Dynamics of ferrimagnetic domain wall driven by oscillating magnetic field

Abstract

Ferrimagnetic materials exhibit ultrafast dynamics similar to those of antiferromagnetic materials near the angular momentum compensation point, where a non-zero net spin density is maintained. This unique feature allows their magnetic structures to be detected and manipulated using traditional magnetic techniques, positioning ferrimagnetic materials as promising candidates for next-generation high-performance spintronic devices. However, effectively controlling the dynamics of ferrimagnetic domain walls remains a significant challenge in current spintronics research.<br>In this work, based on the classic Heisenberg spin model, we employ Landau-Lifshitz-Gilbert (LLG) simulations to investigate the dynamic behavior of ferrimagnetic domain walls driven by sinusoidal and square wave periodic magnetic fields. The results reveal that these two types of oscillating magnetic fields induce distinct domain wall motion modes. Specifically, the domain wall surface, which has non-zero net spin angular momentum, oscillates in response to the external magnetic field. We find that the domain wall velocity decreases as the net spin angular momentum increases. Moreover, the displacement of the ferrimagnetic domain wall driven by a sinusoidal magnetic field increases monotonically with time, while the displacement driven by a square wave magnetic field follows a more tortuous trajectory over time. Under high-frequency field conditions, the domain wall displacement shows more pronounced linear growth, and the domain wall surface rotates linearly with time.This study also explores how material parameters, such as net spin angular momentum, anisotropy, and the damping coefficient, influence domain wall dynamics. Specifically, increasing the anisotropy parameter (<i>d<sub>z</sub></i>) or the damping coefficient (<i>α</i>) results in a reduction of domain wall velocity. Furthermore, the study demonstrates that, compared to square wave magnetic fields, sinusoidal magnetic fields drive the domain wall more efficiently, leading to faster domain wall motion. By adjusting the frequency and waveform of the periodic magnetic field, the movement of ferrimagnetic domain walls can be precisely controlled, enabling fine-tuned regulation of both domain wall velocity and position.<br>Our findings show that sinusoidal magnetic fields, even at the same intensity, offer higher driving efficiency. The underlying physical mechanisms are discussed in detail, providing valuable insights that can guide the design and experimental development of domain wall-based spintronic devices.