Voltage Controlled Magnetic Skyrmion Motion for Racetrack Memory (1507.08001v4)

Abstract: Magnetic skyrmion, vortex-like swirling topologically stable spin configurations, is appealing as information carrier for future nanoelectronics, owing to the stability, small size and extremely low driving current density. One of the most promising applications of skyrmion is to build racetrack memory (RM). Compared to domain wall-based RM (DW-RM), skyrmion-based RM (Sky-RM) possesses quite a few benefits in terms of energy, density and speed etc. Until now, the fundamental behaviors, including nucleation/annihilation, motion and detection of skyrmion have been intensively investigated. However, one indispensable function, i.e., pinning/depinning of skyrmion still remains an open question and has to be addressed before applying skyrmion for RM. Furthermore, Current research mainly focuses on physical investigations, whereas the electrical design and evaluation are still lacking. In this work, we aim to promote the development of Sky-RM from fundamental physics to realistic electronics. First, we investigate the pinning/depinning characteristics of skyrmion in a nanotrack with the voltage-controlled magnetic anisotropy (VCMA) effect. Then, we propose a compact model and design framework of Sky-RM for electrical evaluation. This work completes the elementary memory functionality of Sky-RM and fills the technical gap between the physicists and electronic engineers, making a significant step forward for the development of Sky-RM.

• The paper demonstrates the use of the VCMA effect to modulate skyrmion pinning and depinning in nanotracks.
• It develops a physics-based electrical model validated by micromagnetic simulations to optimize skyrmion velocity and power consumption.
• Dual strategies based on voltage adjustments and current density tuning provide practical approaches for advanced racetrack memory applications.

Voltage Controlled Magnetic Skyrmion Motion for Racetrack Memory

In recent years, magnetic skyrmions have emerged as promising candidates for next-generation memory technologies, specifically racetrack memory (Sky-RM). The paper "Voltage Controlled Magnetic Skyrmion Motion for Racetrack Memory" embarks on an exploration of the fundamental behaviors and practical implementations of skyrmion-based racetrack memory. The authors address a critical gap in the research by focusing on the electrical design and evaluation of skyrmion motion control through the voltage-controlled magnetic anisotropy (VCMA) effect.

Key Contributions

1. Skyrmion Pinning/Depinning: The paper offers a comprehensive investigation into the pinning and depinning characteristics of skyrmions within a nanotrack, enabled by the VCMA effect. This involves the modulation of perpendicular magnetic anisotropy (PMA) to create energy barriers that can pin or depin skyrmions based on the applied voltage.
2. Electrical Model and Simulation: A physics-based electrical model of Sky-RM was developed, facilitating the evaluation and further optimization of the system using standard electronic design tools. The results demonstrate a vital connection between theoretical skyrmion dynamics and practical electronic implementations.
3. Two Design Strategies: The authors propose dual strategies for skyrmion motion control: adjusting the voltage on the VCMA-gated regions, or dynamically altering driving current densities. These strategies enhance the versatility and adaptability of Sky-RM designs, allowing for improved control of skyrmion trajectories.
4. Simulation Metrics: Micromagnetic simulations reveal that skyrmions can be reliably controlled through voltage modulation. The paper shows robust evaluations of the skyrmion motion under various conditions, leading to useful guidelines for optimizing skyrmion velocity and power consumption.

Implications and Future Directions

The implications of this research extend both theoretically and practically in the field of advanced memory technologies. From a practical viewpoint, this work establishes foundational techniques for implementing skyrmion-based devices in real-world applications, with potential benefits in energy efficiency, device density, and data stability compared to traditional domain wall-based approaches.

From a theoretical perspective, the paper pushes the boundary of our understanding by demonstrating the controllability of skyrmions via electric fields, which has been a challenging aspect so far. This bridges the gap between condensed matter physics and electronic engineering, further encouraging interdisciplinary collaborations.

Looking forward, several avenues for future developments emerge. The exploration of material systems with lower PMA values could yield even faster skyrmion motion, offering gains in speed and energy efficiency. Additionally, developing strategies for sophisticated 3D integration of skyrmionic devices could lead to breakthroughs in spintronic circuitry.

Conclusion

This paper represents a significant advancement in the transition from fundamental skyrmion physics to practical electronics, utilizing the VCMA effect to control skyrmion motion in racetrack memory devices. By providing a detailed model and demonstrating its integration with CMOS technologies, the authors lay groundwork that could potentially lead to the commercialization of skyrmion-based devices. As such, these findings hold great promise for future research and development in the field of spintronics and beyond.