Magnetic Co nanodots embedded in the porous anodic alumina films(AAFs)on silicon substrate can be used as the magnetic recording material with high area recording density.For this purpose,pure aluminum films were deposited on Si substrate with the Electron Cyclotron Resonance(ECR)plasma sputtering technique,and AAFs with vertical nano holes were synthesized with the two-step anodization process in oxalic acid.Finally magnetic material Co was deposited into the nano holes with electrochemical method.The results showed that polycrystalline ECR-Al films are homogenous and fit for the synthesis of AAFs with uniform distributed nano holes when ion sheath formed in front of the substrate surface.The diameters of AAF nano holes were in the range from 30 to 70 nm,and the hole pitches were approximately 100 nm,the AAF on silicon substrate was about 100 nm thick after two-step anodization.Magnetic Co nanodots filled into the nano holes of AAF exhibited both fcc and hcp structures. Magnetic Co nanodots embedded in the porous anodic alumina films (AAFs) on silicon substrate can be used as the magnetic recording material with high area recording density. For this purpose, pure aluminum films were deposited on Si substrate with the Electron Cyclotron Resonance (ECR) plasma sputtering technique, and AAFs with vertical nano-holes were synthesized with the two-step anodization process in oxalic acid. Finally magnetic material Co was deposited into the nano holes with electrochemical method. The results showed that polycrystalline ECR-Al films are homogenous and fit for the synthesis of AAFs with uniform distributed nano holes when ion sheath formed in front of the substrate surface. these diameters of AAF nano holes were in the range from 30 to 70 nm, and the hole pitches were approximately 100 nm, the AAF on silicon substrate was about 100 nm thick after two-step anodization. Magnetic Co nanodots filled into the nano holes of AAF exhibited both fcc and hcp structures.