The Formation of High-Coercivity, Oriented, Nanophase Cobalt Precipitates in Al

Ion-implantation and thermal-processing methods have been used to form nanophase magnetic precipitates of metallic cobalt that are embedded in the near-surface region of single crystals of Al{sub 2}O{sub 3}. The Co precipitates are isolated, single-crystal particles that are crystallographically oriented with respect to the host Al{sub 2}O{sub 3} lattice. Embedded nanophase Co precipitates were formed by the implantation of Co+ at an energy of 140 keV and a dose of 8 x l0{sup 16} ions/cm{sup 2} followed by annealing in a reducing atmosphere. The implanted/annealed Co depth profile, particle size distributions and shapes, and the orientational relationship between the nanophase precipitates and the host crystal lattice were determined using RBS/channeling, transmission electron microscopy, and x-ray diffraction