ABSTRACT
By the end of the first decade after the pioneering discovery of femtomagnetism, intensive research efforts have borne fruit, such as the discovery of all-optical spin switching (AOS). This chapter introduces the basic principles and surveys the basic ideas and experimental findings of all-optical spin switching. There are several proposed mechanisms without quantitative calculations. The inverse Faraday effect has long been thought as a possible origin of AOS, but it does not produce a strong enough magnetic field. The magnetic circular dichroism and the angular momentum transfer between spin sublattices are also proposed. Since nearly all AOS materials are amorphous, a first-principles calculation is difficult, if not impossible. Most of the theoretical investigations are highly phenomenological, where the laser field is replaced by an effective magnetic field so that the initial excitation is not taken into account. Thus, there are varieties of laser and system parameters that affect whether and how laser pulses can switch spins.
