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Block-copolymers are known to generate nano-scale microdomains by microphase-separation, if they are annealed at a temperature lower than their order-disorder transition temperatures. We tried to transfer microdomains onto substrates by only using the reactive-ion etching method, which is widely used in semiconductor manufacturing processes. Block-copolymers consisting of an aromatic polymer and an acrylic polymer were used since there is a big difference in the dry-etch resistance, and nanometer-scale dot patterns can be easily obtained on the substrates. Regarding the application of this nano-patterning technique, we demonstrated the first circumferential magnetic patterned media for hard disk, which were prepared on a 2.5-inch diameter glass plate.

A near-field optical head with a beaked metallic plate was used for writing marks on a Co∕Pd bit-patterned medium with a diameter of 20–25nm and a pitch of 30nm. Magnetic-force-microscope images of the medium show that the magnetizations of single bits were selectively reversed by the head. The light-utilization efficiency (defined as the ratio of the absorbed power in the medium to the incident light power) was estimated from the writing condition used and thermal modeling as about 5%.

Etching the damage of a patterned media fabricated with an artificially assisted self-assembled mask is estimated. CoCrPt thin films were etched by ion milling into aligned dots with a diameter of 40 nm. The milling condition was optimized for reducing the etching damage. As a result, the damage to the crystal lattice and crystal orientation was estimated to be slight by transmission electron microscope (TEM) and scanning electron microscope (SEM) analyses. Though strong perpendicular anisotropy was induced by the patterning process, magnetic measurements and Landau-Lifshitz-Gilbert simulation revealed that the magnetic anisotropy energy was almost unchanged throughout this etching process.

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