Performance comparison of unshielded and shielded MR read heads for digital tape recording

The authors report data comparing a shielded magnetoresistive head (SMR) optimized for metal particle tape readback to an unshielded head (UMR) with an identical element. They identify the signal-to-noise ratio penalty for eliminating the shields as a function of tape velocity and data density. They report on the degree of nonlinear distortion for UMR and SMR heads with and without write equalization. From these experiments the performance of an element optimized specifically for the absence of the shields is predicted. An unshielded sensor can be a satisfactory replacement for an SMR sensor at linear densities up to 2500 fr/mm, provided it is redeveloped for optimum signal amplitude and linearity