The Respective Effects of the Free Layer Thickness and Width on the Downtrack and Crosstrack Responses of Read Heads

Miniaturization is very important in magnetic recording. Here, we have micromagnetically evaluated the respective effects of the free layer (FL) thickness and width on the downtrack and crosstrack responses for single spin valves (SSVs) and differential dual spin valves (DDSVs). Our micromagnetic results show that the linear resolution scales down with the free layer thickness for DDSVs, as is the case for SSVs found by the reciprocity theory. We have also found that the crosstrack resolution scales down with free layer width in both SSVs and DDSVs (correspondingly, the side reading increases, which needs to be mitigated). The corresponding scalings of the signal amplitudes with FL thickness and width in SSVs and DDSVs are also discussed in terms of the shape anisotropy of the free layers. Finally, we have found that side shields can provide bias fields for the free layers and, meanwhile, the improvement in track density and the reduction in side reading are not compromised; this bias point of view of side shields is an additional appreciation of the usual roles played by side shields.