A second metastable spin-ordered state on ferrimagnetic single crystal Cu$_{2}$OSeO$_{3}$

DC and AC susceptibilities were executed on ferrimagnetic single crystal Cu$_{2}$OSeO$_{3}$ under magnetic field ($H)$ and hydrostatic pressure ($P)$ circumstance. With increasing $H$, the ferrimagnetic transition at $T_{C} \quad \sim $ 60 K tends to a higher temperature. Furthermore, the $T_{C}$ rises with a linear slope and magnetization is enhanced with increasing $P$. Features of the ladder shown in the $M$ vs. $H$ curve or the peak observed in the d$M$/d$H$ vs. $H$ curve are noted at $H_{SF} \quad \sim $ 0.5 kOe, exhibiting a competing ordered state in magnetic fields below $T_{C}$. Remarkably, another shoulder is observed at $\sim $ 1 kOe in the d$M$/d$H$ vs. $H$ curve, revealing a metastable spin ordered state in Cu$_{2}$OSeO$_{3}$. In addition, the novel state is retained and enhanced by applied pressure. However, at $H$ up to 55 T, there is no more observable slop change in magnetization. These magnetic properties suggest a complex spin orientation in the spin-frustrated system Cu$_{2}$OSeO$_{3}$.