Ultrafast photoinduced magnetization switching in magnetic heterostructures

The possibility that ultrafast coherent magnetization rotation in analog to Bloch equation of magnetic resonance can be triggered by modulation of the exchange field which exists at the interface between magnetically coupled thin film bilayers with ultrashort laser pulses is discussed. The interaction in a heterostructure composed of a ferromagnetic thin (100 angstroms) film on a widegap antiferromagnetic insulator NiO is examined. The details of the dynamics of coherent magnetization are fitted in Landau-Lifshitz-Gilbert equation, with damping constant α to approximately 0.05 and τ to approximately 150 psec as the recovery time of the exchange bias field and also the spin lattice relaxation time.