Mapping of the anomalous magnetotransport regime in the alpha-(BEDT-TTF)(2)MHg(SCN)(4) (M = K, Tl) organic conductors

We present a comprehensive set of pulsed-magnetic-held measurements of the quasi-two-dimensional organic conductors alpha-(BEDT-TTF)(2)MHg(SCN)(4) (M = K, Tl) to map out the boundaries of a high-field regime that was recently associated with the presence of the bulk quantum Hall effect. The phase in version effect observed in the interplane magnetoresistivity and the behavi or of quantum oscillations in the Hall potential are used to investigate th e high-field region as a function of magnetic field, temperature, rotation angle, sweep rate, sample quality, and the anion of the charge-transfer sal t. The inversion of the phase of the oscillations in rho(zz), is found to b e directly related to the quality of the sample, and is suggested to be an intrinsic property of alpha-(BEDT-TTF)(2)MHg(SCN)(4) (M = K, Tl). A detaile d mapping of the phase-inverted region indicates that its boundaries agree qualitatively with those of the recently proposed low-temperature-high-fiel d state.