Dramatic enhancement of the skyrmion phase-space of Cu₂OSeO₃ driven by high pressure

Generally, the skyrmion phase in a bulk helimagnet occurs only over a very restricted magnetic-field – temperature phase space and often at low temperatures. We have expanded and enhanced the skyrmion phase region from the small range of (55-58.5 K) to (5-300 K) in single crystal Cu₂OSeO₃ by pressures up to 42.1 GPa through a series of phase transitions from the cubic P2₁3, through orthorhombic P2₁2₁2₁ and monoclinic P2₁, and finally to the triclinic P1 phase, using our newly developed ultrasensitive high pressure magnetization technique. The results are in agreement with our Ginzburg - Landau free energy analyses that pressure tends to stabilize the skyrmion states and at higher temperatures. These observations also show that the skyrmion state can be achieved at higher temperatures in various crystal symmetries, suggesting the insensitivity of skyrmions to the underlying crystal lattices and thus the possibility of finding more ubiquitous presence of skyrmions in helimagnets.