Investigations of spin dynamics for ZnCr2Se4 and CoCr2O4 chromium spinels in terahertz region

Terahertz (THz) time domain spectroscopy (THz-TDS) of a CoCr
2
O
4
and ZnCr
2
Se
4
single crystals have been performed under magnetic fields up to 10 Tesla and low temperatures. We observed the magnetic resonances originated from the spin dynamics of inter-sublattice exchange and screw spin structure in THz frequency region, which show pronouncedly anisotropic effect. The phase and polarization sensitive detection in THz-TDS allow us to reveal the large circular absorption dichroism and Faraday rotations under magnetic field in these materials.