The magneto-optical Barnett effect: Circularly polarized light induced femtosecond magnetization reversal

Magnetization reversal by a femtosecond circularly polarized laser pulse has been recently demonstrated in rare-earth doped transition metals (RE-TM). The switching mechanism has been attributed to an inverse Faraday effect and thermal effects. Based on the parameters provided in the experimental work, we show that this claim is unlikely to give rise to femtosecond reversal. Using a hybrid itinerant-localized picture of the RE-TM system, we propose a new mechanism that requires the presence of the rare earth element to reduce the symmetry of the system as well as a strong enhancement of spin-orbit coupling between the d electrons and the f moments in the presence of the laser. Our model does not require the heating close to the Curie temperature of the sample.