We report measurements of domain wall dynamics in an ultrathin Au/Co/Au system that exhibits a spin reorientation phase transition as a function of temperature. The domain walls exhibit cooperative motion throughout the temperature range of 150 - 300 K. The decay times were found to exhibit a maximum at the transition temperature. The slowdown has been explained as due to formation of a double well in the energy landscape by the different competing interactions. Our results show that the complex, slow dynamics can provide a more fundamental understanding of magnetic phase transitions.
