Study of chaotic dynamics and hysteresis in bulk ferromagnet and ferromagnetic film based on yttrium iron garnet

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Date
2009
Authors
Toh, Pek Lan
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Abstract
In the beginning of this project, the ferromagnetic phase transition and dynamic responses of bulk ferromagnet based on Yttrium Iron Garnet (YIG) are studied phenomenologically and numerically. The calculus of variations on Landau free energy density expansion of the ferromagnetic system is applied in order to formulate the second order ferromagnetic phase transition. The variations of Landau free energy density expansion is combined with Landau-Lifshitz (LL) equation of motion for the analysis of dynamics in the ferromagnetic system. With material constants of YIG, the results are solved numerically and presented graphically by using various amplitudes and frequencies of the applied field. In the second part of this project, the initial magnetisation profile of the ferromagnetic film, i.e. YIG film is assumed in the beginning by imposing boundary conditions. The calculus of variations on Landau free energy per unit area expansion of ferromagnetic film with the discrete model is applied in order to formulate the initial magnetisation profile. Then, the dynamic responses of YIG film is studied phenomenologically and numerically. The variations of Landau free energy per unit area expansion is combined with LL equation of motion for the analysis of dynamics in the ferromagnetic film. With material constants of YIG, the results are solved numerically and presented graphically by using various surface parameters, thicknesses of the film, amplitudes and frequencies of the applied field. Finally, these results are compared with the corresponding results obtained from the bulk ferromagnet with various frequencies.
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Master
Keywords
Science Physic , Chaotic dynamics , Ferromagnetic film , Yttrium iron garnet
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