Fabrication and characterisation of NiFe nanoparticles and nanowires.

• Main Author: Renuka Prasobhan.
• Other Authors: Lew Wen Siang
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Science
• Online Access: http://hdl.handle.net/10356/49055
• Institution: Nanyang Technological University

Nanoparticles are widely researched upon mainly for its capability and potentials in biomedical applications, such as cancer therapy and as contrast agents in Magnetic Resonance Imaging (MRI). Thus far, iron oxide nanoparticles are considered one of the most appropriate for these applications, due to its paramagnetic nature. But it hardly offers flexibility in manipulating its magnetic properties in order to serve its purposes. As such, disk- shaped nickel-iron (NiFe) nanoparticles were considered in this project. Its strong ferromagnetic nature, as well as its favourable magnetic behaviour under the influence of an external magnetic field, makes them an excellent tool for biomedical applications. A relatively novel method of fabrication was employed to fabricate size controllable nanodisks; which is electrodeposition, followed by selective etching. By monitoring the electrodeposition timings, the aspect ratios of these disks can be controlled. Object Oriented MicroMagnetic Framework (OOMMF) simulations were carried out to investigate closely how external magnetic field application influences these nanodisks of various thicknesses. It was found that under in-plane magnetic field, nanodisks of thickness 60nm were most suitable for heat-dependent medical applications like hyperthermia. On the other hand, out-of-plane magnetic field on 100nm thick nanodisks was found to have vortex chirality, meaning that the spin direction changes from top to bottom of the disk. This can be exploited for heating purposes, as continuous switching of field can generate heat within these disks. NiFe nanowires were also fabricated and characterised magnetically to understand demagnetizing behaviours. MFM image obtained shows clearly the vortex structure formation at both ends of the wire as a form of reducing its internal energy.