Excitation of magnetic precession in bismuth iron garnet via a polarization-independent impulsive photomagnetic effect

A polarization-independent, nonthermal optical effect on the magnetization in bismuth iron garnet is found, in addition to the circular polarization-dependent inverse Faraday effect and the linear polarization-dependent photoinduced magnetic anisotropy. Its impulsive character is demonstrated by the field dependence of the amplitude of the resulting precession, which cannot be explained by a long-living photo or heat-induced anisotropy.