Possible tunneling in ferromagnetics with extraordinary viscosity

Abstract

The velocity of extraordinary viscous wall motion occuring in oxide contaminated ferromagnetic films was measured as a function of magnetic field and temperature in the range 3.2 to 23 K. Down to the lowest temperature the velocity depends exponentially on the field. There is, furthermore, a transition temperature below which the usual marked temperature dependence abruptly stops. The experimental results are explained by assuming relaxing oxide particles with a volume spread to introduce time dependent terms in the wall potential via exchange coupling to the ferromagnetic. Because of the above transition the oxide particle relaxation is believed to proceed both by thermal excitation and a tunneling process.