THERMAL DECAY IN HIGH-DENSITY DISK MEDIA

An experimental technique has been developed to accurately measure the time dependence of playback voltage due to the decay of recorded magn etization patterns. A ''calibration'' procedure is utilized to minimiz e the effect of magnetoresistive head sensitivity variations. This tec hnique is applied to a systematic study of the dependence of the signa l decay on recording bit density and magnetic layer thickness in longi tudinal thin film media. A Neel-Arrhenius type model is introduced to calculate the degradation of a square wave magnetization pattern subje ct to thermal agitation. Because the equivalent external field which r educes the energy barrier is the time and spatially varying magnetosta tic field produced by magnetic transitions, an iterative procedure is utilized to obtain the time dependent magnetization. The model takes i nto account distributions of grain volume and anisotropy axis. The cal culation results are compared with the experimental data and good agre ement is obtained.