EPR and electrical conductivity of the organic superconductor di-tetramethyltetraselenafulvalenium-perchlorate, (TMTSF)2ClO4 and a metastable magnetic state obtained by fast cooling

Abstract
EPR and electrical conductivity measurements under controlled thermal cycles demonstrate that a phase transition is occurring at about 22 K in (TMTSF)2ClO4. Slow cooling (12 K/h) yields a stable ground state exhibiting Pauli paramagnetism above and superconductivity below 1.2 K. In contrast, fast cooling (30 K/min.) yields a metastable magnetic (SDW) state below 4 K as indicated by increasing resistivity and disappearance of the EPR signal with decreasing temperature