CPP–GMR Heads With a Current Screen Layer for 300 ${\hbox{Gb/in}}^{2}$ Recording

Current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) heads with a current screen layer were fabricated, and the recording performance was measured. An output voltage of 1.9 mV and head-amp signal-to-noise ratio (SNR) of about 30 dB were obtained from a 50-nm-wide head with an operating voltage of 120 mV. The MR ratio was 4%–5%, shield gap was 36 nm and resistance was 72 $\Omega$. With using the thermal fly-height control (TFC), the fabricated head showed a potential to yield a 382 ${\hbox{Gb/in}}^{2}$ recording (1252 kBPI $\times$ 305 kTPI). The current screen structure reduced the spin torque noise since just a low sensing current of 1–2 mA was required for obtaining a high output. Newly developed CPP–GMR films with a current screen layer showed the MR ratio of 18%–19% with the RA product of 0.2–0.3 $\Omega\cdot\mu{\hbox{m}}^{2}$. Calculation showed that this film allows us to achieve 30 dB or more in the head-amp SNR when the sensor width was 40 nm or larger. The current screen CPP–GMR head is thus an attractive candidate that has a high potential suitable for an areal density of 500 ${\hbox{Gb/in}}^{2}$ or more. Below 40 nm, an all metal CPP–GMR head with the MR ratio of 10% or more would be the best candidate.