Irreversible magnetic exchange-spring processes in antiferromagnetic exchange-coupled bilayer systems

The demagnetization processes of antiferromagnetic exchange-coupled hard-soft bilayer structures have been studied using a one-dimensional atomic chain model, taking into account the anisotropies of both hard and soft layers. It is found that for very thin soft layers, magnetization/demagnetization involves typical reversible exchange-spring behavior. However as the thickness t of the soft layer is increased, there is a crossover point t(c), after which the exchange spring becomes irreversible. The value of the critical thickness tc is determined inter alia by the magnetic anisotropy of the soft layer. However, an important feature of the irreversible exchange spring is the formation of a large angle domain wall, realized immediately at the bending field transition. (C) 2008 American Institute of Physics.