Ultrafast enhancement of ferromagnetic spin exchange induced by ligand-to-metal charge transfer

Understand

Directly modifying spin exchange energies in a magnetic material with light can enable ultrafast control of its magnetic states.

• Current approaches rely on tuning charge hopping amplitudes that mediate exchange by optically exciting either virtual or real charge-transfer transitions (CT) between magnetic sites.
• Here we show that when exchange is mediated by a non-magnetic ligand, it can be substantially enhanced by optically exciting a real CT transition from the ligand to magnetic site, introducing lower order virtual hopping contributions.
• We demonstrate sub-picosecond enhancement in a superexchange dominated ferromagnet CrSiTe3 through this mechanism using phase-resolved coherent phonon spectroscopy.