title: Superparamagnetic and ferromagnetic Ni nanorod arrays fabricated on Si substrates using electroless deposition.
abstract: The microstructures and magnetic properties of nickel nanorods fabricated using an anodic alumina oxide template and electroless deposition were investigated. The as-deposited nanorods were found to contain nanocrystalline grains with an average size of approximately 2-3 nm. The temperature-dependent magnetic hysteresis curves indicated superparamagnetic behavior of the as-deposited rods as a result of the reduction of ferromagnetic crystallites. The superparamagnetic (SM) Ni nanorods transformed into ferromagnetic (FM) ones when annealed at 400 degrees C. Results from dark-field transmission electron microscopy reveal that the microstructure of the rods tends to form a laminar structure with grain growth parallel to the long axis of the rods, together with the enhancement of ferromagnetic ordering along the same direction. The results suggest that the SM-FM phase transition obtained is microstructure driven. The Ni nanorods manufactured by the electroless deposition also have the potential to serve as magnetic building blocks in nanoscale devices, such as high-frequency inductors. On-chip magnetic spiral inductors were fabricated using these nanorods, and it was demonstrated that the nanorods can enhance inductance up to 6 GHz.
authors.affiliation: Department of Materials Science and Engineering, National Chiao Tung University, Hsin-chu, 30010, Taiwan, Republic of China.
authors.forename: Chien-Min
authors.initials: CM
authors.lastname: Liu
authors.forename: Yuan-Chieh
authors.initials: YC
authors.lastname: Tseng
authors.forename: Chih
authors.initials: C
authors.lastname: Chen
authors.forename: Ming-Chieh
authors.initials: MC
authors.lastname: Hsu
authors.forename: Tzu-Yzan
authors.initials: TY
authors.lastname: Chao
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Cheng
mesh_terms: D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure*; D009532:Nickel / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*
chemical_list: D009532:Nickel; D012825:Silicon