Micromagnetics of spin valve tape heads

Abstract

A micromagnetic model was applied to study the response of large aspect ratio spin valve heads to tape fields. The contribution of a ferrimagnetic TbCo exchange layer is analyzed. The shielded head response to tape fields is then determined by first calculating the average device permeability from a micromagnetic analysis. This permeability is included in a transmission line model to estimate flux decay. The transfer curve for the shielded device (read half-gap g=0.1 μm, head-tape spacing d=0.075 μm) is calculated for an isolated arctangent transition in low remanence Barium Ferrite (BF) tape media. Linear response occurs for |〈cos(θPINN−θFREE)〉|⩽0.4. For a dibit pulse written on the BF tape with a transition length of 0.09 μm, bit length of 2.56 and 0.256 μm, an average PW50 of 0.42 and 0.29 μm is calculated. Pulse asymmetry is −6.6% and −7.1%, respectively. The rolloff for square wave recording indicates a D50 of 96 kfci, with no significant head saturation at low linear densities. For a 1 mA sense current, a zero to peak voltage output of 80 μV/μm trackwidth is predicted. A similar analysis is done for a sinusoidal signal recorded on thick metal particle tape media. Partial head saturation is observed at intermediate linear densities, leading to a second harmonic distortion of −19.9 dB at 30 kfci.