Multiple phases with a tricritical point and a Lifshitz point in the skyrmion host Cu2OSeO3

Magnetic skyrmions, topologically stable spin swirling objects, have attracted a great interest due to their potential applications in future spintronics and ultrahigh dense magnetic memory devices. Existence of a skyrmion phase as well as first- and second-order phase transitions make Cu2OSeO3 a promising candidate for investigating complex magnetic phenomena. Here, we report that both first- and second-order magnetic phase transitions are responsible in determining the phase diagram with at least two multicritical points in Cu2OSeO3. A fluctuation-induced first-order transition is realized as a precursor for the skyrmion phase over a small window of temperature and magnetic field. The evolution of isothermal entropy at the phase transition provides evidence for a tricritical point. Furthermore, the existence of commensurate and incommensurate phases along with the coexistence of three second-order phase transitions provide evidence for the existence of a Lifshitz point.