3D FEM modeling of keeper effect on perpendicular recording

3D FEM modeling of the effects of a soft magnetic underlayer (keeper) on performance of single pole recording head was carried out. Dependence of strength and gradient of the write field on keeper permeability. thickness, saturation magnetization, and head-keeper spacing was studied. The keeper noticeably enhances the strength and gradient of the perpendicular component of the write field and suppresses the longitudinal one. The perpendicular component of the field rapidly increases with the keeper permeability in a range up to 100 and changes marginally at higher values. The write field is sensitive to the keeper thickness with nearly as exponential dependence. The thin keeper could be saturated easily. The saturation of the keeper results in degradation of the writer performance. To prevent the saturation the thickness of the keeper should be matched to sectional area of the main write pole at air bearing surface. The write field depends mostly on saturation flux density Bs of the pole material and marginally on the keeper B-SK Ni45Fe55 alloy as the pole material can generate the write field in the double-layer media up to 12 kOe. The effect of head-keeper spacing on the writer performance is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.