Temperature effects on time-dependent magnetic phenomena in recording media

The effects of time on the magnetization of particles used in magnetic recording media have been studied at different temperatures. The magnetization decay, the magnetic viscosity and the fluctuation field decrease with decreasing temperature in practically all the analyzed materials, coherently with the increase of thermal stability of the magnetization at lower temperatures. The activation volume evolves with temperature following two opposite behaviours. In undoped materials it increases when T decreases, while in the corresponding doped particles and in metal particles the activation volume decreases with temperature. Such diversified behaviours are interpreted on the basis of the different mechanisms of magnetization switching in the two classes of particles and of their evolution with temperature.