Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 6: Magnetic Thin Films I (Heusler Alloys)

MA 6.2: Hauptvortrag

Montag, 22. März 2010, 14:30–15:00, H10

Heusler alloy based magnetic read heads — •Stefan Maat — Hitachi, 5601 Great Oaks Parkway, San Jose, CA 95119 (USA)

All-metal current perpendicular-to-the-plane giant magneto-resistive sensors are an attractive follow-on reader technology to tunnel-magneto-resistance sensors as magnetic recording densities continue to increase. With low resistance-area products in the range 0.05 Ohm*um2, CPP-GMR sensors exhibit low impedance and therefore low noise even at sensor dimensions below 30 nm. Although the magneto-resistance (dR/R) of CPP-GMR sensors increases with thicker magnetic layers due to spin-diffusion length effects their thickness is limited by the desired shield-to-shield spacing determining the maximum linear recording density. Among the challenges that CPP-GMR sensors face are low dR/R for thin magnetic layers as well as current-induced noise and magnetic instability from spin-torque effects, which arise from the interaction of spin-polarized electron current with the magnetization of the electrodes. Highly spin-polarized Heusler based alloys are promising candidates to achieve high dR/R. However, these alloys are challenging to synthesize with full order in a thin film form within the low growth and annealing temperature limitations. Although film-level dR/R of ~ 8 % has been obtained in spin-valves with CoFeGe and Co2MnGe electrodes (compared to 2% with CoFe), these alloys give rise to a high level of spin-torque excitation due to their high spin-polarization and low magnetic damping resulting in sensor noise. Thus, new multilayer structures to suppress excessive spin-torque excitations need to be implemented.