Dynamics of soliton excitations in inhomogeneous magnetic chains

Abstract The interaction of nonlinear excitations with extended inhomogeneities in an on-site anisotropic Heisenberg spin chain is studied numerically. The inhomogeneous segment is modeled by the change in the anisotropy constant of a set of consecutive spins. The modified anisotropy leads to linear and nonlinear additional terms in the nonlinear Schrödinger (NLS) equation for the spin amplitude derived for classical spin vectors and wide excitations. For a homogeneous chain with easy axis anisotropy the NLS equation possesses a bright type soliton solution. When the modification of the anisotropy constant is negative the spin set acts as a complex linear and nonlinear potential with a dominant linear well character and for a given range of initial velocities of the incoming soliton and the mismatch anisotropy the scattering pattern exhibits periodically repeating regions of trapping and transmission as a function of the length of the inhomogeneity. It is shown that the runaway of the soliton is due to a resonance between the period of the shape oscillations of the soliton inside the inhomogeneity and the length of the latter.