Berlin 2005 – wissenschaftliches Programm
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M: Metallphysik
M 37: Symposium Tomographic Methods in Materials Research
M 37.2: Vortrag
Dienstag, 8. März 2005, 11:20–11:40, TU H1058
Stability and Thermal Reaction of GMR NiFe/Cu Thin Films — •Constantin Buzau Ene1, Guido Schmitz2, and Reiner Kirchheim1 — 1Institut für Materialphysik, Friedrich-Hund-Platz 1, D-37077 Göttingen — 2Institut für Materialphysik, Wilhelm-Klemm-Str. 10, D-48149 Münster
Giant magneto-resistance (GMR) model systems of NiFe/Cu multilayer stacks with 2 nm single layer thickness were deposited onto needle-shaped W tips using ion beam sputtering and analyzed by atom probe tomography (TAP) after appropriate heat treatments.
Owing to the outstanding sensitivity of the method, even minor chemical modifications on the nanometer scale can be detected. Although annealing treatments at temperatures up to 250∘C result already in a dramatic decrease of magneto-resistivity, no major structural or chemical transformation of the initial layer system is found. Instead, a slight decrease of the concentration slope at the interfaces is observed, which is attributed to short range interdiffusion induced by non-equilibrium point defects. Annealing at higher temperatures up to 500∘C/40 min still preserves a clear layer structure. However, appreciable amounts of Ni are dissolved inside the Cu layers. In presence of grain boundaries, the onset of significant grain boundary diffusion is at about 350∘C.
According to the nanoanalysis, the low temperature breakdown of the magneto-resistivity in NiFe/Cu systems is related to the short range interdiffusion of Ni in Cu on a mixing width of about 1nm, which happens homogeneously along the interfaces without destroying the clear layer structure.