Berlin 2015 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 19: Ion and electron beam induced processes

DS 19.2: Hauptvortrag

Mittwoch, 18. März 2015, 10:00–10:30, H 2032

Writing magnetic patterns using ion-beams — •Rantej Bali — Helmholtz-Zentrum Dresden-Rossendorf e.V, Bautzner Landstraße 400, 01328 Dresden.

In certain binary alloys, a large increase of the saturation magnetization can be triggered by subtle chemical disordering [1]. This phenomenon is linked to an increase in the number of nearest-neighbor magnetic atoms and local variations in the electronic band-structure due to the existence of disorder sites. An approach to induce disorder is to irradiate a chemically ordered precursor with energetic noble-gas ions; collision cascades formed by the ions knock atoms from their ordered sites and the concomitant vacancies are filled randomly via thermal diffusion of atoms. The ordered structure thereby undergoes a transition into a metastable solid solution. We consider the case of Fe₆₀Al₄₀ where the chemically ordered (B2) structure is paramagnetic; and the chemically disordered (A2) structure is ferromagnetic [2]. Such phase transitions can be deployed to pattern localized ferromagnetic regions, for instance, by irradiation through lithographed masks, or by direct writing using an ion-beam stylus. We demonstrate experimentally, the patterning of highly-resolved magnetic nanostructures embedded within topographically flat thin films. Materials in which the magnetic behavior can be tuned via ion-induced phase transitions may allow the fabrication of novel spin-transport and memory devices, such as lateral spin-valves, using existing patterning tools. [1] R. Bali et al., Nano Lett. 14, 435 (2014). [2] J. Fassbender et al., Phys. Rev. B 77, 174430 (2008).