Fast oscillations in (TMTSF) 2X

Abstract

We report on the temperature dependence of the “fast oscillation” phenomenon in quasi-one dimensional molecular conductors. Magnetoresistance and magnetization measurements to 30T in the ambient pressure spin density wave state have been taken for the X = NO 3, PF 6 and AsF 6 members of the (TMTSF) 2X family. Complementary data on X=AsF 6 are presented by Ulmet et al. in these proceedings. All three compounds exhibit a peak in the transverse magnetoresistances ρ xx (B//c *, I//a) and ρ yy (B//c *, I//b) and thenoscillatory components around 3K, with the oscillations vanishing at higher and lower temperatures. No magnetic moment oscillations are detected in PF 6 or AsF 6, while only extremely weak oscillations (δm~10 −10 emu) are seen in the NO 3 salt above 25T. Also, no oscillations were observed in longitudinal magnetoresistance ρ zz (B//I//c *) measurements performed on AsF 6 and PF 6. Possible scenarios which have been used to explain the data include imperfect nesting at T SDW leaving behind quantizable closed orbits, and quantum interference effects arising from magnetic breakdown orbits. Another may involve a new phase transition inside the SDW state.