▎ 摘　　要

We present an experimental study on terahertz (THz) magneto-optical (MO) properties of tri-layer graphene on quartz substrate, grown by chemical vapor deposition. The MO conductivities are measured in the Faraday geometry by applying optical polarization and using THz time domain spectroscopy (TDS) in high magnetic fields at liquid nitrogen temperature. We find that the real and imaginary parts of the longitudinal and transverse MO conductivities fit well to the classic MO Drude formula for tri-layer graphene. Thus, we are able to determine optically the key sample parameters such as the electron density, the electron effective mass and the relaxation time for tri-layer graphene. The dependence of the relaxation time on magnetic field is examined. This work indicates that THz TDS can be employed as a powerful tool to measure MO properties of tri-layer graphene and other 2D electronic materials in the presence of high magnetic fields.