This thesis concentrates on Magnetic Dissipation Force Microscopy---instrumentation, experiments and theory of the origin of magnetic dissipation. / A home-built vacuum magnetic force microscope (MFM) was debugged. The electronic noise in the system was reduced to below the thermal cantilever noise and the microscope now operates at its theoretical maximum (thermally limited) sensitivity. Then, a new technique, magnetic dissipation imaging, was developed. It allows the imaging of variations of 10-17 W in dissipation with sub-100 nm resolution. A normal MFM image and a magnetic dissipation image can be acquired simultaneously on the same area of a sample. / A theory was developed which correlates the dissipation with micromagnetic structures in domain walls. We consider the energy dissipation through coherent generation of phonons via magnetostriction induced by domain wall width oscillations. A quantitative agreement of theory with experiments for a 110 nm thick Co/Ni multi-layer and a 4 nm thick Co film samples was obtained. This theory predicts two new phenomena: a minimum drive force needed to cause wall width oscillations and wall width resonances. / With the above mentioned microscope, magnetic domain structure, micromagnetic domain wall structure and the associated dissipation have been studied on several samples, including a 30 nm thick Ni80Fe20 patterned into 20 mum squares and a CoPtCr recording medium. The dissipation results show strong correlations with magnetic domain structure. In the Ni80 Fe20 sample, the dissipation signal shows pronounced maxima correlated with the domain wall positions. We suggest magnetoelastic losses and eddy current losses due to wall jumps are the origins of the dissipation. With an in-situ magnetizing stage, we also studied magnetization reversal processes and dissipation hysteresis in the Ni80Fe20 sample. Besides the nucleation and growth of reverse domains, the formation of a 360º wall was observed. The CoPtCr sample shows different dissipation properties with both larger and smaller than average dissipation value observed in the transition regions.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35002 |
| Date | January 1997 |
| Creators | Liu, Yanzhang, 1963- |
| Contributors | Grutter, Peter (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001616646, proquestno: NQ44497, Theses scanned by UMI/ProQuest. |
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