Dynamics of low-dimensional dipolar systems

Time decays of low-dimensional magnetic dipoles with anisotropic energy barriers were studied theoretically. We found that the dynamic behaviors are interaction specific. For a chain with ferromagnetic coupling, a single mode dominates and the decay is essentially exponential. For antiferromagnetic coupling, the dynamics can be characterized by two distinct groups of time scales. The spectrum results in a plateau in the decay of remanent magnetization. This novel behavior differs from the prediction of the mean-field theory. For a two-dimensional rectangular lattice, a transition between the bimodal decay and a quasilogarithmic decay occurs when the ratio of length to width varies.