[194666]``Effects of Boundary Conditions on Magnetization Switching in Kinetic Ising Models of Nanoscale Ferromagnets'' by Howard L. Richards, M. Kolesik, Per-Anker Lindgård, Per Arne Rikvold, and M.A. Novotny
Submitted to Physical Review E - Statistical Physics, Plasmas, Fluids and Related Interdisciplinary Topics.
Magnetization switching in highly anisotropic single-domain ferromagnets has been previously shown to be qualitatively described by the droplet theory of metastable decay and the droplet theory of metastable decay and simulations of two-dimensional kinetic Ising systems with periodic boundary conditions. In this article we consider the effects of boundary conditions on the switching phenomena. A rich range of behaviors is predicted by droplet theory: the specific mechanism by which switching occurs depends on the structure of the boundary, the particle size, the temperature, and the strength of the applied field. The theory predicts the existence of a peak in the switching field as a function of system size in both systems with periodic boundary conditions and in systems with boundaries. The size of the peak is strongly dependent on the boundary effects. It is generally reduced by open boundary conditions, and in some cases it disappears if the boundaries are too favorable towards nucleation. However, we also demonstrate conditions under which the peak remains discernible. This peak arises as a purely dynamic effect and is not related to the possible existence of multiple domains. We illustrate the predictions of droplet theory by Monte Carlo simulations of two-dimensional Ising systems with various system shapes and boundary conditions.
[500997]``Magnetization Switching in Nanoscale Ferromagnetic Grains: Simulations with Heterogeneous Nucleation'' by M. Kolesik, Howard L. Richards, M. A. Novotny, Per Arne Rikvold, Per-Anker Lindgård
To appear in the Proceedings of the 41st Annual Conference on Magnetism and Magnetic Materials, Atlanta, Georgia, November 12--15.
We present results obtained with various types of heterogeneous nucleation in a kinetic Ising model of magnetization switching in single-domain ferromagnetic nanoparticles. We investigate the effect of the presence of the system boundary and make comparison with simulations on periodic lattices. We also study systems with bulk disorder and compare how two different types of disorder influence the switching behavior.