Andrzej Stupakiewicz (Universyty of Bialystok): Ultrafast nonthermal all-optical switching of magnetization

Physikalisches Kolloquium

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 [1].

Additionally, we demonstrated the spectral selectivity of laser-induced magnetization switching using near-infrared laser pulses by selective pumping of optical resonances in garnets [2]. 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 [3]. 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.

1. A. Stupakiewicz, et al. Nature 542, 71 (2017).

2. A. Stupakiewicz, et al. Nat. Commun. 10, 612 (2019).

3. A. Stupakiewicz, et al. Nat. Phys. 17, 489 (2021).

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