Decoherence effects on the tunneling rate of paramagnetic and superparamagnetic particles

We analyze the effects of the environment on the spin tunneling process of paramagnetic and superparamagnetic particles and conclude that the non assisted macroscopic tunneling rate is hardly affected in such case, but other more effective (phonon mediated) processes change the magnetization state of the particle. We conclude that for both, paramagnetic and superparamagnetic particles, the decoherence time scale is extremely short (~ 10^(-8..-16)seg), indicating thar coherent tunneling should be strongly suppressed in favor of incoherent tunneling, i.e., the population of higher levels with subsequent decay.