Influence of sample shape on the production of intrinsic localized modes in an antiferromagnetic lattice

The formation of intrinsic localized modes (ILMs) via the uniform mode instability is considered for different crystal geometries for a layered quasi-1D antiferromagnet (C2H5NH3)(2)CuCl4. By varying the sample shape and hence the demagnetization factor, it is possible to tune the frequency of the uniform mode with respect to the long-wavelength spin wave frequencies. Molecular dynamics simulations predict that the smaller the difference between the two frequencies, the easier to create ILMs from the large amplitude uniform mode. High power nonlinear experiments on samples of different shapes confirm this prediction. (C) 2002 American Institute of Physics.