with a first electrode and a second electrode at both ends, and the first electrode and the second electrode are used to pass a first current;

[0007] A first magnetic tunnel junction is located on the spin current generation layer and includes a first free layer, a first insulating layer, a first reference layer, a first pinned layer, and a first cap layer stacked in sequence; and

[0008] a second magnetic tunnel junction located on the spin current generating layer, comprising a second free layer, a second insulating layer, a second reference layer, a second pinned layer and a second cap layer stacked in sequence;

[0009] wherein the first free layer and the second free layer are configured to have opposite magnetization directions after being initialized by a magnetic field;

[0010] the first magnetic tunnel junction and the second magnetic tunnel junction are arranged side by side and have a spacing configured to enable the first free layer and the second free layer to generate an anti-ferromagnetic coupling;

[0011] wherein the first electrode and the first cap layer are used to pass a second current, or the first electrode and the second cap layer are used to pass the second current.

[0012] According to an aspect of the present application, the easy magnetization direction of the first free layer is perpendicular to a first interface between the spin current generating layer and the first free layer, and the easy magnetization direction of the second free layer is perpendicular to a second interface between the spin current generating layer and the second free layer.

[0013] According to an aspect of the present application, the first free layer is configured such that, when the first current is passed, the first magnetic moment of the first free layer can be pulled to be parallel to the first interface under the effect of spin-orbit coupling, and when the first current is removed, the first free layer can randomly flip in a direction perpendicular to the first interface under the effect of thermal disturbance; and

[0014] the second free layer is configured such that, when the first current is passed, the second magnetic moment of the second free layer can be pulled to be parallel to the second interface under the effect of spin-orbit coupling, and when the first current is removed, the second free layer can randomly flip in a direction perpendicular to the second interface under the effect of thermal disturbance.

[0015] According to an aspect of the present application, the first free layer and the second free layer are further configured such that, when the second current is passed, the first free layer and the second free layer cannot flip. According to an aspect of the present application, the easy magnetization directions of the first reference layer and the second reference layer are perpendicular to a third interface between the insulating layer and the first reference layer and a fourth interface between the insulating layer and the second reference layer, respectively.

[0016] According to an aspect of the present application, the first free layer and the second free layer are made of the same material, and / or the first reference layer and the second reference layer are made of the same material.

[0017] According to an aspect of the present application, the spin current generating layer is made of a heavy metal material or a topological insulator material.

[0018] According to an aspect of the present application, the first free layer and the second free layer are made of a soft magnetic material.

[0019] According to an aspect of the present application, the first insulating layer and the second insulating layer are made of a metal oxide material.

[0020] According to an aspect of the present application, the first reference layer and the second reference layer are made of a ferromagnetic material.

[0021] According to an aspect of the present application, the first pinning layer and the second pinning layer are made of an anti-ferromagnetic material.

[0022] According to an aspect of the present application, the first cap layer and the second cap layer are made of a non-ferromagnetic conductive metal material.

[0023] According to an aspect of the present application, the random number generating module further comprises a substrate under the spin current generating layer, and the substrate comprises a silicon substrate.

[0024] The method for generating a true random number using the true random number generator provided by the present application comprises the following steps:

[0025] The first magnetic tunnel junction and the second magnetic tunnel junction are initialized, so that the first free layer and the second free layer have opposite magnetization directions.

[0026] The first current is applied to the first electrode and the second electrode, wherein the first current comprises a pulse current with a preset interval.

[0027] At the preset interval, the second current is applied to the first electrode and the first cap layer, or the second current is applied to the first electrode and the second cap layer, for measuring the magnetoresistance of the first magnetic tunnel junction or the second magnetic tunnel junction, and obtaining a random number sequence according to the magnetoresistance.

[0028] According to an aspect of the present application, the method further comprises: controlling the rate of generating a true random number by controlling the pulse period of the first current.

[0029] The true random number generator provided by the present application comprises two magnetic tunnel junctions formed by antiparallel perpendicular magnetic anisotropy ferromagnetic heterostructures with a relatively short distance, and the free layers of the two magnetic tunnel junctions form a strong anti-ferromagnetic coupling. The present application reduces the influence of stray magnetic field on randomness by designing the anti-ferromagnetic coupling of the free layer, and can effectively improve the randomness of the true random number generator based on the spin-orbit torque effect (SOT).

[0030] The true random number generator provided by the application has simple structure, small device size, low energy consumption, and is convenient to integrate on various portable devices, and the method for generating the true random number is simple, random, and has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art based on these drawings without exceeding the scope of the present application.

[0032] Figure 1 A front view of a random number generation module of a true random number generator provided by an embodiment of the present application is shown.

[0033] Figure 2 A longitudinal sectional view of the random number generation module of the true random number generator is shown. Figure 1 A top view of the random number generation module of the true random number generator is shown.

[0034] Figure 3 A longitudinal sectional view of the random number generation module of the true random number generator is shown. Figure 1 A longitudinal sectional view of the random number generation module of the true random number generator is shown.

[0035] Figure 4 A longitudinal sectional view of a random number generation module of a true random number generator provided by another embodiment of the present application is shown.

[0036] Figure 5 A method for generating a true random number provided by an embodiment of the present application is shown.

[0037] Figure 6 A pulse current input to the true random number generator provided by an embodiment of the present application is shown. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0039] In the present specification, when it is mentioned that a component (or, region, layer, part, etc.) is "on", "connected to", or "coupled to" another component, it means that the component can be directly on, connected to, or coupled to another component, or a third component can exist between them.

[0040] In the drawings, the thickness, proportions and dimensions of components are exaggerated for effective description. As used herein, the term "and / or" includes all combinations of one or more of the associated items.

[0041] Terms such as first and second can be used to describe various components, but the components should not be limited by such terms. The terms can be only used to distinguish one component from another component. For example, a first component can be referred to as a second component, and similarly, a second component can also be referred to as a first component, without departing from the scope of the present application. The singular form of a term can include the plural form unless otherwise specified.

[0042] In addition, terms such as "below", "under", "above", and "on" are used to describe the relationship between components shown in the drawings. These terms are relative concepts and are described based on the direction shown in the drawings.

[0043] It should be understood that terms such as "include", "contain" and "have" when used herein designate the presence of the stated features, numbers, steps, operations, components, parts or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0044] Unless otherwise defined, all terms used herein, including technical terms and scientific terms, have the same meaning as understood by a person skilled in the art to which the present application belongs. Such terms should be interpreted as having meanings consistent with their meanings in the context of the relevant art, as defined in a common dictionary, and should not be interpreted as having idealized or overly formal meanings, unless explicitly defined in the present application.

[0045] Figures 1-3 A random number generation module 100 of a true random number generator provided by an embodiment of the present application is shown, which includes a spin current generation layer 110 and two magnetic tunnel junctions (MTJs) MTJ1 and MTJ2. Wherein, Figure 1 and Figure 2 are a front view and a top view of the random number generation module 100, respectively, Figure 3 is a longitudinal sectional view of the A part in Figure 1

[0046] In the present embodiment, the spin current generation layer 110 is a bar-shaped structure, and the first electrode T1 and the second electrode T2 are respectively arranged at both ends of the spin current generation layer 110. The first electrode T1 and the second electrode T2 are used to pass a first current (i.e. a write current). In other embodiments of the present application, the spin current generation layer 110 can also have other shapes.

[0047] ​Optionally, the spin current generating layer 110 is made of a material with strong spin coupling effect, such as heavy metal material Pt, Ta, W, topological insulator material Bi2Se3, Sb2Te3, Bi2Te3, new material MoS2, PtTe2, etc.

[0048] As shown in Figure 1 , the first magnetic tunnel junction MTJ1 and the second magnetic tunnel junction MTJ2 are arranged side by side on the spin current generating layer 110. Optionally, the first magnetic tunnel junction MTJ1 and the second magnetic tunnel junction MTJ2 are both nanoscale in size.

[0049] In the following Figure 3 , the structure of the first magnetic tunnel junction MTJ1 and the second magnetic tunnel junction MTJ2 will be described in detail. Figure 3 In the present application, the geometric center of the spin current generating layer 110 in the bar structure is taken as the three-dimensional rectangular coordinate origin, and the extension direction of the bar structure is taken as the X-axis, and the direction perpendicular to the X-axis and along the stacking direction of the first magnetic tunnel junction MTJ1 and the second magnetic tunnel junction MTJ2 is taken as the Z-axis.

[0050] As shown in Figure 3 , the first magnetic tunnel junction MTJ1 includes a first free layer 121, a first insulating layer 131, a first reference layer 141, a first pinned layer 151, and a first cap layer 161, and the second magnetic tunnel junction MTJ2 includes a second free layer 122, a second insulating layer 132, a second reference layer 142, a second pinned layer 152, and a second cap layer 162.

[0051] The first free layer 121 and the second free layer 122 are respectively located above the spin current generating layer 110. Optionally, in the present application, the easy magnetization directions of the first free layer 121 and the second free layer 122 are respectively perpendicular to the first interface between the spin current generating layer 110 and the first free layer 121 and the second interface between the spin current generating layer and the second free layer 122.

[0052] Optionally, in the present application, the first free layer 121 is configured such that, when a first current is passed, the first magnetic moment of the first free layer 121 can be pulled parallel to the first interface under the action of spin-orbit coupling effect, and when the first current is removed, the first free layer 121 can randomly flip in the direction perpendicular to the first interface upward or downward under the action of thermal disturbance.

[0053] Optionally, in the present application, the second free layer 122 is configured such that, when a first current is passed, the second magnetic moment of the second free layer 122 can be pulled parallel to the second interface under the action of spin-orbit coupling effect, and when the first current is removed, the second free layer 122 can randomly flip in the direction perpendicular to the second interface upward or downward under the action of thermal disturbance.

[0054] Optionally, in the present application, the first free layer 121 and the second free layer 122 are further configured to be unable to flip when the second current is applied.

[0055] In the present application, the first free layer 121 and the second free layer 122 are made of a magnetic crystal material with magnetic anisotropy, the magnetization curve is different with the crystal axis direction, the minimum external magnetic field is required to reach the saturation magnetization state in some directions, which is called the easy magnetization direction, the magnetic potential energy is the lowest when the magnetic crystal material is magnetized in the easy magnetization direction; the maximum external magnetic field is required to reach the saturation magnetization state in some other directions, which is called the hard magnetization direction, the magnetic potential energy is the highest when the magnetic crystal material is magnetized in the hard magnetization direction.

[0056] Optionally, the first free layer 121 and the second free layer 122 are made of a material with small damping coefficient, low coercivity and vertical magnetic anisotropy, and optionally, such as Co, CoFe alloy, CoNiCo, CoAuCo and other multilayer film soft magnetic materials. The coercivity can be adjusted by adjusting the growth conditions and film thickness.

[0057] When the first free layer 121 and the second free layer 122 are made into a thin film layer, they are mainly affected by shape anisotropy (demagnetization energy), and the easy magnetization direction is parallel to the film surface. When the first free layer 121 and the second free layer 122 are combined with the spin current generating layer 110, due to the interface effect, under the induction of the spin current generating layer 110, the easy magnetization directions of the first free layer 121 and the second free layer 122 are perpendicular to the first interface between the spin current generating layer 110 and the first free layer 121 and the second interface between the spin current generating layer and the second free layer 122, respectively.

[0058] After the first current is passed through the spin current generation layer 110, the magnetic moments of the first free layer 121 and the second free layer 122 are pulled to the hard axis (horizontal direction, i.e. parallel to the first interface / second interface) due to the spin-orbit torque effect. After the first current is removed, under the action of thermal disturbance, the magnetic moments of the first free layer 121 and the second free layer 122 will randomly flip up or down with equal probability (each 50%), i.e. along the easy magnetization direction, respectively perpendicular to the first interface between the spin current generation layer 110 and the first free layer 121 and the second interface between the spin current generation layer 110 and the second free layer 122, and randomly flip up or down. Alternatively, the first free layer 121 and the second free layer 122 are prepared as single-domain two-state magnetic devices, i.e. the magnetic moments of the first free layer 121 and the second free layer 122 are in the same direction at the same time. The magnetic moment direction of the first free layer 121 and the second free layer 122 is used as the carrier of information, and the randomness of the magnetic moment flip generates true random numbers. Thermal disturbance is a true random entropy source in nature, so the probability of the magnetic moments of the first free layer 121 and the second free layer 122 flipping up or down perpendicular to the first interface and the second interface is each 50%. Different magnetic moment directions correspond to different Hall resistances, and by measuring the Hall resistance, the true random number sequence can be obtained.

[0059] The first insulating layer 131 and the second insulating layer 132 are respectively located above the first free layer 121 and the second free layer 122. Alternatively, the first insulating layer 131 and the second insulating layer 132 are made of metal oxide material, and alternatively include MgO or AlO x .

[0060] The first reference layer 141 and the second reference layer 142 are respectively located above the first insulating layer 131 and the second insulating layer 132. Alternatively, the easy magnetization directions of the first reference layer 141 and the second reference layer 142 are respectively perpendicular to the third interface between the first insulating layer 131 and the first reference layer 141 and the fourth interface between the second insulating layer 132 and the second reference layer 142. Alternatively, the first reference layer 141 and the second reference layer 142 are made of material with large damping coefficient, high coercivity and magnetic anisotropy, and alternatively include ferromagnetic material.

[0061] In the present application, the first insulating layer 131 and the second insulating layer 132 induce the first free layer 121 and the second free layer 122 to have magnetic anisotropy perpendicular to the interface through interface effect; on the other hand, the first insulating layer 131 and the second insulating layer 132 form a "sandwich" structure with the first free layer 121, the first reference layer 141, the second free layer 122 and the second reference layer 142 to form a first magnetic tunnel junction MTJ1 and a second magnetic tunnel junction MTJ2, which are used to generate the magnetoresistance of the magnetic tunnel junction.

[0062] The first pinning layer 151 and the second pinning layer 152 are respectively located above the first reference layer 141 and the second reference layer 142. The first pinning layer 151 and the second pinning layer 152 are used to fix the magnetic moment direction of the first reference layer 141 and the second reference layer 142. Under the induction of the first pinning layer 151 and the second pinning layer 152, the magnetic moment of the first reference layer 141 and the second reference layer 142 is fixed in the direction perpendicular to the interface between the first reference layer 141 and the first pinning layer 151 and upward or downward. Optionally, the first pinning layer 151 and the second pinning layer 152 are made of anti-ferromagnetic material, and optionally, include IrMn or NiMn.

[0063] The first cap layer 161 and the second cap layer 162 are respectively located above the first pinning layer 151 and the second pinning layer 152. The first cap layer 161 and the second cap layer 162 are used to protect the layers below. In the present application, the first cap layer 161 and the second cap layer 162 also serve as a read signal electrode. The read current (also referred to as the second current in the present application) is passed into the first electrode T1 (or the second electrode T2) and the first cap layer 161, or passed into the first electrode T1 (or the second electrode T2) and the second cap layer 162. Optionally, the first cap layer 161 and the second cap layer 162 are made of non-ferrous conductive metal material, and optionally, include Ta, Ti or Cu and the like.

[0064] The true random number generator based on the spin orbit torque effect (SOT) drives the magnetization of the free layer to the hard axis (planar direction) by applying a current in the spin current generation layer, removes the current pulse, and under thermal disturbance, the magnetic moment will relax to one of the two easy axis directions with equal probability (50%). This process is greatly affected by the external environment, such as temperature, stray magnetic field, current density, etc., and its essence is to destroy the balance of the magnetic moment flipping to the vertical direction after the current is removed.

[0065] In the present application, strong anti-ferromagnetic coupling can be generated between the first magnetic tunnel junction MTJ1 and the second magnetic tunnel junction MTJ2. When there is an external stray magnetic field (whether it is a horizontal magnetic field or a vertical magnetic field), the free layer of one of them based on the spin orbit coupling effect will flip to up or down, the free layer of the other magnet will always be the corresponding opposite down or up (for a vertical magnetic field, there is an action interval, when the external magnetic field is greater than its coupling strength or coercive force, the design fails). Since the spin orbit coupling effect and the external magnetic field have no difference in the action on the two magnets, the combination of such coupled nanomagnets will have balanced randomness and the ability to resist the influence of stray magnetic fields.

[0066] Optionally, the first current comprises a pulse current with a preset interval. Optionally, the first current is a large pulse current. The first current with a preset interval is applied to the first electrode T1 and the second electrode T2 along the X-axis direction. Optionally, the heat generated by the first current in a pulse period is greater than the energy required for the magnetic moments of the first free layer 121 and the second free layer 122 to randomly flip, and thus the current intensity and the pulse width of the first current can be determined according to the flipping energy barrier of the magnetic moments of the first free layer 121 and the second free layer 122.

[0067] The second current is applied to the first electrode T1 and the first cap layer 161, or the first electrode T1 and the second cap layer 162 with a preset interval along the Z-axis direction, for measuring the magnetoresistance of the first magnetic tunnel junction MTJ1 or the second magnetic tunnel junction MTJ2, and obtaining a random number sequence according to the magnetoresistance. Optionally, when the first current is applied, the magnetic moments of the first free layer 121 and the second free layer 122 randomly flip, and in the interval between two pulses or the interval when the pulse current is removed, the random number can be obtained by detecting the magnetoresistance of the magnetic tunnel junction, and thus the rate of true random number generation can be controlled by controlling the pulse interval of the first current.

[0068] The second current is small and cannot overcome the flipping energy barrier of the magnetic moments, and thus the directions of the magnetic moments of the first free layer 121 and the second free layer 122 remain unchanged under the action of the second current, maintaining the flipped state. The magnetic moments of the first reference layer 141 and the second reference layer 142 are fixed by the first pinning layer 151 and the second pinning layer 152, respectively, and have perpendicular magnetic anisotropy and remain in one direction. When the first current is applied, the magnetic moment of the first free layer 121 randomly flips in the direction perpendicular to the interface between the first free layer 121 and the spin current generation layer 110, and the magnetic moment of the second free layer 122 randomly flips in the direction perpendicular to the interface between the second free layer 122 and the spin current generation layer 110. At this time, the magnetic moments of the first free layer 121 and the first reference layer 141 are in two states of parallel or antiparallel, and the magnetic moments of the second free layer 122 and the second reference layer 142 are in two states of parallel or antiparallel. Due to the giant magnetoresistance effect, when the magnetic moments of the first free layer 121 and the first reference layer 141 are parallel, and when the magnetic moments of the second free layer 122 and the second reference layer 142 are parallel, a lower magnetoresistance can be measured; when the magnetic moments of the first free layer 121 and the first reference layer 141 are antiparallel, and when the magnetic moments of the second free layer 122 and the second reference layer 142 are antiparallel, a higher magnetoresistance can be measured. Different resistance values are defined as logic "0" and "1", respectively, and repeated operations can achieve an output random number sequence.

[0069] The true random number generator and method for generating true random numbers provided by this invention utilize the spin-orbit coupling effect and thermal disturbance to drive the magnetic moment of the magnetic layer to randomly flip. One flip cycle can generate a random bit, and the magnetic moment can still maintain its state after the current is removed. The generated random bit is non-volatile and readable.

[0070] Furthermore, by designing two nanomagnetic structures based on antiferromagnetic coupling, the sensitivity of the true random number generator based on the spin orbital moment effect (SOT) to external stray magnetic fields was reduced, the magnitude of magnetic moment reversal deviation from equilibrium (50% each) was significantly reduced, and the randomness of the true random number generator based on the spin orbital moment effect (SOT) was improved.

[0071] The true random number generator provided by this invention has a simple structure, small device size, low power consumption, and is easy to integrate into various portable devices, and has good application prospects.

[0072] Figure 4 This diagram shows a partial longitudinal cross-sectional view of the random number generation module of a true random number generator provided in another embodiment of the present invention, which also corresponds to... Figure 1 Part A of the middle section. (and) Figure 3 Unlike the structure shown, the random number generation module in this embodiment also includes a substrate 180, which is located below the spin flow generation layer 110. Optionally, the substrate includes a silicon substrate or other materials with low surface roughness.

[0073] In the above embodiments, the spin flow generation layer 110 is shown as a strip structure. Optionally, the first free layer 121 and the second free layer 122, the first insulating layer 131 and the second insulating layer 132, the first reference layer 141 and the second reference layer 142, the first pinning layer 151 and the second pinning layer 152, the first capping layer 161 and the second capping layer 162 are thin film layers with the same cross-sectional shape (i.e., all are strip-shaped). Of course, in other embodiments of the present invention, they can also be other shapes.

[0074] Optionally, when fabricating the first magnetic tunnel junction MTJ1 and the second magnetic tunnel junction MTJ2, a spin flow generation layer 110, a first free layer 121 and a second free layer 122, a first insulating layer 131 and a second insulating layer 132, a first reference layer 141 and a second reference layer 142, a first pinning layer 151 and a second pinning layer 152, a first capping layer 161 and a second capping layer 162 are sequentially fabricated on the substrate 180. The first free layer 121 and the second free layer 122, the first insulating layer 131 and the second insulating layer 132, the first reference layer 141 and the second reference layer 142, the first pinning layer 151 and the second pinning layer 152, the first capping layer 161 and the second capping layer 162 are stacked in the central region of the strip-shaped spin flow generation layer 110 by etching.

[0075] Figure 5 The method for generating a true random number by using the true random number generator is shown, which comprises the following steps S510-S530.

[0076] S510: initializing the first magnetic tunnel junction and the second magnetic tunnel junction, so that the first free layer and the second free layer have opposite magnetization directions.

[0077] The specific initialization method of this step is a known technology in the art, which is not described here.

[0078] S520: passing a first current to the first electrode and the second electrode.

[0079] The first current comprises a pulse current with a preset interval.

[0080] S530: passing a second current to the first electrode and the first cap layer, or passing a second current to the first electrode and the second cap layer at the preset interval, for measuring the magnetoresistance of the first magnetic tunnel junction or the second magnetic tunnel junction, and obtaining a random number sequence according to the magnetoresistance.

[0081] The method for generating a true random number provided by the application is simple, has good randomness, and has a good application prospect.

[0082] Figure 6 The periodic and alternating first current and second current passed to the random number generation module of the true random number generator are shown. The first current is a high-amplitude pulse current, and the second current is a low-amplitude pulse current.

[0083] In one pulse period P, the high-amplitude pulse current is first passed to pull the magnetic moments of the first free layer 121 and the second free layer 122 to the horizontal direction, and then the current is removed. Under thermal disturbance, the magnetic moments of the first free layer 121 and the second free layer 122 randomly flip up or down perpendicular to the interface. Due to the perpendicular magnetic anisotropy of the first free layer 121 and the second free layer 122, the magnetic moment direction of the first free layer 121 and the second free layer 122 does not change after being magnetized. After the preset interval of the first current, that is, the low-amplitude pulse current is passed within the preset interval time, the magnetoresistance of the first magnetic tunnel junction MTJ1 or the second magnetic tunnel junction MTJ2 in the Z-axis direction is detected. Different resistance values are defined as logic "0" and "1", and repeated operation can realize output of a random number sequence. In the next pulse period P, the first free layer 121 and the second free layer 122 are magnetized again by passing the high-amplitude pulse current, and the magnetic moment direction randomly flips. Then, the magnetoresistance of the first magnetic tunnel junction MTJ1 or the second magnetic tunnel junction MTJ2 in the Z-axis direction is detected by passing the low-amplitude current, and after periodic and repeated operation, a random number sequence can be output.

[0084] As mentioned above, when the first current is applied, the magnetic moments of the first free layer 121 and the second free layer 122 are randomly flipped, and in the interval between two pulses or during the interval when the pulse current is removed, the random number can be obtained by detecting the magnetoresistance of the magnetic tunnel junction. Therefore, the method provided by the present application can also control the rate of generating true random numbers by controlling the pulse period of the first current.

[0085] The present application adjusts the direction of the magnetic moments of the free layers with perpendicular anisotropy in the two magnetic tunnel junctions close to the current path into an anti-parallel state by designing the anti-ferromagnetic coupling structure, so that the free layers of the two magnetic tunnel junctions form a strong anti-ferromagnetic coupling. When there is external horizontal magnetic field interference, it will jointly act with the spin-orbit coupling effect to make the flipping probability of the magnetic moment to a certain direction deviate from the equilibrium state of 50% (a vertical magnetic field smaller than the coercive force can also achieve the same effect). This influence is simultaneously applied to one magnetic tunnel junction for detection (i.e., the magnetic tunnel junction to which the read current is applied) and another magnetic tunnel junction (i.e., the magnetic tunnel junction to which the read current is not applied), but there is a coupling field between them. When the horizontal magnetic field and the spin-orbit coupling effect or the vertical magnetic field make the magnetic moment pulled to the hard axis direction deviate, this coupling field can play an opposite role (for example, the magnetic moment of the free layer of the magnetic tunnel junction to which the read current is applied deviates upward, and the magnetic moment of the free layer of the magnetic tunnel junction to which the read current is not applied deviates downward, so the coupling field caused will correct the magnetic moment deviating upward), so the combination of the coupled nanomagnets, any of which will have relatively balanced randomness.

[0086] The above merely describes example embodiments of the present disclosure and is not intended to limit the present disclosure. Although the present disclosure is described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A true random number generator, characterized by, The random number generation module comprises: A spin current generation layer, two ends of which are respectively provided with a first electrode and a second electrode, the first electrode and the second electrode being used for inputting a first current; A first magnetic tunnel junction located on the spin current generation layer and comprising a first free layer, a first insulating layer, a first reference layer, a first pinned layer and a first cap layer which are stacked in sequence; and A second magnetic tunnel junction located on the spin current generation layer and comprising a second free layer, a second insulating layer, a second reference layer, a second pinned layer and a second cap layer which are stacked in sequence; The first free layer and the second free layer are configured to have opposite magnetization directions after magnetic field initialization; The first magnetic tunnel junction and the second magnetic tunnel junction are arranged side by side and have a spacing, the spacing being configured to enable the first free layer and the second free layer to generate antiferromagnetic coupling, the antiferromagnetic coupling being used to offset the interference of an external stray magnetic field on the random flipping balance of the magnetic moments of the first free layer and the second free layer; The first electrode and the first cap layer are used for inputting a second current, or the first electrode and the second cap layer are used for inputting the second current.

2. The true random number generator of claim 1, wherein, The easy magnetization direction of the first free layer is perpendicular to a first interface between the spin current generation layer and the first free layer, and the easy magnetization direction of the second free layer is perpendicular to a second interface between the spin current generation layer and the second free layer.

3. The true random number generator of claim 2, wherein, The first free layer is configured to, when the first current is input, be pulled to be parallel to the first interface under the action of a spin-orbit coupling effect, and when the first current is removed, be able to randomly flip in a direction perpendicular to the first interface upward or downward under the action of thermal disturbance; and The second free layer is configured to, when the first current is input, be pulled to be parallel to the second interface under the action of a spin-orbit coupling effect, and when the first current is removed, be able to randomly flip in a direction perpendicular to the second interface upward or downward under the action of thermal disturbance.

4. The true random number generator of claim 3, wherein, The first free layer and the second free layer are further configured to, when the second current is input, be unable to flip.

5. The true random number generator of claim 2, wherein, The easy magnetization directions of the first reference layer and the second reference layer are respectively perpendicular to a third interface between the insulating layer and the first reference layer and a fourth interface between the insulating layer and the second reference layer.

6. The true random number generator of claim 1, wherein, The first free layer and the second free layer are made of the same material, and / or the first reference layer and the second reference layer are made of the same material.

7. The true random number generator according to claim 1, wherein The spin current generation layer is made of a heavy metal material or a topological insulator material; The first free layer and the second free layer are made of a soft magnetic material; The first insulating layer and the second insulating layer are made of a metal oxide material; The first reference layer and the second reference layer are made of a ferromagnetic material; The first pinning layer and the second pinning layer are made of an anti-ferromagnetic material; and / or The first cap layer and the second cap layer are made of a non-ferrous conductive metal material.

8. The true random number generator of claim 1, wherein, The random number generation module further comprises a substrate under the spin current generation layer, and the substrate comprises a silicon substrate.

9. A method of generating a true random number using the true random number generator according to any one of claims 1-8, characterized in that, Comprise: The first magnetic tunnel junction and the second magnetic tunnel junction are initialized to make the first free layer and the second free layer have opposite magnetization directions; The first current is input to the first electrode and the second electrode, wherein the first current comprises pulse current with a preset interval; At the preset interval, the second current is input to the first electrode and the first cap layer, or the second current is input to the first electrode and the second cap layer, for measuring the magnetoresistance of the first magnetic tunnel junction or the second magnetic tunnel junction, and obtaining a random number sequence according to the magnetoresistance.

10. The method of claim 9, wherein, Further comprise: By controlling the pulse period of the first current, the rate of generating true random numbers is controlled.

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