Funding acknowledgement:200465 -Interconversion of charge, spin and heat currents in spintronic devices (SNF) 178825 -Dynamical processes in systems with strong electronic correlations (SNF) 694955 -In-situ second harmonic generation for emergent electronics in transition-metal oxides (EC) SEED-20 19-2 -Electrical manipulation and imaging of domains in antiferromagnets (ETHZ)This page was generated automatically upon download from the ETH Zurich Research Collection. For more information, please consult the Terms of use.

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.

Intense current pulses are often required to operate microelectronic and spintronic devices. Notably, strong current pulses have been shown to induce magnetoresistance changes attributed to domain reorientation in antiferromagnet/heavy metal bilayers and non-centrosymmetric antiferromagnets. In such cases, nonmagnetic resistivity changes may dominate over signatures of antiferromagnetic switching. We report systematic measurements of the current-induced changes of the transverse and longitudinal resistance of Pt and Pt/NiO layers deposited on insulating substrates, namely Si/SiO 2 , Si/Si 3 N 4 , and Al 2 O 3. We identify the range of pulse amplitude and length that can be used without affecting the resistance and show that it increases with the device size and thermal diffusivity of the substrate. No significant difference is observed in the resistive response of Pt and NiO/Pt devices, thus precluding evidence on the switching of antiferromagnetic domains in NiO. The variation of the transverse resistance is associated to a thermally-activated process in Pt that decays following a double exponential law with characteristic timescales of a few minutes to hours. We use a Wheatstone bridge model to discriminate between positive and negative resistance changes, highlighting competing annealing and electromigration effects. Depending on the training of the devices, the transverse resistance can either increase or decrease between current pulses. Further, we elucidate the origin of the nonmonotonic resistance baseline, which we attribute to training effects combined with the asymmetric distribution of the current. These results provide insight into the origin of current-induced resistance changes in metal layers and a guide to minimize nonmagnetic artifacts in switching experiments of antiferromagnets.

We investigate the motion of magnetic domain walls driven by magnetic fields and current-driven spin-orbit torques in an exchange-biased system with perpendicular magnetization. We consider Cr 2 O 3 /Co/Pt trilayers as a model system, in which the magnetization of the Co layer can be exchanged biased out-of-plane or inplane depending on the field-cooling direction. In field-driven experiments, the in-plane exchange bias favors the propagation of the domain walls with internal magnetization parallel to the exchange-bias field. In current-driven experiments, the domain walls propagate along the current direction, but the domain wall velocity increases and decreases symmetrically (antisymmetrically) for both current polarities when the exchange bias is parallel (perpendicular) to the current line. At zero external field, the exchange bias modifies the velocity of currentdriven domain wall motion by a factor of 10. We also find that the exchange bias remains stable under external fields up to 15 kOe and nanosecond-long current pulses with current density up to 3.5 × 10 12 A/m. Our results demonstrate versatile control of the domain wall motion by exchange bias, which is relevant to achieve fieldfree switching of the magnetization in perpendicular systems and current-driven manipulation of domain walls velocity in spintronic devices.