Micromagnetic simulation of thermal ripple in thin films: “Roller-coaster” visualization

We present simulations of pulse-induced magnetization-rotation experiments in Permalloy. These lead to temporary domain formation (“thermal ripple”) and help to explain the time dependence of experimental results. To understand and visualize the motion, we find it very useful to exploit a mathematical isomorphism of this problem (in the limit $Ms≫Hpulse)$ to the problem of a massive particle on a circular track (“roller coaster”). The height (gravitational potential energy) of this track is proportional to the Stoner–Wohlfarth energy. The fact that the resulting “precession” is really oscillation in a plane, and the fact that this oscillation overshoots the minimum-energy configuration (the inertia effect) are much more intuitive in the roller coaster picture than in the conventional “M precesses about the effective field” picture. Animated simulations of this behavior are available on the web (http://bama.ua.edu/∼visscher/mumag/).