Theory of the inverse Faraday effect in view of ultrafast magnetization experiments

We supplement the theory of the inverse Faraday effect, which was developed in the 1960s, to the conditions used today in ultrafast magnetization experiments. We show that assumptions used to derive the effective Hamiltonian and magnetization are not valid under these conditions. We extended the approach to be applicable to describe magnetization dynamics at femtosecond time scales. We show that after the action of an ultrafast laser pulse the system is brought with a certain probability to a state, the magnetic signature of which is different from before the excitation.