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 (T_N), 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 T_N. 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 T_N.

The impact of antisite disorder $x$ on the intrinsic Gilbert damping ${\alpha }_0$ in well-ordered $L{1}_0$ FePt films is investigated by time-resolved magneto-optical Kerr effect. The variation of $x$ mainly affects the electron scattering rate $1/{\tau }_{\mathrm{e}}$, while other leading parameters remain unchanged. The experimentally observed linear dependence of ${\alpha }_0$ on $1/{\tau }_{\mathrm{e}}$ indicates that spin relaxation is through electron interband transitions, as predicted by the spin-orbit coupling torque correlation model. Measurements at low temperature show that ${\alpha }_0$ remains unchanged with temperature even for FePt with very high chemical order, indicating that electron-phonon scattering is negligible. Moreover, as $x$ decreases, the perpendicular magnetic anisotropy increases, and the Landau $g$ factor exhibits a negative shift due to an increase in orbital momentum anisotropy. Our results will facilitate the design and exploration of magnetic alloys with large magnetic anisotropy and desirable damping properties.

The development of highly efficient active integrated photonic circuits is crucial for advancing information and computing science. Lead halide perovskite semiconductors, with their exceptional optoelectronic properties, offer a promising platform for such devices. In this study, active micro multifunctional photonic devices were fabricated on monocrystalline CsPbBr₃ perovskite thin films using a top-down etching technique with focused ion beams. The etched microwire exhibited a high-quality micro laser that could serve as a light source for integrated devices, facilitating angle-dependent effective propagation between coupled perovskite-microwire waveguides. Employing this strategy, multiple perovskite-based active integrated photonic devices were realized for the first time. These devices included a micro beam splitter that coherently separated lasing signals, an X-coupler performing transfer matrix functions with two distinguishable light sources, and a Mach-Zehnder interferometer manipulating the splitting and coalescence of coherent light beams. These results provide a proof-of-concept for active integrated functionalized photonic devices based on perovskite semiconductors, representing a promising avenue for practical applications in integrated optical chips.

Optical control of spin is of central importance in the research of ultrafast spintronic devices utilizing spin dynamics at short time scales. Recently developed optical approaches such as ultrafast demagnetization, spin-transfer and spin-orbit torques open new pathways to manipulate spin through its interaction with photon, orbit, charge or phonon. However, these processes are limited by either the long thermal recovery time or the low-temperature requirement. Here we experimentally demonstrate ultrafast coherent spin precession via optical charge-transfer processes in the exchange-coupled Fe/CoO system at room temperature. The efficiency of spin precession excitation is significantly higher and the recovery time of the exchange-coupling torque is much shorter than for the demagnetization procedure, which is desirable for fast switching. The exchange coupling is a key issue in spin valves and tunnelling junctions, and hence our findings will help promote the development of exchange-coupled device concepts for ultrafast coherent spin manipulation.