Superparamagnetic and ferromagnetic Ni nanorod arrays fabricated on Si substrates using electroless deposition.
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.
Liu
Chien-Min
CM
Department of Materials Science and Engineering, National Chiao Tung University, Hsin-chu, 30010, Taiwan, Republic of China.
Tseng
Yuan-Chieh
YC
Chen
Chih
C
Hsu
Ming-Chieh
MC
Chao
Tzu-Yzan
TY
Cheng
Yu-Ting
YT
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*
D009532:Nickel; D012825:Silicon