Strange Energy Loss and Chaotic Entropy of Domain-Wall Motion

抄録

The strange behavior of thermal energy loss in chaotic motion of a Bloch wall is studied by using entropy. The thermal energy loss due to domain-wall motion is calculated by integrating a damping term. The entropy of domain-wall motion is calculated by using the probability of the state-points distribution in the phase space. The results of computer simulation show that the thermal energy loss in the periodic window of the bifurcation diagram increases in spite of the decrease in randomness of domain-wall motion, which seems to conflict with the first and second laws of thermodynamics. The chaotic entropy S_c of domain-wall motion is introduced into the equation of energy balance to solve the above conflict. S_c is a kind of “mechanical entropy”, and differs from thermodynamic entropy. The entropy S of the system is expressed as the sum of the chaotic entropy S_c of the domain-wall motion in the phase space and the entropy S_m related to the thermal energy loss by using the property of additivity of entropy. The results of computer simulation are interpreted as indicating that the value of Temperature ×∫²₁ dS_m (the thermal energy loss) increases so that it compensates for the decrease of Temperature ×∫²₁ dS_c (the randomness of motion) in the periodic window. It is explained that the thermal energy loss increases in spite of the decrease in randomness of motion in the periodic window.