Advanced Dual-Free-Layer CPP GMR Sensors for High-Density Magnetic Recording

Abstract

All-metal current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) read sensors with a shield-to-shield spacing (S2S) of 16–21 nm and a narrow track width of down to 25 nm were fabricated using ferromagnetic CoFeMnSi Heusler-alloy-based spin valves. Room temperature GMR ratios from these read sensors are obtained of up to 6% and 14–24% ( $\Delta \textrm {RA}= 7.1$ –12.0 $\text{m}\Omega \mu \text{m}^{2}$ ) at $\mathrm {S2S} = 16$ and 21 nm, respectively. Studies and results of electron transport and CPP GMR support the sustainability and scalability of the CPP GMR process for Tb/in2 the areal density of magnetic recording. A universal parameter defined as magnetic resistivity for a sensor device, $\Delta \textrm {RA}/\mathrm {S2S}$ in ohm micrometers, is proposed to gauge the practically and rationally applicable CPP GMR for the read sensor process. The investigation of the CPP GMR operation range and micromagnetic simulation demonstrates the feasibility of the CPP GMR read sensors at $\mathrm {S2S} = 21$ nm for sustaining 1.0 Tb/in2 and of those at $\mathrm {S2S}= 16$ nm for marginally supporting 2.0 Tb/in2 the areal density of magnetic recording, The future path to and potential of the technology for ever increasing areal density beyond 2.0 Tb/in2 are addressed with emphasis on the importance of further enhancing the CPP GMR for process margin improvement.