Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

The use of focussed beams of ions to induce strong saturation magnetization (Ms) can lead to unprecedented flexibility in rapidly producing modulated magnetic materials of desired geometry. True flexibility is achieved if the process is non-destructive i.e., Ms is activated at the point of ion impact. Furthermore, the ion is ideally chemically inert and of low mass, such that it escapes the lattice after undergoing the collision process with host atoms and coming to rest. Here we describe the possibility of using a nano-focussed beam of Ne+ ions to generate ferromagnetic phases within initially non-ferromagnetic B2 materials such as Fe60Al40 and Fe50Rh50. The transition occurs as the penetrating ions displace atoms, and the subsequent vacancy creation and recombination leading to the formation of the chemically disordered A2 structure, which is ferromagnetic. The beam has a diameter of ≈ 2 nm and the transformed region is confined to the interaction volume of the ions with the host atoms, with a diameter < 50 nm. Such an ion-beam is readily available in a He+-ion microscope (where Ne+ can also be loaded). The locally formed ferromagnetic nanostructures are embedded within the electrically conducting B2 precursor material. In the case of Fe60Al40 ferromagnetic regions of Ms = 780 kAm-1 [1] are embedded within a non-ferromagnetic matrix. For Fe50Rh50, ferromagnetic regions of Ms = 1000 kAm-1 [2] can be embedded within an antiferromagnetic matrix. The ion-induced B2 → A2 phase transition is the most viable route to achieving well-defined ferromagnetic nanostructures of desired geometry within non-ferromagnetic metallic matrices. We describe our recent direct nanoscale imaging of ion-induced magnetic regions [3] and our attempts to demonstrate possible applications in spin-transport and magnonic devices.
References:
[1] R. Bali, S. Wintz, F. Meutzner, R. Hübner, R Boucher, A. A. Ünal, S Valencia, A. Neudert, K. Potzger,
J. Bauch, F. Kronast, S. Facsko, J. Lindner, and J. Fassbender, Nano Letters 14, 2, 435 (2014).
[2] Alireza Heidarian, Rantej Bali, Jörg Grenzer, Richard A. Wilhelm, Rene Heller, Oguz Yildirim, Jürgen Lindner and
Kay Potzger, Nucl. Instrum. Methods Phys. Res. B 358, 251-254 (2015).
[3] Falk Röder, Gregor Hlawacek, Sebastian Wintz, René Hübner, Lothar Bischoff, Hannes Lichte, Kay Potzger,
Jürgen Lindner, Jürgen Fassbender, and Rantej Bali, under review, Scientific Reports (2015).