Large ultrafast-modulated Voigt effect in noncollinear antiferromagnet Mn3Sn

Abstract

The time-resolved magneto-optical (MO) Voigt effect can be utilized to study the Néel order dynamics in antiferromagnetic (AFM) materials, but it has been limited for collinear AFM spin configuration. Here, we have demonstrated that in Mn3Sn with an inverse triangular spin structure, the quench of AFM order by ultrafast laser pulses can result in a large Voigt effect modulation. The modulated Voigt angle is significantly larger than the polarization rotation due to the crystal-structure related linear dichroism effect and the modulated MO Kerr angle arising from the ferroic ordering of cluster magnetic octupole. The AFM order quench time shows negligible change with increasing temperature approaching the Néel temperature (TN), in markedly contrast with the pronounced slowing-down demagnetization typically observed in conventional magnetic materials. This atypical behavior can be explained by the influence of weakened Dzyaloshinskii–Moriya interaction rather than the smaller exchange splitting on the diminished AFM order near TN. The temperature-insensitive ultrafast spin manipulation can pave the way for high-speed spintronic devices either working at a wide range of temperature or demanding spin switching near TN.

Time-Dependent Multistate Switching of Topological Antiferromagnetic Order in Mn3Sn

“…This problem can be elegantly solved by turning to noncollinear antiferromagnets, which combine topologically nontrivial electronic properties with chiral magnetic order. In these systems, the broken timereversal symmetry and large Berry curvature in momentum space give rise to strong anomalous Hall effect (AHE) [12,13] and magneto-optical responses [14][15][16][17], similar to those of ferromagnets but in the absence of significant magnetization. Theoretical work shows that these materials can even exhibit a large tunneling magnetoresistance [18], whereas the emergence of exotic phenomena such as the chiral anomaly [19] and magnetic spin Hall effect [20][21][22][23] makes them a very interesting playground for * krishnag@mat.ethz.ch investigating the interplay of topology, electron transport, and magnetism [24][25][26].…”

Evolution of anisotropic magnetic properties through helix-to-fan transition in helical antiferromagnetic EuCo2As2

“…Helimagnets have a prototypical noncollinear spin structure, in which the spin direction is rotated spatially in the plane, but the rotation axis is parallel to the propagation direction 25 . The zero net moment associated with rotating spins in a helimagnet shares the advantages of collinear-type antiferromagnets, such as the absence of a stray field and ultrafast spin dynamics [26][27][28][29][30] . However, the study of magnetic anisotropy in noncollinear antiferromagnets remains to be explored because of the difficulty in analyzing the complicated spin states formed during the application and rotation of the magnetic field.…”

How closely does transient magnetic linear dichroism follow the spin moment?

“…Magnetic linear dichroism (MLD), on the other hand, with quadratic dependence on the magnetisation, can be observed 13,14 . This therefore represents a key spectroscopic technique for investigating laser pumped antiferromagnetic order, and indeed a number of recent experiments probing the time-evolution of antiferromagnetic order via MLD have been performed 15,16 .…”