Application of phenomenological Landau approach to the description of magnetic phase transitions in the ferromagnetic superconductor at ambient pressure

Abstract

We study the possibility to apply phenomenological approach to the description of magnetic transitions in UGe2 with the help of Landau free energy expanded to 8-th order in magnetisation. The analysis shows that for certain values of parameters in front of M^4, and M^6 terms in the free energy there id possibility for the appearance of two successive phase transitions between the low-magnetisation and high-magnetisation phase with the same structure. We establish the relation of the parameters in Landau energy, for which the phase transition from the disordered to low-magnetisation phase is of second order as the experimental data shows. Within our approximation the transition between two magnetically ordered phases is of first order

arXiv comment16 pages, 8 figures