We present measurements on the single-molecule magnet ${\mathrm{Fe}}_8$ in the presence of pulsed microwave radiation at $118\mathrm{GHz}$. The spin dynamics is studied via time-resolved magnetization experiments using a Hall-probe magnetometer. We investigate the relaxation behavior of magnetization after the microwave pulse. The analysis of the experimental data is performed in terms of different contributions to the magnetization after-pulse relaxation. We find that the phonon bottleneck with a characteristic relaxation time of $\sim 10–100\mathrm{ms}$ strongly affects the magnetization dynamics. In addition, the spatial effect of spin diffusion is evidenced by using samples of different sizes and different ways of the sample’s irradiation with microwaves.

• Received 28 October 2006

DOI:https://doi.org/10.1103/PhysRevB.75.064408