Spin-density wave and field-induced spin-density wave transitions of (TMTSF)2ClO4 at high magnetic fields

The magnetic field dependence of the SDW transition in (TMTSF)(2)ClO4 for various anion cooling rates has been measured, with the field up to 27 T parallel to the lowest conductivity direction c*. For quenched (TMTSF)(2)ClO4, the SDW transition temperature T-SDW increases from 4.5 K in zero field up to 8.4 K at 27 T. A quadratic behavior is observed below 18 T, followed by a saturation behavior. These results are consistent with the prediction of the mean-field theory. From these behaviors, T-SDW is estimated as T-SDW0 = 13.5 K for the perfect nesting case. This indicates that the SDW phase in quenched (TMTSF)(2)ClO4, where T-SDW is less than 6 K, is strongly suppressed by the two-dimensionality of the system. In the intermediate cooled state in which the SDW phase does not appear in zero field, the transition temperature for the field-induced SDW shows a quadratic behavior above 12 T and there is no saturation behavior even at 27 T, in contrast to the FISDW phase in the relaxed state. This behavior can probably be attributed to the difference of the dimerized gap due to anion ordering.