Regensburg 2019 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 22: Terahertz spintronics

MA 22.5: Vortrag

Dienstag, 2. April 2019, 15:00–15:15, H52

Terahertz spin dynamics with a field-derivative torque — •Ritwik Mondal¹, Andreas Donges¹, Ulrike Ritzmann², Peter M. Oppeneer², and Ulrich Nowak¹ — ¹Fachbereich Physik, Universität Konstanz, DE-78457 Konstanz, Germany — ²Department of Physics and Astronomy, Uppsala University, P. O. Box 516, Uppsala, SE-75120, Sweden

Efficient manipulation of magnetization at the ultrashort timescales is of particular interest for future technology. In a previous work, we developed a relativistic Dirac theory to derive the Landau-Lifshitz-Gilbert equation of motion that showed an additional contribution, the “field-derivative torque” (FDT) that is frequency and damping dependent [1]. Our analytical results show that the FDT effects can become important for pulses at terahertz frequencies or higher. In this work, we numerically investigate the contribution of field-derivative torques to the magnetization dynamics. We propose that only considering the THz field underestimates the spin excitation in antiferromagnetic oxide systems (NiO, CoO etc.), however, accounting for both, the THz and the FDT, the theory can quantitatively explain earlier experiments [2]. We also study the damping dependence of FDT effects for spin excitation in these systems.

[1] R. Mondal, M. Berritta and P. M. Oppeneer Phys. Rev. B 94, 144419 (2016) [2] Kamfrath et al., Nature Photonics 5, 31 (2011)