Regensburg 2004 – scientific programme

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M: Metallphysik

M 24: Nanoskalige Materialien III

M 24.3: Talk

Thursday, March 11, 2004, 10:45–11:00, H16

Thermal reaction and stability of GMR Cu/NiFe thin films — •Constantin Buzau Ene¹, Guido Schmitz², and Reiner Kirchheim¹ — ¹Tammann-Str. 1, D-37077 Göttingen — ²Wilhelm-Klemm-Str. 10, D-48149 Münster

In recent years reading heads based on the giant magnetoresistance effect (GMR) made possible a dramatic increase in magnetic recording density. However, for many potential applications the thermal stability of the magnetic multilayers are an important issue. In our study Cu/Ni₇₉Fe₂₁ (permalloy) multilayer stacks were deposited onto needle-shaped W tips by ion beam sputtering and analyzed by atom probe tomography after appropriate heat treatments. This analysis technique has been proven to yield a real three-dimensional quantitative chemical and structural analysis at a subnanometer scale.

After annealing at 250^∘C for 30min, no significant structural or chemical transformation of the initial layer system is detected, although such a heat treatment reduces the magnetoresistivity already appreciably. Clear grain boundary wetting is observed after annealing at 400^∘C for 30min. Further annealing at 500^∘C for 20min and 40min still preserves the layered structure with a homogeneous solution of Ni inside the Cu layers of up to 25 at.% Ni.