Abstract
Investigations of the structures and electronic properties of neat single crystals of the organic metals and —a tempered phase of —are presented and compared. It will be shown that in contrast to the -phase crystals, where only 30% of the crystals become superconducting at , all crystals of the -phase become superconducting at about . The origin for this behavior is discussed. Temperature-dependent resistivity and susceptibility measurements as well as electron spin resonance investigations of both types of crystals are presented and discussed. The Fermi surfaces of both materials were investigated by de Haas van Alphen and Shubnikov de Haas experiments at . The results are compared with predictions of a band structure calculation as well as experiments on a similar material, namely, , known from literature. In addition, the effective masses of two orbits of were investigated as a function of the angle of the magnetic field with respect to the conducting planes. Furthermore, it will be shown that in high magnetic fields “inverse” saw-tooth oscillations in magnetization in crystals occur, whereas in crystals under the same conditions, very symmetric oscillations are observed. The origin of the “inverse” saw-tooth is discussed and magnetic interaction as the most probable origin is proposed.
13 More- Received 10 October 2006
DOI:https://doi.org/10.1103/PhysRevB.75.054509
©2007 American Physical Society