Intra-unit-cell Magnetic Order in Stoichiometric La$_2$CuO$_4$
  Muon spin rotation measurements supported by magnetization experiments have been carried out in a stoichiometric high-$T_c$ parent compound La$_2$CuO$_4$ in %the a temperature range from 2~K to 340~K and in transverse magnetic fields up to 5~T. Along with the antiferromagnetic local field, muon spin rotation spectra indicate presence of an additional source of magnetic field on the muon. The characteristic splitting of about 45~G coming from this additional magnetic field is consistent with spontaneous circulating currents model of Varma. 
Vyacheslav G. Storchak, Jess H. Brewer, Dmitry G. Eshchenko, Patrick   W. Mengyan, Oleg E. Parfenov, Andrey M. Tokmachev, Pi...
cond-mat.str-el