Experimental demonstration of skyrmionic magnetic tunnel junction at room temperature

Chiral magnetic skyrmions are topological swirling spin textures that hold promise for future information technology. The electrical nucleation and motion of skyrmions have been experimentally demonstrated in the last decade, while electrical detection compatible with semiconductor processes has not been achieved, and this is considered one of the most crucial gaps regarding the use of skyrmions in real applications. Here, we report the direct observation of nanoscale skyrmions in Co Fe B/Mg O-based magnetic tunnel junction devices at room temperature. High-resolution magnetic force microscopy imaging and tunneling magnetoresistance measurements are used to illustrate the electrical detection of skyrmions,which are stabilized under the cooperation of interfacial Dzyaloshinskii–Moriya interaction, perpendicular magnetic anisotropy, and dipolar stray field. This skyrmionic magnetic tunnel junction shows a stable nonlinear multilevel resistance thanks to its topological nature and tunable density of skyrmions under current pulse excitation. These features provide important perspectives for spintronics to realize highdensity memory and neuromorphic computing.

Mo-based perpendicularly magnetized thin films with low damping for fast and low-power consumption magnetic memory

Perpendicular magnetic anisotropy-based magnetic tunnel junctions(p-MTJs) with low Gilbert damping constant(α) are of particular interest for fast and low-power consumption magnetic random-access memory(MRAM). However, obtaining a faster switching speed and lower power consumption is still a big challenge. Herein, we report a Mo-based perpendicular double free layer structure with a low Gilbert damping constant of 0.02 relative to W-based films, as measured by time-resolved magnetooptical Kerr effect equipment. To show the influence of different film structures on the Gilbert damping constant, we measured the Mo-based single free layer. Thereafter, we deposited the full stacks with the Mo-based double free layer and obtained a high tunneling magnetoresistance of 136.3% and high thermal stability. The results of high-resolution transmission electron microscopy(HR-TEM) and energy-dispersive X-ray spectroscopy(EDS) showed that the Mo-based films had better crystallinity,sharper interfaces, and weaker diffusion than the W-based films and thus produced a weaker external contribution of the Gilbert damping constant. As a result of the weak spin-orbit coupling in the Mo-based structure, the intrinsic contribution of the Gilbert damping constant was also weak, thereby leading to the small Gilbert damping constant of the Mo-based stacks. In addition, the macro-spin simulation results demonstrated that the magnetization switching by the spin transfer torque of the Mo-based MTJs was faster than that of the W-based MTJs. These findings help to understand the mechanism behind the good performance of Mo-based p-MTJ films and show the great promise of these structures in low-power consumption MRAM or other spintronic devices.

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.

Resonance cavity-enhanced all-optical switching in a GdCo alloy absorber

In spintronic applications,there is a constant demand for lower power consumption,high densities,and fast writing speed of data storage.All-optical switching(AOS)is a technique that uses laser pulses to switch the magnetic state of a recording medium without any external devices,offering unsurpassed recording rates and a simple structure.Despite extensive research on the mechanism of AOS,low energy consumption and fast magnetization reversing remain challenging engineering questions.In this paper,we propose a newly designed cavity-enhanced AOS in Gd Co alloy,which promotes optical absorption by twofold,leading to a 50%reduction in energy consumption.Additionally,the time-resolved measurement shows that the time of reversing magnetization reduces at the same time.This new approach makes AOS an ideal solution for energy-effective and fast magnetic recording,paving the way for future developments in high-speed,low-power-consumption data recording devices.