Magnetization reversal of Co/Pt multilayer systems with weak perpendicular magnetic anisotropy

Perpendicular anisotropy thin film systems are well known for their highly periodic magnetic stripe domains. Here we study [Co(3.0 nm)/Pt(0.6 nm)]_X multilayers in the regime of transitional in-plane to out-of-plane anisotropy. For this we vary the number of repeats X in order to tune the remanent state from purely in-plane (IP) via tilted stripe domains (tilted), i.e. with significant out-of plane as well as in-plane magnetization component, to fully out-of-plane stripe domains (OOP). Vibrating Sample Magnetometry and Magnetic Force Microscopy are used to investigate three characteristic samples with X = 6,11 and 22, which represent the three above mentioned remanent states, respectively. In contrast to fully in-plane or fully out-of-plane systems experimental data and corresponding micromagnetic simulation of the tilted magnetization regime (X=11) reveals fully reversible field regions as well as distinct points of irreversibility during an external field sweep. This collective reversal behavior seems at first sight somewhat counter intuitive for a macroscopic system and has qualitative similarities with microscopic systems, such as the Stoner Wohlfarth particle and the vortex reversal in an in-plane magnetized disk, which both show as well distinct points of irreversibility.