TEMPERATURE EFFECTS ON TIME-DEPENDENT MAGNETIC PHENOMENA IN RECORDINGMEDIA

The effects of time on the magnetization of particles used in magnetic recording media have been studied at different temperatures. The magn etization decay, the magnetic viscosity and the fluctuation field decr ease with decreasing temperature in practically all the analyzed mater ials, coherently with the increase of thermal stability of the magneti zation at lower temperatures. The activation volume evolves with tempe rature following two opposite behaviours. In undoped materials it incr eases 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 differ ent mechanisms of magnetization switching in the two classes of partic les and of their evolution with temperature.