Transition curvature analysis

On-track recording losses associated with transition curvature in a merged magnetoresistive-read/inductive-write recording system were investigated. Variations in write head design resulted in a wide variation of reproduced pulse width. Magnetic force microscope (MFM) observation of written tracks revealed that transition curvature was related to the pulse width variation. The effect of transition curvature is modeled as a separable loss function by convolving a reader cross-track sensitivity function with a cross-track phase delay profile. Curvature loss has a different spectral content than transition broadening, allowing us to separate the two effects by comparing discrete Fourier transforms of isolated pulses. Results of such an analysis agree satisfactorily with MFM measurements. Planarization of mid-shields had minimal impact on the pulse width, but a notched write head design mitigated the effect. Transition curvature must be taken into account during write head design and in decisions regarding relative read and write widths