Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 23: Spin Dynamics and Transport: Ultrafast Effect

MA 23.5: Vortrag

Dienstag, 21. März 2017, 10:30–10:45, HSZ 403

Picosecond time-evolution of Cu₂OSeO₃’s helimagnetic order parameter after photoexcitation studied by time-resolved spontaneous Raman spectroscopy — •Rolf B. Versteeg¹, Jingyi Zhu¹, Christoph Boguschewski¹, Petra Becker², and Paul H.M. van Loosdrecht¹ — ¹II. Physikalisches Institut, Universität zu Köln, Cologne, Germany — ²Abteilung Kristallographie, Institut für Geologie und Mineralogie, Cologne, Germany

Time-resolved Raman spectroscopy is a seldom used tool in the investigation of picosecond magnetization dynamics. This is mostly due to a combination of the low inelastic light scattering rate, and the restrictions on time-resolution, and needed spectral resolution. A successful realization of such an experiment would however lead to valuable insights into symmetry changes after optical perturbation, quasiparticle population statistics, and excitation energy changes on ultrafast timescales.

Here, we present the ultrafast dynamics of helimagnetic order in the chiral magnet Cu₂OSeO₃ studied by time-resolved picosecond spontaneous Raman spectroscopy. This material has attracted significant research interest due to the presence of a Skyrmion lattice phase. The ground state of this material consists of helimagnetically ordered S = 1 spin clusters, which are composed of 3-up-1-down Cu S = 1/2 spins. The magnetic excitations within the spin-cluster are Raman-active, and serve as a probe for helimagnetic order. We show that after photoexcitation the helimagnetic order "melts" through spin-lattice relaxation on typical timescales of ∼100 ps.