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We have measured Hall resistance and magnetic torque in the field-induced spin-density-wave (FISDW) phase of deuterated (TMTSF) 2 ClO 4 for various cooling rates through the anion ordering temperature. The Hall resistance with the magnetic field parallel to c* is not sensitive to cooling rate above 16T. On the other hand, the Hall resistance between 9 and 14 T rapidly and continuously decreases with increasing cooling rate. This result means that the Hall resistance in the semimetallic SDW phase between 9 and 14 T is not quantized in the intermediate cooled states. A new phase transition from the non-quantized phase to the quantized (n = 1) Hall phase exists with hysteresis of the Hall resistance. Moreover, the new phase boundary is shifted towards a lower field when the cooling rate is increased. We have also found that the magnetic torque in the non-quantized phase rapidly decreases with increasing cooling rate. A possible ground state of non-quantized and Hall phase of the FISDW phase of (TMTSF) 2 ClO 4 is discussed from the viewpoint of the peculiar SDW nesting vector.

Magnetoresistance and Hall resistance measurements have been carried out in the FISDW phase of deuterated (TMTSF)2C1O4 for various cooling rates through the anion ordering temperature. The Hall resistance in the intermediate cooled state, observed a very stable quantum Hall state above 9.0 T for slowly cooled, shows a step-like change from the phase between 10 and 17 T to the phase between 20 and 25 T with hysteresis between 14 and 21 T. This result suggests that there is a new phase transition around 15 T in deuterated (TMTSF)4ClO4. A possible ground state of the FISDW phase of (TMTSF)2C1O4 for various cooling rates is discussed from the viewpoint of the peculiar SDW nesting vector stabilized by the dimerized gap due to anion ordering.

Magnetic properties of the spin density wave (SDW) phase in (TMTSF) 2 X (X=AsF 6 , PF 6 ) and (TMTTF) 2 Br were investigated through analyses of 1 H-NMR and static magnetization measurements. A divergent peak was observed, at the temperature T * well below the SDW transition temperature, in the 1 H spin-lattice relaxation rate in the incommensurate SDW phase of (TMTSF) 2 X. A decrease of the differential magnetic susceptibility of (TMTSF) 2 X with the field parallel to the a-axis was observed around T * . This anomaly indicates a difference of the spin canting above and below T * which divides the SDW phase. In the measurements of magnetic susceptibility on the commensurate SDW phase of (TMTTF) 2 Br, a large decrease of the spin susceptibility was observed above T SDW and non-activated type behavior in the b'-axis susceptibility is observed below the spin-flop field at low temperature. The data are discussed on the basis of commensurability.

The magnetic field dependence of the SDW transition in (TMTSF) 2 ClO 4 for various anion quenching rates has been measured up to 27T , with the field parallel to the lowest conductivity direction c * . The SDW transition temperature T SDW decreases with decreasing quenching rate and the rate of increase with magnetic field increases with decreasing T SDw . For quenched (TMTSF) 2 ClO 4 , T SDW increases from 4.5K in zero field up to 8.4K at 27T. As predicted, a quadratic behavior is observed below 18T, followed by a saturation behavior. These results are consistent with the prediction of the mean-field theory. For the perfect nesting case, T SDW is estimated as T SDWo =13.5K. This means that the SDW phase of quenched (TMTSF) 2 Cl0 4 is strongly suppressed by the two-dimensionality of the system. In the intermediate cooling state in which there is no SDW phase in zero field, T SDW shows a quadratic behavior above 12T and there is no saturation even at 27T, which is different to the field induced SDW phase of the relaxed state. This may be attributed to the difference of the anion gap structure.