Time-Dependent Multistate Switching of Topological Antiferromagnetic Order in Mn3Sn

Abstract

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.

Nanoscale Magnetic Domains in Polycrystalline Mn3Sn Films Imaged by a Scanning Single-Spin Magnetometer

“…A clear conclusion clarifying the exact mechanism underlying electrically driven magnetic switching in Mn 3 Sn may not be possible based on the current study. Meanwhile, we do notice that observable difference in stray field patterns emerges after a complete current cycling loop (between the magnetic states “A” and “H”), suggesting nonreversible reconstruction of Mn 3 Sn magnetic structures during current-induced magnetic switching, which could be related to local thermal effects. , It is instructive to note that extended scanning NV measurements have been performed on different Mn 3 Sn samples to ensure the consistency of the presented results (see Supporting Information Section 6 for details).…”

“…Due to the weak intergrain interactions, measured stray field maps of polycrystalline Mn 3 Sn films largely follow the same pattern for the two oppositely polarized magnetic states in field-driven magnetic switching processes. In contrast, variations of stray field maps of polycrystalline Mn 3 Sn samples during current-induced magnetic switching show clear inhomogeneous features together with nonreversible domain reconstruction behaviors which is potentially related to Joule heating induced local demagnetization-remagnetization processes. , Our results highlight the advantages of the “non-invasive” NV quantum metrology in both spatial and field sensitivity for studying nanomagnetism hosted by emergent condensed matter systems (see Supporting Information Section 2 for details). The current work also adds an additional ingredient to the emerging topic of Mn 3 X compounds, contributing to a comprehensive understanding of unconventional spin related phenomena in the family of noncollinear antiferromagnets.…”

“…In addition to the static magnetic field, current-induced spin–orbit torques (SOTs) can also be used to achieve efficient control of the local spin orders of Mn 3 Sn. − , Next, we utilize our scanning NV microscope to reveal evolutions of the measured stray field patterns during electrically driven perpendicular magnetic switching of Mn 3 Sn. For these measurements, we prepared Mn 3 Sn (70 nm)/W (7 nm) bilayer samples and patterned them to standard Hall cross devices for magneto-transport characterizations as shown in the left panel of Figure a.…”

“…Harnessing magnetic domain motions for advanced information processing, transfer, and storage constitutes a key mission of modern spintronic technologies. − Over the past decade, (ferri)­ferromagnetic materials with net magnetization, robust stray field patterns, and prominent magneto-transport responses naturally played a leading role in this contest, and a variety of cutting-edge spintronic devices have been developed along this direction. − More recently, antiferromagnets featuring vanishingly small net magnetization and exchange-enhanced magnetic interactions emerge as a new contender of this field. , Novel functionalities such as ultrahigh-density magnetic memory, improved stability, , and unconventional magnetic switching strategies − are under intensive investigation for developing next-generation, transformative micromagnetic devices. The family of noncollinear antiferromagnets Mn 3 X (X = Sn, Ge, Ga, Ir, Pt, Rh) are naturally relevant in this context, owing to their emergent electronic and magnetic structures.…”

“…For these measurements, we prepared Mn 3 Sn (70 nm)/W (7 nm) bilayer samples and patterned them to standard Hall cross devices for magneto-transport characterizations as shown in the left panel of Figure a. The W capping layer serves as an efficient source of spin–orbit torques (SOTs) , for driving the magnetic switching in Mn 3 Sn, arguably together with other potential contributions such as local heating effects and intergrain spin transfer torques. − Current driven magnetic switching measurements follow the standard procedure as reported in the previous literature. , Electrical write current pulses I write are applied through the current channel of a patterned Hall cross device, generating transverse spin currents through spin Hall effect in the W layer, assuming the diffusive picture of spin transport is valid and spin currents are approximately well-defined. The spin current then flows across the heterostructure interface and exerts SOTs on the local magnetic moments in Mn 3 Sn, resulting in reversible switching of the canted ferromagnetic moment with the assistance of a longitudinal bias field (see Supporting Information Section 5 for details).…”