Observation of magnetization saturation of CuGeO3 in ultrahigh magnetic fields up to 500 T

The magnetization in a spin-Peierls material CuGeO3 was measured by means of the Faraday rotation in ultrahigh magnetic fields up to 500 T. The experimental magnetization curve shows a nonlinear increase against the magnetic field which is a typical behavior of a one-dimensional quantum spin system. A distinct saturation of the magnetization was observed at 253 T, from which the exchange parameter is evaluated as 183 K. A large hysteresis of the magnetization was observed in the magnetic phase, whereas it was indiscernible in the uniform phase.