Role of Dipolar Interactions on the Thermal Stability of High-Density Bit-Patterned Media

We have characterized the magnetic reversal and thermal stability of bit-patterned media with a composite structure of [Co (0.25 nm)/Pd (0.7 nm)]
₅
/Fe(
X
)/[Pd (0.7 nm)/Co (0.25 nm)]
₅
, where
X
= 1, 1.5 , and 2 nm. For 25 nm diameter islands separated by 35 nm, the average thermal stability of the islands is confirmed by analyzing the time-dependent coercive fields. However, by further analyzing the time-dependent hysteresis loop shape, we find a broad distribution of the effective energy barriers. We quantitatively show that this energy barrier distribution arises primarily from the dipolar interactions in these densely packed arrays and not from intrinsic distributions.