Patent ID: 8338005

Claim:
A device comprising: a substrate; a hard magnetic layer; and a Soft UnderLayer (SUL) formed between the substrate and the hard magnetic layer and comprising: a first sub-underlayer; and a second sub-underlayer, wherein the first sub-underlayer and the second sub-underlayer are adjacent and anti-ferromagnetically coupled (AFC), one of the sub-underlayers deposited to differ in one or more of thickness, magnetic moment, and anisotropy from the other sub-underlayer, respective magnetic field responses of each sub-underlayer to a magnetic field established during dynamic reversal interfere to create a total SUL magnetic field response to the dynamic reversal magnetic field that is approximately zero at one or more points in the hard magnetic layer, and the second sub-underlayer has a greater magnetic moment and is further away from the hard magnetic layer than the first sub-underlayer.