The magnetization dynamics of a rectangular magnetic thin film are studied using micromagnetic simulations. The film is excited by an inplane external magnetic field that is perpendicular to the easy axis. The dynamics that govern the rotation of the magnetization were extracted assuming quasistatic equilibrium before the external field was changed. The power spectral density (PSD) of the time series, spatially averaged over the sensor geometry, reveal the existence of a fundamental precession frequency and an upper sideband. At a critical angle of rotation, the collision of edge domains causes the excitation of spin waves which appear as multiple peaks in the PSD. The process of collision and formation of domain walls causes the central portion of the sensor to switch abruptly between horizontal and vertical directions. The distance betwen the domain walls before collision becomes a measure of the quiescent state stability of the sensor. We also observe wall displacement waves along the edges of the domains using temporal snapshots of the precession frequency within a micromagnetic cell. © 2007 IEEE.