Phase diagrams for diamagnetic phase transitions in two-dimensional conductors

We consider under conditions of the nonlinear de Haas–van Alphen effect temperature–magnetic-field (T-B) phase diagrams for diamagnetic phase transitions into homogeneous single-domain state in two-dimensional (2D) conductors and superconductors (i.e., with cylindrical Fermi surface) to estimate the T-B regions where magnetoquantum oscillations are strongly distorted by magnetic interactions. A universal relation is obtained between maximal transition temperature T_dm and cyclotron mass m_c at a given magnetic induction B_dm : ℏω_c =Q_m k_B T_dm with Q_m =5.45. Simple expressions are derived for maximal transition temperature T_dm corresponding field B_dm , and limiting field B₀ (above which the transition does not occur at any temperature), via Fermi energy, cyclotron mass, and geometrical factors (lattice constant in anisotropic direction c and demagnetizing coefficient). Phase diagrams are drawn for characteristic parameters of the nearly 2D organic conductors and superconductors of the (ET)₂ X type.