Muon Spin Relaxation Studies of Magnetic-Field-Induced Effects in   High-$T_{c}$ Superconductors
  Muon spin relaxation ($\mu$SR) measurements in high transverse magnetic fields ($\parallel \hat c$) revealed strong field-induced quasi-static magnetism in the underdoped and Eu doped (La,Sr)$_{2}$CuO$_{4}$ and La$_{1.875}$Ba$_{0.125}$CuO$_{4}$, existing well above $T_{c}$ and $T_{N}$. The susceptibility-counterpart of Cu spin polarization, derived from the muon spin relaxation rate, exhibits a divergent behavior towards $T \sim 25$ K. No field-induced magnetism was detected in overdoped La$_{1.81}$Sr$_{0.19}$CuO$_{4}$, optimally doped Bi2212, and Zn-doped YBa$_{2}$Cu$_{3}$O$_{7}$. 
A.T. Savici, A. Fukaya, I.M. Gat-Malureanu, T. Ito, P.L. Russo, Y.J.   Uemura, C.R. Wiebe, P.P. Kyriakou, G.J. MacDougall, M...