2021/08/23 by L. Y. Shi, Shi, L. Y., Di Wu +15
Engineering · Physics and Astronomy · Materials Science · #Magneto-Optical Properties and Applications #Magnetic properties of thin films #Multiferroics and related materials
paper · pdf · doi:10.48550/arxiv.2108.10258
Multiferroic materials offer a promising platform for ultrafast optical control of coupled magnetic and polar orders. However, a prerequisite for such control is to precisely identify how the magnetically induced polarization manifests itself on the ultrafast timescale, and then to probe its dynamics upon external perturbations. Here, we address this issue in the polar magnet Fe2Mo3O8 by combining static and time-resolved second harmonic generation (SHG). Temperature-dependent static SHG reveals that, among the symmetry-allowed tensor elements, only χ(2)ccc exhibits a pronounced anomaly at the antiferromagnetic transition (T\rm N ≈ 60 K), identifying the c-axis polar response as the primary degree of freedom coupled to the magnetic order. Guided by this result, time-resolved SHG selectively tracks the dynamics of this tensor element following ultrafast photoexcitation. We observe a rapid enhancement of the χ(2)ccc-related SHG signal, followed by biexponential recovery. The response is independent of the pump polarization, consistent with an ultrafast thermal origin, but is achieved at a fluence significantly below that required for conventional lattice heating. These results establish SHG as tensor-selective probe of ultrafast magnetoelectric dynamics and demonstrate the high sensitivity of the magnetically induced polarization in Fe2Mo3O8 to optical excitation.