True random-number generator based on quadrature magnetic tunnel junctions

Abstract

The invention discloses a true random-number generator based on quadrature magnetic tunnel junctions. The generator has a multi-layer magnetic tunnel junction structure, and includes electrode layers,magnetic layers and tunneling layers arranged in a multi-layer tower-shaped structure from a bottom to a top. The magnetic layers are a ferromagnetic material. The tunneling layers are a metal oxide.Two magnetic layers located at an upper portion both have in-plane uniaxial magnetic anisotropy. A magnetic layer located at a lower portion has a uniaxial magnetic anisotropy perpendicular to a filmplane direction. In a writing phase, a writing current is applied to the true random-number generator, and a magnetization direction becomes perpendicular to a film plane, and is in a temporary steady state; and in a reading phase, the writing current is stopped, and magnetization directions of the magnetic layers return to directions of anisotropy axes under the combined action of an anisotropyfield and a demagnetizing field, the magnetization direction is randomly biased to any side in a case of thermal perturbation, a specific bias is obtained by applying a reading current to the magnetictunnel junctions formed by all the magnetic layers and the tunneling layers, and thus a true random number is stably generated.

Description

technical field [0001] The invention relates to a true random number generator based on an orthogonal magnetic tunnel junction, which belongs to the technical field of digital information security. Background technique [0002] The earliest method of random number generation is manual method, that is, drawing lots, shaking dice and other methods. The random number sequence generated by this method is highly unpredictable, but with the development of computer technology, this method cannot meet the demand for a large amount of random data, and the use of mathematical methods can occupy very little memory to quickly generate random numbers, or It is a sequence of random numbers generated by a certain distribution and generated according to a certain calculation method. They have properties similar to the independent sampling sequence of random variables of this distribution. Since these numbers are generated according to a certain algorithm, they cannot be truly random number...

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Problems solved by technology

[0004] The Chinese invention patent "Non-Volatile Magnetic Memory Units and Devices" (CN99110623) discloses that the first generation of MRAM uses the magnetic field generated by the current to write, and its disadvantage is that it requires a large device size to operate correctly; "Magnetic Random Access Memory with Soft Adjacent Layer" (CN200410006749) uses current to write the state of the magnetic tunnel junction. When the size of the device is reduced, the current density is very large, which poses great difficulties for the manufacture of the device; invention Patent "Memory Cell and Method for Forming Magnetic Tunnel Junction (MTJ) of Memory Cell" (CN200980101856) Although it is a magnetoresistive random access storage using the spin transfer torque effect, the current is used as a writing method to achieve non-volatility Storage, but the manufacturing process is complex and has high requirements for the etching process; similarly, the invention patent "Non-Volatile Magnetic Tunnel Junction Transistor" (CN201180054198) contains two magnetic tunnel junctions in the transistor, one of which uses a reverse Ferromagnetic coupling leads to problems such as complex layered structure and difficult manufacturing process; the invention patent "Spin Transfer Torque-Magnetic Tunnel Junction Device and Operation Method" (CN201080023820) although it is switched by current in the spin transfer torque magnetic tunnel junction device The magnetic moment direction of the free layer of the magnetic element, but on the basis of using the spin transfer torque effect to control the magnetic tunnel junction, it still needs to use the magnetic field generated by the current to assist flipping; the invention patent "bipolar spin transfer switching" (CN201180063255 ) can achieve bipolar reversal, but it cannot reprogrammably control the magnetization direction of the magnetic layer; the invention patent "Magnetic Tunnel Junction Structure for MRAM Devices" (CN201580005078) only realizes non-volatile Volatile storage, not a true random number generator structure based on magnetic tunnel junctions;

[0005] The paper "Spin dice: A scalable truly random number generator based on spintronics" (Applied Physics Express 7.083001, 2014) discloses that the magnetic tunnel junction is used as the basic random number generation unit, and the spin transfer torque effect is used as the writing method , but it is necessary to strictly control the temperature of the environment where the random number generator is located and the size of the write current to ensure that the flip probability is 0.5; the paper "Spin-Orbit-Torque-Based Spin-Dice: A True Random-Number Generator" (IEEE MAGNETICSLETTERS.Volume 6, 2015), although the magnetization direction of the target layer (the place where the random number is generated) is first pulled to the direction of the transient state, and its random bias is used to obtain the random number in the second stage, The spin-orbit torque is used to make the magnetization direction of the target layer (the place where the random number is generated) temporarily stable, but because the spin-transfer torque and the spin-orbit torque are comprehensively used, the random number generator is a 3-terminal device, so that complex structure

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