Interface-Induced Magnetic Coupling in Multiferroic/Ferromagnetic Bilayer: An Ultrafast Pump-Probe Study*

By use of optical pump-probe measurement, we study the relaxation dynamics of a muliferroic-ferromagnetic TbMnO$_{3}$/La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ bilayer. The relaxation dynamics of both layers are well separated in time allowing us to investigate the magnetic coupling across the bilayer. We observe that the relaxation dynamics of the individual layers in the bilayer sample are the result of the interplay between the intrinsic magnetic order and the induced interfacial effect. Our data suggest the existence of induced ferromagnetic order in the TbMnO$_{3}$ layer, and antiferromagnetic order in the La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ layer.