Characterization of the Inter-grain Coupling in Uniaxial Antiferromagnets via Domain Wall Patterns

Antiferromagnets (AFMs) as materials with a high degree of magnetic compensation and complex dynamics attract attention for fundamental research and use in high-speed and low-energy-cosuming electronics. Technologically relevant AFM thin films usually possess a granular crystal structure, which alters the properties of domain walls and skyrmions [1,2]. Here, we provide a material model of a granular AFM and describe domain wall pinning at grain boundaries [3]. The model is applied to Cr2O3 films with a maze-like domain pattern visualized using nitrogen vacancy magnetometry. Using the statistical analysis of domain size and measuring the self-similarity parameters of the domain wall pattern, we estimate the material parameters characterizing the inter-grain coupling. Namely, for the films with a grain size of about 50 nm, the distribution of exchange bonds between grains is characterized by an average of 10% from the bulk value and a wide standard deviation, including a small amount of ferromagnetic bonds. The presented approach is compatible with machine learning techniques. Based on the material model, we provide design rules for the granular AFM recording media.

[1] Jing et al, Phys. Rev. B 103, 174430 (2021)
[2] Veremchuk et al, ACS Appl. El. Mat. 4, 2943 (2022); Erickson et al, RCS Adv. 13, 178 (2023)
[3] Pylypovskyi et al, Phys. Rev. Appl. 20, 014020 (2023)