It has been realized for decades that spatially localized vibrational modes can occur in purely
harmonic lattices only when disorder is introduced so that the translational invariance of the
underlying lattice is removed. In recent years it has been recognized that some excitations in
perfect periodic lattices which contain both nonlinearity and discreteness can localize
resulting in inhomogeneous dynamical patterns, thus the study of this intrinsic localization in
nonlinear periodic lattices is now under intense investigation for a variety of different
physical systems. For macroscopic nonlinear systems such as Josephson junction arrays intrinsic
localized modes (ILMs) have been readily observed. For condensed matter the spins in an
antiferromagnetic crystal provide an experimentally accessible atomic system and here I describe
our continuing investigation of the production of nanoscale localization for spin excitations.
Our experimental and simulation studies show that in certain cases when the uniform mode is
excited into a highly nonlinear regime it becomes modulationally unstable and breaks up into
ILMs. This talk will outline the physically exciting context that is currently emerging: how
macroscopic parameters such as crystal shape, DC magnetic field, and details of the E&M coupling
can influence the nanoscale ILM generation process.
*Work supported by NSF-DMR and carried out in collaboration with L. English, B. Hubbard, R. Lai, and M. Sato.