Regensburg 2004 – scientific programme

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MA: Magnetismus

MA 16: Magn. Kopplungsph
änomene

MA 16.5: Talk

Wednesday, March 10, 2004, 16:15–16:30, H22

Reduction of Néel "orange peel"coupling in magnetic tunnel junctions due to interface smoothing using low energy ion beams — •P.A. Beck, B.F.P. Roos, S.O. Demokritov und B. Hillebrands — Fachbereich Physik und Forschungsschwerpunkt MINAS, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 56, 67663 Kaiserslautern

The most decisive and sensitive characteristic of magnetic tunnel junctions (MTJ), which are used in magnetic sensors and memory, is a small and reproducible switching field. Due to the magnetic dipole coupling (Neel "orange peel"coupling) between the free and the pinned magnetic layers this field is strongly affected by the morphology of the interfaces in MTJ.

In this work we have used normal incident argon ions with their energy of 20−90eV to smooth the interfaces of MTJs. First, to study the influence of the ion bombardment a single layer 15nm Ni₈₀Fe₂₀ /SiO₂/Si, identical to a free magnetic layer of a typical MTJ has been used. We have studied the influence of the ion energy on the smoothing and have determined the optimum conditions for this process. The morphology of the layer surface has been imaged using an in-situ scanning tunneling microscope (STM). The obtained images document the reduction of the roughness of over 40% after the bombardment. Second, MTJs were prepared based on the smoothed layers, and their remagnetization curves have been recorded. In agreement with the STM results, the "orange peel"coupling determined from the curves is significantly reduced due to bombardment.