Dynamical response on magnetic soft underlayers

In this paper, we have made the first direct dynamical measurements of both exchange coupled and non-exchange coupled magnetic soft underlayer (SUL) materials suitable for perpendicular recording. We have found that damping increased by a factor of 2 to 3 for the exchange coupled sample compared to the non-exchange coupled samples. The exchange coupled sample consisted were composed of 50 nm of FeCo with three different 2.5 nm thick seedlayers:Cu, NiFe, and Ru.