  Although there have been many studies of statistical mechanical models of
magnetic friction, most of these have focused on the behavior in the steady
state. In this study, we prepare a system composed of a chain and a lattice of
Ising spins that interact with each other, and investigate the relaxation of
the system when the relative velocity $v$ changes suddenly. The situation where
$v$ is given is realized by attaching the chain to a spring, the other end of
which moves with a constant velocity $v$. Numerical simulation finds that, when
the spring constant has a moderate value, the relaxation of the frictional
force is divided into two processes, which are a sudden change and a slow
relaxation. This behavior is also observed on regular solid surfaces, although
caused by different factors than our model. More specifically, the slow
relaxation process is caused by relaxation of the magnetic structure in our
model, but is caused by creep deformation in regular solid surfaces.
