Intra-grain perpendicular percolated L1₁ CoPt thin films

Ultrathin percolated high-K_u magnetic films with thicknesses of 2 nm are realized simply by using sputter deposition and post annealing. L1₁ CoPt:MgO, with K_u on the order of 10⁷ erg cm⁻³, was deposited on a MgO(111) substrate at 350 °C, followed by post annealing to induce complete segregation of the added MgO dopants. The optimized film shows significant enhancement of the out-of-plane coercivity, approximately an order of magnitude greater than that of the CoPt binary film, a remanence ratio close to unity, considerably reduced in-plane magnetization, sharp perpendicular magnetic reversal, and reduced surface roughness in the range of a few angstroms. Microstructure results indicate that MgO precipitates into grains within the interconnected L1₁ grains after appropriate post annealing. The MgO grains, with sizes in the range 2–7 nm, form coherent interfaces to the CoPt matrix and penetrate through the whole depth of the film. The development of ideal non-magnetic domain wall pinning sites explains the optimization of the perpendicular magnetic properties. The advantages of a simple fabrication process, a thin film layer structure, and remarkable enhancement of the magnetic characteristics demanded by ultrahigh-density recording reveal its potential for practical applications. (paper)