| Time：1150415 (Wed.) 14:20~16:20 Speaker：Prof.許華書(HSU, Hua-Shu) 國立屏東大學應用物理系/Department of Applied Physics, National Pingtung University Title：Spin- and Thermally Driven Control of Optical Chirality in Ferrimagnetic Thin Films Abstract： We report recent advances in the electrical control of optical chirality in two ferrimagnetic thin-film platforms: GdFeCo alloys and TmIG/Pt heterostructures. In both systems, circular dichroism (CD) can be continuously tuned across the visible to ultraviolet (vis–UV) spectral range through spin-dependent processes coupled to thermally driven magnetization dynamics. In GdFeCo, controlled Joule heating at low current densities, together with a small out-of-plane magnetic field (~3.5 mT), enables magnetization switching in the vicinity of the magnetic compensation temperature (Tcomp). This leads to reversible, multilevel modulation of optical ellipticity with minimal optical loss, governed by the broadband response of the FeCo sublattice. In contrast, TmIG/Pt heterostructures exploit the spin Seebeck effect to generate thermally induced spin currents at the magnetic insulator/metal interface. This mechanism enables both volatile (current-driven, field-free) and non-volatile (field-assisted) switching of ultraviolet CD. The behavior is attributed to a transition from collinear to noncollinear spin configurations, driven by Tm 4f–5d electronic interactions, consistent with electronic structure calculations. Together, these results highlight the versatility of ferrimagnetic systems—both metallic and insulating—for dynamic and broadband manipulation of optical chirality, providing a pathway toward chiral optoelectronic functionalities and spin-based photonic devices. Reference: 1.Wan-Hsiu Chang Chien, Hsiu-An Liu, Jun-Xiao Lin, Wei-Hsiang Liao, Yu-Ying Chang, Chun-Kai Hu, Jiann-Shing Lee, Simon Granville, Jiunn Chen*, Hua-Shu Hsu*, Adv. Electron. Mater. 2024, 2400459. 2.Jun-Xiao Lin, Bo-Jun Chen, Shih-Min Hung, Wei-Hsiang Liao, Michel Hehn, Shih-Jye Sun, Yu-Ying Chang, Thomas Hauet, Julius Hohlfeld, Stéphane Mangin*, and Hua-Shu Hsu*, ACS Applied Electronic Materials, 2025,7(1), 177-184 Place：S101, Gongguan Campus, NTNU |
