Probabilistically controlled spin random number generator
By using spintronic devices to generate controllable random numbers through the random orientation of the magnetic moment direction of a free magnetic layer, the problems of complex circuitry and uncontrollable probability in traditional random number generators are solved. This achieves small-size, high-efficiency generation of true random numbers, which is suitable for probability calculations and neural network calculations.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INSTITUTE OF PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2021-09-14
- Publication Date
- 2026-06-26
Smart Images
Figure CN115809044B_ABST
Abstract
Description
Technical Field
[0001] This invention relates generally to the field of electronic devices, and more particularly to a random number generator based on spintronics devices, which can have a controllable random number generation probability. Background Technology
[0002] Random number generators are widely used in cryptography, network security, and identity recognition. Furthermore, they can be used to construct probability bits (p-bits) for probabilistic computation, simulated / quantum annealing algorithms, nonlinear optimization, combinatorial optimization, and many other computational fields, making them one of the core components of novel computing devices. Traditional random number generators utilize thermal noise as a source of random numbers. The thermal noise is amplified by an amplifier circuit to control a voltage-controlled oscillator (VCO), and a high-frequency oscillator collects the VCO's output data. Random numbers are generated by statistically analyzing data exceeding a threshold within a certain time period. These generated random numbers are truly random, possessing non-repeatable and unpredictable characteristics. However, this type of random number generator circuit still has many drawbacks. For example, its circuitry is generally complex, and it cannot control the probability of generating "0" and "1" bits, thus failing to meet the needs of certain specific applications, such as neural network computation. Summary of the Invention
[0003] To address the aforementioned and other issues, this application is proposed. This application provides a random number generator incorporating a spintronic device, which utilizes the random orientation of the magnetic moment direction of a free magnetic layer to generate truly random numbers. It offers numerous advantages, including small size, high density, high speed, simple circuitry, and ease of on-chip integration. Furthermore, the spintronic device-based random number generator of this application allows for continuous and flexible control of the probability of generating "0" bits and "1" bits, making it particularly suitable for use in dedicated chips for probability calculations, neural network calculations, and other applications.
[0004] According to one embodiment, a random number generator is provided, comprising: a spin current generating layer formed of a conductive material having a spin Hall effect; and a spintronic device disposed on the spin current generating layer, the spintronic device comprising: a free magnetic layer disposed on the spin current generating layer and formed of a conductive magnetic material; a non-magnetic intermediate layer disposed on the free magnetic layer and formed of a conductive or insulating non-magnetic material; and a reference magnetic layer disposed on the non-magnetic intermediate layer and formed of a conductive magnetic material, wherein the spin current generating layer is configured to receive a first in-plane current along a first direction to rotate the magnetic moment of the free magnetic layer from the easy magnetization axis direction to the difficult magnetization axis direction, and after the first in-plane current is stopped being applied, the magnetic moment of the free magnetic layer randomly rotates back from the difficult magnetization axis direction to the positive or negative direction of the easy magnetization axis, the magnetic moment of the reference magnetic layer is fixed in the positive or negative direction of the easy magnetization axis, and the spintronic device is configured to receive a vertical current to read the resistance state of the spintronic device.
[0005] In some embodiments, the spin current generating layer is further configured to receive a second in-plane current along a second direction to control the probability of the magnetic moment of the free magnetic layer rotating from the direction of the difficult magnetization axis back to the positive and negative directions of the easy magnetization axis.
[0006] In some embodiments, the first direction is parallel to the easy magnetization axis direction, the second direction is parallel to the difficult magnetization axis direction, and the first direction is perpendicular to the second direction.
[0007] In some embodiments, the direction of the second in-plane current is adjustable in the positive and negative directions of the second direction, and the magnitude of the second in-plane current is adjustable to control the probability that the magnetic moment of the free magnetic layer rotates from the direction of the difficult magnetization axis back to the positive and negative directions of the easy magnetization axis.
[0008] In some embodiments, the spintronic device has shape anisotropy to induce the easy magnetization axis of the free magnetic layer to be in the long axis direction and the difficult magnetization axis to be in the short axis direction.
[0009] In some embodiments, the maximum in-plane dimension of the spintronic device is below 200 nm.
[0010] In some embodiments, the random number generator is a true random number generator.
[0011] According to another embodiment, a method for operating the above-mentioned random number generator to generate random numbers is provided, comprising: applying a first in-plane current along a first direction to the spin current generating layer to rotate the magnetic moment of the free magnetic layer from the easy magnetization axis direction to the difficult magnetization axis direction; stopping the application of the first in-plane current to cause the magnetic moment of the free magnetic layer to randomly rotate back from the difficult magnetization axis direction to the positive or negative direction of the easy magnetization axis; and applying a vertical current flowing perpendicularly through the spintronic device to read the resistance state of the spintronic device, thereby determining the random number bit "0" or "1".
[0012] In some embodiments, the method further includes: while applying the first in-plane current, applying a second in-plane current along a second direction to the spin current generating layer to control the probability of the magnetic moment of the free magnetic layer rotating from the direction of the difficult magnetization axis back to the positive and negative directions of the easy magnetization axis.
[0013] In some embodiments, the vertical current is applied after the application of the first in-plane current and the second in-plane current is stopped.
[0014] The above and other features and advantages of the present invention will become apparent from the following description of specific embodiments taken in conjunction with the accompanying drawings. Attached Figure Description
[0015] Figure 1 A schematic diagram of a random number generator including a spintronic device according to an embodiment of the present invention is shown.
[0016] Figure 2 A top view of a random number generator including spintronic devices according to an embodiment of the present invention is shown.
[0017] Figure 3 A schematic diagram illustrating the random flipping principle of a random number generator including a spintronic device according to an embodiment of the present invention is shown. Detailed Implementation
[0018] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Note that the drawings may not be drawn to scale. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments of this application, and this application is not limited to the exemplary embodiments described herein.
[0019] Figure 1 This diagram illustrates the structure of a random number generator 100 including spintronic devices according to an embodiment of the present invention. Figure 2A top view of the random number generator 100 is shown. For ease of description, a magnetic tunnel junction (MTJ) will be used as an example of a spintronic device in the following description; however, it should be understood that the spintronic device used in the random number generator 100 may also be a giant magnetoresistive (GMR) device.
[0020] Reference Figure 1 The random number generator 100 includes a spin flow generation layer 110 and a spintronic device 120 disposed on the spin flow generation layer 110. Figure 1 The diagram shows a magnetic tunnel junction (MTJ) 120. The spin current generating layer 110 is formed of a material capable of generating spin current, such as a spin Hall effect material. When current flows through the spin Hall effect material, due to strong spin-orbit coupling, a spin-polarized electron flow, also known as a polarized spin current, is generated at the surface of the material. The spin polarization direction is perpendicular to the electron flow direction according to the right-hand rule; this is also known as the spin Hall effect. When the spin generating layer 110 is in direct contact with a magnetic layer, the polarized spin current accumulated on its surface diffuses into the adjacent magnetic layer, exerting a torque on the magnetic moment of the magnetic layer, thereby causing the magnetic moment of the magnetic layer to rotate in the spin polarization direction. Examples of materials exhibiting the spin Hall effect include, but are not limited to, Pt, Au, Ta, Pd, Ir, W, Bi, Pb, Hf, IrMn, PtMn, AuMn, Bi₂Se₃, and Bi₂Te₃.
[0021] The spintronic device 120 disposed on the spin current generation layer 110 includes a free magnetic layer 121, a non-magnetic intermediate layer 122, and a reference magnetic layer 123. The free magnetic layer 121 may be formed of a conductive magnetic material, such as a ferromagnetic material, and it has a free magnetic moment, meaning that the magnetization direction of the free magnetic layer 121 can rotate freely. The free magnetic layer 121 can be in direct contact with the spin current generation layer 110, so that when an in-plane current is applied to the spin current generation layer 110, the spin current diffusing from the spin current generation layer 110 to the free magnetic layer 121 will cause the magnetization direction of the free magnetic layer 121 to rotate. Examples of materials that can be used to form the free magnetic layer 121 include, but are not limited to, Co, Fe, Ni, and alloys thereof.
[0022] A non-magnetic interlayer 122 is located between the free magnetic layer 121 and the reference magnetic layer 123, and is formed of a non-magnetic material. For magnetic tunnel junction (MTJ) devices, the non-magnetic interlayer 122 may be formed of an insulating material such as a metal oxide such as MgO or Al2O3; for giant magnetoresistive (GMR) devices, the non-magnetic interlayer 122 may be formed of a conductive material with a long spin diffusion mean free path, such as Cu or Ru.
[0023] The reference magnetic layer 123 may be formed of a conductive magnetic material, such as a ferromagnetic material, and has a fixed magnetic moment, meaning that the magnetization direction of the reference magnetic layer 123 remains constant during the operation of the random number generator 100. In some embodiments, the magnetization direction of the reference magnetic layer 123 may be fixed by a pinning layer 124, which may be formed of an antiferromagnetic material, such as IrMn, and biases the magnetic moment of the reference magnetic layer 123 in a predetermined direction. In other embodiments, the reference magnetic layer 123 may have a self-pinning structure, in which case the pinning layer 124 may be omitted. For example, the reference magnetic layer 123 may be formed of a hard magnetic material with high coercivity, or the reference magnetic layer 123 may include an artificial antiferromagnetic structure comprising two ferromagnetic layers and an antiferromagnetic coupling layer located between the two ferromagnetic layers, which induces the two ferromagnetic layers to be antiferromagnetically coupled to each other, i.e., the magnetic moments are antiparallel, so that the artificial antiferromagnetic structure has a very small net magnetic moment and is not easily affected by external magnetic fields to rotate.
[0024] In some embodiments, the spintronic device 120 may further include a protective layer 125 formed over the pinning layer 124, which may be formed of a corrosion- and oxidation-resistant metal material such as Ta.
[0025] exist Figure 2 The top view shows that the spintronic device 120 has an elliptical shape, thereby inducing shape anisotropy. This shape anisotropy allows the easy magnetization axis of the free magnetic layer 121 in the spintronic device 120 to be aligned along its major axis. Figure 2 The X-axis is in the middle, and the difficult-to-magnetize axis is in the direction perpendicular to the easy-to-magnetize axis. Figure 2 The Y-axis is shown in the middle. However, it should be understood that the spintronic device 120 can also induce anisotropy in other ways, such that the easy and difficult magnetization axes of the free magnetic layer 121 are perpendicular to each other and lie in the plane of the free magnetic layer 121. Making the easy and difficult magnetization axes of the free magnetic layer 121 lie in the plane of the layer has many advantages, such as reducing the current density used for flipping the magnetic moment compared to perpendicular magnetization, since in-plane anisotropy is generally weaker, and making it easier to control the probability of random bits, which will be described in detail below.
[0026] Continue to refer to Figure 1 and 2 The spin current generating layer 110 can be configured to receive a first in-plane current I. R Second surface in-plane current I D The current I in the first plane R The current I in the second surface can be parallel to the easy magnetization axis of the free magnetic layer 121 in the X-axis direction. D It can be parallel to the hard magnetization axis of the free magnetic layer 121 in the Y-axis direction. When a first in-plane current I is applied to the spin current generating layer 110... RBased on the principle described above, the magnetic moment of the free magnetic layer 121 can be rotated from the easy magnetization axis to the difficult magnetization axis. This depends on the in-plane current I. R Whether in the positive or negative direction of the X-axis, the magnetic moment of the free magnetic layer 121 can be rotated to the positive or negative direction of the difficult-to-magnetize axis, i.e., the Y-axis. When an in-plane current I is applied... R At the same time, a second in-plane current I is also applied. D At that time, according to the principle described above, a torque is applied to the magnetic moment of the free magnetic layer 121 in the direction of the difficult magnetization axis, towards the direction of the easy magnetization axis, so that the magnetic moment of the free magnetic layer 121 is shifted by an angle from the direction of the difficult magnetization axis towards the direction of the easy magnetization axis. This is achieved by adjusting the in-plane current I in the positive and negative Y-axis directions. D The direction can be adjusted to shift the magnetic moment of the free magnetic layer 121 from the direction of the difficult magnetization axis towards the positive or negative direction of the easy magnetization axis; by adjusting the in-plane current I... D The size of the free magnetic layer 121 can be adjusted to regulate the angle by which its magnetic moment shifts from the difficult-to-magnetize axis direction toward the easy-to-magnetize axis direction. The spin flow generating layer 110 can be formed, for example... Figure 2 The cross shape shown allows for convenient application of in-plane and in-plane currents I. R and I D Furthermore, multiple random number generators 100 can be conveniently arranged in the row and / or column directions to form an array structure.
[0027] Figure 3 The principle of random magnetic moment reversal in the free magnetic layer 121 of the random number generator 100 is illustrated below. Figure 1 , Figure 2 and Figure 3 This describes the operation and principle of the random number generator 100. Initially, the magnetic moments of the free magnetic layer 121 and the reference magnetic layer 123 can be aligned parallel or antiparallel along the easy magnetization axis, i.e., the X-axis, for example, the positive or negative X-axis. In one embodiment, a first in-plane current I can be applied only to the spin current generating layer 110. R This causes the magnetic moment of the free magnetic layer 121 to rotate from the easy magnetization axis to the difficult magnetization axis, at which point the system is at its energy peak. This depends on the in-plane current I. R The magnetic moment of the free magnetic layer 121 can rotate to either the positive or negative direction of the easy magnetization axis. To ensure uniform rotation of the magnetic moment of the free magnetic layer 121, the dimensions of the spintronic device 120 can be controlled, for example, to make its maximum in-plane dimension, such as the major axis of an elliptical structure, below 200 nm, so that the free magnetic layer 121 has a single magnetic domain structure, thereby achieving uniform rotation of the magnetic moment. When the first in-plane current I is stopped... RWhen the free magnetic layer 121 relaxes towards the easy magnetization axis, the system energy is reduced. At this time, the magnetic moment of the free magnetic layer 121 may relax towards the positive or negative direction of the easy magnetization axis, with a probability of 50% each. Then, a vertical current flowing perpendicularly through the spintronic device 120 can be applied to read the resistance state of the spintronic device 120. Since the probability of the magnetic moment of the free magnetic layer 121 relaxing to the positive or negative direction of the easy magnetization axis is 50% each, the probability of reading the spintronic device 120 in a high-resistance state (where the magnetic moments of the free magnetic layer 121 and the reference magnetic layer 123 are antiparallel) and a low-resistance state (where the magnetic moments of the free magnetic layer 121 and the reference magnetic layer 123 are parallel) is also 50% each. The high-resistance state can correspond to bit "1", the low-resistance state can correspond to bit "0", or vice versa. Therefore, the probability of reading a bit "1" and a bit "0" is 50% each, successfully generating a random bit. When multiple random number generators 100 are used, multi-bit random numbers can be generated. The random numbers generated in this way are non-repeatable and unpredictable, and are truly random numbers; therefore, random number generator 100 is a true random number generator.
[0028] In other embodiments, when a first in-plane current I is applied... R At the same time, a second in-plane current I can also be applied. D The current I in the first plane R The magnetic moment of the free magnetic layer 121 is rotated from the easy magnetization axis to the difficult magnetization axis, such as the positive Y-axis or the negative Y-axis, while the in-plane current I... D This will cause the magnetic moment of the free magnetic layer 121 to deflect by an angle from the direction of the difficult magnetization axis toward the direction of the easy magnetization axis. The in-plane current I... D The direction can be adjusted between the positive and negative Y-axis directions, thereby adjusting the offset direction of the magnetic moment of the free magnetic layer 121 from the difficult-to-magnetize axis towards the easy-to-magnetize axis in either a positive or negative direction. The in-plane current I... D The size can also be adjusted, thereby adjusting the angle by which the magnetic moment of the free magnetic layer 121 shifts from the direction of the difficult magnetization axis toward the positive or negative direction of the easy magnetization axis. Consequently, the in-plane current I... D The probability of generating random bits "0" and "1" can be controlled. For example, when the current I in the second surface... D When the current is along the positive Y-axis and has a small value, the magnetic moment of the free magnetic layer 121 shifts by a small angle from the direction of the difficult-to-magnetize axis toward the positive direction of the easy-to-magnetize axis (i.e., the positive X-axis direction). When the in-plane current I is removed... R Second surface in-plane current I DAt this time, although the magnetic moment of the free magnetic layer 121 will relax to the positive direction of the easy magnetization axis (i.e., the positive X-axis direction) with a greater probability, due to factors such as thermal perturbation, the magnetic moment of the free magnetic layer 121 will still have a certain probability of relaxing to the negative direction of the easy magnetization axis (i.e., the negative X-axis direction). Assuming that the magnetic moment of the reference magnetic layer 123 is in the positive X-axis direction, the probability of reading bit "0" (corresponding to the low resistance state of the parallel state) will be slightly greater than the probability of reading bit "1" (corresponding to the high resistance state of the antiparallel state). When the current I in the second surface D When the current is along the positive Y-axis and has a large value, or when the in-plane current I can be reduced simultaneously. R The magnitude of the current causes the magnetic moment of the free magnetic layer 121 to shift by a larger angle from the direction of the difficult-to-magnetize axis towards the positive direction of the easy-to-magnetize axis (i.e., the positive X-axis direction). This further increases the probability that the magnetic moment of the free magnetic layer 121 relaxes to the positive direction of the easy-to-magnetize axis (i.e., the positive X-axis direction), while further decreasing the probability of relaxing to the negative direction of the easy-to-magnetize axis (i.e., the negative X-axis direction). At this point, the probability of reading bit "0" (low resistance state) is significantly greater than the probability of reading bit "1" (high resistance state).
[0029] The above describes some embodiments of a true random number generator based on spintronic devices. This generator utilizes the random orientation of the magnetic moment direction of a free magnetic layer to generate true random numbers, offering advantages such as small size, high density, high speed, simple circuitry, and ease of on-chip integration. Furthermore, the spintronic random number generator of this application allows for continuous and flexible control of the probability of generating "0" bits and "1" bits, making it particularly suitable for use in dedicated chips for probability calculations, neural network calculations, and other applications.
[0030] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.
[0031] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.
[0032] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.
[0033] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.
[0034] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.
Claims
1. A random number generator, comprising: The spin flow generation layer is formed of a conductive material exhibiting the spin Hall effect; as well as A spintronic device disposed on the spin flow generation layer, the spintronic device comprising: A free magnetic layer is disposed on the spin current generating layer and is formed of a conductive magnetic material; A non-magnetic intermediate layer, disposed on the free magnetic layer, and formed of a conductive or insulating non-magnetic material; and A reference magnetic layer is disposed on the non-magnetic intermediate layer and is formed of a conductive magnetic material. The spin current generating layer is configured to receive a first in-plane current along a first direction to rotate the magnetic moment of the free magnetic layer from the easy magnetization axis direction to the difficult magnetization axis direction. After the first in-plane current is stopped, the magnetic moment of the free magnetic layer randomly rotates back from the difficult magnetization axis direction to the positive or negative direction of the easy magnetization axis. The spin current generating layer is further configured to receive a second in-plane current along a second direction, thereby controlling the probability of the magnetic moment of the free magnetic layer rotating from the difficult-to-magnetize axis direction back to the positive and negative directions of the easy-to-magnetize axis. The magnetic moment of the reference magnetic layer is fixed in the positive or negative direction of the easy magnetization axis, and The spintronic device is configured to receive a vertical current in order to read the resistance state of the spintronic device.
2. The random number generator as described in claim 1, wherein, The first direction is parallel to the easy magnetization axis direction, the second direction is parallel to the difficult magnetization axis direction, and the first direction is perpendicular to the second direction.
3. The random number generator as described in claim 1, wherein, The direction of the in-plane current is adjustable in both the positive and negative directions of the second direction, and the magnitude of the in-plane current is adjustable to control the probability of the magnetic moment of the free magnetic layer rotating from the direction of the difficult magnetization axis back to the positive and negative directions of the easy magnetization axis.
4. The random number generator as described in claim 1, wherein, The spintronic device has shape anisotropy to induce the easy magnetization axis of the free magnetic layer to be in the long axis direction and the difficult magnetization axis to be in the short axis direction.
5. The random number generator as described in claim 1, wherein, The maximum in-plane dimension of the spintronic device is below 200 nm.
6. The random number generator as described in claim 1, wherein, The random number generator is a true random number generator.
7. A method of operating a random number generator according to any one of claims 1-6 to generate random numbers, comprising: A first in-plane current along a first direction is applied to the spin current generating layer to rotate the magnetic moment of the free magnetic layer from the easy magnetization axis direction to the difficult magnetization axis direction; Stop applying the first in-plane current so that the magnetic moment of the free magnetic layer randomly rotates from the direction of the hard magnetization axis back to the positive or negative direction of the easy magnetization axis; as well as A vertical current is applied through the spintronic device to read its resistance state, thereby determining a random number bit "0" or "1".
8. The method of claim 7, further comprising: While applying the first in-plane current, a second in-plane current along the second direction is also applied to the spin current generating layer to control the probability of the magnetic moment of the free magnetic layer rotating from the direction of the difficult magnetization axis back to the positive and negative directions of the easy magnetization axis.
9. The method of claim 8, wherein, After the application of the first in-plane current and the second in-plane current is stopped, the vertical current is applied.