The influence of porous alumina underlayer on structure and magnetization reverals of hybrid recording media

A self-ordered hexagonal array of nanopores has been fabricated by anodizing a thin film of A1 on glass and subsequently the magnetic properties of TbFeCo on this templates were studied. We carried out anodic oxidation of a sputtered Al film at the anodic voltage in the range of 10-30 V and temperature in the range of 5-40 degrees C, and found that the density of the nanohole arrays increased with the decrease in anodization voltage and temperature. On the other hand, hole diameter decreased with the decrease in anodic voltage and temperature. Then TbFeCo was deposited onto this porous array by sputtering with a thickness of around 90 nm and subsequently was overcoated with 10 nm SiN for the protection from surface oxidation. The TbFeCo deposited on this porous layer shows complete perpendicular anisotropy and the AAO template can promot the growth of the microcolumnar structure in TbFeCo films. The coercivity increased with the decrease of hole diameter. The coercivity of the TbFeCo deposited on the porous array with a mean hole diameter of around 15 nm is 5.6 kOe and larger than that on bare glass, but the squareness ratio gets poorer than that on bare glass. Experience and simulation indicate that the magnetization reversal mode follows the Stoner-Wohlfarth