Fig. 3
From: Evidence of spontaneous vortex ground state in an iron-based ferromagnetic superconductor
Evidence of the first-order transition from a Meissner state to a spontaneous vortex phase with decreasing temperature in Eu(Fe0.91Rh0.09)2As2 crystals. a Field-cooling magnetization (M c ) on both heating (FCH) and cooling (FCC) processes under magnetic fields along the c axis. The rectangles with arrows schematically represent different statuses of sample in the presence of external field (multi-domains and pinned fluxes are not shown). See the text for the inserted cartoon pictures b The magnetization difference ΔM c between the FCH and FCC data. c ΔM c at T m (left axis) and M c at 30 K (right axis) as functions of the applied field. d ΔM c /H vs. T in an expanded temperature range
