Effective collective barrier for magnetic relaxation in frozen ferrofluids
arXiv:cond-mat/0312087 · doi:10.1016/j.jmmm.2004.04.120
Abstract
Magnetic relaxation and frequency response were measured in frozen ferrimagnetic colloids of different concentrations. A crossover from reversible to irreversible behavior is observed for concentrated colloids. In irreversible state, magnetic relaxation is time-logarithmic over seven orders of magnitude of experimental time windows. A master curve construction within mean field phenomenological model is applied to extract effective collective barrier as a function of the irreversible magnetization. The barrier logarithmically diverges, providing evidence for self-organized critical behavior during magnetic relaxation in frozen ferrofluids.