Laser-driven spin generation in the conduction bands of ferrimagnetic metals

Ferrimagnetic metals show an extraordinary phenomenon of all-optical switching of magnetization. Ongoing research has revealed the relevant physics of crossing a compensation temperature, occurrence of a transient ferromagneticlike state, and transferring angular momentum between sublattices during the all-optical switching. However, most studies were focused on the spin dynamics of local bands, and the role of the conduction band is unknown. Here, we investigate spin generation in conduction bands of ferrimagnetic metals by measuring spin transport from a ferrimagnetic metal to a nonmagnetic metal or to a ferromagnetic metal. We find that two sublattices of ferrimagnets generate spins in the conduction band with different signs and times.