Anisotropy in collective precessional dynamics in arrays of Ni80Fe20 nanoelements

The anisotropy in the collective precessional dynamics with the variation of azimuthal angle of the bias magnetic field is studied in arrays of permalloy (Ni80Fe20) nanoelements by an all-optical time-resolved Kerr microscope. When the nanoelements are very closely spaced (inter-element separation = 50 nm), a gradual transition from completely uniform collective regime to a completely non-collective regime is observed as the azimuthal angle varies from 0 degrees to 45 degrees. On the other hand, for inter-element separation of 100 nm, a non-uniform collective dynamics is observed at 0 degrees and a non-collective dynamics is observed at 45 degrees but no clear trend in the transition is observed. (C) 2012 American Institute of Physics. [doi:10.1063/1.3672402]