Eizo Fukami

Low-resistance tunnel magnetoresistive head

A tunnel magnetoresistive (TMR) head with a low resistance of about 30 /spl Omega/ and effective track width of 1.4 /spl mu/m was fabricated using an in situ natural oxidation (ISNO) technique. Its read-output was almost the same as that expected from test elements at the wafer level. We found no large difference in noise voltages between TMR head and GMR head when their resistance was about 30 /spl Omega/. A very low-resistivity TMR element with a resistance-area product of 14 /spl Omega//spl middot//spl mu/m/sup 2/ and a fairly high /spl Delta/R/R of 14% was also developed using ISNO. A signal-to-noise ratio consideration suggests that such low resistance is a key to TMR heads for high recording densities.

Read performance of tunneling magnetoresistive heads

We discuss the read performance, including the off-track performance and noise characteristics, of TMR heads. A vortex-like sense current field in TMR heads creates insensitive zones in the free layer and affects the output voltage and effective read width. The 1/f noise in the MHz-order frequency range was observed. To achieve a low-noise TMR head for high-density recording with small junction area, a high-quality thin barrier is a key to obtaining low 1/f noise, as well as small R/spl middot/A products to reduce the shot noise.