Magnetically coupled nanomagnets have multiple applications in nonvolatile memories, logic gates, and sensors. The most effective couplings have been found to occur between the magnetic layers in a vertical stack. We achieved strong coupling of laterally adjacent nanomagnets using the interfacial Dzyaloshinskii-Moriya interaction. This coupling is mediated by chiral domain walls between out-of-plane and in-plane magnetic regions and dominates the behavior of nanomagnets below a critical size. We used this concept to realize lateral exchange bias, field-free current-induced switching between multistate magnetic configurations as well as synthetic antiferromagnets, skyrmions, and artificial spin ices covering a broad range of length scales and topologies. Our work provides a platform to design arrays of correlated nanomagnets and to achieve all-electric control of planar logic gates and memory devices.

The ability to represent information using an antiferromagnetic material is attractive for future antiferromagnetic spintronic devices. Previous studies have focussed on the utilization of antiferromagnetic materials with biaxial magnetic anisotropy for electrical manipulation. A practical realization of these antiferromagnetic devices is limited by the requirement of material-specific constraints. Here, we demonstrate current-induced switching in a polycrystalline PtMn/Pt metallic heterostructure. A comparison of electrical transport measurements in PtMn with and without the Pt layer, corroborated by x-ray imaging, reveals reversible switching of the thermally-stable antiferromagnetic Néel vector by spin-orbit torques. The presented results demonstrate the potential of polycrystalline metals for antiferromagnetic spintronics.

Ferrimagnetic alloys are model systems for understanding the ultrafast magnetization switching in materials with antiferromagnetically-coupled sublattices. Here we investigate the dynamics of the rare-earth and transition-metal sublattices in ferrimagnetic GdFeCo and TbCo dots excited by spin-orbit torques with combined temporal, spatial, and elemental resolution. We observe distinct switching regimes in which the magnetizations of the two sublattices either remain synchronized throughout the reversal process or switch following different trajectories in time and space. In the latter case, we observe a transient ferromagnetic state that lasts up to 2 ns. The asynchronous switching of the two magnetizations is ascribed to the master-agent dynamics induced by the spin-orbit torques on the transition-metal and rare-earth sublattices and their weak antiferromagnetic coupling, which depends sensitively on the alloy microstructure. Larger antiferromagnetic exchange leads to faster switching and shorter recovery of the magnetization after a current pulse. Our findings provide insight into the dynamics of ferrimagnets and the design of spintronic devices with fast and uniform switching.Ferrimagnetic alloys have raised strong interest owing to their ultrafast magneto-optical switching properties [1, 2, 3, 4] and high speed current-induced magnetic domain wall motion [5,6,7]. These characteristics make ferrimagnets optimal candidates for nonvolatile memory applications [8,9,4] as well as for testing models of magnetization dynamics in multi-element systems [10,11,12,6,13,14,15]. Several rare-earth (RE) transition-metal (TM) alloys are ferrimagnetic because the localized 4 f magnetic moments of the RE and the itinerant 3d moments of the TM couple antiparallel to each other, forming two spin sublattices with distinct properties that can

The manipulation of antiferromagnetic order by means of spin-orbit torques opens opportunities to exploit the dynamics of antiferromagnets in spintronic devices. In this work, we investigate the currentinduced switching of the magnetic octupole vector in the Weyl antiferromagnet Mn 3 Sn as a function of pulse shape, magnetic field, temperature, and time. We find that the switching behavior can be either bistable or tristable depending on the temporal structure of the current pulses. Time-resolved Hall effect measurements performed during the current pulsing reveal that Mn 3 Sn switching proceeds via a two-step demagnetization-remagnetization process caused by self-heating over a timescale of tens of nanoseconds followed by cooling in the presence of spin-orbit torques. Single-shot switching measurements with 50ps temporal resolution indicate that chiral spin rotation is either damped or incoherent in polycrystalline Mn 3 Sn. Our results shed light on the switching dynamics of Mn 3 Sn and prove the existence of extrinsic limits on its switching speed.

We report the observation of a unidirectional magnetoresistance (UMR) that originates from the nonequilibrium orbital momentum induced by an electric current in a naturally oxidized Cu/Co bilayer. The orbital-UMR scales with the torque efficiency due to the orbital Rashba-Edelstein effect upon changing the Co thickness and temperature, reflecting their common origin. We attribute the UMR to orbital-dependent electron scattering and orbital-to-spin conversion in the ferromagnetic layer. In contrast to the spin-current induced UMR, the magnon contribution to the orbital-UMR is absent in thin Co layers, which we ascribe to the lack of coupling between low energy magnons and orbital current. The magnon contribution to the UMR emerges in Co layers thicker than about 5 nm, which is comparable to the orbitalto-spin conversion length. Our results provide insight into orbital-to-spin momentum transfer processes relevant for the optimization of spintronic devices based on light metals and orbital transport.