Magnetic nanopatterning of CoPt thin layers

Ionic irradiation is used to magnetically pattern CoPt alloy films, using an appropriate mask to protect arrays of CoPt dots with a 1 μm2 size, while the remainder of the film is exposed to ionic irradiation. Before irradiation, we obtain a layer with the Ll0 tetragonal structure, ordered and with a strong perpendicular magnetic anisotropy energy in the growth direction. After irradiation, the unprotected regions become disordered and magnetically soft, whereas the protected regions remain magnetically hard. Spatially selective irradiation thus provides a spatial distribution of magnetic anisotropy and hence of the magnetization direction, perpendicular to plane in the ordered zones and in-plane in the disordered zones. The interest of ionic irradiation is that the film recovers its initial roughness after elimination of the mask which is promising for the data storage applications.