Cooperative freezing in spin glasses and magnetic nanostructures

Relaxation processes in disordered nanostructures and spin glasses are inve stigated by examining the role of the magnetic anisotropy. To abstract from freezing processes associated with phase transitions, the consideration is restricted to a one-dimensional bond-disordered Ising spin glass. Using a Mattis-type gauge transformation, the spin glass is mapped onto a disordere d ferromagnet. Based on the behavior of the spin chain we argue that spin-g lass freezing is not necessarily related to a phase transition. The magneti c anisotropy, which is largely ignored in the Glauber approach to Ising dyn amics, gives rise to cooperative deviations from the Arrhenius behavior and mimics Vogel-Fulcher relaxation. (C) 2001 American Institute of Physics.