Low-temperature magnetization relaxation in magnetic molecular solids

• A novel set of non-linear rate equations for the coupled evolution of the magnetization and dipole field distribution.
• An analytic derivation of the short-time square root in time behavior of the magnetization relaxation.
• Agreement between theory and simulations without further fitting parameters.

The low temperature relaxation of the magnetization in molecular magnetic solids such as Fe8 is studied using Monte Carlo simulations. A set of rate equations is then developed to understand the simulations, and the results are compared. The simulations show that the magnetization of an initially saturated sample deviates as a square-root in time at short times, as observed experimentally, and this law is derived from the rate equations analytically.