Antiferromagnetic spin dynamics in exchanged-coupled Fe/GdFeO3 heterostructure Project supported by the National Key Research Program of China (Grant Nos. 2018YFF01010303, 2017YFB0702702, and 2016YFA0300701), the National Natural Sciences Foundation of China (Grant Nos. 52031015, 1187411, 51427801, and 51871235), and the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (Grant Nos. QYZDJ-SSW-JSC023, KJZD-SW-M01, and ZDYZ2012-2)

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. [ABSTRACT FROM AUTHOR]