1. Sequences of magnetic field-induced phase transitions in frustrated helimagnets of low symmetry

Oleg Utesov

St. Petersburg State University, Russia

1 December 2022 Thu 4 pm

                                      IBS Center for Theoretical Physics of Complex Systems (PCS), Administrative Office (B349), Theory Wing, 3rd floor

                                      Expo-ro 55, Yuseong-gu, Daejeon, South Korea, 34126 Tel: +82-42-878-8633                     

So-called multiferroics of spin origin, materials combining magnetic and ferroelectric order in the same phase, are considered promising materials for various applications. They allow for establishing cross-control between electrical and magnetic degrees of freedom, e.g., magnetic order switching using an electrical field. In this context, helical magnetic structures play an important role. They break inversion symmetry, thus allowing for nonzero electrical polarization. It makes studies on phase transitions involving non-collinear magnetic orderings an actual problem.

In the present study, we theoretically discuss rather complicated sequences of magnetic field induced phase transitions in three-dimensional anisotropic frustrated magnets at zero temperature. We treat a low-symmetry model, which allows only magnetic structures with a single modulation vector. Exchange interaction favors simple helical magnetic ordering; however, biaxial anisotropy (or magnetodipolar interaction) and the external magnetic field, as well as competition with commensurate orders, complicate the model behavior. Taking advantage of the anisotropy smallness, we analytically describe various phase transitions and their sequences. For instance, five consecutive transitions observed in multiferroic MnWO4 for the external field along the easy axis were successfully discussed within the developed approach. Moreover, a good correspondence of the critical fields with the other research teams’ numerics can be highlighted.