Optically induced tunable magnetization dynamics in nanoscale co antidot lattices.

We report the time-domain measurements of optically induced precessional dynamics in a series of Co antidot lattices with fixed antidot diameter of 100 nm and with varying lattice constants (S) between 200 and 500 nm. For the sparsest lattice, we observe two bands of precessional modes with a band gap, which increases substantially with the decrease in S down to 300 nm. At S = 200 nm, four distinct bands with significant band gaps appear. The numerically calculated mode profiles show various localized and extended modes with the propagation direction perpendicular to the bias magnetic field. We numerically demonstrate some composite antidot structures with very rich magnonic spectra spreading between 3 and 27 GHz based upon the above experimental observation.

Detection of picosecond magnetization dynamics of 50 nm magnetic dots down to the single dot regime.

We report an all-optical time-domain detection of picosecond magnetization dynamics of arrays of 50 nm Ni(80)Fe(20) (permalloy) dots down to the single nanodot regime. In the single nanodot regime the dynamics reveals one dominant resonant mode corresponding to the edge mode of the 50 nm dot with slightly higher damping than that of the unpatterned thin film. With the increase in areal density of the array both the precession frequency and damping increase significantly due to the increase in magnetostatic interactions between the nanodots, and a mode splitting and sudden jump in apparent damping are observed at an edge-to-edge separation of 50 nm.