Charge density wave system in high magnetic fields: competition between Pauli and orbital effects

A detailed angular dependent magneto-transport and magnetization study of t he charge transfer salt alpha-(ET)(2)MHg(SCN)(4), where M = K, Rb, or Tl, r eveals multiple electronic sub-phases with respect to temperature, held str ength, and field orientation. We find that the low temperature ground state undergoes two subsequent held-induced phase transitions above a critical a ngle, theta (c), of the magnetic held with respect to the crystallographic axes (theta (c) greater than or equal to 50 degrees). This new T-B-theta ph ase diagram may be qualitatively described assuming a charge density wave f ramework with the held-induced transitions arising from the interplay betwe en orbital and Pauli effects. This implies well (but not perfectly) nested quasi-one-dimensional Fermi sheets. (C) 2001 Elsevier Science B.V. All righ ts reserved.