In this work, domain wall (DW) formation in patterned nanowires has been investigated with Magnetic Force Microscopy (MFM) measurement and Object Oriented MicroMagnetic Framework (OOMMF) simulations. There has been intensive research interest into the behaviour of individual DWs in patterned nanostructures for potential applications in memory storage, logic gates and sensors. For memory applications, DWs can be pinned in patterned notched nanowires, creating multiple domains and hence multiple memory states which could be read out either in shift registers or directly if an entire nanowire forms the free layer of an MRAM (Magnetoresistive Random-Access Memory). For logic applications, simple geometric designed planer magnetic wires that are less than a micrometer in width can be used to construct DW logic element architecture and they can be integrated together into one circuit. For sensor applications, biosensors in particular, DWs can be pinned in the free layer of GMR (Giant Magnetoresistance) or MTJ (Magnetic Tunnel Junction) arrays, by magnetic membrane coated nanotags, with different states when the nanotag is absent. In this study, zigzag-shaped nanowires and twin pinning sites in nanowire have been investigated for potential RM (Racetrack Memory) applications, and notched fork- shaped nanowires have been considered in order to perform AND/OR logic functions. Also, the shape effect of the nanotag and its interaction with the free layer of the biosensor have been simulated quantitatively and qualitatively. Polycrystalline Permalloy (NisoFe2o) has been the material choice for the investigations of patterned magnetic elements in this study, due to its very high magnetic permeability, low coercivity, negligible magnetocrystalline anisotropy, significant anisotropy magnetoresistance and small magnetostriction. Consequently the magnetization can be largely constrained by shape anisotropy so as to lie along the long axis of the wire with spins parallel to the surfaces and edges.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:583367 |
| Date | January 2012 |
| Creators | Ding, An |
| Publisher | University of York |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.0027 seconds