Spin-valve head with specularly reflective oxide layers for over 100 Gb/in2

We have developed spin valves with thin oxide reflective layers, which exhibit a greatly improved magnetoresistance (MR) performance while keeping other good properties, such as an exchange bias field of over 1000 Oe and a coercivity and an interlayer coupling field of less than 10 Oe. The giant magnetoresistance (GMR) values reached over 12% for the spin valve with a single specular layer and over 15% for the spin valve with double specular layers. The oxide reflective layers helped improve MR performance due to enhanced specularity at the oxide interfaces. Evidence of enhanced specularity was provided by the observed reduced sheet resistance and oscillatory interlayer exchange coupling between the free layer and the spacer in the spin valve. The observation of the oscillation was possible due to amplified Ruderman-Kittel-Kasuya-Yoshida (RKKY) coupling, as seen in a multilayered superlattice composed of ferromagnetic layers with nonmagnetic spacers. We successfully fabricated read heads by incorporating such spin valves. In particular, very narrow read track width was achieved in the head with double reflective layers. The read track width was estimated to be less than 0.14 μm. The head was tested on a low noise CoCrPt-based alloy disk with a coercivity of 3170 Oe and an areal moment of 0.36 memu/cm². The head showed a normalized output of 8.6 mV/μm with an asymmetry of 0.5% at 2 mA sense current, a ∼40% increase over that of the head with a single reflective layer that was used in the demonstration of 56.1 Gb/in². We have therefore demonstrated that our head with the specular layers can be used for an areal density of over 100 Gb/in² in magnetic recording with the help of advanced media and integration techniques.