  We describe the dynamics of quantum discord of two interacting spin-1/2
subjected to controllable time-dependent magnetic fields. The exact time
evolution of discord is given for various input mixed states consisting of
classical mixtures of two Bell states. The quantum discord manifests a complex
oscillatory behaviour in time and is compared with that of quantum
entanglement, measured by concurrence. The interplay of the action of the
time-dependent magnetic fields and the spin-coupling mechanism in the
occurrence and evolution of quantum correlations is examined in detail.
