Fig. 4: Magnetic phase diagram of NiI2.

The magnetic phase diagram of the NiI2 flake as a function of pressure and temperature. TN and TN2 are obtained from Raman and SHG measurements, respectively. Here, the orange, green region, blue, and gray regions represent the paramagnetic (PM), helimagnetic (HM), antiferromagnetic (AFM) and intermediate (IMS) states, respectively.