On the phase diagrams of the ferromagnetic superconductors UGe2 and ZrZn2

Theory of Ferromagnetic Unconventional Superconductors with Spin-Triplet Electron Pairing

“…These and other possible shapes of T − P phase diagrams are described within the framework of the general theory of Ginzburg-Landau (GL) type [18][19][20] in a conformity with the experimental data; see also Ref. [21].…”

“…We propose a simple, yet comprehensive, modeling of P dependence of the free energy parameters, resulting in a very good compliance of our theoretical predictions for the shape the T − P phase diagrams with the experimental data (for some preliminary results, see Ref. [18,19]). …”

“…A third variant is related with the possible splitting of the point (0, P c ), so that the N-FM line terminates at (0, P c ), whereas the FM-FS line terminates at another zero temperature point (0, P 0c ); P 0c P c . In this case, the p-wave ferromagnetic superconductor has three points of quantum (zero temperature) phase transitions [18,19].…”

Phenomenological description of anisotropy effects in some ferromagnetic superconductors

“…In earlier papers [6,7] we did not consider the Cooper-pair and crystal anisotropy as the main purpose was to describe the P − T phase diagram. Because the coexisting phase of UGe 2 is totally within the domain of ferromagnetic phase we have assumed that it is the presence of ferromagnetism that triggers the appearance of superconductivity under external pressure.…”

“…The anisotropic properties of superconductivity in these compounds are vastly studied experimentally, especially the anisotropic properties of upper critical field [4]. Here we will study phenomenologically the role of magnetic, crystal and Cooper-pair anisotropy on the phase diagram and possible phases using the previously derived Ginzburg-Landau free energy [6,7].…”