Radiation- and phonon-bottleneck-induced tunneling in the Fe8 single-molecule magnet

We measure magnetization changes in a single crystal of the single-molecule magnet Fe-8 when exposed to intense, short (<= 20 mu s) pulses of microwave radiation resonant with the m = 10 to 9 transition. We find that radiation induces a phonon bottleneck in the system with a time scale of similar to 5 mu s. The phonon bottleneck, in turn, drives the spin dynamics, allowing observation of thermally assisted resonant tunneling between spin states at the 100 ns time scale. Detailed numerical simulations quantitatively reproduce the data and yield a spin-phonon relaxation time T-1 similar to 40 ns. Copyright (c) EPLA, 2008.