Prof. Dr. Olav Hellwig
Research Group Head
Tel.: (0351) 260 - 2461

Ion irradiation of antiferromagnetically (AF) coupled perpendicular anisotropy multilayer systems

Ion irradiation of antiferromagnetically (AF) coupled perpendicular anisotropy multilayer systems may be able to locally alter the balance between demagnetization and exchange energies, thus providing a tool to locally define new remanent phases for creating tailored laterally heterogeneous infrastructures for data processing.



Figure 4: (10 mm)2 MFM images summarizing the various types of domain structures as observed in perpendicular AF-coupled Co/Pt/Ru multilayers after in-plane demagnetization along the horizontal axis. (a) two-dimensional AF domains with sharp domain walls. (b) two-dimensional AF domains with domain walls consisting of a one-dimensional FM stripe domain phase. (c) mixed phase of two-dimensional AF domains and FM stripe domains. (d) FM stripe domains aligned along the in-plane demagnetization direction. 


We want to explore and optimize such ion irradiation processes for systems based on Co/Pt and Co/Pd perpendicular anisotropy multilayers that are antiferromagnetically coupled via Ru or Ir interlayers that reveal naturally a phase transition from large antiferromagnetic antiphase domains to relatively small (order of 100 nm)  ferromagnetic stripe domains as shown in the images [1-3]. The antiferromagnetic structure being fully magnetically compensated in vertical direction with no stray fields penetrating through the surface is complemented by ferromagnetic stripe domains that create large stray fields above the surface and thus are able to interact with neighboring layers via their demagnetization fields even if direct magnetic exchange is not present. Using ion irradiation it may be possible to write ferromagnetic structures (irradiated regions) into an antiferromagnetic background (non-irradiated region) and thus create an infrastructure information processing in adjacent magnetic layers [4-6]. We want to explore the potential of such ion irradiated heterogeneous infrastructures interacting with other magnetic thin film systems via direct exchange as well as via indirect dipolar interactions.



[1] O. Hellwig, T. L. Kirk, J. B. Kortright, A. Berger, and E. E. Fullerton, Nature Materials 2 (2003) 112.

[2] O. Hellwig, A. Berger and E. E. Fullerton, Phys. Rev. Lett. 91 (2003) 197203

[3] O. Hellwig, J. B. Kortright, A. Berger and E. E. Fullerton, J. Magn. Magn. Mater. 319 (2007) 13.

[4] C. Chappert et al., Science 280, 1919 (1998).

[5] A. Mougin, T. Mewes, M. Jung, D. Engel, A. Ehresmann, H. Schmoranzer, J. Fassbender, and B. Hillebrands, Phys. Rev. B 63, 060409 (2001).

[6] Arno Ehresmann, Olav Hellwig, Oliver Buhl, Nicolas David Müglich, Tanja Weis, and Dieter Engel, J. Appl. Phys. 112 (2012) 063901.


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