Rotational coupling effects on the spin relaxation of free ferromagnetic clusters

A model based on resonant spin-rotation coupling is used to reproduce the magnetization of free iron clusters experimentally observed by Stern-Gerlach deflections. Due to the interaction with the rotating magnetocrystalline anisotropy field, the dynamics of the magnetic moment of the clusters cannot be explained only in terms of thermal relaxation. As in magnetic resonance experiments, modified Bloch equations can describe the interaction of the particle spin with the deflecting field and the rotating anisotropy field. The dependence of the magnetization on the rotational temperature of the clusters and the relaxation time is discussed.