Size effect on single pulse all-optical helicity-independent switching in GdFeCo disk arrays

We experimentally demonstrate single pulse toggle switching of the magnetization of GdFeCo disks with perpendicular to film plane anisotropy, which diameter ranges from 3 mu m to 400 nm using 35 fs linearly polarized laser pulses. Two different magnetic states can be observed depending on the laser fluence: either a deterministic switching of the disk magnetization or a randomly oriented disk. We report that the fluence required to observe both magnetic states show a non-monotonic behavior with disk diameter and that the smallest disks require the lowest minimum fluence for achieving single pulse all-optical helicity-independent switching. Different evolution of the fluence thresholds for both phenomenon as a function of the disk size is observed and discussed.