Switching and locking of magnetostatically coupled ferromagnetic thin films

Magnetostatically coupled films with an internal conductor were studied using a dual-beam Kerr apparatus which enabled the magnetization of both the top and the bottom films of the structure to be monitored. The easy- and hard-axis components of the magnetizations were recorded in succession with sampling techniques during the switching processes, and the traces were combined to provide trajectories of throughout the switching. In the case of easy-axis coupled films, certain trajectories lead to a stable multidomain state (locking); a new technique using current pulses through the Ag conductors in conjunction with an externally applied variable hard-axis field provides a quick method of determining the locus of applied fields for which locking occurs. The locked-state trajectories and complete-switching trajectories are found to be composed of three regions of switching: 1) a coherent rotation of the magnetization, 2) an incoherent rotation, and 3) wall motion. From the data used to construct the trajectories, the times to reach a locked state and the durations of each different switching mechanism is determined.