Direct observation of ultrafast magnetization dynamics in Co/Ni bit patterned media by time-resolved scanning Kerr microscopy

Bit patterned recording (BPR) has attracted much attention due to its promising potential in achieving high densities in magnetic storage devices. The materials with strong perpendicular magnetic anisotropy (PMA) are always preferred in designing the BPR. Here, the patterned Co/Ni multilayers showing d-d hybridization induced PMA was studied. In particular, we record the ultrafast spin dynamics by means of time-resolved scanning magneto-optical Kerr effect (TRMOKE) microscopy. We are able to acquire the "snapshot" magnetic maps of the sample surface because of both the femtosecond temporal and submicrometer spatial resolution in our TRMOKE microscopy. Furthermore, the spatially inhomogeneous ultrafast demagnetization was observed in experiment, and this has been evidenced by simulations.