Shen Li

Achieving giant tunneling magnetoresistance (TMR) in antiferromagnetic (AFM) tunnel junctions remains a central challenge in AFM spintronics. Conventional antiferromagnets suffer from insufficient spin polarization due to spin degeneracy, which severely limits further readout of magnetic states. Here, we propose exploiting the ferromagnetic-like spin splitting in filling-enforced fully compensated ferrimagnets (fFIMs) to realize giant TMR in a simple bilayer van der Waals tunnel junction based on NiICl/CrI3. First-principles calculations reveal that NiICl exhibits spin-polarized bands near the Fermi level similar to those of ferromagnets, thereby overcoming the momentum-space limitation of conventional antiferromagnets. Leveraging the pronounced spin polarization of NiICl, the tunnel junction achieves a giant TMR of up to 2.065 × 104% around the Fermi level. Further investigation shows that strong exchange coupling at the NiICl/CrI3 interface induces an exchange-bias field of 0.765 T, which stabilizes the ferromagnetic layer against external perturbations and is beneficial for reliable device operation. This work highlights the unique advantages of ferromagnetic-like spin polarization in fFIMs and provides an alternative approach for designing structurally simple and high-performance spintronic devices.

Interlayer Dzyaloshinskii–Moriya interaction (IL‐DMI) in synthetic magnetic structures has attracted extensive interest for greatly facilitating deterministic spin‐orbit torque (SOT)‐driven information writing and topologically non‐trivial 3D magnetic Hopfion forming. However, its distinct role in synthetic ferrimagnets (SFi) remains unexplored, where the conjunction of asymmetric magnetic moments and antisymmetric nature of IL‐DMI leads to more diverse spin configurations and applications. Here, we reveal the unidirectional and chiral nature of IL‐DMI in SFi, further unlocking application directions of IL‐DMI in neuromorphic computing. Particularly, the IL‐DMI‐induced effective field increases approximately twentyfold while interacting with two asymmetric antiparallel‐aligned moments, greatly facilitating future IL‐DMI detection. Unlike previous digital‐like switching, we find that the interplay of IL‐DMI, SOT, and thermal effect gives rise to an analog‐like switching behavior. Leveraging this, we develop an SOT‐based non‐probabilistic leaky‐integrate‐fire neuron device utilizing the micromagnetic analog‐like switching model. Compared to probabilistic neurons, this provides a hardware support Spiking neural network, interlayer Dzyaloshinskii–Moriya interaction, spin‐orbit torque, synthetic ferrimagnetsfor ultralow power, high‐sparsity, and high‐accuracy spiking neural networks.

The recent demonstration of single-shot ultrafast magnetization reversal in ferromagnetic spin valves—combining spin-transfer torque with optically induced ultrafast switching—has offered a promising avenue for next-generation magnetic storage technologies. However, a comprehensive theoretical framework is currently lacking to validate and elucidate the reversal mechanisms across different initial magnetic states. Here, we develop a theoretical model for optically induced ultrafast magnetization reversal by integrating the s-d exchange model with an atomistic spin dynamics approach. The proposed model's validity is corroborated through detailed comparisons with experimental time-resolved magneto-optic Kerr effect data. Our findings highlight distinct contributions from ultrafast demagnetization and ultrafast spin currents to the switching process. Furthermore, we systematically explore the influence of laser pulse parameters, such as fluence and width, as well as material-specific properties like magnetic anisotropy and Gilbert damping coefficients on ultrafast ferromagnetic reversal. Our findings indicate that increasing laser pulse fluence intensifies ultrafast demagnetization and enhances spin current strength, whereas extending pulse width delays demagnetization and diminishes spin current intensity. Notably, magnetic anisotropy exerts minimal influence on spin current generation, while higher damping coefficients amplify spin current intensity, thereby facilitating ultrafast reversal. Comparative simulations across various spin valve materials reveal that CoFe exhibits superior ultrafast spin current conversion efficiency compared to [Co/Ni]n and CoPt-based systems. This work establishes a robust theoretical framework for optically induced ultrafast magnetization reversal and provides critical insights for the design of future picosecond-scale, low-power, and nonvolatile magnetic recording devices.

Multiferroic tunnel junctions (MFTJs), integrating ferroelectric and ferromagnetic functionalities within a single nanoscale device, hold significant promise for nonvolatile, multistate memory and innovative computing paradigms. In conventional MFTJs, tunneling resistance modulation relies primarily on ferroelectric (FE) polarization switching, which alters interfacial electric fields and shifts the Fermi level of adjacent ferromagnetic electrodes. However, achieving high tunnel electroresistance (TER) through this approach demands strong built-in electric fields, which simultaneously hinder FE polarization switching, creating an intrinsic trade-off between reliable data reading and efficient writing. Here, we propose a dual mechanism that combines antiferroelectric (AFE) phase-transition modulation of the evanescent decay states with interfacial spin filtering based on Fe₃GaTe₂/bilayer-α-In₂Se₃/Fe₃GaTe₂ heterostructure. Beyond altering the electrostatic potential as in AFE-FE switching, the transitions between head-to-head type and tail-to-tail type AFE states preserve the centrosymmetric potential profile yet fundamentally modulate the momentum-resolved distribution of evanescent decay rates across the Brillouin zone. When integrated with perfect spin filtering at the Fe₃GaTe₂/α-In₂Se₃ interface, this mechanism yields a giant TER (∼7.6 × 10³%), over 4 times that of conventional FE-based MFTJs, and a TMR exceeding 6.8 × 10⁵%, enhanced by 2 orders of magnitude over typical MFTJs. These mechanisms resolve the performance trade-off in MFTJs, enabling six distinct nonvolatile resistance states at room temperature.

The modulation of the interfacial chiral magnetic exchange interaction, i.e., Dzyaloshinskii–Moriya interaction (DMI), is promising to realize ultralow-power information storage or logic devices. Recently, researchers used Brillouin light scattering to demonstrate that mechanical strain can be used to modulate the DMI in Pt/Co/Pt and switch its sign, i.e., the chirality. Toward practical storage applications, here, we utilize electric field-induced strain to modulate the DMI and measure it through asymmetric bubble expansion. The strain is generated by applying an electrical potential over a ferroelectric substrate PMN-PT [011] and then transferred to the ferromagnetic films above. The measurement results show that DMI in Pt/Co/Pt exhibits a butterfly-shaped curve following the strain variation as expected from PMN-PT [011]. The dependence of DMI on strain can be explained using the triatomic model based on the Fert-Levy theory. We find a significant DMI modulation between 0.09 and 0.29 mJ/m2; indeed, no sign switching is observed in our work, which we attribute to the initial state preparation of the film. This work provides a reference for future electric-field controlled ultralow-power spintronic devices.

Magnetic racetrack memory has significantly evolved and developed since its first experimental verification and is considered one of the most promising candidates for future high-density on-chip solid-state memory. However, both the lack of a fast and precise magnetic domain wall (DW) shifting mechanism and the required extremely high DW motion (DWM) driving current make the racetrack difficult to commercialize. Here, we propose a method for coherent DWM that is free from the above issues, which is driven by chirality switching (CS) and an ultralow spin-orbit-torque (SOT) current. The CS, as the driving force of DWM, is achieved by the sign change of the Dzyaloshinskii-Moriya interaction, which is further induced by a ferroelectric switching voltage. The SOT is used to break the symmetry when the magnetic moment is rotated in the Bloch direction. We numerically investigate the underlying principle and the effect of key parameters on the DWM by micromagnetic simulations. Under the CS mechanism, a fast (∼10² m/s), ultralow energy (∼5 attoJoule), and precisely discretized DWM can be achieved. Considering that skyrmions with topological protection and smaller size are also promising for future racetracks, we similarly evaluate the feasibility of applying such a CS mechanism to a skyrmion. However, we find that the CS causes it to "breathe" instead of moving. Our results demonstrate that the CS strategy is suitable for future DW racetrack memory with ultralow power consumption and discretized DWM.

Spintronic neural devices are attracting growing interest for its potential capability in processing massive data with extremely low power consumption. The devices based on magnetic domain walls (DWs) are considered as promising solutions for its nonvolatility, high density, and flexible design. Among the device mechanisms, strong chiral coupling of laterally adjacent nanomagnets through interfacial Dzyaloshinsky–Moriya interaction (DMI) enables field-free correlated switching of neighboring nanomagnets and planar DW racetrack cascading. Here, we apply this lateral coupling mechanism to realize a current-driven magnetic neural device and network. With the spin-orbit-torque (SOT)-driven DW motion and chiral coupling between laterally neighboring out-of-plane (OOP) and in-plane (IP) nanomagnets, this device achieves nonvolatile binary neuromorphic computing. By racetrack cascading of this device, we further implement a three-layer binary neural network (BNN) capable of recognizing images. This device, which realizes all-electric nonvolatile in-memory computing, may inspire the development of ultralow-power spin artificial neurons.

In this work, the phase transition of a highly disordered amorphous VO₂ film is studied. It is found that the electronic transport behavior follows the Arrhenius or Vogel–Tammann–Fulcher model, showing different thermal sensitivity under different thicknesses. Based on it, the concept of a prototype device with overheating protection capability is demonstrated. The results, reflecting the relationship between phase transition and structural disorder, open up a unique pathway to understand the metal insulator transition in strongly correlated electronic systems and to its functionality in electronic devices.

The integration of data sensing and processing within a single device is of great significance in the future intelligent application scenarios due to its advantages in reducing power consumption and time delay. Nevertheless, most of the current investigations focus on sensing a single type of external stimuli, which is a hindrance for an accurate and complete sensing and processing of information. Here, based on the combination of optically controlled phase-change material (vanadium dioxide, VO ₂ ) and magnetoresistive sensing component (magnetic tunnel junction, MTJ), a device with in-sensor computing ability of optical and magnetic signals is demonstrated. To ensure the functionality integration, the thickness of VO ₂ is optimized in terms of resistance matching with MTJ. The device exhibits multiresistance states under the stimuli of light illumination and magnetic field. Further, the reconfigurable logic functions of the two types of captured information are achieved, realizing a multifunctional sensory processing integrated system. This work could pave the way for high-performance intelligent sensing and the Internet of Things.

Magnetic anisotropy modulation is an effective method to simultaneously reduce the switching current and extend the data retention of magnetic tunnel junction (MTJ), which is promising to be used in the next-generation spin transfer torque (STT) magnetic random-access memory. However, to meet the requirements of high storage life and harsh environments, the improved perpendicular magnetic anisotropy of MTJ makes the conventional modulation methods suffer from high breakdown risk owing to the relatively low efficiency. In this paper, a method of phase-change controlled magnetic anisotropy (PCMA) is introduced to a physical model of VO₂/CoFeB/MgO/CoFeB perpendicular MTJ with superior modulation capability proved by systematical simulation. The time sequence of phase change pulse and STT pulse is studied, proving that there exists a specific interval to achieve both rapid and low-power switching. With the joint effect of PCMA and STT, low-energy (68.2 fJ), low-error-rate (0.08), and fast (2 ns) write operation can be achieved in the MTJ accompanied by a high thermal stability factor (78). The results demonstrate that the PCMA-STT switching strategy is most suitable for MTJ with large perpendicular magnetic anisotropy, paving a promising way to replace NOR flash memories.