Critical thickness for high-remanent single-domain configurations in square ferromagnetic thin platelets

By means of three-dimensional micromagnetic finite element modeling, zero-field magnetization patterns of ferromagnetic thin film elements of square shape are simulated and energetically compared. The geometry of the sample (edge length (formula presented) thickness (formula presented) and its intrinsic material parameters (hardness (formula presented) are systematically varied. Based on the results the corresponding phase diagram is set up which identifies a quasihomogeneous single-domain phase (C, S, and flower states) and a vortex phase (Landau state). For the transition between the two phases a material- and edge-length-dependent critical film thickness is found. The numerical results can be confirmed qualitatively using a simple analytical model calculation.