The discovery of the magnetization switching only by a femtosecond laser pulse triggered intense discussions about mechanisms responsible for laser-induced changes. All-optical magnetization switching, investigated so far predominantly in metallic systems, was recently also discovered in transparent dielectrics. We demonstrated ultrafast nonthermal all-optical switching in Co-doped iron garnet films using time-resolved magneto-optical spectroscopy. In this garnet a single linearly polarized femtosecond laser pulse promote switching of the magnetization without external magnetic field via precessional mechanism .
Additionally, we demonstrated the spectral selectivity of laser-induced magnetization switching using near-infrared laser pulses by selective pumping of optical resonances in garnets . The switching properties at the observed resonances are vastly different, related to the crystal site hosting the excited Co-ions. As these ions are the source of the strong magnetic anisotropy in a garnet, their excitation between the crystal filed split states results in a coherent and ultrafast manipulation of spin-orbital interaction. Moreover, another nonthermal mechanism of ultrafast magnetization switching was found in these unique magnetic garnets by resonant pumping of phonon modes at infrared spectral range . Our results reveal the principles to be employed in achieving cold and ultrafast magnetic recording in dielectrics far beyond today’s state of the art.
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