ABSTRACT
Anodic Aluminum Oxide (AAO) produced with the two-step anodization process has recently attracted much attention for the fabrication of nanomaterials due to its highly ordered pore distribution. Chemical etching, employed between the two anodization steps to remove the disordered aluminum oxide layer formed in the first anodization step, has utmost importance for the morphological properties of AAO templates. The most common etching solution is a mixture of H3PO4 (6 wt%) and H2CrO4 (2 wt%) and the temperature of the process is usually between 45 and 80ºC.1 The interest of the scientific community on magnetic nanostructures experienced a continuous increase over the last years thanks to the high potential of these materials in many technological applications, as well as for the study of several fundamental properties.2,3 For antidot arrays, these holes function as domain wall pinning centers hindering the propagation of the domain walls in the film, and the size and distribution of the, holes greatly influence the coercive field of the film. The presence of the holes can also modify the local magnetic anisotropy of the continuous film to conform to the shape of the holes and symmetry of the arrays. As a result of the competition among the various magnetic energies, well-defined periodic magnetic domains were observed to nucleate in the proximity of the holes. The magnetic behavior of thin films can be tailored by introducing artificial defects.4-6 Patterned magnetic domain structures have revealed many useful
of H3PO4 (6 wt%) and CrO3 (2 wt%) until the AAO was totally etched and a shiny aluminum surface. Subsequently, the second anodizing treatment conditions are the same as the first anode, but at different times anodized for 8 hours. During the pore-widening process, the cell pore wall can be tailored and the pore diameter can be tuned without changing the pore density of the AAO template. Then, the AAO template was immersed into a 5 wt% phosphoric acid solution to widen the pores for 5, 10 and 15 min. The pore diameters are different and the anodized voltage increases with increasing pore distance. The Permalloy (Py) thin film with nanohole arrays is with hexagonal structure on the AAO substrate. Magnetic hysteresis loops were measured using a AGM (Micremag 2900), and characterization was performed by FESEM (JEOL JSM-7500F & Hitachi S4800-l).
