Ultrafast optical modulation of an exchange biased ferromagnetic/antiferromagnetic bilayer

Time-resolved magneto-optical Kerr techniques are employed to study optically induced ultrafast modulation in an antiferromagnetic (AF) exchange biased ferromagnetic (FM) thin epitaxial bilayer (NiFe/NiO). The interface region between the antiferromagnetic NiO and coupled ferromagnetic NiFe layers is photoexcited with femtosecond laser pulses, following which the transient magneto-optical response of the NiFe layer is measured. When compared with optically induced effects on “bare” epitaxial NiFe thin films, we observe a large enhancement to the transient Kerr effect in the exchange biased bilayers, interpreted as a modulation of the AF/FM exchange coupling on a picosecond timescale. © 1998 The American Physical Society.