High-frequency inductance measurements and performance projections made for cusp-field single-pole heads

High-frequency measurements of the inductance of cusp-field single-pole heads for perpendicular recording are made out to 13.5 GHz to determine their performance. The inductance of the pole heads examined are typically 1.2-1.9 nH with a self resonance at about 7-10 GHz. Inductance versus current measurements allow construction of a nonlinear eddy-current damped, thin-film head model. Comparison is made to a longitudinal recording head of similar size and turns. The effect of the medium underlayer as part of the head return path is shown to have minimal effect on the head inductance. Contact Tri-Pad heads are used to demonstrate the changes produced by the underlayer and to demonstrate apex and yoke saturation. The contact behavior is similar to that for a longitudinal thin-film head. The frequency dependence of the pole material permeability is discussed. The conclusions provide a practical bit rate limit for the cusp-field head based on head and write channel modeling, experimental high-frequency inductance data, and spin reversal considerations.