Existence of two-dimensional closed orbits and delocalized carriers in the spin-ordered state of quasi-one-dimensional (TMTSF)2PF6

The magnetoresistance in spin-ordered state of quasi-one-dimensional (TMTSF)2PF6 has been studied. Both the frequency and anisotropy of the magnetoresistance oscillations are found to be independent of temperature; this proves the temperature independence of the geometry of two-dimensional closed contours at the Fermi level. At the same time, the oscillation amplitude decreases with the temperature, indicating the depopulation of the closed contours in the T = 0 limit. An explanation for the above seemingly controversial results has been proposed.