Dependence of magnetization process on thickness of Permalloy antidot arrays

Nanohole films or antidot arrays of Permalloy have been prepared by the sputtering of Ni80Fe20 onto anodic alumina membrane templates. The film thickness varies from 5 to 47 nm and the antidot diameters go from 42 to 61 nm, for a hexagonal lattice parameter of 105 nm. For the thinner antidot films (5 and 10 nm thick), magnetic moments locally distribute in a complex manner to reduce the magnetostatic energy, and their mostly reversible magnetization process is ascribed to spin rotations. In the case of the thicker (20 and 47 nm) antidot films, pseudodomain walls appear and the magnetization process is mostly irreversible where hysteresis denotes the effect of nanoholes pinning to wall motion. (C) 2011 American Institute of Physics. [doi:10.1063/1.3544483]