Element-specific probing of ultrafast spin dynamics in multisublattice magnets with visible light.

We demonstrate the feasibility of element-specific probing of ultrafast spin dynamics in the multisublattice magnet TbFe in the visible spectral range. In particular, we show that one can selectively study the dynamics of Tb and Fe sublattices choosing the wavelength of light below and above 610 nm, respectively. We observe that, despite their antiferromagnetic coupling in the ground state, the Tb and Fe spins temporarily align ferromagnetically after excitation with an intense 55-fs laser pulse, after which they relax to their initial states due to the strong anisotropy in Tb.