Abstract-Micromagnetic modeling of terahertz oscillations in an antiferromagnetic material driven by the spin Hall effect

V. Puliafito, R. Khymyn, M. Carpentieri, B. Azzerboni, V. Tiberkevich, A. Slavin, and G. Finocchio

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.024405

The realization of terahertz (THz) sources is a fundamental aspect for a wide range of applications. Over different approaches, compact THz oscillators can be realized, taking advantage of dynamics in antiferromagnetic thin films driven by the spin Hall effect. Here we perform a systematic study of these THz oscillators within a full micromagnetic solver based on the numerical solution of two coupled Landau-Lifshitz-Gilbert-Slonczewski equations, considering ultrathin films. We find two different dynamical modes depending on the strength of the Dzyaloshinskii-Moriya interaction (DMI). At low DMI, a large-amplitude precession is excited, where both the magnetizations of the sublattices are in a uniform state and rotate in the same direction. At large enough DMI, the ground state of the antiferromagnet becomes nonuniform and the antiferromagnetic dynamics is characterized by ultrafast domain-wall motion.

• 
• 
• 
• 
• 
• 
• 

Abstract-Ultrafast excitation of coherent phonons in iron garnet

Pritam Khan, Masataka Kanamaru, Wei-Hung Hsu, Minori Kichise, Yasuhiro Fujii, Akitoshi Koreeda, Takuya Satoh

https://arxiv.org/abs/1802.04515

We employed a femtosecond pump-probe technique to investigate the dynamics of coherent phonons in iron garnet. A phenomenological symmetry-based theory reveals that oscillations of the terahertz Eg mode are excited. Selective excitation by a linearly polarized pump and detection by a circularly polarized probe confirm that impulsive stimulated Raman scattering (ISRS) is the driving force for the coherent phonons. Experimental results obtained from ISRS measurements show an excellent agreement with spontaneous Raman spectroscopy data, analyzed by considering the symmetry of the phonon modes and corresponding excitation and detection selection rules.