Directly probing spin dynamics in insulating antiferromagnets using ultrashort terahertz pulses

TL;DR

This study uses ultrashort terahertz pulses to directly probe spin dynamics in insulating antiferromagnets, revealing spin-lattice thermalization times and confirming the technique's effectiveness for magnetic materials.

Contribution

It demonstrates that THz pump-probe spectroscopy can directly measure spin order dynamics in insulating AFMs, validated by comparison with x-ray diffraction.

Findings

Spin-lattice thermalization time of 25 ps at 6 K

THz transmission change correlates with spin order

Method confirms direct probing of spin dynamics in AFMs

Abstract

We investigate spin dynamics in the antiferromagnetic (AFM) multiferroic TbMnO3 using optical- pump, terahertz (THz)-probe spectroscopy. Photoexcitation results in a broadband THz transmission change, with an onset time of 25 ps at 6 K that becomes faster at higher temperatures. We attribute this time constant to spin-lattice thermalization. The excellent agreement between our measurements and previous ultrafast resonant x-ray diffraction measurements on the same material confirms that our THz pulse directly probes spin order. We suggest that this could be the case in general for insulating AFM materials, if the origin of the static absorption in the THz spectral range is magnetic.