Quantum dynamics and response in nanoscale spin systems

We study the quantum dynamics with the effect of dissipative environments in nanoscale magnetic systems, e.g. the molecular magnets such as Mn ₁₂, Feg and V₁₅ and also the locally induced magnetizations in the so-called gaped spin systems. We analyze the dynamics from a view point of nonadiabatic transition at the avoided level crossing points which is called the resonant tunneling point. By the quantum master equation, we study effects of the heat contact on an adiabatic process (magnetic Föhn effect) which is relevant for systems with a large gap such as V₁₅. By the quantum Langevin equation we study how successive random crossings cause a nonexponential decay of the magnetization in the systems with very small energy gap such as Mn₁₂ and Feg.