Theory of relaxation of magnetic clusters in a Stern-Gerlach setup

We use a stochastic theory approach to discuss different scenarios such as “locked moment” and “superparamagnetic” behavior of magnetic clusters seen in Stern-Gerlach (SG) experiments. A dimensionless parameter $\lambda {\tau }_E$ (where λ is an internal spin relaxation rate and ${\tau }_E$ is the time spent by the cluster in the field gradient region) and the initial polarization of the cluster moment are shown to determine sensitively the position of the cluster beam on the SG screen.