Thermal processes and stability of longitudinal magnetic recording media

Thermally activated magnetization reversal processes in longitudinal magnetic recording media are the origin of signal decay and time dependence of the coercivity. The former may limit the lifetime of the stored data and the latter determines the minimal write fields at short pulse widths. Both effects depend on the ratio of the reversal barrier and the thermal energy. Signal decay and time dependent coercivity measurements are combined in this paper to experimentally derive a stability ratio, 1/C, as a function of film thickness, recording density and temperature. The experiments are performed with a contact write/read tester using a merged read/write head in physical contact with the sample. Samples are mounted on a variable temperature stage (300-390 K) allowing to vary the stability ratios. The samples are a series of CoPtCr recording media with thicknesses from 5.5 nm to 13.0 nm. In the low density limit (500 fc/mm) the onset of thermal decay is observed near (1/C)₉≈38