Quantum ignition of deflagration in the Fe8 molecular magnet

We report spatially resolved, time-dependent, magnetization reversal measurements of an Fe8 single molecular magnet using a microscopic Hall bar array. We found that a deflagration process, where molecules reverse their spin direction along a moving front, can be ignited quantum mechanically (T→0) at a resonance field, with no phonon pulse. The avalanche front velocity is of the order of 1m/s and is sensitive to field gradients and sweep rates. We also measured the thermal diffusivity κ in Fe8. This allows us to estimate the "flame" temperature.