Аннотация:Magnetic systems are currently considered attractive candidates in which to look for quantum phenomena such as the tunneling of the total magnetization of a small (\ensuremath{\sim}100 \AA{} diameter) particle out of a metastable easy direction or between degenerate easy directions. The effect of nuclear spins as a dissipative environment for such a particle is considered and shown to be significant. Two dimensionless parameters characterize the dissipation: a coupling strength varying as the number of nuclear spins, and the ratio of the nuclear and electronic Larmor frequencies.
