Exceptional Point Location Dependence on Dipolar Interactions in Synthetic Antiferromagnets

Synthetic antiferromagnets (S-AFMs) have recently been suggested as ideal macroscopic systems to search for Exceptional Points (EPs). Both optical and acoustic modes exist within S-AFM structures [1]. Within S-AFMs, dipolar interactions and symmetry-breaking external fields can hybridize acoustic and optical magnons [2]. Physically, an EP is the point at which the optical and acoustic modes coalesce and are indistinguishable from one another. Beyond this, only a single magnon branch exists. This implies that there is no magnon-magnon interaction.
In this work, we calculate EPs in S-AFMs using micromagnetic simulations [2]. We have determined that adjusting the saturation magnetization leads to a shift in the EP location. This suggests that dipolar interactions play a much larger role than previously considered. The results indicate an opportunity for simulation-supported experimental strategies to use EPs for magnon manipulation.

[1] J. Sklenar et al. arXiv:2008.01298 (2020).
[2] Y. Shiota et al. Physical Review Letters 125.1 (2020): 017203.