Integration of high-performance spin-orbit torque MRAM devices by 200-mm-wafer manufacturing platform

We demonstrate in-plane field-free-switching spin-orbit torque(SOT)magnetic tunnel junction(MTJ)devices that are capable of low switching current density,fast speed,high reliability,and,most importantly,manufactured uniformly by the 200-mm-wafer platform.The performance of the devices is systematically studied,including their magnetic properties,switch-ing behaviors,endurance and data retention.The successful integration of SOT devices within the 200-mm-wafer manufactur-ing platform provides a feasible way to industrialize SOT MRAMs.It is expected to obtain excellent performance of the devices by further optimizing the MTJ film stacks and the corresponding fabrication processes in the future.

Spintronics intelligent devices

Intelligent computing paradigms have become increasingly important for the efficient processing of massive amounts of data.However,using traditional electronic devices to implement these intelligent paradigms is currently mismatched and limited by their energy,area,and speed.Spintronics,which exploits the magnetic and electrical properties of electrons,could break through these limitations and bring new possibilities to electrical devices.In particular,the tunneling magnetoresistance effect,merging quantum and spintronics,enables spintronic devices to be compatible with standard integrated circuits with a magnetic tunnel junction(MTJ)design,showing great potential for implementing hardware-based intelligent frameworks.In this review,we introduce the specific capabilities of MTJs,including nonvolatility,stochasticity,plasticity,and nonlinearity,which are highly favorable in artificial intelligence algorithms.We then present how these devices could impact the development of intelligent computing,including in-memory computing,probabilistic computing,and neuromorphic computing.Finally,we discuss their challenges and perspectives in intelligent hardware implementations.

Tunneling magnetoresistance materials and devices for neuromorphic computing

Artificial intelligence has become indispensable in modern life,but its energy consumption has become a significant concern due to its huge storage and computational demands.Artificial intelligence algorithms are mainly based on deep learning algorithms,relying on the backpropagation of convolutional neural networks or binary neural networks.While these algorithms aim to simulate the learning process of the human brain,their low bio-fidelity and the separation of storage and computing units lead to significant energy consumption.The human brain is a remarkable computing machine with extraordinary capabilities for recognizing and processing complex information while consuming very low power.Tunneling magnetoresistance(TMR)-based devices,namely magnetic tunnel junctions(MTJs),have great advantages in simulating the behavior of biological synapses and neurons.This is not only because MTJs can simulate biological behavior such as spike-timing dependence plasticity and leaky integrate-fire,but also because MTJs have intrinsic stochastic and oscillatory properties.These characteristics improve MTJs’bio-fidelity and reduce their power consumption.MTJs also possess advantages such as ultrafast dynamics and non-volatile properties,making them widely utilized in the field of neuromorphic computing in recent years.We conducted a comprehensive review of the development history and underlying principles of TMR,including a detailed introduction to the material and magnetic properties of MTJs and their temperature dependence.We also explored various writing methods of MTJs and their potential applications.Furthermore,we provided a thorough analysis of the characteristics and potential applications of different types of MTJs for neuromorphic computing.TMR-based devices have demonstrated promising potential for broad application in neuromorphic computing,particularly in the development of spiking neural networks.Their ability to perform on-chip learning with ultra-low power consumption makes them an exciting prospect for future advances in the era of the internet of things.

Mechanism of field-like torque in spin-orbit torque switching of perpendicular magnetic tunnel junction

The current-induced spin-orbit torque(SOT) is one of the most promising ways for high speed and low power spintronics devices. However, the mechanism of SOT driven magnetization reversal, especially the role of the field-like torque(FLT), is still unclear. Here, we report the observed promotion and suppression of switching by FLT, which depends on the relative direction of FLT and spin polarization. Our results reveal that the FLT could modulate the switching speed and power consumption by affecting the work done by the damping-like torque, and leads two different reversal dynamical paths during the switching.Furthermore, the origin of incubation time in SOT induced switching is clarified simultaneously.

Observation of magnetic droplets in magnetic tunnel junctions

Magnetic droplets,a class of highly nonlinear magnetodynamic solitons,can be nucleated and stabilized in nanocontact spintorque nano-oscillators.Here we experimentally demonstrate magnetic droplets in magnetic tunnel junctions(MTJs).The droplet nucleation is accompanied by power enhancement compared with its ferromagnetic resonance modes.The nucleation and stabilization of droplets are ascribed to the double-Co Fe B free-layer structure in the all-perpendicular MTJ,which provides a low Zhang-Li torque and a high pinning field.Our results enable better electrical sensitivity in fundamental studies of droplets and show that the droplets can be utilized in MTJ-based applications and materials science.