Transient Chaos in Nanomagnets Subject to Elliptically Polarized AC Applied Fields

Magnetization dynamics in single-domain particles driven by elliptically polarized ac external fields is studied. It is shown that such dynamics exhibits chaotic and fractal nature at a moderate power level. This is due to the phenomenon of heteroclinic tangle produced by the combined action of ac excitations and saddle-type dynamics. By using the special perturbation technique based on the Melnikov function, analytical formulas for the threshold ac excitation amplitudes necessary to create the heteroclinic tangle are derived as a function of frequency and general elliptic polarization of the applied ac field. Numerical simulations confirm that the heteroclinic tangle implies the erosion of the safe basin around stable magnetization states.