Remanent state studies of truncated conical magnetic particles

The remanent state of truncated conical particles is investigated as a function of their size, aspect ratio, and anisotropy, using a micromagnetic model based on the Landau-Lifshitz-Gilbert equation. Particles with a base diameter smaller than three times the exchange length show a "flower" state, while larger particles show a "vortex" magnetization state. The critical size for this transition increases with increasing anisotropy. Small flower-state particles show abrupt reorientation from out-of-plane to in-plane magnetization at a critical aspect ratio of 0.9. For vortex-state particles, the axial remanence gradually increases as the aspect ratio increases, and high aspect ratio particles have significant remanence even at larger diameters. (C) 2001 American Institute of Physics.