Ferromagnetic antidot arrays with complex geometries

Author / Creator

MMM 2020 (2020)

Conferences

MMM 2020 B1: Artificial Spin Ice (2020)

Available as

Online

Summary

The magnetic behaviour of ferromagnetic antidot thin films can be tuned by engineering their geometry, such as the hole diameter, inter-hole distance and film thickness [1,2]. Although antidot patt...

The magnetic behaviour of ferromagnetic antidot thin films can be tuned by engineering their geometry, such as the hole diameter, inter-hole distance and film thickness [1,2]. Although antidot patterned nanostructures are grown by template-assisted methods mostly using lithographical techniques [1,2], the use of anodic alumina templates has also been checked successfully [3]. However, this latter alternative shows some challenging aspects for the patterning of large areas with sufficiently high ordering and/or complex antidot geometries. These limitations are partly overcome by performing a mechanical nanoimprinting process before a single anodization process [4-6]. This work introduces an easy and less-expensive route to synthesize highly ordered nanoporous alumina templates in large areas and subsequently magnetic antidot arrays with different and complex geometries. The procedure is based on large-scale nanoimprint using patterned commercial disks as a 1-D grating stamp (e.g., CD, DVD and BR disks) followed by single anodization process which allows obtaining 1-D anodic alumina templates (Figure 1a). In addition, complex 2-D patterned nanoporous alumina templates, with square or triangular ordering (Figures 1b and c), were generated using the 1-D grating stamp by multiple imprinting steps at different angles. Afterwards, Co antidot thin films were sputtered onto these templates with different thickness (from 20 to 100 nm) and symmetries. Magnetic studies confirm the presence of in-plane anisotropy with easy axis parallel to the nanostripes in Co antidot films, while a modest in-plane bi-axial magnetic anisotropy with perpendicular magnetization easy axes is concluded in Co squared nanodot arrays. In summary, a non-expensive methodology, combining soft-imprint and single anodization, is introduced for massive mould production and complex pattern generation, avoiding standard lithographical techniques. The magnetic response of the final sputtered antidot films can be engineered by the appropriate nanoimprinted processes.References: 1. R. P. Cowburn, A. O. Adeyeye, and J. A. C. Bland, Appl. Phys. Lett. 70, 2309 (1997). 2. N. G. Deshpande, M. S. Seo, X. R. Jin, S. J. Lee, Y. P. Lee, J. Y. Rhee and K. W. Kim, Appl. Phys. Lett. 96, 122503 (2010). 3. K. J. Merazzo, C. Castán-Guerrero, J. Herrero-Albillos, F. Kronast, F. Bartolomé, J. Sesé, R.P. Del Real, L. M. García and M. Vázquez, Phys. Rev. B. 85, 184427 (2012). 4. W. Lee, R. Ji, C. A. Ross, U. Gosele and K. Nielsch, Small, 2, 978 (2006). 5. J. Choi, R.B. Wehrspohn, and A. Gösele, Adv. Mater., 15, 1531 (2003). 6. J. Um, M. R. Z. Kouhpanji, S. Liu, Z. N. Porshokouh, S.-Y. Sung, J. Kosel and B. Stadler, IEEE Trans. Magn. 56, 6701006 (2020).

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