Third angular effect of (TMTSF)2ClO4 in R- and Q-states under pressure

Fermi surface of (TMTSF)2ClO4 was studied under pressure by utilizing the third angular effect (TAE) of magnetoresistance (MR) of quasi-one-dimensional (Q1D) metals. The TAE anomalies, which appear as dips or bends of the MR, were observed at 1.2 K and 5 T between 0 and 13 kbar for the slowly cooled (R) state, but only above 10 kbar for the rapidly cooled (Q) one. The width (Δφ) of the TAE anomaly increases by pressure for R-state. It was found that Δφ is almost the same above 10 kbar for both R- and Q-states. From the present result, we determine that: (i) the anisotropy of the transfer integral (|tx/ty|) within the conducting plane is 12 at ambient pressure and (ii) the anion potential in R-state is 0.028|tx|.