Fig. 5
From: Evidence of spontaneous vortex ground state in an iron-based ferromagnetic superconductor
Temperature dependence of real and imaginary parts (χ′ and χ″) of ac susceptibility at zero dc magnetic field. The amplitude of the driving ac magnetic field (along the c axis) is, H ac = 2.5 Oe. The demagnetization effect has been taken into consideration. T sc, T m, and T sg are the superconducting, ferromagnetic, and spin-glass transition temperatures, respectively. The inset plots the imaginary part of the ac magnetization at 1.9 K as a function of H ac. The solid line is the linear fit
