Development of spatial inhomogeneity of internal magnetic field above   $T_{\rm c}$ in Bi$_2$Sr$_2$Ca$_{1-x}$Y$_x$Cu$_2$O$_{8+\delta}$ observed by   longitudinal-field muon-spin-relaxation
  Longitudinal-field muon-spin-relaxation measurements have revealed inhomogeneous distribution of the internal magnetic field at temperatures above the bulk superconducting (SC) transition temperature, $T_{\rm c}$, in slightly overdoped Bi$_2$Sr$_2$Ca$_{1-x}$Y$_x$Cu$_2$O$_{8+\delta}$. The distribution width of the internal magnetic field, $\Delta$, evolves continuously with decreasing temperature toward $T_{\rm c}$. The origin of the increase in $\Delta$ is discussed in terms of the creation of SC domains in a sample. 
Yoichi Tanabe, Tadashi Adachi, Kensuke M. Suzuki, Megumi Akoshima,   Satoshi Heguri, Takayuki Kawamata, Yasuyuki Ishii, Taka...
cond-mat.supr-con cond-mat.str-el