Study of Nanostructured Array of Antidots Using Pulsed Magnetic Fields

The absence of the superparamagnetic limit in nanostructured antidots makes them strong candidates for ultra-high density recording media. In this work, nanoporous alumina templates (NpATs), with average pore diameters ～35 nm and separation ～100 nm, were grown using a two-step anodization method. A Ni₈₀Fe₂₀ thin film of 6.5 nm was then sputtered on top of such NpATs, building an antidot network. A detailed study of the magnetoresistance (MR) (fields up to 25 T and temperatures down to 77 K) was performed. The antidot network sample revealed an anomalous MR and R(T) behaviour at T _M ～250 K arising from a spin-flip transition occurring in a thin iron oxide layer.