Quantum depinning of domain walls in ferromagnets

The authors report on the magnetic relaxation of thin films of Fe of 1000 AA thickness separated by layers of Ag of 15 AA thickness. It is argued that the flattening of the magnetic viscosity at low temperature may be due to quantum diffusion of domain walls. Both the crossover temperature, T c , from the classical to the quantum regime and the magnetic viscosity extrapolated to T=0 depend on the value of the applied field, in agreement with theories of quantum tunnelling in magnets.