Micromagnetic study of nonlinear effects in soft magnetic materials

Numerical simulation is used to study the linear and nonlinear effects of increasing incident power density on soft magnetic materials at the microscale. A magnetic field pulse with Gaussian time dependence and variable strength is numerically applied to a magnetic particulate in an equilibrium state. The field-dependent dynamic susceptibility (M/H) is calculated from the Fourier transform of the magnetization response. Calculations show that as the magnitude of the excitation field exceeds a critical value, the system becomes nonlinear. At this point, the ferromagnetic resonance should become suppressed and span a wider range of frequencies. Two systems are simulated in the linear and nonlinear regimes; one system shows complete agreement with established nonlinear theory, while the other shows unusual behavior. Both systems agree with linear theory at low fields, and vanishing susceptibility at excessively high fields is observed for both. (C) 2003 American Institute of Physics.