A large-area mesoporous array of magnetic nanostructure with perpendicular anisotropy integrated on Si wafers

Large-area, over several square centimeters, mesoporous array of magnetic nanostructure with perpendicular anisotropy is prepared by depositing Co/Pt multilayers (MLs) on a mesopore array of anodized alumina (AAO) fabricated on Si wafers. The MLs are mainly deposited on the top of AAO walls and perimeters of the pores; very small amounts of magnetic material reach the bottom due to the high aspect ratio of AAO. Consequently, ordered pores are present in the magnetic MLs. The mean pore diameter of the fabricated mesoporous array is 8.83 nm with a standard deviation of 3.16 nm and density of about 2.1 × 10(11) cm(-2). The Co/Pt MLs deposited on AAO and Si both exhibit strong perpendicular magnetic anisotropy, but the perpendicular coercivity (H(c)) increases by 15 times on AAO compared to that on Si. On the other hand, the magnetic cluster size decreases from 1000 nm (on Si) to 100 nm due to the presence of high-density pores. The dramatic increase in H(c) and the decrease in magnetic cluster size suggest that the pores behave as effective pinning sites. The magnetization-switching characteristics of the fabricated porous structure are different from those of the continuous films or Stoner-Wohlfarth-type (S-W) particles. One of the potential applications of this mesoporous structure may be in the field of high-density magnetic data storage.