Title: Ultrahigh Magnetic Field Phases in Frustrated Triangular-lattice Magnet CuCrO$_2$,
Abstract: The magnetic phases of a triangular-lattice antiferromagnet, CuCrO$_2$, were
investigated in magnetic fields along to the $c$ axis, $H$ // [001], up to 120
T. Faraday rotation and magneto-absorption spectroscopy were used to unveil the
rich physics of magnetic phases. An up-up-down (UUD) magnetic structure phase
was observed around 90--105 T at temperatures around 10 K. Additional distinct
anomalies adjacent to the UUD phase were uncovered and the Y-shaped and the
V-shaped phases are proposed to be viable candidates. These ordered phases are
emerged as a result of the interplay of geometrical spin frustration, single
ion anisotropy and thermal fluctuations in an environment of extremely high
magnetic fields.