Dynamical response of local magnetic structures induced by inhomogeneities to time-dependent magnetic field

Local magnetic structures induced by the bond impurities in the S = 1/2 bond alternating system are found to be looked on as an effective S = 1/2 spin at low temperatures. The response of such structures to a time dependent magnetic field is an interesting problem to study and it would be important for the analysis of the nanoscale materials. In realistic systems the effect of coupling to the environment causes fluctuation and dissipation and plays a crucial role in such dynamics. We study the tunneling process in noise by solving the time-dependent Schrodinger equation numerically from the viewpoint of non adiabatic transition in the two level system, and make clear basic properties. We investigate the dependence of the tunneling probability on sweeping velocity of the applied field and also on the direction of the random noise and its relaxation time. (C) 2001 Elsevier Science B.V. All rights reserved.