Berlin 2018 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 6: Ultrafast magnetism I

MA 6.2: Vortrag

Montag, 12. März 2018, 09:45–10:00, EB 407

Optically induced symmetry breaking in multiferroic h-YMnO₃ probed by second harmonic generation — •Christian Tzschaschel¹, Mads Weber¹, Manfred Fiebig¹, and Takuya Satoh^2,3 — ¹ETH Zürich, Switzerland — ²The University of Tokyo, Japan — ³Kyushu University, Japan

Recent advances in antiferromagnetic spintronics demand for a better understanding of the order-parameter dynamics on ultrafast time scales. Here, we demonstrate an optically induced coherent modulation of the antiferromagnetic (AFM) order parameter in the multiferroic phase of hexagonal YMnO₃. We employ optical second harmonic generation (SHG) as a highly symmetry sensitive probe that couples directly to the AFM order. Exploiting the inverse Faraday effect (IFE), we optically induce a spin precession, which transiently reduces the symmetry of the magnetic lattice from 6mm to 3. Probing the symmetry of the magnetic lattice by SHG, we observe a periodic anisotropy modulation. The periodicity corresponds to a magnon mode in YMnO₃. This is further verified by simultaneous measurements of the transiently occuring Faraday rotation. The observed SHG modulation and the Faraday rotation can be described by a combined model of the microscopic spin system with a phenomenological description of the IFE. This model furthermore allows us to directly extract the basal plane spin rotation angle from the SHG data – a quantity that is hardly accessible by established magneto-optical techniques.