Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 33: Poster II

MA 33.16: Poster

Friday, March 26, 2010, 11:00–14:00, Poster B1

Evolution of magnetoresistance in electromigrated ferromagnetic break junctions — •Arndt von Bieren¹, Ajit Kumar Patra¹, Stephen Krzyk¹, Jakoba Heidler¹, Jan Rhensius^1,2, Laura Heyderman², Regina Hoffmann³, and Mathias Kläui¹ — ¹Fachbereich Physik, Universität Konstanz, Germany — ²Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, Villingen, Switzerland — ³Physikalisches Institut, Universität Karlsruhe, Germany

Recently, magnetotransport measurements of magnetic nanocontacts have led to a better understanding of the interactions between spin-polarized charge carriers and magnetization taking place at extremely small length scales. Here, we present the evolution of magnetoresistance (MR) in clean electrical break junctions. Ferromagnetic nanocontacts with variable constriction width are fabricated by performing in-situ controlled electromigration of notched magnetic half ring structures in UHV. Low temperature MR measurements, in agreement with micromagnetic simulations, indicate that the dominant contribution in Py (Ni₈₀Fe₂₀) contacts down to the size of a few nm is anisotropic magnetoresistance (AMR). Moreover, Ni shows enhanced AMR in constrictions approaching the atomic limit and high tunnelling anisotropic magnetoresistance (TAMR) after carefully opening the contact, suggesting that material-specific parameters such as the electron mean free path play a crucial role. By analyzing the angle-dependent MR we can furthermore extract the domain wall pinning strength of the constriction as a function of its size down to the atomic scale.