Relationship between the intrinsic thermal switching field at 10-9 s and the anisotropy field in magnetic recording media

Summary form only given. Recently, time dependent coercivity has become a major concern in new high-density recording media. For thermally unstable media, the coercivity at 1 ns can be ~50% larger than that measured at 100s while at longer timescales, further decrease in the coercivity can lead to the loss of stored data. To combat this problem, an increase in the anisotropy has typically been used to make the media more thcrmally stable. However, the effect of increasing the anisotropy on the intrinsic switching field at 1ns has not been well documented. In this paper, we compare the anisotropy field to the intrinsic switching field in a variety of particulate and thin film media. For each sample, the rotational hysteresis was measured from torque curves taken by rotating the sample clockwise and counterdockwise through 360degrees in a field. The torque curves for the oriented particulate samples showed uniaxial behavior while the torque curves for the thin film samples showed no structure hut were non-zero and exhibited rotational hysteresis. The energy loss which is equal to twice the rotational hysteresis was calculated from the area difference between the curves. The anisotropy field was then found by plotting the rotational hysteresis versus inverse field and finding the intercept by linear extrapolation to zero hysteresis.