The PI has studied viscous behavior at elevated temperature in 1-2 micron glass-ceramic magnetite. The goal of these experiments has been to identify the physical mechanism that causes VRM unblocking temperatures to be substantially higher than what traditional theories predict. She will now extend the previous studies of high-temperature viscosity, with the following goals: (1) to determine whether there is a causal link between diffusion after-effect and anomalously high unblocking temperatures, by combining viscosity studies with measurements of susceptibility as a function of time at elevated temperatures, and (2) to characterize viscous behavior and domain structure as functions of temperature and initial thermal/magnetic state.
