Single-pole/TMR heads for 140-gb/in2 perpendicular recording

Single-pole writers and tunneling magnetoresistive (TMR) readers for 140-Gb/in² perpendicular recording were fabricated and their recording performance was tested. Data erasure, which is observed as write instability in a repeated read-write operation, can be suppressed by combining a laminated pole and low throat height. Fe-Co/Ni-Cr laminated film was used to reduce the remanent magnetization of the main pole after patterning. Narrow track writers with a 120-nm-wide trapezoidal pole showed a good write ability of 30 dB or more in overwrite for media with high coercivity of up to 7 kOe. Also, negligibly small skew writing was confirmed. TMR heads with a sensor width of 85 nm and a head resistance of 250 Ω showed approximately 30 dB of head signal-to-noise ratio (SNR). A potentially higher SNR with a higher operating voltage was suggested from a measured output versus sensing current curve. Calculations showed that the side reading was suppressed in a side-shielded design. A 10% amplitude width of the microtrack profile of a 100-nm-wide reader was reduced from 198 to 162 nm by applying the side shields.