Antiferromagnetic spin dynamics in exchanged-coupled Fe/GdFeO₃ heterostructure

We investigate the ultrafast spin dynamics of an antiferromagnet in a ferromagnet/antiferromagnet heterostructure Fe/GdFeO₃ via an all-optical method. After laser irradiation, the terahertz spin precession is hard to be excited in a bare GdFeO₃ without spin reorientation phase but efficiently in Fe/GdFeO₃. Both quasi-ferromagnetic and impurity modes, as well as a phonon mode, are observed. We attribute it to the optical modification of interfacial exchange coupling between Fe and GdFeO₃. Moreover, the excitation efficiency of dynamics can be modified significantly via the pump laser influence. Our results elucidate that the interfacial exchange coupling is a feasible stimulation to efficiently excite terahertz spin dynamics in antiferromagnets. It will expand the exploration of terahertz spin dynamics for antiferromagnet-based opto-spintronic devices.