Magnetic susceptibility and resistive transitions of superconducting (TMTSF)Cl2O4: Critical magnetic fields

Abstract

We report measurements of the ac magnetic susceptibility and dc resistive transition in the zero-pressure organic superconductor di-tetramethylselenafulvalene perchlorate ((TMTSF)/sub 2/ClO/sub 4/). Inductive measurements show complete diamagnetic shielding below a broad transition and initial flux penetration at very low fields (H/sub c/1(0)<1 Oe). The resistive transition is also broad, but occurs at a significantly higher temperature than the inductive transition, T/sub c/ = 1.0 and 0.65 K, respectively. Magnetic-field-induced transitions, measured both inductively and resistively, are broad and characteristically different. Critical magnetic fields measured inductively are moderately anisotropic (H/sup primeprime//sub c/2/H/sup perpendicular//sub c/2roughly-equal3.2) and relatively small in magnitude (H/sup perpendicular//sub c/2(0)roughly-equal150 Oe). Measured resistively, the critical magnetic fields are highly anisotropic (H/sup primeprime//sub c/2/H/sup perpendicular//sub c/2roughly-equal20) and large in magnitude (H/sup perpendicular//sub c/2(0)roughly-equal1500 Oe). Results suggest that (TMTSF)/sub 2/ClO/sub 4/ is a quasi-one-dimensional or quasi-two-dimensional superconductor at high temperatures and high magnetic fields and an anisotropic bulk superconductor at low temperatures and fields.