Low-Temperature Magnetization Relaxation in Magnetic Molecular Solids

The low temperature relaxation of the magnetization in magnetic molecular solids such as Fe${}_8$ is studied using Monte Carlo simulations. A set of rate equations is developed to understand the simulations, and the results are compared. The simulations show that the magnetization of an initially saturated samples deviates as a square-root in time at short times, as observed experimentally, and this law is derived from the rate equations analytically.