Department of Physics inviting you to a colloquium on Magnetization Dynamics from Femto to Nanosecond Time Scale

The research on the light mater interaction is immensely increased, in last decades, as it leads to various novel effects such as all optical switching [1], heat assisted magnetic recording, optical intersite spin transfer effect [2], spin current [3], etc. When a ferromagnet is excited by a femtosecond laser pulse, the magnetization of a ferromagnet is quenched in sub pico second time scale. This is known as ultrafast demagnetization. At longer time scale the precession of magnetization is observed. The damping associated with magnetization precession as well as spin waves are observed from subns to tens of ns time scale. In this talk I will describe two different systems showing two different magnetization dynamics at two different time scales.

The first system is an antiferromagnetically coupled magnetic trilayer system which achieved huge attention of scientific community due to its potential applications in spintronic devices. We use tabletop high harmonic generation (HHG) in the extreme ultraviolet (XUV) regime to investigate the underlying mechanisms for the M-edge spectroscopy at femtosecond time scale. The second system is a quasi - magnonic crystals [5,6] where spin waves, which are the fundamental magnetic excitation in a metallic ferromagnetic material with frequencies in the microwave regime, propagate in a similar fashion to electromagnetic waves in a photonic crystal. Both the observations have a significant impact on the fundamental understanding of the ultrafast processes and application of spinwaves in future spintronic devices.

SS gratefully acknowledges the financial support of SERB with file number SRG/2022/000191 and the
Axis Grant at Ashoka University for the funding.

1. T. A. Ostler et al., Nat. Commun. 3, 666 (2012)
2. J.K. Dewhurst et al., Nano Lett. 18, 1842 (2018)
3. D. Rudolf et al. Nat. Commun. 3, 1037 (2012)
4. J. Zhou et. al Phys. Rev. B 105, 174415 (2022)
5. R. Mehta, Journal of Physics: Condensed Matter 35, 324002 (2023)

All are cordially invited.