Perpendicular magnetic anisotropy tuning of macrospin-to-vortex transitions in Co-based artificial spin-vortex ice
We investigate the macrospin-to-vortex (MS-to-V) transition in Co-based artificial spin-vortex ice (ASVI) in the presence of perpendicular magnetic anisotropy (PMA) by spin-wave spectroscopy. Detailed micromagnetic simulations using mumax3 reveal that the PMA modifies the magnetic energy landscape and facilitates vortex formation, suggesting that PMA can enhance the transition probability. To seek experimental validation of this hypothesis, we prepared Ti (3 nm)/Co (10 nm)/Ti (3 nm)/Pt (2 nm) (TCT) and Ti (3 nm)/Co (10 nm)/Pt (2 nm) (TCP) multilayer stacks. Vibrating sample magnetometry measurements confirm that the TCP film exhibits a larger PMA than the TCT film. Using these stacks, we then investigate the MS-to-V transition probability in ASVIs and found that TCP ASVIs exhibit a higher transition probability than TCT ASVIs, in agreement with the simulation prediction. These findings identify PMA as an effective design parameter for controlling vortex formation in ASVIs and provide a promising route toward task-dependent tuning of fading-memory properties for physical reservoir computing based on artificial spin lattices.