[1] Univ Florida, Dept Mat Sci & Engn, Gainesville, FL 32611 USA
[2] Seagate Technol, Recording Head Operat, Bloomington, MN 55435 USA
[3] City Univ Hong Kong, Dept Phys & Mat Sci, Hong Kong, Hong Kong, Peoples R China
[4] Georgia Inst Technol, Dept Chem & Biochem, Atlanta, GA 30332 USA
[5] Georgia Inst Technol, Dept Mat Sci & Engn, Atlanta, GA 30332 USA