Unshielded perpendicular recording head for 1 Tb/in2

A full three-dimensional (3-D) self-consistent micromagnetic code has been employed to design an unshielded perpendicular writer for an areal density of 1 Tb/in². The head consists of a probe-type tip protruding from a collar. The tip has saturation magnetization (M_S) of 24 kG while the collar has lower M_S. The magnitude and orientation of anisotropy field (H_k) in the tip is varied to obtain the best recording performance. The combination of high anisotropy write tip with low M_s collar is shown to produce effective write fields in excess of 19 kOe and less than 20% track erasure for 10⁷ passes. Introduction of in-plane anisotropy within the pole tip reduces head remanence sufficiently that on-track erasure exceeds a benchmark of 10⁸ passes. The damping constant in Landau-Lifshitz-Gilbert equation has been varied to improve the frequency response. With damping constant equal to 1.0, simulations show that the head is capable of switching in approximately 0.15 ns.