Synchrotron X-ray Diffraction Studies of the Incommensurate Phase of a Spin–Peierls System CuGeO3in Strong Magnetic Fields

Synchrotron X-ray diffraction measurements on a spin–Peierls material CuGeO 3 in applied magnetic fields, H , up to 15 T are made. We find that the temperature, T , dependence of the incommensurate Bragg peak at a lower H is quite different from that at a higher H . At sufficiently high fields, we find that the lattice incommensurability, δ l , is almost independent of T , while at H slightly above the critical field = 12.25 T for the commensurate to incommensurate transition, δ l decreases with increasing T . We interpret that this finding is due to a stabilization of the incommensurate state by a strong magnetic field which suppresses thermal fluctuations.