Dynamics of the coercivity in ultrafast pump–probe experiments

In this paper we devote ourselves to the coercivity as a measured variable in femtosecond magnetism. We stress the fact that an all optical pump–probe technique is in general not suitable to gain access to the time-dependent behaviour of the coercivity, since the switching in a fixed external field is an irreversible process. We comment on the possible mechanisms leading to the observed reduction in the coercivity with increasing pump power and propose a potential solution to clarify the origin of such behaviour. (Some figures in this article are in colour only in the electronic version) 1.