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The antiferromagnet- (AFM-)ferromagnet (FM) interfaces are of central importance in recently developed pure electric or ultrafast control of FM spins, where the underlying mechanisms remain unresolved. Here we report the direct observation of an Dzyaloshinskii-Moriya interaction (DMI) across the AFM-FM interface of IrMn/CoFeB thin films. The interfacial DMI is quantitatively measured from the asymmetric spin-wave dispersion in the FM layer using Brillouin light scattering. The DMI strength is enhanced by a factor of 7 with increasing IrMn layer thickness in the range of 1-7.5 nm. Our findings provide deeper insight into the coupling at the AFM-FM interface and may stimulate new device concepts utilizing chiral spin textures such as magnetic Skyrmions in AFM-FM heterostructures. [ABSTRACT FROM AUTHOR]

Magnetism in topological insulators (TIs) opens a topologically nontrivial exchange band gap, providing an exciting platform for manipulating the topological order through an external magnetic field. Here, we show that the surface of an antiferromagnetic thin film can magnetize the top and the bottom TI surface states through interfacial couplings. During the magnetization reversal, intermediate spin configurations are ascribed from unsynchronized magnetic switchings. This unsynchronized switching develops antisymmetric magnetoresistance spikes during magnetization reversals, which might originate from a series of topological transitions. With the high Néel ordering temperature provided by the antiferromagnetic layers, the signature of the induced topological transition persists up to ~90 K. [ABSTRACT FROM AUTHOR]