With the increasing demand for high storage density, magnetic recording media will soon have as their basic components single-domain ferromagnetic grains. Recently experimentalists working with powerful new microscopic techniques have discovered that the process of magnetization reversal in these grains is much more complicated than had been previously realized. In this dissertation we investigate the applicability of the two-dimensional kinetic Ising model on a square lattice as a model for the switching dynamics. The process of metastable decay is studied by two means: Monte Carlo simulations and analytical arguments based on droplet theory. The simulations are shown to be consistent with the analytical arguments and qualitatively similar to the experimental measurements of single-domain ferromagnets. / For a periodic Ising system with an initial magnetization $m\sb0$ = +1 in a negative magnetic field, the field $H\sb{\rm sw}$ which causes the magnetization to decay to zero in a specified length of time is found as a function of the system size L. The probability that the magnetization remains greater than zero is also found as a function of time for fixed applied field and as a function of applied field for fixed decay time. / The magnetostatic dipole-dipole interaction in real magnetic materials is modeled to lowest order by adding to the Ising Hamiltonian a term proportional to the square of the magnetization. The analytical predictions show excellent agreement with Monte Carlo simulations with no fitted parameters that depend on the $m\sp2$ term. / Finally, $H\sb{\rm sw}$ is found from Monte Carlo simulations of octagonal systems with a variety of boundary conditions. The results are explained in terms of the scaling form of the free-energy barrier which must be overcome for the metastable state to decay, and they demonstrate the importance that surface effects such as adsorption and reconstruction might have on magnetization switching. / Source: Dissertation Abstracts International, Volume: 57-04, Section: B, page: 2634. / Major Professor: Per Arne Rikvold. / Thesis (Ph.D.)--The Florida State University, 1996.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77720 |
| Contributors | Richards, Howard Lamar., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 97 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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