Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 40: Magnetism in Thin Films: Interaction Phenomena and Heterostructures

DS 40.4: Invited Talk

Friday, February 29, 2008, 13:15–13:45, H 2032

Ion Beam Induced Magnetic Nanostructures — •Peter Varga — Inst.f.Allgemeine Physik, TU Wien, Austria

For iron films with 5 to 10 layers epitaxially grown on Cu(100) stabilization of the face-centered cubic (fcc) γ-phase (which is non magnetic,) can be obtained above room temperature. This is in contrast to bulk iron for which the fcc phase is stable only above 1184 K, whereas below this temperature the body-centered cubic (bcc) α-phase (which is ferromagnetic) is thermodynamically stable. Films with more than 10 layers will exhibit a spontaneous structural transition to the bcc structure with in palne magnetization whereas below 5 layers a strained bcc structure shows an out of plane magnetic moment at room temperature[1]. We have shown by STM (Scanning tunneling microscopy) with atomic resolution and LEED (Low Energy Electron Diffraction) that this 5-10 ML thick fcc Fe films undergo a transition from fcc to bcc by ion beam irradiation. Since iron is ferromagnetic only if it is bcc or at least strained bcc but never if it is fcc[1] this gives the possibility to transform a nonmagnetic film into a ferromagnetic one directly by ion bombardment and especially to form magnetic nanostructures with a size determined by the diameter of the used ion beam only [2].

[1] A. Biedermann et al. Phys. Rev. Lett. 86 (2001), pp. 464*467 and 87 (2001) 86103 [2] W.Rupp, B.Kamenik, R.Ritter, A.Biedermann, Ch.Klein, E.Platzgummer, M.Schmid, and P.Varga, to be published