Orbital domain dynamics in Magnetite below the Verwey transition

Mesoscale phenomena play an important role in the dynamics of phase transitions in correlated systems. In order to fully understand and tailor their functionalities detailed access to the nanoscale regime, correlation length scales and temporal evolution of the order parameter is required. In this study, we utilized X-ray photon correlation spectroscopy (XPCS) to investigate the orbital domain dynamics of the insulating phase undergoing the insulator-to-metal transition in magnetite (T_v=123 K). XPCS provides a unique way to characterize disorder (domains, phase separation etc.) and their correlations by allowing us to capture high resolution coherent speckle patterns. By tuning to the Fe L₃-edge, we studied the evolution of the orbitally ordered superlattice peak present in the low temperature insulating phase and forbidden in the metallic phase. We observed two distinct regimes below the Verwey transition. In the first regime at lower temperatures, magnetite follows an Arrhenius behavior and the characteristic timescale for orbital fluctuations decreases as the temperature increases. In the second regime near Tv, magnetite phase separates into metallic and insulating domains, and the kinetics of phase transition is dictated by metallic-insulating interfacial boundary conditions.