School of Physics and Astrophysics

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Rebecca Fuller

Phone: (+61 8) 6488 4441


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Rebecca Fuller

Thesis

Relaxation and properties of in fine magnetic particles

Summary

Research has involved synthesis of FePt nanoparticles and new transition and rare earth thiacalixarene clusters. Fundamental properties and magnetic relaxation of these systems has been investigated through SQUID magnetometry.

Why my research is important

As particle size decreases it becomes energetically unfavourable to form domain walls in the system. Stoner and Wohlfarth and NĂ©el pioneered research in the middle of the last century into a model for describing magnetic reversal of these single domain systems. This has become a prominent field of active research. In recent times vast improvements in fabrication of nano-sized materials has occurred. This has provided researchers with greater access to materials which are typically single domain. These particles tend to exhibit properties that differ greatly to their bulk analogues. The rapid development of these materials has largely arisen out of possible technological applications including high density magnetic storage, biomedical sensors, catalysis and new electronic devices including qubits in quantum computers. Besides applications these materials have also provided a means for understanding the fundamental nature of materials. These include magnetic reversal by quantum tunnelling and the effect of surface spins on the magnetic properties of the particle. Experimentally nanoparticles are complicated systems as their physical properties are governed by a number of parameters which affect the structure and magnetic properties of the system. To overcome this further reduction in size of the system can be achieved through fabrication of small molecular clusters. A range of systems exist, in this dissertation only clusters consisting of metal ion centers complexed with ligands are of relevance. These materials allow the magnetic interaction between metal ion centers to be observed. One classical example is copper acetate where spin-spin interactions are observed. Since the direct effect of structure on magnetic properties was observed, scientists have developed these systems to enhance these features. These complexes behave as single domain systems in the same manner as nanoparticles where magnetisation is the result of the intrinsic property of the molecular unit. Thus like nanoparticles molecular systems are ideal for applications in magnetic storage as well as studying fundamental properties like quantum tunnelling.

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Last updated:
Monday, 2 August, 2010 2:54 PM

http://www.physics.uwa.edu.au/1023927