  Based on the Liouville-von Neumann equation, we obtain closed system of
equations for the description of a qutrit or coupled qutrits in arbitrary
time-dependent external magnetic field. The dependence of the dynamics on the
initial states and magnetic field modulation is studied analytically and
numerically. We compare the relative entanglement measure's dynamics in the
bi-qutrit system with permutation particle symmetry. We find the magnetic field
modulation which retains the entanglement in the system of two coupled qutrits.
Analytical formulas for entanglement measures in the chain from 2 to 6 qutrits
are presented.
