Anomalous in-plane coercivity behaviour in hexagonal arrangements of ferromagnetic antidot thin films.

An anomalous magnetic behaviour has been observed for transition metal (Fe, Co and Ni) based antidot nanostructures by modifying only the lattice geometry of the nanoholes array. A series of ferromagnetic, FM, antidot arrays have been fabricated by depositing them onto nanoporous alumina membranes with different pore diameters, d, varying in the range between 32 ± 2 and 93 ± 1 nm and maintaining fixed the inter-holes distance, D int = 103 ± 2 nm, and layer thickness, t = 20 nm, but reducing the edge-to-edge separation between adjacent antidots, (W = D int – d). A noticeable change of the in-plane coercivity dependence with W has been observed with an in-plane critical edge to edge distance, W C// , at which the in-plane coercivity behaviour with W is changed. In addition, for antidot samples with large W the in-plane hysteresis loops show single-step magnetic behaviour. Meanwhile, the INP hysteresis loops with W < W C// show multistep magnetic behaviour. The decreasing of the in-plane coercivity for FM-antidot samples with W < W C// is correlated with the increase of the out-of-plane contribution to the magnetic anisotropy i.e. increase the out-of-plane coercivity with increasing the nanohole size of antidots. These findings point towards a new nanotechnological strategy of fabrication arrays of magnetic bits, i.e., basic elements for magneto-optic perpendicular recording patterned media, embedded into a continuous 2D structural system and spintronic devices. [ABSTRACT FROM AUTHOR]