Evidence for a transition from a bulk Meissner-state to a spontaneous vortex phase in RuSr2GdCu2O8 from DC magnetisation measurements
نویسندگان
چکیده
From magnetisation measurements we provide evidence that the ferromagnetic superconductor RuSr2GdCu2O8 with Tc=45 K and TM=137 K exhibits a sizeable diamagnetic signal at low temperature (T<Tms=30 K) and low magnetic field (H<30 Oe), corresponding to a bulk Meissner-phase. At intermediate temperatures, Tms<T<Tc, a spontaneous vortex phase forms which is characterized by unique thermal hysteresis effects. We argue that a recent negative report [C.W. Chu et al., cond-mat/9910056] regarding the Meissner-effect in Ru-1212 can be explained by impurity scattering or grain size effects. Typeset using REVTEX
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