Fire in a Magnetic Quantum Mechanical Forest

The energy released in a magnetic material by reversing spins as they relax toward equilibrium can lead to a dynamical magnetic instability in which all the spins in a sample rapidly reverse in a run-away process similar to what occurs in a forest fire. In a chemical system the process consists of the ignition of the flammable substance and the subsequent release of heat that sustains the spreading reaction along a well-defined front separating the burnt and unburnt regions. I will describe our experiments on quantum Ising spins on a lattice, a molecular magnet single crystal. In a magnetic system the reaction is the reversal of spins that releases Zeeman energy and the Ising anisotropy barrier is the reaction’s activation energy. An interesting aspect of magnetic systems is that these key energies—the activation energy and the energy released—can be independently controlled by applied magnetic fields enabling systematic studies of the instabilities. Further, no material is actually consumed in the experiments; the burnt regions are the unburnt regions when the applied field is reversed.

P. Subedi, S. Velez, F. Macia, S. Li, M. P. Sarachik, J. Tejada, S. Mukherjee and G. Christou and A. D. Kent, Physica Review Letters 110, 207203 (2013).