Commensurability effect on field-induced spin-density-wave transitions

The dependence of field-induced spin-density-wave (FISDW) transitions on th e magnetic field orientation has been studied by magnetoresistance experime nts in (TMTSF)(2)ClO4 and mean-field theory. Experimentally, when the magne tic field is rotated in the b 'c*-plane normal to the 1D axis, the threshol d field B-th(theta) is almost scaled by 1/cos theta (theta :angle from the c*-axis), but it shows small but sharp decrease at Lebed's magic angles p/q =1 and -1. This means stabilization of FISDW at magic angles. On the other hands, the mean-field theory based on linearized band model with multiple t ransfers concludes suppresion of FISDW at magic angles due to increase of e ffective dimensionality.