Ultrafast Spin-Charge Conversion Schemes in Magnets: THz Time Domain Spectroscopy Study

This PhD thesis uses terahertz time-domain spectroscopy to study how spin ordering, spin dynamics and spin currents in magnetic materials generate ultrafast charge currents, a key requirement for fast, energy-efficient spintronic devices. First, it proposes a new way of estimating spin diffusion lengths with THz spectroscopy, tested on CoFeB/Pt bilayers. Next, it studies FeRh/Pt heterostructures over a wide range of temperatures and magnetic fields, and reports a previously unreported enhancement of the spin current in the mixed antiferromagnetic–ferromagnetic phase at low temperatures. Finally, it reports helicity-dependent ultrafast photocurrents in the noncollinear antiferromagnet Mn₃Sn, linked to the material’s nontrivial spin ordering. The THz set-up uses a pair of wire-grid polarizers, one on a motorised rotation stage, for polarization-resolved detection.