Direct imaging of nanoscale field-driven domain wall oscillations in Landau structures

• Published in: Nanoscale Vol. 14; no. 37; pp. 13667 - 13678
• Main Authors: Singh, Balram, Ravishankar, Rachappa, Otálora, Jorge A, Soldatov, Ivan, Schäfer, Rudolf, Karnaushenko, Daniil, Neu, Volker, Schmidt, Oliver G
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 29.09.2022
• Subjects: Anisotropy; Domain walls; Field strength; Giant magnetoimpedance; Harmonic oscillators; Imaging; Magnetic fields; Magnetic force microscopy; Magnetic structure; Magnetoresistivity; Microscopy; Oscillations; Spatial resolution; Thickness
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d2nr03351h

Linear oscillatory motion of domain walls (DWs) in the kHz and MHz regime is crucial when realizing precise magnetic field sensors such as giant magnetoimpedance devices. Numerous magnetically active defects lead to pinning of the DWs during their motion, affecting the overall behavior. Thus, the direct monitoring of the domain wall's oscillatory behavior is an important step to comprehend the underlying micromagnetic processes and to improve the magnetoresistive performance of these devices. Here, we report an imaging approach to investigate such DW dynamics with nanoscale spatial resolution employing conventional table-top microscopy techniques. Time-averaged magnetic force microscopy and Kerr imaging methods are applied to quantify the DW oscillations in Ni 81 Fe 19 rectangular structures with Landau domain configuration and are complemented by numeric micromagnetic simulations. We study the oscillation amplitude as a function of external magnetic field strength, frequency, magnetic structure size, thickness and anisotropy and understand the excited DW behavior as a forced damped harmonic oscillator with restoring force being influenced by the geometry, thickness, and anisotropy of the Ni 81 Fe 19 structure. This approach offers new possibilities for the analysis of DW motion at elevated frequencies and at a spatial resolution of well below 100 nm in various branches of nanomagnetism. We demonstrate a direct imaging approach to capture the DW oscillation with nanoscale resolution and study its dependency on various physical parameters. This study confirms that the DW oscillations behave as a damped harmonic oscillator.