Effective collective barrier for magnetic relaxation in frozen ferrofluids

TL;DR

This study investigates magnetic relaxation in frozen ferrofluids, revealing a transition from reversible to irreversible behavior and demonstrating a diverging collective barrier indicative of self-organized criticality.

Contribution

It introduces a mean field phenomenological model to extract the effective collective barrier, highlighting the divergence and critical behavior during magnetic relaxation.

Findings

Crossover from reversible to irreversible magnetic behavior in concentrated ferrofluids

Magnetic relaxation follows a time-logarithmic pattern over seven orders of magnitude

Effective barrier diverges logarithmically, indicating self-organized criticality

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.