A universal approach for template-directed assembly of ultrahigh density magnetic nanodot arrays.

L1(0) ordered alloys, such as FePt, CoPt and FePd alloys with high magnetocrystalline anisotropy, have attracted much attention due to their potential applications in ultrahigh density data storage. The assembly or organization of nanoparticle arrays is necessary for device application. A facile and general method to fabricate highly ordered ferromagnetic nanostructure arrays was demonstrated. It is found that simple oxygen plasma can make a hydrophilic polymer template, which would easily integrate with the widely used spin-coating process. With simple block copolymer lithography and spin-coating process, uniform ferromagnetic nanoparticle arrays can be easily fabricated over a large area. It is also significant that a very high coercivity up to 10 kOe was obtained in CoPt nanodot arrays. This method can find attractive applications in ultrahigh density storage media.