Fig. 4

Shape of the tricritical wing lines (T _w, p _w, H _w). Projection of the wings in a T-H, b T-p and c H-p planes. Black solid squares and green solid circles represent the FM1-wing and FM2-wing, respectively. Red lines (represented in the T-p-H space in Fig. 5) are guides to the eyes and open symbols represent the extrapolated quantum wing critical point (QWCP). d H-p phase diagram at 2 K. The arrow represents the pressure p _c  = 2.1 GPa. The green color cross symbols represent the AFM _Q′ phase boundary. Dark blue, light blue, and green color shaded areas represent the FM2, FM1, and AFM _Q′ phases, respectively. The error bars in pressure for b–d are determined by the superconducting transition width of the Pb manometer. For a–d, the error bars in temperature and magnetic field are determined as half the data spacing