Non-equilibrium magnetization dynamics in the Fe8 single-molecule magnet induced by high-intensity microwave radiation

Resonant microwave radiation applied to a single crystal of the molecular magnet Fe8 induces dramatic changes in the sample's magnetization. Transitions between excited states are found even though at the nominal system temperature these levels have negligible population. We find evidence that the sample heats significantly when the resonance condition is met. In addition, heating is observed after a short pulse of intense radiation has been turned off, indicating that the spin system is out of equilibrium with the lattice.