  We consider a single-domain ferromagnetic particle with uniaxial anisotropy
coupled to a single-domain soft ferromagnetic particle (superparamagnetic
particle). The problem of thermally agitated magnetization reversal in this
case can be reduced to the random magnetization dynamics of the first particle
with an effectively larger anisotropy field. The magnetic external field is
also altered in a manner that depends on the sign of the coupling and can be
either enhanced or suppressed.
